Sally R. Frenkel, Ph.D.

Granulin epithelin precursor: a bone morphogenic protein 2-inducible growth factor that activates Erk1/2 signaling and JunB transcription factor in chondrogenesis
Feng, Jian Q; Guo, Feng-Jin; Jiang, Bai-Chun; Zhang, Yan; Frenkel, Sally; Wang, Da-Wei; Tang, Wei; Xie, Yixia; Liu, Chuan-Ju
2010 Jun;24(6):1879-1892, FASEB journal
Granulin epithelin precursor (GEP) has been implicated in development, tissue regeneration, tumorigenesis, and inflammation. Herein we report that GEP stimulates chondrocyte differentiation from mesenchymal stem cells in vitro and endochondral ossification ex vivo, and GEP-knockdown mice display skeleton defects. Similar to bone morphogenic protein (BMP) 2, application of the recombinant GEP accelerates rabbit cartilage repair in vivo. GEP is a key downstream molecule of BMP2, and it is required for BMP2-mediated chondrocyte differentiation. We also show that GEP activates chondrocyte differentiation through Erk1/2 signaling and that JunB transcription factor is one of key downstream molecules of GEP in chondrocyte differentiation. Collectively, these findings reveal a novel critical role of GEP growth factor in chondrocyte differentiation and the molecular events both in vivo and in vitro
— id: 109846, year: 2010, vol: 24, page: 1879, stat: Journal Article,

Adenosine A2A receptor agonists: Can they prevent/treat joint prosthesis loosening?
Mediero A.; Frenkel S.R.; Wilder T.; Immerman I.; Hadley S.; Howell R.D.; Hawly M.
2010 ;62:1470-1470, Arthritis & rheumatism
Purpose: Survival of bone implants depends on biological fixation, and prosthesis loosening can be catastrophic leading to replacement of prostheses. Inflammation and osteoclast-mediated bone resorption in response to wear particles near prostheses contribute to loosening. Because we have demonstrated that adenosine A_2Areceptor activation is anti-inflammatory and prevents osteoclast formation and function we hypothesized that adenosine A_2Areceptor agonists might prevent osteoclast-mediated bone resorption at the site of prosthesis wear in a calvarial model of wear particle-induced bone resorption. Methods: Eighteen C57Bl/6 mice age 6-8 weeks were anesthetized by intraperitoneal injection of ketamine and xylazine and a 1cm midline sagittal incision was made over the calvarium anterior to the line connecting both ears. Six animals received no particles (control), and 12 received 15 ml of polyethylene particle suspension. Of the 12 mice receiving particulate, 6 were injected subcutaneously at the surgical site with 20 ml of 10 muM CGS21680 (A_2Areceptor agonist), and 6 mice were injected with saline 0.9%, beginning immediately after incision closure and continuing every other day until sacrifice. Animals were sacrificed after 14 days and the calvaria were removed, fixed, and prepared for microCT and histological staining with TRAP. Results: Histologic examination of calvaria demonstrated lymphocytic infiltration in both particle-exposed groups. TRAP staining revealed a reduction in osteoclast differentiation after treatment with CGS21680. mCT showed pitting and increased porosity in both particle-exposed groups compared to controls, although in CGS21680-treated mice the reduction in cortical bone was significantly less than in the untreated particle-exposed mice (p<0.01). Control bone volume/trabecular volume was significantly greater (p<0.005) than in either particulate group, however, calvarial bone from CGS21680-treated mice had significantly greater mean bone volume than did the untreated group (p<0.0005). Trabecular thickness was significantly reduced in both CGS21680-treated and untreated particle-exposed groups as compared to control mice (p<0.05). Finally, digital morphometric analysis of microCTs reveals that CGS21680 significantly reduced the area of bone pitting compared to control particle-treated mice (p<0.05). (Table presented) Conclusions: Adenosine A_2Areceptor activation reduces inflammation and bone destruction due to prosthetic wear particles. This observation suggests that delivery of an adenosine A_2Aagonist in the cement may enhance orthopedic implant survival, delaying or eliminating the need for revision arthroplasty surgery
— id: 130923, year: 2010, vol: 62, page: 1470, stat: Journal Article,

Adenosine A2A receptor agonists: can they prevent/treat joint prosthesis loosening?
Munoz, Aranzazu Mediero; Frenkel, Sally R.; Immerman, Igor; Hadley, Scott; Howell, Damani; Cronstein, Bruce N.
2010 JUN ;6(6000):159-160, Purinergic signalling
— id: 113753, year: 2010, vol: 6, page: 159, stat: Journal Article,

The efficacy of intra-articular hyaluronan injection after the microfracture technique for the treatment of articular cartilage lesions
Strauss, Eric; Schachter, Aaron; Frenkel, Sally; Rosen, Jeffrey
2009 Apr;37(4):720-726, American journal of sports medicine
BACKGROUND: Although the exact mechanism of action has yet to be elucidated, recent animal studies have demonstrated chondroprotective and anti-inflammatory properties of hyaluronic acid viscosupplementation. HYPOTHESIS: Intra-articular hyaluronic acid after microfracture improves the quality of the repair leading to a more hyaline-like repair tissue with better defect fill and adjacent area integration. STUDY DESIGN: Controlled laboratory study. METHODS: Full-thickness cartilage defects were created in the weightbearing area of the medial femoral condyle in 36 female New Zealand White rabbits. The defects were then treated with surgical microfracture. Eighteen rabbits formed the 3-month cohort and the other 18 formed the 6-month cohort. Within each cohort, 6 rabbits were randomly assigned to receive 3 weekly injections of hyaluronic acid (group A), 5 weekly injections (group B), or control injections of normal saline (group C). At 3 and 6 months postmicrofracture, the animals were sacrificed and the operative knee harvested. Repair tissue was assessed blinded- both grossly, using a modified component of the International Cartilage Repair Society (ICRS) Cartilage Repair Assessment scoring scale, and histologically, using the modified O'Driscoll histological cartilage scoring system. Comparisons were made with respect to gross and histologic findings between treatment groups at each time point. Effects of each treatment type were also evaluated longitudinally by comparing the 3-month results with the 6-month results. Statistical analysis was performed using unpaired Student t tests with significance defined as P < .05. RESULTS: At 3 months, gross and histologic evaluation of the repair tissue demonstrated that the 3-injection group had significantly better fill of the defects and more normal appearing, hyaline-like tissue than controls (a mean ICRS score of 1.92 vs 1.26; P < .05 and a mean modified O'Driscoll score of 10.3 vs 7.6; P < .02). Specimens treated with 5 weekly injections were not significantly improved compared with controls. At 6 months, the mean gross appearance and histologic scores between the 3 specimen cohorts were not significantly different. However, examination of the entire operative knee demonstrated a significantly greater extent of degenerative changes (synovial inflammation and osteophyte formation) in the control group than in both hyaluronic acid treatment groups (P < .05). CONCLUSION: Supplementing the microfracture technique with 3 weekly injections of intra-articular hyaluronic acid had a positive effect on the repair tissue that formed within the chondral defect at the early follow-up time point. This improvement was not found for the 3-injection group at 6 months or for the 5-injection group at either time point. Additionally, hyaluronic acid supplementation had a possible chondroprotective and anti-inflammatory effect, limiting the development of degenerative changes within the knee joint. CLINICAL RELEVANCE: The adjunctive use of hyaluronic acid appears to hold promise in the treatment of chondral injuries and warrants further investigation
— id: 100949, year: 2009, vol: 37, page: 720, stat: Journal Article,

p204 Protein Overcomes the Inhibition of Core Binding Factor {alpha}-1-mediated Osteogenic Differentiation by Id Helix-Loop-Helix Proteins
Luan, Yi; Yu, Xiu-Ping; Yang, Ning; Frenkel, Sally; Chen, Lin; Liu, Chuan-Ju
2008 May;19(5):2113-2126, Molecular biology of the cell
Id proteins play important roles in osteogenic differentiation; however, the molecular mechanism remains unknown. In this study, we established that inhibitor of differentiation (Id) proteins, including Id1, Id2, and Id3, associate with core binding factor alpha-1 (Cbfa1) to cause diminished transcription of the alkaline phosphatase (ALP) and osteocalcin (OCL) gene, leading to less ALP activity and osteocalcin (OCL) production. Id acts by inhibiting the sequence-specific binding of Cbfa1 to DNA and by decreasing the expression of Cbfa1 in cells undergoing osteogenic differentiation. p204, an interferon-inducible protein that interacts with both Cbfa1 and Id2, overcame the Id2-mediated inhibition of Cbfa1-induced ALP activity and OCL production. We show that 1) p204 disturbed the binding of Id2 to Cbfa1 and enabled Cbfa1 to bind to the promoters of its target genes and 2) that p204 promoted the translocation from nucleus to the cytoplasm and accelerated the degradation of Id2 by ubiquitin-proteasome pathway during osteogenesis. Nucleus export signal (NES) of p204 is required for the p204-enhanced cytoplasmic translocation and degradation of Id2, because a p204 mutant lacking NES lost these activities. Together, Cbfa1, p204, and Id proteins form a regulatory circuit and act in concert to regulate osteoblast differentiation
— id: 78379, year: 2008, vol: 19, page: 2113, stat: Journal Article,

Estrogen's role in osteoarthritis: chondoprotective or condodestructive?
Frenkel SR; Liu C; Patel V; Leslie M; Sankin A; Siu S; DiCesare PE
2007 ;1:38-40, Probe: the publication of research on biomedical endeavors
— id: 75329, year: 2007, vol: 1, page: 38, stat: Journal Article,

Regional gene therapy for full-thickness articular cartilage lesions using naked DNA with a collagen matrix
Di Cesare, Paul E; Frenkel, Sally R; Carlson, Cathy S; Fang, Carrie; Liu, Chuanju
2006 May;24(5):1118-1127, Journal of orthopaedic research
A novel gene therapy approach for treating damaged cartilage is proposed that involves placing endotoxin-free cDNA containing the gene for bone morphogenetic protein-2 (BMP-2) in type I collagen sponges and then transferring the naked plasmid DNA construct to the injury site. A full-thickness cartilaginous defect in rabbits implanted with plasmid containing a marker gene (beta-galactosidase) showed expressed protein as detected by immunostaining. At 1 week postimplantation, mesenchymal cells subjacent to the defect had incorporated the implanted naked plasmid DNA and, once transfected, served as local bioreactors, transiently producing the gene product. Plasmids containing the gene for BMP-2 implanted in collagen sponges in cartilage lesions stimulated hyalinelike articular cartilage repair at 12 weeks postimplantation, nearly equivalent in quality to that induced by collagen sponges with recombinant BMP-2 protein. Our approach circumvents the risks of inflammation and immunogenic response associated with the use of viral vectors. Naked plasmid DNA as a vehicle for transferring therapeutic genes has been shown to be effective in a therapeutic model within rabbit articular cartilage and appears to be safe and cost effective
— id: 64747, year: 2006, vol: 24, page: 1118, stat: Journal Article,

The repair response to osteochondral implant types in a rabbit model
Frenkel, Sally R; Kubiak, Erik N; Truncale, Kate G
2006 ;7(1):29-37, Cell & Tissue Banking
Current treatments for damaged articular cartilage (i.e., shaving the articular surface, perforation or abrasion of the subchondral bone, and resurfacing with periosteal and perichondrial resurfacing) often produce fibrocartilage, or hyaline-appearing repair that is not sustained over time (Henche 1967, Ligament and Articular Cartilage Injuries. Springer-Verlag, New York, NY, pp. 157-164; Insall 1974, Clin. Orthop. 101: 61-67; Mitchell and Shepard 1976, J. Bone Joint Surg. [Am.] 58: 230-233; O'Driscoll et al. 1986, J. Bone Joint Surg. [Am.] 68: 1017-1035; 1989, Trans. Orthop. Res. Soc. 14: 145; Kim et al. 1991, J. Bone Joint Surg. [Am.] 73: 1301-1315). Autologous chondrocyte transplantation, although promising, requires two surgeries, has site-dependent and patient age limitations, and has unknown long-term donor site morbidity (Brittberg et al. 1994, N Engl. J. Med. 331: 889-895; Minas 2003, Orthopedics 26: 945-947; Peterson et al. 2003, J. Bone Joint Surg. Am. 85-A(Suppl. 2): S17-S24). Osteochondral allografts remain a widely used method of articular resurfacing to delay arthritic progression. The present study compared the histological response to four types of osteochondral implants in a rabbit model: autograft, frozen, freeze-dried, and fresh implants. Specimens implanted in the femoral groove were harvested at 6 and 12 weeks. Results showed similar restoration of the joint surface regardless of implant type, with a trend toward better repair at the later timepoint. As has been observed in other studies (Frenkel et al. 1997, J. Bone Joint Surg. 79B: 281-286; Toolan et al. 1998, J. Biomed. Mater. Res. 41: 244-250), each group in this study had at least one specimen in which a healthy-appearing surface on the implant was not well-integrated with host tissues. Although the differences were not statistically significant, freeze-dried implants at both timepoints had the best histological scores. The osteochondral grafts tested successfully restored the gross joint surface and congruity. At 12 weeks, no significant differences were observed between the various allografts and autologous osteochondral grafts
— id: 69334, year: 2006, vol: 7, page: 29, stat: Journal Article,

Regeneration of articular cartilage--evaluation of osteochondral defect repair in the rabbit using multiphasic implants
Frenkel, S R; Bradica, G; Brekke, J H; Goldman, S M; Ieska, K; Issack, P; Bong, M R; Tian, H; Gokhale, J; Coutts, R D; Kronengold, R T
2005 Sep;13(9):798-807, Osteoarthritis & cartilage
OBJECTIVE: To investigate whether two different multiphasic implants could initiate and sustain repair of osteochondral defects in rabbits. The implants address the malleable properties of cartilage while also addressing the rigid characteristics of subchondral bone. DESIGN: The bone region of both devices consisted of D, D-L, L-polylactic acid invested with hyaluronan (HY). The cartilage region of the first device was a polyelectrolytic complex (PEC) hydrogel of HY and chitosan. In the second device the cartilage region consisted of type I collagen scaffold. Eighteen rabbits were implanted bilaterally with a device, or underwent defect creation with no implant. At 24 weeks, regenerated tissues were evaluated grossly, histologically and via immunostaining for type II collagen. RESULTS: PEC devices induced a significantly better repair than untreated shams. Collagen devices resulted in a quality of repair close to that of the PEC group, although its mean repair score (19.0+/-4.2) did not differ significantly from that of the PEC group (20.4+/-3.7) or the shams (16.5+/-6.3). The percentage of hyaline-appearing cartilage in the repair was highest with collagen implants, while the degree of bonding of repair to the host, structural integrity of the neocartilage, and reconstitution of the subchondral bone was greatest with PEC devices. Cartilage in both device-treated sites stained positive for type II collagen and GAG. CONCLUSIONS: Both implants are capable of maintaining hyaline-appearing tissue at 24 weeks. The physicochemical region between the cartilage and bone compartments makes these devices well suited for delivery of different growth factors or drugs in each compartment, or different doses of the same factor. It also renders these devices excellent vehicles for chondrocyte or stem cell transplantation
— id: 61417, year: 2005, vol: 13, page: 798, stat: Journal Article,

Scaffolds for articular cartilage repair
Frenkel, Sally R; Di Cesare, Paul E
2004 Feb;32(1):26-34, Annals of biomedical engineering
Tissue engineering of articular cartilage seeks to restore the damaged joint surface, inducing repair of host tissues by delivering repair cells, genes, or polypeptide stimulatory factors to the site of injury. A plethora of devices and materials are being examined for their potential to deliver these agents to wound sites, and to act as scaffolds for ingrowth of new tissue. This review will discuss various promising scaffolds for cartilage tissue engineering applications
— id: 46211, year: 2004, vol: 32, page: 26, stat: Journal Article,

Bone response to a novel highly porous surface in a canine implantable chamber
Frenkel, Sally R; Jaffe, William L; Dimaano, Fred; Iesaka, Kazuho; Hua, Tian
2004 Nov 15;71B(2):387-391, Journal of biomedical materials research. Part B, Applied biomaterials
Long-term survival of uncemented hip components is dependent upon successful biological fixation. This study examined a new prosthetic surface treatment consisting of a highly porous open structure of commercially pure titanium, Tritanium Dimensionalized Metal; its overall porosity is approximately 65-70%. With the use of an implantable chamber in dogs, the effects of this treatment on bone ingrowth and strength of attachment were compared to both titanium (overall porosity of 30-35%) and cobalt chrome beads (overall porosity of 35-40%), with and without hydroxyapatite coating. At 6 and 12 weeks, chambers were explanted and specimens underwent high-resolution radiographic imaging and mechanical testing. At 12 weeks, Tritanium surfaces had greater bone penetration and tensile strength than remaining surface types. Over 40% of the Tritanium specimens had a tensile strength greater than 500 N, exceeding the testing capability of the servohydraulic equipment. The highly porous Tritanium surfaces allow for a far greater amount of bone ingrowth than beaded surfaces, and may create a geometry that enhances mechanical strength. Tritanium Dimensionalized Metal surface treatment may result in a clinically valuable implant fixation surface to induce rapid ingrowth and a strong bone-implant interface, contributing to increased implant survivorship
— id: 51386, year: 2004, vol: 71B, page: 387, stat: Journal Article,

Estrogen and osteoarthritis
Gokhale, Jayashree A; Frenkel, Sally R; Dicesare, Paul E
2004 Mar;33(2):71-80, American journal of orthopedics (Belle Mead, NJ)
In menopausal women and the elderly, populations most often affected by osteoarthritis (OA), estrogen levels are lower than normal, which suggests that estrogen may be an important regulator of OA. Estrogen can influence chondrocyte function on multiple levels by interacting with cellular growth factors, adhesion molecules, and cytokines. Nevertheless, findings regarding a correlation between estrogen and OA are inconsistent and inconclusive and range from estrogen protecting against OA to cartilage damage mediated by high levels of estrogen and higher binding to estrogen receptors. In this review, we summarize current in vivo and in vitro research and discuss future directions for analyses of the role of estrogen in OA
— id: 46195, year: 2004, vol: 33, page: 71, stat: Journal Article,

Clinical applications of growth factors for articular cartilage repair
Hickey, Derrick G; Frenkel, Sally R; Di Cesare, Paul E
2003 Feb;32(2):70-76, American journal of orthopedics (Belle Mead, NJ)
Articular cartilage injuries and degeneration present a challenge for orthopedic surgeons. Chondrocytes have limited regenerative and reparative abilities. Healing of a defect results in a fibrocartilaginous repair tissue that lacks the structural and biomechanical properties of hyaline cartilage and that degrades over time. Polypeptide growth factors have an important role in regulating the behavior of all cells, including articular chondrocytes. Our understanding of growth factor effects on and interactions with chondrocytes is progressing rapidly. The most prominent growth factors identified for articular cartilage include insulin-like growth factor, fibroblast growth factor, the transforming growth factor-beta superfamily, hepatocyte growth factor, platelet-derived growth factor, Indian hedgehog and parathyroid hormone-related peptide, bone morphogenetic proteins, and the interleukin-1 receptor antagonist. Orthopedic surgeons need to be familiar with the properties of these growth factors, as they hold great therapeutic promise. In-progress clinical studies are examining how growth factors may have applications in treatments of bone
— id: 69335, year: 2003, vol: 32, page: 70, stat: Journal Article,

Efficacy of chondroprotective agents
Frenkel S; DiCesare PE
2002 ;13(1):9-13, Current opinion in orthopaedics
Chondroprotective agents are substances capable of preventing, delaying, or reversing cartilage lesions due to osteoarthritis. Typically, aspirin and nonsteroidal antiinflammatory drugs (NSAIDs) have been prescribed for pain relief in OA; their use is, however, associated with significant gastrotoxicity, and does not prevent joint deterioration. COX-2 inhibitors, while having fewer side effects, have recently been linked to cardiovascular complications. In the past several years, there have been reports of chondroprotective effects, as well as amelioration of pain, following intraarticular injection of hyaluronic acid derivatives or oral administration of the so-called nutraceuticals, glucosamine and chondroitin sulfate. Because no mechanism of action for these agents has been demonstrated and sample sizes in many clinical trials have been small, their use remains controversial. This review examines the most recent clinical studies of these therapeutic modalities. (C) 2002 Lippincott Williams & Wilkins, Inc. [References: 41] <21>
— id: 26865, year: 2002, vol: 13, page: 9, stat: Journal Article,

Osseointegration on metallic implant surfaces: effects of microgeometry and growth factor treatment
Frenkel, Sally R; Simon, Jordan; Alexander, Harold; Dennis, Michael; Ricci, John L
2002 ;63(6):706-713, Journal of biomedical materials research
Orthopedic implants often loosen due to the invasion of fibrous tissue. The aim of this study was to devise a novel implant surface that would speed healing adjacent to the surface, and create a stable interface for bone integration, by using a chemoattractant for bone precursor cells, and by controlling tissue migration at implant surfaces via specific surface microgeometry design. Experimental surfaces were tested in a canine implantable chamber that simulates the intramedullary bone response around total joint implants. Titanium and alloy surfaces were prepared with specific microgeometries, designed to optimize tissue attachment and control fibrous encapsulation. TGF beta, a mitogen and chemoattractant (Hunziker EB, Rosenberg LC. J Bone Joint Surg Am 1996;78:721-733) for osteoprogenitor cells, was used to recruit progenitor cells to the implant surface and to enhance their proliferation. Calcium sulfate hemihydrate (CS) was the delivery vehicle for TGF beta; CS resorbs rapidly and appears to be osteoconductive. Animals were sacrificed at 6 and 12 weeks postoperatively. Results indicated that TGFbeta can be reliably released in an active form from a calcium sulfate carrier in vivo. The growth factor had a significant effect on bone ingrowth into implant channels at an early time period, although this effect was not seen with higher doses at later periods. Adjustment of dosage should render TGF beta more potent at later time periods. Calcium sulfate treatment without TGF beta resulted in a significant increase in bone ingrowth throughout the 12-week time period studied. Bone response to the microgrooved surfaces was dramatic, causing greater ingrowth in 9 of the 12 experimental conditions. Microgrooves also enhanced the mechanical strength of CS-coated specimens. The grooved surface was able to control the direction of ingrowth. This surface treatment may result in a clinically valuable implant design to induce rapid ingrowth and a strong bone-implant interface, contributing to implant longevity
— id: 69336, year: 2002, vol: 63, page: 706, stat: Journal Article,

The effect of alendronate (Fosamax) and implant surface on bone integration and remodeling in a canine model
Frenkel, S R; Jaffe, W L; Valle, C D; Jazrawi, L; Maurer, S; Baitner, A; Wright, K; Sala, D; Hawkins, M; Di Cesare, P E
2001 ;58(6):645-650, Journal of biomedical materials research
Patients at high risk for osteoporosis and its associated morbidity, including postmenopausal women, are being pharmacologically managed to stabilize and improve bone mass. Alendronate sodium (Fosamax) is a commonly used antiresorptive agent effective in osteopenic women for reducing bone resorption, increasing bone density, and decreasing fracture incidence. With the increased incidence of alendronate-treated women who are undergoing hip replacement or fracture repair by prosthesis placement, data are needed to predict how alendronate affects host bone integration with uncemented surfaces. The aim of this study was to determine the effect of alendronate on new bone formation and attachment to implant surfaces in a normal and simulated estrogen-deficient, calcium-deficient canine model, using an implantable bone growth chamber. Alendronate did not affect host bone integration to surfaces commonly used in uncemented total joint arthroplasty, but there were significant differences dependent solely on the type of surface
— id: 105470, year: 2001, vol: 58, page: 645, stat: Journal Article,

Transforming growth factor beta superfamily members: role in cartilage modeling
Frenkel SR; Saadeh PB; Mehrara BJ; Chin GS; Steinbrech DS; Brent B; Gittes GK; Longaker MT
2000 Mar;105(3):980-990, Plastic & reconstructive surgery
Normal and abnormal extracellular matrix turnover is thought to result, in part, from the balance in the expression of metalloproteinases and tissue inhibitors of metalloproteinases (TIMPs). The clinical manifestations of an imbalance in these relationships are evident in a variety of pathologic states, including osteoarthritis, deficient long-bone growth, rheumatoid arthritis, tumor invasion, and inadequate cartilage repair. Articular cartilage defects commonly heal as fibrocartilage, which is structurally inferior to the normal hyaline architecture of articular cartilage. Transforming growth factor-beta 1 (TGF-beta1), a cytokine central to growth, repair, and inflammation, has been shown to upregulate TIMP-1 expression in human and bovine articular cartilage. Additionally, members of the TGF-beta superfamily are thought to play key roles in chondrocyte growth and differentiation. Bone morphogenetic protein-2 (BMP-2), a member of this superfamily, has been shown to regulate chondrocyte differentiation states and extracellular matrix composition. It was proposed that, by optimizing extracellular matrix composition, BMP-2 would enhance articular cartilage healing. After determining the release kinetics of BMP-2 from a collagen type I implant (Long-Evans male rats; two implants/rat, n = 14), it was found that, in a tissue engineering application, BMP-2 induced a hyaline-like repair of New Zealand White rabbit knee articular cartilage defects (3-mm full-thickness defects in the femoral trochlea; 2 defects/rabbit, n = 36). The quality of cartilage repair with BMP-2 (with or without chondrocytes) was significantly better than defects treated with BMP-2, as assessed by a quantitative scoring scale. Immunohistochemical staining revealed TIMP-1 production in the cartilage defects treated with BMP-2. When studied in vitro, it was found that BMP-2 markedly increased TIMP-1 mRNA by both bovine articular and human rib chondrocytes. Additionally, increased TIMP-1 mRNA was translated into increased TIMP-1 protein production by bovine chondrocytes. Taken together, these data suggest that BMP-2 may be a useful cytokine to improve healing of cartilaginous defects. Furthermore, these data suggest that the beneficial effects of BMP-2 may be, in part, related to alterations in extracellular matrix turnover
— id: 27858, year: 2000, vol: 105, page: 980, stat: Journal Article,

Repair of articular cartilage defects: part I. Basic Science of cartilage healing
Chen FS; Frenkel SR; Di Cesare PE
1999 Jan;28(1):31-33, American journal of orthopedics (Belle Mead, NJ)
Articular cartilage injuries result in numerous clinical symptoms, such as pain and decreased functional levels. The limited reparative capabilities of hyaline cartilage results in the generation of repair tissue that lacks the structure and biomechanical properties of normal cartilage. Chondrocytes are unable to adequately proliferate, migrate, and synthesize high-quality repair tissue in response to blunt, superficial, or deep penetrating trauma. Extensive research has been conducted to understand the healing process and devise techniques that would enhance this response. Part I of this paper will discuss the basic science of cartilage repair. Part II, which will be published in the February issue, will present the treatment options
— id: 6051, year: 1999, vol: 28, page: 31, stat: Journal Article,

Repair of articular cartilage defects: part II. Treatment options
Chen FS; Frenkel SR; Di Cesare PE
1999 Feb;28(2):88-96, American journal of orthopedics (Belle Mead, NJ)
Articular cartilage injuries result in numerous clinical symptoms, such as pain and decreased functional levels. Current therapeutic options being used include articular surface debridement, such as chondral shaving, abrasion chondroplasty, and subchondral perforation; soft-tissue arthroplasties, such as perichondrial and periosteal grafts; and osteochondral transplantation. None of these therapies, however, has resulted in the successful regeneration of a hyaline-like tissue that withstands normal joint loading and activity over prolonged periods. As a result, research is also being conducted on alternative therapeutic procedures to enhance the repair process and to stimulate the regeneration of a repair tissue with hyaline-like structural and biologic properties. Part I of this paper, which was published in January, discussed the basic science of cartilage healing. Part II presents the treatment options
— id: 6054, year: 1999, vol: 28, page: 88, stat: Journal Article,

Degradation and repair of articular cartilage
Frenkel SR; Di Cesare PE
1999 Oct 15;4:D671-D685, Frontiers in biosciences
Approximately 95,000 total knee replacements and 41,000 other surgical procedures to repair cartilaginous defects of the knee are performed annually in the United States (1). The response of normal articular cartilage to injury or arthritic degeneration is often a sub-optimal repair; the biochemical and mechanical properties of the new tissue differ from the native cartilage, resulting in inadequate or altered function. It is believed that the chondrocytes from the surrounding areas, although perhaps capable of some limited migration at the damaged site, are not able to proliferate and produce the macromolecules necessary to create an organized matrix characteristic of normal articular cartilage (2,3). Current therapeutic options for articular cartilage injuries and degeneration have resulted in repair tissue which may be hyaline-like, but does not approximate the durability and function of the normal articular surface. Numerous studies have been performed to increase our understanding of the normal repair process of articular cartilage and its limitations, and to devise methods and materials to regenerate the joint surface
— id: 56478, year: 1999, vol: 4, page: D671, stat: Journal Article,

Transforming growth factor beta superfamily members in cartilage repair
Frenkel S; Saadeh P; Mehrara B; Steinbrech D; Gittes G; Longaker MT
1998 ;49:516-518, Surgical forum
— id: 105479, year: 1998, vol: 49, page: 516, stat: Journal Article,

Chondrocyte transplantation using a collagen bilayer matrix for cartilage repair - Reply
Frenkel, S
1998 JUL ;80B(4):743-744, Journal of bone & joint surgery (British volume)
— id: 53407, year: 1998, vol: 80B, page: 743, stat: Journal Article,

Development of a novel osteochondral graft for cartilage repair
Toolan, B C; Frenkel, S R; Pereira, D S; Alexander, H
1998 Aug;41(2):244-250, Journal of biomedical materials research
This study reports the development of a novel osteochondral graft for cartilage repair. A technique of proteoglycan extraction via timed enzymatic digestion with hyaluronidase and trypsin and subsequent processing with a chloroform-methanol solution to remove cellular debris from a fresh-frozen bovine osteochondral sample is a method described to prepare a stable biological carrier of low immunogenicity. Lyophilization of the carrier followed by rehydration in a suspension of lapine chondrocytes produced a chimeric xenograft that succeeded in vivo in enhancing cartilage repair. In a pilot study, full-thickness articular cartilage defects treated with these xenografts demonstrated improved healing compared to untreated defects or defects treated with unseeded grafts at 2, 6, and 12 weeks postimplantation. The xenograft provoked a mild inflammatory response; however this did not impede the repair process. Further investigation of this novel chimeric xenograft eventually may yield a method of cartilage repair superior to current methods of treatment
— id: 105478, year: 1998, vol: 41, page: 244, stat: Journal Article,

Transplantation of adenovirally transduced allogeneic chondrocytes into articular cartilage defects in vivo
Baragi VM; Renkiewicz RR; Qiu L; Brammer D; Riley JM; Sigler RE; Frenkel SR; Amin A; Abramson SB; Roessler BJ
1997 Jul;5(4):275-282, Osteoarthritis & cartilage
Gene transfer to chondrocytes followed by intra-articular transplantation may allow for functional modulation of chondrocyte biology and enhanced repair of damaged articular cartilage. We chose to examine the loss of chondrocytes transduced with a recombinant adenovirus containing the gene for Escherichia coli beta-galactosidase (Ad.RSVntlacZ), followed by transplantation into deep and shallow articular cartilage defects using New Zealand White rabbits as an animal model. A type I collagen matrix was used as a carrier for the growth of the transduced chondrocytes and to retain the cells within the surgically created articular defects. Histochemical analysis of matrices recovered from the animals 1, 3 and 10 days after implantation showed the continued loss of lacZ positive chondrocytes. The number of cells recovered from the matrices was also compared with the initial innoculum of transduced cells present within the matrices at the time of implantation. The greatest loss of transduced cells was observed in the first 24 h after implantation. The numbers of transduced cells present within the matrices were relatively constant between 1 and 3 days postimplantation, but had progressively declined by 10 days postimplantation. These results suggest that transduction of chondrocytes followed by intra-articular transplantation in this rabbit model may enable us to examine the biological effects of focal transgenic overexpression of proteins involved in cartilage homeostasis and repair
— id: 9731, year: 1997, vol: 5, page: 275, stat: Journal Article,

Chondrocyte transplantation and experimental treatment options for articular cartilage defects
Chen FS; Frenkel SR; Di Cesare PE
1997 Jun;26(6):396-406, American journal of orthopedics (Belle Mead, NJ)
Current treatment options for injured articular cartilage have resulted in temporary improvements in clinical symptoms and functional levels. None of these modalities, however, has resulted in restoration of an articular surface that is able to withstand long-term joint loading and function. As a result, numerous investigators have attempted to devise alternative therapies. The limited regnerative potential of articular cartilage has led investigators to attempt using cells with the potential for differentiation and proliferation to repair chondral defects. Chondrocyte transplantation, both allogeneic and autogenous, has shown early promising results in regenrating hyaline-like tissue in both animals and humans. Encouraging results in animals have also been demonstrated with alternative sources of osteoprogenitor cells as grafts, as well as with natural/synthetic implants and the use of growth factors and cytokines. However, despite encouraging short-term results, long-term data concerning the regenerate tissue are still needed. As more research is being conducted to understand the processes of cartilage maintenance and healing, there is hope that cartilage regeneration and neochondrogenesis will be possible in the future
— id: 7129, year: 1997, vol: 26, page: 396, stat: Journal Article,

Outside-in signaling in the chondrocyte. Nitric oxide disrupts fibronectin-induced assembly of a subplasmalemmal actin/rho A/focal adhesion kinase signaling complex
Clancy RM; Rediske J; Tang X; Nijher N; Frenkel S; Philips M; Abramson SB
1997 Oct 1;100(7):1789-1796, Journal of clinical investigation
Elevated levels of fibronectin (Fn) in articular cartilage have been linked to the progression of both rheumatoid and osteoarthritis. In this study, we examined intracellular events which follow ligation of Fn to its receptor, the integrin alpha5beta1. In addition, we examined the regulatory influence of nitric oxide on these events, since this free radical has been implicated in cartilage degradation. Exposure of chondrocytes to Fn-coated beads resulted in the circumferential clustering of the alpha5beta1 integrin receptor, which was accompanied by the subplasmalemmal assembly of a focal activation complex comprised of F-actin, the tyrosine kinase, focal adhesion kinase (FAK), the ras related G protein rho A, as well as tyrosine-phosphorylated proteins. Treatment with exogenous nitric oxide (NO) or catabolic cytokines which induce nitric oxide synthase blocked the assembly of F-actin, FAK, rho A and tyrosine-phosphorylated proteins while not affecting the total number of beads bound per cell nor the clustering of alpha5beta1 integrin. Use of a cGMP antagonist (Rp-8-Br cGMPS) or cGMP agonist (Sp-cGMPS) either abolished or mimicked the NO effect, respectively. Adherence of chondrocytes to fibronectin enhanced proteoglycan synthesis by twofold (vs. albumin). In addition, basic fibroblast growth factor (FGF) and insulin growth factor (IGF-1) induced proteoglycan synthesis in chondrocytes adherent to Fn but not albumin suggesting a costimulatory signal transduced by alpha5betal and the FGF receptor. Both constitutive and FGF stimulated proteoglycan synthesis were completely inhibited by nitric oxide. These data indicate that the ligation of alpha5beta1 in the chondrocyte induced the intracellular assembly of an activation complex comprised of the cytoplasmic tail of alpha5beta1 integrin, actin, and the signaling molecules rho A and FAK. We show that NO inhibits the assembly of the intracellular activation complex and the synthesis of proteoglycans, but has no effect on the extracellular aggregation of alpha5beta1 integrin. These observations provide a basis by which nitric oxide can interfere with chondrocyte functions by affecting chondrocyte-matrix interactions
— id: 9733, year: 1997, vol: 100, page: 1789, stat: Journal Article,

Chondrocyte transplantation using a collagen bilayer matrix for cartilage repair
Frenkel, S R; Toolan, B; Menche, D; Pitman, M I; Pachence, J M
1997 Sep;79(5):831-836, Journal of bone & joint surgery (British volume)
We have developed a novel, two-layered, collagen matrix seeded with chondrocytes for repair of articular cartilage. It consists of a dense collagen layer which is in contact with bone and a porous matrix to support the seeded chondrocytes. The matrices were implanted in rabbit femoral trochleas for up to 24 weeks. The control groups received either a matrix without cells or no implant. The best histological repair was seen with cell-seeded implants. The permeability and glycosaminoglycan content of both implant groups were nearly normal, but were significantly less in tissue from empty defects. The type-II collagen content of the seeded implants was normal. For unseeded implants it was 74.3% of the normal and for empty defects only 20%. The current treatments for articular injury often result in a fibrous repair which deteriorates with time. This bilayer implant allowed sustained hyaline-like repair of articular defects during the entire six-month period of observation
— id: 105471, year: 1997, vol: 79, page: 831, stat: Journal Article,

''Outside/in'' signalling in the chondrocyte: Effect of nitric oxide on fibronectin induced actin assembly and focal adhesion kinase-dependent tyrosine phosphorylation
Clancy, RM; Rediske, J; Tang, X; Frenkel, S; Abramson, SB
1996 MAR ;44(3):A241-A241, Journal of investigative medicine
— id: 52955, year: 1996, vol: 44, page: A241, stat: Journal Article,

alpha 5 beta 1 integrin signaling in the chondrocyte: Nitric oxide disrupts fibronectin induced assembly of a subplasmalemmal actin Rho A FAK activation complex
Clancy, RM; Rediske, J; Tang, XY; Frenkel, SR; Abramson, SB
1996 SEP ;39(9):843-843, Arthritis & rheumatism
— id: 52781, year: 1996, vol: 39, page: 843, stat: Journal Article,

Effects of nitric oxide on chondrocyte migration, adhesion, and cytoskeletal assembly
Frenkel SR; Clancy RM; Ricci JL; Di Cesare PE; Rediske JJ; Abramson SB
1996 Nov;39(11):1905-1912, Arthritis & rheumatism
OBJECTIVE: The migration of cells of chondrocyte lineage is believed to play a role in cartilage growth and repair. The present study examined 1) whether chondrocytes are capable of migration in vitro; and 2) the effects of nitric oxide (NO) on chondrocyte migration, adhesion, and cytoskeletal assembly. METHODS: Chondrocyte migration was evaluated by 2 assays: 1) 'centrifugal' migration within a 3-dimensional collagen matrix (dot culture); and 2) directed migration under agarose in response to bone morphogenetic protein. To assess the effects of NO, chondrocytes were treated with either exogenous NO (S-nitrosoglutathione [SNO-GSH]) or a mixture of cytokines known to induce endogenous NO production. The effects of NO on chondrocyte adhesion to fibronectin-coated surfaces, as well as on actin polymerization (determined by indirect immunofluorescence), were also examined. RESULTS: The capacity of chondrocytes to migrate was demonstrated both by the dot culture and by agarose methods. Both SNO-GSH and endogenous NO induced by cytokines inhibited this migration. Exposure to NO also inhibited attachment of chondrocytes to fibronectin and disrupted assembly of actin filaments. These effects of SNO-GSH and cytokine-induced NO production were reversed in the presence of hemoglobin and the NO synthase inhibitor NG-monomethyl arginine, respectively. CONCLUSION: NO interferes with chondrocyte migration and attachment to fibronectin, an extracellular matrix protein, probably via effects on the actin cytoskeleton. These effects of NO may result in impairment of cartilage repair, by interfering with the extracellular matrix regulation of chondrocyte function
— id: 9737, year: 1996, vol: 39, page: 1905, stat: Journal Article,

A comparison of abrasion burr arthroplasty and subchondral drilling in the treatment of full-thickness cartilage lesions in the rabbit
Menche, D S; Frenkel, S R; Blair, B; Watnik, N F; Toolan, B C; Yaghoubian, R S; Pitman, M I
1996 Jun;12(3):280-286, Arthroscopy
The purpose of this study was to observe the difference in healing of full-thickness articular cartilage defects treated with burr arthroplasty versus subchondral drilling. Cartilage was shaved off the medial femoral condyles of 39 rabbits without penetrating the subchondral plate. In left knees, two 2.0-mm holes were drilled into the condyle until bleeding was obtained. Right knees underwent a burr arthroplasty until punctate bleeding was observed. Animals were sacrificed at 6, 12, and 24 weeks postoperatively. Joint resurfacing and degenerative changes were evaluated grossly and histologically. Degenerative changes in the cartilage surface were observed with both treatments. Rabbits undergoing subchondral drilling had increased fibrocartilaginous healing with time, with a slight increase in degenerative changes. With burr arthroplasty, there was significant decrease in cartilaginous coverage of the exposed surface as well as progressive increase in degenerative changes. Although both techniques were suboptimal, histological evidence at 6 months suggests that subchondral drilling may result in a longer-lived repair than abrasion arthroplasty in the treatment of full-thickness lesions
— id: 105473, year: 1996, vol: 12, page: 280, stat: Journal Article,

Dynamics of p55 soluble TNF alpha receptor (p55sTNF-R) release by human OA cartilage
Rediske, J; Koehne, C; Frenkel, S; Skiles, J
1996 SEP ;39(9):1454-1454, Arthritis & rheumatism
— id: 52787, year: 1996, vol: 39, page: 1454, stat: Journal Article,

Effects of growth-factor-enhanced culture on a chondrocyte-collagen implant for cartilage repair
Toolan, B C; Frenkel, S R; Pachence, J M; Yalowitz, L; Alexander, H
1996 Jun;31(2):273-280, Journal of biomedical materials research
The effects of incubation and addition of growth factors to a chondrocyte-seeded collagen implant for cartilage repair were studied. Type I collagen matrices seeded with lapine articular chondrocytes and unseeded controls cultured in the presence and absence of fibroblast growth factor and insulin for 2, 6, and 9 weeks were subjected to biomechanical, biochemical, and histological analysis. Aggregate modulus of elasticity of seeded implants decreased by half at 6 weeks, then rose by a factor of 10 above initial values. Permeability of seeded implants and their controls decreased steadily. Glycosaminoglycan content peaked at 6 weeks, coinciding with the greatest number of chondrocytes and mitotic activity in seeded implants. Chondrocytes remained phenotypically stable and metabolically active; they incorporated glycosaminoglycan into the extracellular matrix, and formed an organized pericellular environment despite the predicted resorption of the collagen matrix. Adding fibroblast growth factor and insulin tripled the rate of cell turnover and doubled the glycosaminoglycan content of seeded implants, but had no effect on their material properties. In vitro incubation for 6 weeks in the presence of fibroblast growth factor and insulin creates a metabolically and mitotically active chondrocyte-collagen composite for implantation into articular cartilage defects
— id: 105472, year: 1996, vol: 31, page: 273, stat: Journal Article,

NITRIC-OXIDE INHIBITS CHONDROCYTE ADHESION TO FIBRONECTIN VIA EFFECTS ON INTRACELLULAR ACTIN POLYMERIZATION
CLANCY, RM; FRENKEL, SR; DICESARE, P; ABRAMSON, S
1995 SEP ;38(9):429-429, Arthritis & rheumatism
— id: 86694, year: 1995, vol: 38, page: 429, stat: Journal Article,

Demineralized bone matrix. Enhancement of spinal fusion
Frenkel SR; Moskovich R; Spivak J; Zhang ZH; Prewett AB
1993 Sep 15;18(12):1634-1639, Spine
A study was conducted to determine the ability of demineralized bone matrix gel to act as an osteoconductive/osteoinductive material to enhance canine spinal fusion. Seven dogs underwent posterior spinal fusion. Four-level fusions were performed with one of four procedures at each level: decortication alone, with gel added, with autograft, or with both gel and autograft. Dogs were killed at 6 weeks and early histologic response was studied. At untreated control sites, little bone formation was evident. Gel-filled sites showed abundant osteoid, with 60% of demineralized particles fused to or surrounded by new bone. Sites filled with autograft had more new bone, but there was more osteoid at gel-treated sites. Autograft augmented with gel showed the most vigorous response, with extensive bridging between demineralized particles, host bone, autograft, and new bone. Significantly less autograft was needed to induce a similar amount of new bone formation when gel was added. Use of the gel as an autograft extender may improve the chance for successful spinal fusion
— id: 35852, year: 1993, vol: 18, page: 1634, stat: Journal Article,

Diffusion of fibroblast growth factor from a plaster of Paris carrier
Rosenblum, S F; Frenkel, S; Ricci, J R; Alexander, H
1993 Spring;4(1):67-72, Journal of applied biomaterials (Orlando)
Fibroblast growth factor (FGF) is a polypeptide that has been shown to have a stimulatory effect on osseous tissues in vitro. This study characterized the release of FGF from plaster of Paris (PLP) and measured the dissolution of PLP in various solutions with the aim of developing a reliable carrier system for the release of FGF in vivo. The study consisted of five experiments: (I) FGF diffusion from PLP pellets, (II) FGF diffusion from PLP discs, (III) PLP dissolution in saline, (IV) PLP dissolution in serum, and (V) FGF adsorption by commercially pure titanium. FGF was observed to be released at a rate directly proportional to the rate of dissolution of the PLP carrier, suggesting that either the FGF binds to the PLP; or, alternatively, the FGF may be entrapped by the PLP. Dissolution rate, and thus release rate, could be varied by varying the mass of the carrier. Greater diffusion of FGF was observed in larger, more slowly dissolving PLP carriers. Dissolution of PLP was observed to be slower in serum than in saline, apparently due to stabilization by factors in the serum but not due to a concentration gradient effect. Titanium coupons did not adsorb significant amounts of FGF. These results indicate that PLP, which has been shown in the past neither to aggravate inflammatory response nor to interfere with bone ingrowth, may serve as delivery vehicle for FGF to osseous tissues in vivo
— id: 105474, year: 1993, vol: 4, page: 67, stat: Journal Article,

Fibroblast growth factor: effects on osteogenesis and chondrogenesis in the chick embryo
Frenkel, S R; Herskovits, M S; Singh, I J
1992 ;145(3):265-268, Acta anatomica
In vivo effects of fibroblast growth factor (FGF) on osteogenesis were evaluated in the chick embryo. Autoradiographic studies of 3H-proline labeling over bone matrix indicated that 24 h after treatment on day 11, FGF stimulated osteogenic cell proliferation, while inhibiting the production of bone matrix collagen. However, 4 days after multiple doses of FGF, the large pool of newly formed osteogenic and chondrogenic cells expressed their function with the increased formation of matrix. The data provide in vivo evidence of the effects of exogenous FGF on osteogenesis and also point to a possible role for FGF both in embryonic osteogenesis and in fracture repair
— id: 105475, year: 1992, vol: 145, page: 265, stat: Journal Article,

Fibroblast growth factor in chick osteogenesis
Frenkel, S R; Grande, D A; Collins, M; Singh, I J
1990 Jul;11:38-40, Biomaterials
In vivo effects of FGF on osteogenesis in the chick embryo were evaluated. Day-11 embryos were injected with FGF followed by radiotracers. 3H-thymidine labelling of osteogenic cells was significantly higher following FGF administration; 3H-proline labelling over bone matrix was greater in the controls. Cartilage cells and matrix were sparsely labelled indicating a low level of metabolic activity. These data provide the first in vivo evidence that FGF stimulates osteogenic cell proliferation, while inhibiting production of bone matrix collagen. A role for FGF in embryonic osteogenesis and in fracture repair is suggested
— id: 105476, year: 1990, vol: 11, page: 38, stat: Journal Article,

Nerve growth factor in skeletal tissues of the embryonic chick
Frenkel, S R; Guerra, L A; Mitchell, O G; Singh, I J
1990 May;260(3):507-511, Cell & tissue research
This study demonstrates, via immunohistochemistry and bioassay, the presence of NGF in embryonic bone and cartilage of the chick. Embryos were killed on days 6-9 of incubation at 12 h intervals, and on days 10-18 at 24 h intervals. Paraffin-embedded sections of hind limbs or buds were immunostained with a polyclonal antibody against NGF and the biotin-avidin-horseradish peroxidase technique. Immunostaining was positive in both bone and cartilage, with cartilage staining more intensely. For bioassay, bones from the hind limbs of 9- and 12-day embryos were fast-frozen, lyophilized, and homogenized with Medium 199 (M199). Dorsal root ganglia from 8-day embryos were cultured for 24-36 h with rooster plasma, M199, and varying concentrations of bone homogenate. Significant neurite outgrowth was seen, with the greatest response elicited by 12-day bone homogenate. Addition of anti-NGF to the cultures abolished neurite outgrowth. The results indicate that NGF is present in cartilage and bone of the chick embryo; it may determine the density of sympathetic innervation to the developing skeletal tissues
— id: 105477, year: 1990, vol: 260, page: 507, stat: Journal Article,