bFGF influences human articular chondrocyte differentiation

Injectable TG-linked recombinant human collagen hydrogel loaded with bFGF for rat cranial defect repair

The basic fibroblast growth factor (bFGF) plays a significant role in promoting the process of bone repair, but bFGF cannot keep its biological activity stable under normal physiological conditions. Therefore, the development of better biomaterials to carry bFGF remains a challenge for bone repair and regeneration. Here we designed a novel recombinant human collagen (rhCol), which could be cross-linked by transglutaminase (TG) and loaded bFGF to prepare rhCol/bFGF hydrogels. The rhCol hydrogel possessed a porous structure and good mechanical properties. The assays, including cell proliferation, migration, and adhesion assay, were performed to evaluate the biocompatibility of rhCol/bFGF and the results demonstrated that the rhCol/bFGF promoted cell proliferation, migration and adhesion. The rhCol/bFGF hydrogel degraded and released bFGF controllably, enhancing utilization rate of bFGF and allowing osteoinductive activity. The results of RT-qPCR and immunofluorescence staining also proved that rhCol/bFGF promoted expression of bone-related proteins. The rhCol/bFGF hydrogels were applied in the cranial defect in rats and the results confirmed that it accelerates bone defect repair. In conclusion, rhCol/bFGF hydrogel has excellent biomechanical properties and can continuously release bFGF to promote bone regeneration, suggesting that rhCol/bFGF hydrogel is a potential scaffold in clinic application.

"Genetic scissors" CRISPR/Cas9 genome editing cutting-edge biocarrier technology for bone and cartilage repair

CRISPR/Cas9 is a revolutionary genome editing technology with the tremendous advantages such as precisely targeting/shearing ability, low cost and convenient operation, becoming an efficient and indispensable tool in biological research. As a disruptive technique, CRISPR/Cas9 genome editing has a great potential to realize a future breakthrough in the clinical bone and cartilage repairing as well. This review highlights the research status of CRISPR/Cas9 system in bone and cartilage repair, illustrates its mechanism for promoting osteogenesis and chondrogenesis, and explores the development tendency of CRISPR/Cas9 in bone and cartilage repair to overcome the current limitations.

Fibroblast Growth Factors and Cellular Communication Network Factors: Intimate Interplay by the Founding Members in Cartilage

Fibroblast growth factors (FGFs) constitute a large family of signaling molecules that act in an autocrine/paracrine, endocrine, or intracrine manner, whereas the cellular communication network factors (CCN) family is composed of six members that manipulate extracellular signaling networks. FGFs and CCNs are structurally and functionally distinct, except for the common characteristics as matricellular proteins. Both play significant roles in the development of a variety of tissues and organs, including the skeletal system. In vertebrates, most of the skeletal parts are formed and grow through a process designated endochondral ossification, in which chondrocytes play the central role. The growth plate cartilage is the place where endochondral ossification occurs, and articular cartilage is left to support the locomotive function of joints. Several FGFs, including FGF-2, one of the founding members of this family, and all of the CCNs represented by CCN2, which is required for proper skeletal development, can be found therein. Research over a decade has revealed direct binding of CCN2 to FGFs and FGF receptors (FGFRs), which occasionally affect the biological outcome via FGF signaling. Moreover, a recent study uncovered an integrated regulation of FGF and CCN genes by FGF signaling. In this review, after a brief introduction of these two families, molecular and genetic interactions between CCN and FGF family members in cartilage, and their biological effects, are summarized. The molecular interplay represents the mutual involvement of the other in their molecular functions, leading to collaboration between CCN2 and FGFs during skeletal development.

Synoviocyte-Derived Extracellular Matrix and bFGF Speed Human Chondrocyte Proliferation While Maintaining Differentiation Potential

Improving the ability of human chondrocytes to proliferate, while maintaining their differentiation potential, has presented a great challenge in cartilage tissue engineering. In this study, human chondrocytes were cultured under four unique growth conditions at physiologic oxygen tension: tissue culture plastic (TCP) only, synoviocyte matrix (SCM)-coated flasks only, SCM-coated flasks with bFGF media supplement, and TCP with bFGF media supplement. The results indicated that, compared to standard TCP, all test conditions showed significantly increased cell expansion rates and an increase in both glycosaminoglycan (GAG) and collagen content during redifferentiation culture. Specifically, the combined SCM + bFGF growth condition showed an additive effect, with an increase of approximately 36% more cells per passage (5-7 days) when compared to the SCM alone. In conclusion, the results of this study demonstrate that bFGF and SCM can be used as supplements to enhance the growth of human chondrocytes both as individual enhancers and as a combined additive.

Cartilage Regeneration Characteristics of Human and Goat Auricular Chondrocytes

Although cartilage regeneration technology has achieved clinical breakthroughs, whether auricular chondrocytes (AUCs) represent optimal seed cells to achieve stable cartilage regeneration is not clear. In this study, we systematically explore biological behaviors of human- and goat-derived AUCs during in vitro expansion as well as cartilage regeneration in vitro and in vivo. To eliminate material interference, a cell sheet model was used to evaluate the feasibility of dedifferentiated AUCs to re-differentiate and regenerate cartilage in vitro and in vivo. We found that the dedifferentiated AUCs could re-differentiate and regenerate cartilage sheets under the chondrogenic medium system, and the generated chondrocyte sheets gradually matured with increased in vitro culture time (2, 4, and 8 weeks). After the implantation of cartilage sheets with different in vitro culture times in nude mice, optimal neocartilage was formed in the group with 2 weeks in vitro cultivation. After in vivo implantation, ossification only occurred in the group with goat-regenerated cartilage sheet of 8 weeks in vitro cultivation. These results, which were confirmed in human and goat AUCs, suggest that AUCs are ideal seed cells for the clinical translation of cartilage regeneration under the appropriate culture system and culture condition.

The role of the fibroblast growth factor family in bone-related diseases

Fibroblast growth factor (FGF) family members are important regulators of cell growth, proliferation, differentiation, and regeneration. The abnormal expression of certain FGF family members can cause skeletal diseases, including achondroplasia, craniosynostosis syndrome, osteoarthritis, and Kashin-Beck disease. Accumulating evidence shows that FGFs play a crucial role in the growth and proliferation of bone and in the pathogenesis of certain bone-related diseases. Here, we review the involvement of FGFs in bone-related processes and diseases; FGF1 in the differentiation of human bone marrow mesenchymal stem cells and fracture repair; FGF2, FGF9, and FGF18 in osteoarthritis; FGF6 in bone and muscle injury; FGF8 in osteoarthritis and Kashin-Beck disease; and FGF21 and FGF23 on bone regulation. These findings indicate that FGFs are targets for novel therapeutic interventions for bone-related diseases.

[The role and mechanism of S100 calcium binding protein B in osteoarthritis cartilage damage repair]

Objective

To investigate the role and mechanism of S100 calcium binding protein B (S100B) in osteoarthritis (OA) cartilage damage repair.

Methods

Twenty New Zealand rabbits were randomly divided into control group and model group, with 10 rabbits in each group. Rabbits in the model group were injured by the right knee joint immobilization method to make the artilage injury model, while the control group did not deal with any injury. After 4 weeks, the levels of interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α) in synovial fluid were detected by ELISA method; the mRNA and protein expressions of S100B, fibroblast growth factor 2 (FGF-2), and FGF receptor 1 (FGFR1) in cartilage tissue were examined by real-time fluorescence quantitative PCR (qRT-PCR) and Western blot assay. Human synovial fibroblasts (SF) were isolated and cultured in vitro. The effects of S100B overexpression and knockdown on the levels of IL-1β and TNF-α (ELISA method) and the expressions of FGF-2 and FGFR1 gene (qRT-PCR) and protein (Western blot) were observed. Moreover, the effects of FGFR1 knockdown in above S100 overexpression system on the levels of IL-1β and TNF-α (ELISA method) and the expressions of FGF-2 and FGFR1 gene (qRT-PCR) and protein (Western blot) were observed.

Results

ELISA detection showed that the expressions of IL-1β and TNF-α in the synovial fluid of the model group were significantly higher than those of the control group ( P<0.05); qRT-PCR and Western blot detection showed that the mRNA and protein expressions of S100B, FGF-2, and FGFR1 in cartilage tissue were significantly higher than those of the control group ( P<0.05). Overexpression and knockdown S100 could respectively significantly increase and decrease lipopolysaccharides (LPS) induced IL-1β and TNF-α levels elevation and the mRNA and protein expressions of FGF-2 and FGFR1 ( P<0.05); whereas FGFR1 knockdown could significantly decrease LPS induced IL-1β and TNF-α levels elevation and the mRNA and protein expressions of FGF-2 and FGFR1 ( P<0.05).

Conclusion

S100B protein can regulate the inflammatory response of SF and may affect the repair of cartilage damage in OA, and the mechanism may be related to the activation of FGF-2/FGFR1 signaling pathway.

Basic Fibroblast Growth Factor Regulates Gene and Protein Expression Related to Proliferation, Differentiation, and Matrix Production of Human Dental Pulp Cells

INTRODUCTION

Basic fibroblast growth factor (bFGF) plays differential effects on the proliferation, differentiation, and extracellular matrix turnover in various tissues. However, limited information is known about the effect of bFGF on dental pulp cells. The purposes of this study were to investigate whether bFGF influences the cell differentiation and extracellular matrix turnover of human dental pulp cells (HDPCs) and the related gene and protein expression as well as the role of the mitogen-activated protein kinase (MEK)/extracellular-signal regulated kinase (ERK) signaling pathway. The expression of fibroblast growth factor receptors (FGFRs) in HDPCs was also studied.

METHODS

The expression of FGFR1 and FGFR2 in HDPCs was investigated by reverse-transcription polymerase chain reaction. HDPCs were treated with different concentrations of bFGF. Cell proliferation was evaluated using the 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Cell differentiation was evaluated using alkaline phosphatase (ALP) staining. Changes in messenger expression of cyclin B1 and tissue inhibitor of metalloproteinase (TIMP) 1 were determined by reverse-transcription polymerase chain reaction. Changes in protein expression of cdc2, TIMP-1, TIMP-2, and collagen I were determined by Western blotting. U0126 was used to clarify the role of MEK/ERK signaling.

RESULTS

HDPCs expressed both FGFR1 and FGFR2. Cell viability was stimulated by 50-250 ng/mL bFGF. The expression and enzyme activities of ALP were inhibited by 10-500 ng/mL bFGF. At similar concentrations, bFGF stimulates cdc2, cyclin B1, and TIMP-1 messenger RNA and protein expression. bFGF showed little effect on TIMP-2 and partly inhibited collagen I expression of pulp cells. U0126 (a MEK/ERK inhibitor) attenuated the bFGF-induced increase of cyclin B1, cdc2, and TIMP-1.

CONCLUSIONS

bFGF may be involved in pulpal repair and regeneration by activation of FGFRs to regulate cell growth; stimulate cdc2, cyclin B1, and TIMP-1 expression; and inhibit ALP. These events are partly associated with MEK/ERK signaling.

Articular cartilage tissue engineering: the role of signaling molecules

Effective early disease modifying options for osteoarthritis remain lacking. Tissue engineering approach to generate cartilage in vitro has emerged as a promising option for articular cartilage repair and regeneration. Signaling molecules and matrix modifying agents, derived from knowledge of cartilage development and homeostasis, have been used as biochemical stimuli toward cartilage tissue engineering and have led to improvements in the functionality of engineered cartilage. Clinical translation of neocartilage faces challenges, such as phenotypic instability of the engineered cartilage, poor integration, inflammation, and catabolic factors in the arthritic environment; these can all contribute to failure of implanted neocartilage. A comprehensive understanding of signaling molecules involved in osteoarthritis pathogenesis and their actions on engineered cartilage will be crucial. Thus, while it is important to continue deriving inspiration from cartilage development and homeostasis, it has become increasingly necessary to incorporate knowledge from osteoarthritis pathogenesis into cartilage tissue engineering.

Clinical Trial and In Vitro Study for the Role of Cartilage and Synovia in Acute Articular Infection

OBJECTIVE

Osteoarthritis is a long-term complication of acute articular infections. However, the roles of cartilage and synovia in this process are not yet fully understood.

METHODS

Patients with acute joint infections were enrolled in a prospective clinical trial and the cytokine composition of effusions compared in patients with arthroplasty (n = 8) or with intact joints (n = 67). Cytokines and cell function were also analyzed using a human in vitro model of joint infection.

RESULTS

Synovial IL-1β levels were significantly higher in patients with arthroplasty (p = 0.004). Higher IL-1β concentrations were also found in the in vitro model without chondrocytes (p < 0.05). The anti-inflammatory cytokines IL-4 and IL-10 were consistently expressed in vivo and in vitro, showing no association with the presence of cartilage or chondrocytes. In contrast, FasL levels increased steadily in vitro, reaching higher levels without chondrocytes (p < 0.05). Likewise, the viability of synovial fibroblasts (SFB) during infection was higher in the presence of chondrocytes. The cartilage-metabolism markers aggrecan and bFGF were at higher concentrations in intact joints, but also synthesized by SFB.

CONCLUSIONS

Our data suggest an anti-inflammatory effect of cartilage associated with the SFBs' increased resistance to infections, which displayed the ability to effectively synthesize cartilage metabolites.The trial is registered with DRKS 00003536, MISSinG.

Silk fibroin sponges with cell growth-promoting activity induced by genetically fused basic fibroblast growth factor

Transgenic silkworm technology has enabled the biological properties of silk fibroin protein to be altered by fusion to recombinant bioactive proteins. However, few studies have reported the fabrication of genetically modified fibroin proteins into three-dimensional spongy structures to serve as scaffolds for tissue engineering. We generated a transgenic silkworm strain that produces fibroin fused to basic fibroblast growth factor (bFGF) and processed the fibroin into a spongy structure using a simple freeze/thaw method. NIH3T3 mouse embryonic fibroblasts grown on bFGF-fused fibroin sponges proliferated and spread out well, showing half the population doubling time of cells cultured on wild-type fibroin sponges. Furthermore, the number of primary rabbit articular chondrocytes growing on bFGF-fused fibroin sponges was around five-times higher than that of the wild-type control at 3-days post cell-seeding. As the physical properties of wild-type and bFGF-fused fibroin sponges were almost identical, it is suggested that bFGF fused to fibroin retained its biological activity, even after the bFGF-fused fibroin was fabricated into the spongy structure. The bFGF-fused fibroin sponge has the potential for widespread application in the field of tissue engineering, and the method of fabricating this structure could be applicable to other recombinant bioactive fibroin proteins.

Synovial cytokine expression in ankle osteoarthritis depends on age and stage

PURPOSE

Aim of the study was the analysis of cytokine expression in ankle osteoarthritis (OA) hypothesizing age-dependent regulation patterns.

METHODS

Forty-nine patients undergoing an arthroscopy of the ankle with different stages of chronic OA were prospectively included in a clinical trial comparing the group <18 years (n = 9, Ø15.1 ± 2.0 years) with the older patients (≥18 years, n = 40, Ø36.5 ± 11.9). Lavage fluids were analysed by ELISA for levels of aggrecan, BMP-2/7, IGF-1/R, bFGF, CD105, MMP-13, and IL-1β. Additionally, clinical parameters and scores (FFI, CFSS, AOFAS) were evaluated and supplemented by radiographic scores [Kellgren-Lawrence Score (KLS) for conventional X-rays, Ankle Osteoarthritis Scoring System (AOSS) for MRI].

RESULTS

In contrast to distribution of gender and BMI (p < 0.005), parameters characterizing the cartilage defect as ICRS grading, size, and duration of symptoms were not dependent on age. The incidence of osteochondritis dissecans (OCD) was higher in the group <18 years (p < 0.006), but the average degree of OCD grading was not different. KLS and AOSS were significantly higher in the group ≥18 years (p < 0.02). Correlating with the higher degree of OA in the elderly, clinical function measured by FFI and AOFAS was statistically significantly worse (p < 0.05). Intra-articular concentrations of aggrecan (3.1-fold), bFGF (8.7-fold), BMP-7 (2.7-fold), and CD105 (1.5-fold) were statistically significantly higher in the group ≥18 years (p < 0.03).

CONCLUSIONS

Confirming the hypothesis, increased synovial levels of aggrecan, bFGF, BMP-7, and CD105 were found in patients over 18 years. This correlated with a higher stage of OA determined by radiographic changes or deteriorated function and may offer starting points for new diagnostics and interventional strategies.

LEVEL OF EVIDENCE

II.

Slow release of basic fibroblast growth factor (b-FGF) enhances mechanical properties of rat trachea

AIM

Severe tracheomalacia is a life-threatening disease, but symptoms usually improve with growth. The aims of this study were to investigate how slow release basic-Fibroblast Growth Factor (b-FGF) acts on tracheal cartilage, and whether growth-promoted trachea is more resistant against an increase in externally-applied pressure.

METHODS

Biodegradable gelatin hydrogel sheets soaked in 10 μl of distilled water (sham) or 0.5 or 5 μg/10 μl of b-FGF solution were inserted behind the cervical trachea of three-week-old male Wistar rats. The cervical trachea was harvested 4 weeks later. Extratracheal pressure was increased from 0 to 40 cmH2O in a chamber, while video-recording the internal lumen. The luminal area at each pressure was expressed as a proportion to that at 0 cmH2O. The amounts of collagen type II and glycosaminoglycan were measured by ELISA.

RESULTS

The luminal areas at 40 cmH2O in the control (no intervention), sham, and each of the b-FGF groups were 0.65, 0.62, 0.72, and 0.73, respectively. The amounts of collagen type II and glycosaminoglycan in each group were 127, 136, 193, 249 μg/mg, respectively, and 15, 16, 19, 33 μg/mg, respectively. There were significant differences between the control group and the FGF 5 group (P=0.02, 0.01, 0.01, for luminal area, collagen, and glycosaminoglycan, respectively).

CONCLUSION

5 μg of slow-release b-FGF promotes matrix production (collagen type II and glycosaminoglycan). The growth-enhanced trachea was more resistant to collapse, suggesting that slowly released b-FGF might be useful in patients with severe tracheomalacia.

Induction of Osteogenic Differentiation in Human Mesenchymal Stem Cells by Crosstalk with Osteoblasts

Natural bone healing following fractures is initiated by osteoblasts (OBs) and mesenchymal stem cells (MSCs), a cell combination with possible potential in tissue engineering techniques for bony defects. The aim of the study was to investigate MSC/OB-crosstalk, in order to determine optimal cell culture conditions for osteogenic differentiation. Human OBs and MSCs interactions were investigated in an in vitro trans-well co-culture study over a time period of 28 days. Calcification was determined by optical density (OD) at 450 nm and Alizarin red staining. Messenger RNA expression was assessed by quantitative PCR. Osteogenic medium containing 1% fetal bovine serum resulted in superior levels of calcification in MSCs in co-culture with OBs compared to 2% or 5% fetal bovine serum (p<0.05). Comparing MSCs and OBs alone with the MSC/OB co-culture, calcification, as measured by OD 450 nm, increased over time in all groups. The highest values were recorded in the co-culture (p<0.05). Osteogenic differentiation potential showed significant interindividual differences. In order to predict differentiation potential, OD 450 nm measurements and mRNA expression of alkaline phosphatase were correlated with the population doubling rate during the expansion period. For OBs and MSCs, statistically significant associations of proliferation and differentiation potential were found (p<0.001). The addition of transforming growth factor beta resulted in up-regulation of collagen type I and Sp7 mRNA, and down-regulation of alkaline phosphatase mRNA. The results suggest the idea of soluble paracrine factors being secreted by OBs to induce osteogenic differentiation of MSCs.

Association between intraarticular cytokine levels and clinical parameters of osteochondritis dissecans in the ankle

Background

Reliable data about in vivo regulation of cytokines in osteochondritis dissecans (OCD) of the ankle are still missing. Disease-specific regulation patterns were hypothesized.

Methods

28 patients with a mean age of 30.7 ± 14.8 years undergoing an arthroscopy of the ankle because of OCD were prospectively included in a clinical trial. Lavage fluids were analyzed by ELISA for levels of aggrecan, BMP-2, BMP-7, IGF-1, IGF-1R, bFGF, endoglin, MMP-13, and IL-1β. Additionally, clinical parameters and scores (FFI, CFSS, AOFAS) were evaluated and supplemented by the Kellgren Lawrence Score (KLS) for conventional X-rays and the Ankle Osteoarthritis Scoring System (AOSS) for MRI.

Results

Grading of OCD lesions statistically significant increased with age and was higher in case of previously performed operations (p < 0.03). A worse clinical function reflected by low AOFAS and CFSS scores or high FFI was associated with high grading of cartilage damage or OCD (p < 0.03). Similarly, high radiological scores (KLS and AOSS) indicating progress of OA positively correlated with grading of cartilage damage and OCD. The concordance between the MRI and arthroscopic classification was overall moderate (κ = 0.52). Biochemically, only IGF/IGF-1R levels were consistently negatively associated with OCD grading, ICRS score, FFI and KLS (p < 0.05). Correlation data is supported by post hoc statistics.

Conclusions

Radiological and clinical parameters in association with synovial IGF-1/IGF-1R levels indicated an increasing joint degeneration with rising OCD stage.

Trial registration

German Clinical Trials Register DRKS00000365, 11/03/2008.

Early intra-articular complement activation in ankle fractures

Cytokine regulation possibly influences long term outcome following ankle fractures, but little is known about synovial fracture biochemistry. Eight patients with an ankle dislocation fracture were included in a prospective case series and matched with patients suffering from grade 2 osteochondritis dissecans (OCD) of the ankle. All fractures needed external fixation during which joint effusions were collected. Fluid analysis was done by ELISA measuring aggrecan, bFGF, IL-1β, IGF-1, and the complement components C3a, C5a, and C5b-9. The time periods between occurrence of fracture and collection of effusion were only significantly associated with synovial aggrecan and C5b-9 levels (P < 0.001). Furthermore, synovial expressions of both proteins correlated with each other (P < 0.001). Although IL-1β expression was relatively low, intra-articular levels correlated with C5a (P < 0.01) and serological C-reactive protein concentrations 2 days after surgery (P < 0.05). Joint effusions were initially dominated by neutrophils, but the portion of monocytes constantly increased reaching 50% at day 6 after fracture (P < 0.02). Whereas aggrecan and IL-1β concentrations were not different in fracture and OCD patients, bFGF, IGF-1, and all complement components were significantly higher concentrated in ankle joints with fractures (P < 0.01). Complement activation and inflammatory cell infiltration characterize the joint biology following acute ankle fractures.

Development and retranslational validation of an in vitro model to characterize acute infections in large human joints

Bacterial infections can destroy cartilage integrity, resulting in osteoarthritis. Goal was to develop an in vitro model with in vivo validation of acute joint inflammation. Inflammation in cocultivated human synovial fibroblasts (SFB), chondrocytes (CHDR), and mononuclear cells (MNC) was successively relieved for 10 days. Articular effusions from patients with (n = 7) and without (n = 5) postoperative joint infection in healthy patients (ASA 1-2) were used as model validation. Inflammation in vitro resulted in an enormous increase in IL-1 and a successive reduction in SFB numbers. CHDR however, maintained metabolic activity and proteoglycan synthesis. While concentrations of bFGF in vivo and in vitro rose consistently, the mRNA increase was only moderate. Concurring with our in vivo data, cartilage-specific IGF-1 steadily increased, while IGF-1 mRNA in the CHDR and SFB did not correlate with protein levels. Similarly, aggrecan (ACAN) protein concentrations increased in vivo and failed to correlate in vitro with gene expression in either the CHDR or the SFB, indicating extracellular matrix breakdown. Anabolic cartilage-specific BMP-7 with highly significant intra-articular levels was significantly elevated in vitro on day 10 following maximum inflammation. Our in vitro model enables us to validate early inflammation of in vivo cell- and cytokine-specific regulatory patterns. This trial is registered with MISSinG, DRKS 00003536.

Biochemical characterization of early osteoarthritis in the ankle

Purpose. Reliable data about in vivo regulation of cytokines in early ankle osteoarthritis (OA) are still missing. Methods. 49 patients with a mean age of 33 ± 14 years undergoing an arthroscopy of the ankle with different stages of chronic OA were prospectively included in a clinical trial. Lavage fluids were analyzed by ELISA. Additionally, clinical parameters and scores (FFI, CFSS, and AOFAS) were evaluated and supplemented by the Kellgren Lawrence Score (KLS) and the ankle osteoarthritis scoring system (AOSS). Results. ICRS grading of cartilage damage, previous operations, and duration of complains were strong indicators for OA progress and showed correlations to age, clinical scores, validated KLS, and AOSS (P < 0.04). Systemic and intraarticular inflammatory parameters were low in all patients. Biochemically, aggrecan and BMP-7 positively indicated OA with statistically significant associations with duration of symptoms, FFI, AOFAS, and KLS (P < 0.04). In contrast, BMP-2 levels showed statistically significant negative correlations to aggrecan or BMP-7 concentrations, which is in line with the negative association with ICRS score and KLS and the positive correlation with FFI (P < 0.03). Conclusions. We were able to identify different key markers of OA in the ankle as aggrecan, BMP-7, and BMP-2, offering starting points for new ways in diagnostics and interventional strategies.

Fibroblast growth factor 2 involved in the pathogenesis of synovial chondromatosis of temporomandibular joint

BACKGROUND

Synovial chondromatosis (SC) of temporomandibular joint (TMJ) is a rare proliferative disorder characterized by the formation of cartilaginous or osteocartilaginous nodules in synovium and joint space. Fibroblast growth factor 2 (FGF-2) is frequently applied in chondrogenic differentiation assays. Therefore, we hypothesized that FGF-2 might involved in the pathogenesis of SC.

METHODS

SC synovium and loose bodies (LBs) specimens were observed by histological and immunohistochemical methods. Real-time PCR was conducted for comparing genes expressions in SC and normal synovium. SC synoviocytes were stimulated by FGF-2 in the presence or absence of its antagonist long pentraxin-3 (PTX3) for 6 days. Real-time PCR and alkaline phosphatase (ALP) activity were performed to examine the effects exerted by FGF-2 and PTX3.

RESULTS

SC synovium, no matter facing the articular cavity or covering LB, was characterized by increased quantity of synoviocytes and blood vessels. FGF-2 was expressed in chondrocytes and fibroblast-like cells of LBs, and the wall of blood vessels. Expressions of chondrogenic genes (Sox9 and Wnt-4), osteogenic genes (Foxc2), FGF-2, and VEGF-A mRNA were significantly higher in SC synovium than that of the control group. The stimulation of FGF-2 on SC synoviocytes increased ALP activity and expressions of chondrogenic genes (Sox9, Col2α1, and Aggrecan), osteogenic genes (Foxc2, osteocalcin, and Col1α1), and VEGF-A, but PTX3 inhibited these effects.

CONCLUSION

FGF-2 was responsible for the formation of cartilaginous loose bodies and involved in the pathogenesis of SC.

Genetic inhibition of fibroblast growth factor receptor 1 in knee cartilage attenuates the degeneration of articular cartilage in adult mice

OBJECTIVE

Fibroblast growth factor (FGF) family members are involved in the regulation of articular cartilage homeostasis. The aim of this study was to investigate the function of FGF receptor 1 (FGFR-1) in the development of osteoarthritis (OA) and its underlying mechanisms.

METHODS

FGFR-1 was deleted from the articular chondrocytes of adult mice in a cartilage-specific and tamoxifen-inducible manner. Two OA models (aging-associated spontaneous OA, and destabilization-induced OA), as well as an antigen-induced arthritis (AIA) model, were established and tested in Fgfr1-deficient and wild-type (WT) mice. Alterations in cartilage structure and the loss of proteoglycan were assessed in the knee joints of mice of either genotype, using these 3 arthritis models. Primary chondrocytes were isolated and the expression of key regulatory molecules was assessed quantitatively. In addition, the effect of an FGFR-1 inhibitor on human articular chondrocytes was examined.

RESULTS

The gross morphologic features of Fgfr1-deficient mice were comparable with those of WT mice at both the postnatal and adult stages. The articular cartilage of 12-month-old Fgfr1-deficient mice displayed greater aggrecan staining compared to 12-month-old WT mice. Fgfr1 deficiency conferred resistance to the proteoglycan loss induced by AIA and attenuated the development of cartilage destruction after surgically induced destabilization of the knee joint. The chondroprotective effect of FGFR-1 inhibition was largely associated with decreased expression of matrix metalloproteinase 13 (MMP-13) and up-regulation of FGFR-3 in mouse and human articular chondrocytes.

CONCLUSION

Disruption of FGFR-1 in adult mouse articular chondrocytes inhibits the progression of cartilage degeneration. Down-regulation of MMP-13 expression and up-regulation of FGFR-3 levels may contribute to the phenotypic changes observed in Fgfr1-deficient mice.

Species-specific biological effects of FGF-2 in articular cartilage: implication for distinct roles within the FGF receptor family

Existing literature demonstrates that fibroblast growth factor-2 (FGF-2) exerts opposing, contradictory biological effects on cartilage homeostasis in different species. In human articular cartilage, FGF-2 plays a catabolic and anti-anabolic role in cartilage homeostasis, driving homeostasis toward degeneration and osteoarthritis (OA). In murine joints, however, FGF-2 has been identified as an anabolic mediator as ablation of the FGF-2 gene demonstrated increased susceptibility to OA. There have been no previous studies specifically addressing species-specific differences in FGF-2-mediated biological effects. In this study, we provide a mechanistic understanding by which FGF-2 exerts contradictory biological effects in human versus murine tissues. Using human articular cartilage (ex vivo) and a medial meniscal destabilization (DMM) animal model (in vivo), species-specific expression patterns of FGFR receptors (FGFRs) are elucidated between human and murine articular cartilage. In the murine OA model followed by intra-articular injection of FGF-2, we further correlate FGFR profiles to changes in behavioral pain perception, proteoglycan content in articular cartilage, and production of inflammatory (CD11b) and angiogenic (VEGF) mediators in synovium lining cells. Our results suggest that the fundamental differences in cellular responses between human and murine tissues may be secondary to distinctive expression patterns of FGFRs that eventually determine biological outcomes in the presence of FGF-2. The complex interplay of FGFRs and the downstream signaling cascades induced by FGF-2 in human cartilage should add caution to the use of this particular growth factor for biological therapy in the future.

Development of a refined tenocyte expansion culture technique for tendon tissue engineering

The aim of this study was to efficiently expand less differentiated tenocytes with minimum use of fetal bovine serum (FBS) for tenocyte-based tendon tissue engineering. To achieve this goal, human tenocytes were cultured in different concentrations of FBS and combinations of growth factors PDGF(BB), IGF-1 and bFGF. A number of growth factors were selected that could support tenocyte expansion at reduced differentiated state with minimum FBS usage. Results showed that the expansion of the tenocytes cultured for 14 days with 1% FBS, 50 ng/ml PDGF(BB) and 50 ng/ml bFGF was similar to that cultured in the 10% FBS control group. The tenocytes cultured in the treatment group showed significantly lower collagen synthesis and down-regulation of mRNA expression of tendon differentiation markers. Cell morphology confirmed that tenocytes cultured in the growth factors had reduced collagen fibril formation compared to tenocytes cultured in 10% FBS. Our findings confirm the feasibility of inducing human tenocyte expansion in vitro with the least amount of FBS usage, while controlling their differentiation until required.

Cell bricks-enriched platelet-rich plasma gel for injectable cartilage engineering - an in vivo experiment in nude mice

Clinical application of platelet-rich plasma (PRP)-based injectable tissue engineering is limited by weak mechanical properties and a rapid fibrinolytic rate. We proposed a new strategy, a cell bricks-stabilized PRP injectable system, to engineer and regenerate cartilage with stable morphology and structure in vivo. Chondrocytes from the auricular cartilage of rabbits were isolated and cultured to form cell bricks (fragmented cell sheet) or cell expansions. Fifteen nude mice were divided evenly (n = 5) into cells-PRP (C-P), cell bricks-PRP (CB-P) and cell bricks-cells-PRP (CB-C-P) groups. Cells, cell bricks or a cell bricks/cells mixture were suspended in PRP and were injected subcutaneously in animals. After 8 weeks, all the constructs were replaced by white resilient tissue; however, specimens from the CB-P and CB-C-P groups were well maintained in shape, while the C-P group appeared distorted, with a compressed outline. Histologically, all groups presented lacuna-like structures, glycosaminoglycan-enriched matrices and positive immunostaining of collagen type II. Different from the uniform structure presented in CB-C-P samples, CB-P presented interrupted, island-like chondrogenesis and contracted structure; fibrous interruption was shown in the C-P group. The highest percentage of matrix was presented in CB-C-P samples. Collagen and sGAG quantification confirmed that the CB-C-P constructs had statistically higher amounts than the C-P and CB-P groups; statistical differences were also found among the groups in terms of biomechanical properties and gene expression. We concluded that cell bricks-enriched PRP gel sufficiently enhanced the morphological stability of the constructs, maintained chondrocyte phenotypes and favoured chondrogenesis in vivo, which suggests that such an injectable, completely biological system is a suitable cell carrier for cell-based cartilage repair.

Anabolic/Catabolic balance in pathogenesis of osteoarthritis: identifying molecular targets

Osteoarthritis is the most common degenerative musculoskeletal disease. In healthy cartilage, a low turnover of extracellular matrix molecules occurs. Proper balance of anabolic and catabolic activities is thus crucial for the maintenance of cartilage tissue integrity and for the repair of molecular damages sustained during daily usage. In persons with degenerative diseases such as osteoarthritis, this balance of anabolic and catabolic activities is compromised, and the extent of tissue degradation predominates over the capacity of tissue repair. This mismatch eventually results in cartilage loss in persons with osteoarthritis. Tissue homeostasis is controlled by coordinated actions and crosstalk among a number of proanabolic and antianabolic and procatabolic and anticatabolic factors. In osteoarthritis, an elevation of antianabolic and catabolic factors occurs. Interestingly, anabolic activity is also increased, but this response fails to repair the tissue because of both quantitative and qualitative insufficiency. This review presents an overview of the anabolic and catabolic activities involved in cartilage degeneration and the interplay among different signaling and metabolic factors. Understanding the basic molecular mechanisms responsible for tissue degeneration is critical to identifying and developing means to efficiently block or reverse the pathobiological symptoms of osteoarthritis.

Fibroblast growth factor receptor 1 is principally responsible for fibroblast growth factor 2-induced catabolic activities in human articular chondrocytes

INTRODUCTION

Cartilage degeneration driven by catabolic stimuli is a critical pathophysiological process in osteoarthritis (OA). We have defined fibroblast growth factor 2 (FGF-2) as a degenerative mediator in adult human articular chondrocytes. Biological effects mediated by FGF-2 include inhibition of proteoglycan production, up-regulation of matrix metalloproteinase-13 (MMP-13), and stimulation of other catabolic factors. In this study, we identified the specific receptor responsible for the catabolic functions of FGF-2, and established a pathophysiological connection between the FGF-2 receptor and OA.

METHODS

Primary human articular chondrocytes were cultured in monolayer (24 hours) or alginate beads (21 days), and stimulated with FGF-2 or FGF18, in the presence or absence of FGFR1 (FGF receptor 1) inhibitor. Proteoglycan accumulation and chondrocyte proliferation were assessed by dimethylmethylene blue (DMMB) assay and DNA assay, respectively. Expression of FGFRs (FGFR1 to FGFR4) was assessed by flow cytometry, immunoblotting, and quantitative real-time PCR (qPCR). The distinctive roles of FGFR1 and FGFR3 after stimulation with FGF-2 were evaluated using either pharmacological inhibitors or FGFR small interfering RNA (siRNA). Luciferase reporter gene assays were used to quantify the effects of FGF-2 and FGFR1 inhibitor on MMP-13 promoter activity.

RESULTS

Chondrocyte proliferation was significantly enhanced in the presence of FGF-2 stimulation, which was inhibited by the pharmacological inhibitor of FGFR1. Proteoglycan accumulation was reduced by 50% in the presence of FGF-2, and this reduction was successfully rescued by FGFR1 inhibitor. FGFR1 inhibitors also fully reversed the up-regulation of MMP-13 expression and promoter activity stimulated by FGF-2. Blockade of FGFR1 signaling by either chemical inhibitors or siRNA targeting FGFR1 rather than FGFR3 abrogated the up-regulation of matrix metalloproteinases 13 (MMP-13) and a disintegrin and metalloproteinase with a thrombospondin type 1 motif 5 (ADAMTS5), as well as down-regulation of aggrecan after FGF-2 stimulation. Flow cytometry, qPCR and immunoblotting analyses suggested that FGFR1 and FGFR3 were the major FGFR isoforms expressed in human articular chondrocytes. FGFR1 was activated more potently than FGFR3 upon FGF-2 stimulation. In osteoarthritic chondrocytes, FGFR3 was significantly down regulated (P < 0.05) with a concomitant increase in the FGFR1 to FGFR3 expression ratio (P < 0.05), compared to normal chondrocytes. Our results also demonstrate that FGFR3 was negatively regulated by FGF-2 at the transcriptional level through the FGFR1-ERK (extracellular signal-regulated kinase) signaling pathway in human articular chondrocytes.

CONCLUSIONS

FGFR1 is the major mediator with the degenerative potential in the presence of FGF-2 in human adult articular chondrocytes. FGFR1 activation by FGF-2 promotes catabolism and impedes anabolism. Disruption of the balance between FGFR1 and FGFR3 signaling ratio may contribute to the pathophysiology of OA.

Remodelling of human osteoarthritic cartilage by FGF-2, alone or combined with Sox9 via rAAV gene transfer

Compensating for the loss of extracellular cartilage matrix, as well as counteracting the alterations of the chondrocyte phenotype in osteoarthritis are of key importance to develop effective therapeutic strategies against this disorder. In the present study, we analysed the benefits of applying a potent gene combination to remodel human osteoarthritic (OA) cartilage. We employed the promising recombinant adeno-associated virus (rAAV) vector to deliver the mitogenic fibroblast growth factor 2 (FGF-2) factor, alone or simultaneously with the transcription factor Sox9 as a key activator of matrix synthesis, to human normal and OA articular chondrocytes. We evaluated the effects of single (FGF-2) or combined (FGF-2/SOX9) transgene expression upon the regenerative activities of chondrocytes in three dimensional cultures in vitro and in cartilage explants in situ. Single overexpression of FGF-2 enhanced the survival and proliferation of both normal and OA chondrocytes, without stimulating the matrix synthetic processes in the increased pools of cells. The mitogenic properties of FGF-2 were maintained when SOX9 was co-overexpressed and concomitant with an increase in the production of proteoglycans and type-II collagen, suggesting that the transcription factor was capable of counterbalancing the effects of FGF-2 on matrix accumulation. Also important, expression of type-X collagen, a marker of hypertrophy strongly decreased following treatment by the candidate vectors. Most remarkably, the levels of activities achieved in co-treated human OA cartilage were similar to or higher than those observed in normal cartilage. The present findings show that combined expression of candidate factors in OA cartilage can re-establish key features of normal cartilage and prevent the pathological shift of metabolic homeostasis. These data provide further motivation to develop coupled gene transfer approaches via rAAV for the treatment of human OA.

Effect of gelatin hydrogel incorporating fibroblast growth factor 2 on human meniscal cells in an organ culture model

Efforts to use growth factors to enhance the healing potential of the meniscus have been impeded because their half-lives are too short to maintain the biological activity. The thread was coated with gelatin hydrogel and fibroblast growth factor 2 (FGF 2) was biologically stabilized by incorporating in a gelatin hydrogel-coated thread. The purpose of this study is to investigate the effect of gelatin hydrogel-coated thread incorporating FGF 2 on human meniscal cells in an organ culture. Twenty-five menisci were cut into small pieces, and selected pieces were sutured with gelatin hydrogel-coated thread incorporating FGF 2 (FGF(+) group) or physiologic saline (FGF(-) group), followed by organ culture. The meniscal samples histologically evaluated 4, 7, and 14 days later. The cell density and the number of PCNA-positive cells for the FGF(+) group were higher than those of the FGF(-) group, while the number of TUNEL-positive cells was lower. These results suggest that FGF 2 stimulates the proliferation of meniscal cells and inhibits meniscal cell death. Gelatin hydrogel-coated threads releasable FGF 2 may be useful to promote repairing of human meniscus.

Inhibition of histone deacetylases antagonized FGF2 and IL-1beta effects on MMP expression in human articular chondrocytes

Fibroblast growth factor-2 (FGF2) and interleukin-1beta (IL-1beta) stimulate the expression of matrix metalloproteinases (MMPs) in articular chondrocytes, which may contribute to cartilage degradation and development of osteoarthritis. Histone deacetylases (HDACs) have recently been implicated in the regulation of MMP gene expression. To investigate the functional involvement of HDACs in the signaling pathway of FGF2 and IL-1beta, we examined the effects of HDAC inhibition on activities of FGF2 or IL-1beta on gene expression of MMP-1, MMP-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS5), collagen type II, and aggrecan. Human articular chondrocyte cultures were treated with FGF2 or IL-1beta in the presence or absence of HDAC inhibitor (trichostatin A, TSA). Gene expression levels after treatments were assessed using quantitative real time PCR. Results showed that FGF2 and IL-1beta both increased MMP-1 and -13 expression, while IL-1beta also increased MMP-3 mRNA levels. These effects were attenuated in the presence of TSA in a dose dependent manner. In contrast to the effects on MMPs, FGF2 decreased mRNA levels of ADAMTS-5, which was not affected by HDAC inhibition. FGF2, IL-1beta, and TSA inhibited expression of aggrecan, while TSA also decreased mRNA levels of collagen type II. These findings showed that HDAC inhibition antagonized FGF2 and IL-1beta induced MMP expression. Combination of FGF2 and the HDAC inhibitor decreases both anabolic and catabolic genes, which may slow the cartilage turnover and be beneficial for maintaining cartilage integrity.

Biological impact of the fibroblast growth factor family on articular cartilage and intervertebral disc homeostasis

Two members of the fibroblast growth factor (FGF) family, basic FGF (bFGF) and FGF-18, have been implicated in the regulation of articular and intervertebral disc (IVD) cartilage homeostasis. Studies on bFGF from a variety of species have yielded contradictory results with regards to its precise role in cartilage matrix synthesis and degradation. In contrast, FGF-18 is a well-known anabolic growth factor involved in chondrogenesis and articular cartilage repair. In this review, we examined the biological actions of bFGF and FGF-18 in articular and IVD cartilage, the specific cell surface receptors bound by each factor, and the unique signaling cascades and molecular pathways utilized to exert their biological effects. Evidence suggests that bFGF selectively activates FGF receptor 1 (FGFR1) to exert degradative effects in both human articular chondrocytes and IVD tissue via upregulation of matrix-degrading enzyme activity, inhibition of matrix production, and increased cell proliferation resulting in clustering of cells seen in arthritic states. FGF-18, on the other hand, most likely exerts anabolic effects in human articular chondrocytes by activating FGFR3, increasing matrix formation and cell differentiation while inhibiting cell proliferation, leading to dispersed cells surrounded by abundant matrix. The results from in vitro and in vivo studies suggest the potential usefulness of bFGF and FGFR1 antagonists, as well as FGF-18 and FGFR3 agonists, as potential therapies to prevent cartilage degeneration and/or promote cartilage regeneration and repair in the future.