Connective tissue growth factor (CTGF) is a novel cysteine-rich, secreted protein. Recently, we found that inhibition of the endogenous expression of CTGF by its antisense oligonucleotide and antisense RNA suppresses the proliferation and migration of vascular endothelial cells. In the present study, the following observations demonstrated the angiogenic function of CTGF in vitro and in vivo: (i) purified recombinant CTGF (rCTGF) promoted the adhesion, proliferation and migration of vascular endothelial cells in a dose-dependent manner under serum-free conditions, and these effects were inhibited by anti-CTGF antibodies; (ii) rCTGF markedly induced the tube formation of vascular endothelial cells, and this effect was stronger than that of basic fibroblast growth factor or vascular endothelial growth factor; (iii) application of rCTGF to the chicken chorioallantoic membrane resulted in a gross angiogenic response, and this effect was also inhibited by anti-CTGF antibodies. (iv) rCTGF injected with collagen gel into the backs of mice induced strong angiogenesis in vivo. These findings indicate that CTGF is a novel, potent angiogenesis factor which functions in multi-stages in this process.

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Connective tissue growth factor (CTGF/CCN2) is a member of the CCN family of matricellular proteins and also has been designated Hcs24, FISP12, IGFBP8, IGFBP-rP2, ␤IG-M2, and ecogenin. The other CCN proteins include Cyr61/CCN1, NOV/CCN3, WISP1/CCN4, WISP2/CCN5, and WISP3/CCN6 (5, 26, 38, 39) as well, and they are structurally and functionally related glycoproteins involved in cell differentiation, proliferation, adhesion, migration, and the formation of the extracellular matrix. These matricellular functions of CCNs are involved in physiological processes such as wound healing, angiogenesis, morphogenesis, and embryogenesis as well as in pathological states including fibrotic disorders, cancer, and arthritis.Earlier we showed that CCN2 promotes endochondral ossification by acting on chondrocytes, osteoblasts, and endothelial cells (35,37,46). For example, CCN2 promotes physiological chondrocytic proliferation and extracellular matrix (ECM) formation. We also reported the regeneration of defects in articular cartilage in rat knee joints following treatment with recombinant CCN2 (36). Furthermore, ctgf-null mice were dead on delivery and were characterized by defective angiogenesis, the derangement of endochondral ossification, and dysmorphisms that occurred as a result of impaired chondrocyte proliferation and an abnormal ECM composition within the hypertrophic zone (24).Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that are involved in the remodeling and turnover of the ECM in physiological processes such as angiogenesis, wound healing, embryogenesis, and morphogenesis as well as in pathological states including cancers, myocardial infarction, fibrotic disorders, rheumatism, and osteoarthritis (33, 49). Cartilage is a connective tissue that is constructed by chondrocytes embedded within an ECM predominantly composed of collagens and proteoglycans. ECM remodeling is achieved by regulating the production and degradation of specific ECM components. MMPs, which comprise a large family of enzymes with differential abilities to degrade specific ECM components, play a vital role in this process. MMPs also cleave growth factors and their binding proteins, thereby activating or inhibiting specific signaling events (15). Of note, the expression and role of MMP3 have been investigated in the pathological status of articular cartilage, such as in osteoarthritis and rheumatism (1,52).Recent study has demonstrated the existence and functions of intracellular MMPs and tissue inhibitors of metalloproteinases (TIMPs). TIMP-1 accumulates in the cellular nuclei in association with the cell cycle (54). Alternative splicing and promoter usage generate an intracellular MMP11 isoform directly translated as an active MMP (31). MMP2 is found in the nuclei of cardiac myocytes and is capable of cleaving poly-(ADP-ribose) polymerase (PARP) in vitro (28). MMP3 also is detected in the nuclei of hepatocytes and is involved in apop-* Corresponding author. Mailing address:

CTGF/CCN2, a hypertrophic chondrocyte-specific gene product, possessed the ability to repair damaged articular cartilage in two animal models, which were experimental osteoarthritis and full-thickness defects of articular cartilage. These findings suggest that CTGF/CCN2 may be useful in regeneration of articular cartilage.Introduction: Connective tissue growth factor (CTGF)/CCN2 is a unique growth factor that stimulates the proliferation and differentiation, but not hypertrophy, of articular chondrocytes in vitro. The objective of this study was to investigate the therapeutic use of CTGF/CCN2. Materials and Methods:The effects of recombinant CTGF/CCN2 (rCTGF/CCN2) on repair of damaged cartilage were evaluated by using both the monoiodoacetic acid (MIA)-induced experimental rat osteoarthritis (OA) model and full-thickness defects of rat articular cartilage in vivo. Results: In the MIA-induced OA model, quantitative real-time RT-PCR assays showed a significant increase in the level of CTGF/CCN2 mRNA, and immunohistochemical analysis and in situ hybridization revealed that the clustered chondrocytes, in which clustering indicates an attempt to repair the damaged cartilage, produced CTGF/CCN2. Therefore, CTGF/CCN2 was suspected to play critical roles in cartilage repair. In fact, a single injection of rCTGF/CCN2 incorporated in gelatin hydrogel (rCTGF/CCN2-hydrogel) into the joint cavity of MIA-induced OA model rats repaired their articular cartilage to the extent that it became histologically similar to normal articular cartilage. Next, to examine the effect of rCTGF/CCN2 on the repair of articular cartilage, we created defects (2 mm in diameter) on the surface of articular cartilage in situ and implanted rCTGF/CCN2-hydrogel or PBS-hydrogel therein with collagen sponge. In the group implanted with rCTGF/CCN2-hydrogel collagen, new cartilage filled the defect 4 weeks postoperatively. In contrast, only soft tissue repair occurred when the PBS-hydrogel collagen was implanted. Consistent with these in vivo effects, rCTGF/CCN2 enhanced type II collagen and aggrecan mRNA expression in mouse bone marrow-derived stromal cells and induced chondrogenesis in vitro. Conclusion: These findings suggest the utility of CTGF/CCN2 in the regeneration of articular cartilage.

MicroRNAs (miRNAs) are small RNA molecules of 21–25 nucleotides that regulate cell behavior through inhibition of translation from mRNA to protein, promotion of mRNA degradation and control of gene transcription. In this study, we investigated the miRNA expression signatures of cell cultures undergoing osteoblastic and osteocytic differentiation from mesenchymal stem cells (MSC) using mouse MSC line KUSA-A1 and human MSCs. Ninety types of miRNA were quantified during osteoblastic/osteocytic differentiation in KUSA-A1 cells utilizing miRNA PCR arrays. Coincidently with mRNA induction of the osteoblastic and osteocytic markers, the expression levels of several dozen miRNAs including miR-30 family, let-7 family, miR-21, miR-16, miR-155, miR-322 and Snord85 were changed during the differentiation process. These miRNAs were predicted to recognize osteogenic differentiation-, stemness-, epinegetics-, and cell cycle-related mRNAs, and were thus designated OstemiR. Among those OstemiR, the miR-30 family was classified into miR-30b/c and miR-30a/d/e groups on the basis of expression patterns during osteogenesis as well as mature miRNA structures. In silico prediction and subsequent qRT-PCR in stable miR-30d transfectants clarified that context-dependent targeting of miR-30d on known regulators of bone formation including osteopontin/spp1, lifr, ccn2/ctgf, ccn1/cyr61, runx2, sox9 as well as novel key factors including lin28a, hnrnpa3, hspa5/grp78, eed and pcgf5. In addition, knockdown of human OstemiR miR-541 increased Osteopontin/SPP1 expression and calcification in hMSC osteoblastic differentiation, indicating that miR-541 is a negative regulator of osteoblastic differentiation. These observations indicate stage-specific roles of OstemiR especially miR-541 and the miR-30 family on novel targets in osteogenesis.

We previously reported that connective tissue growth factor/hypertrophic chondrocyte-specific gene product 24 (CTGF/Hcs24) stimulated the proliferation and differentiation of rabbit growth cartilage (RGC) cells in vitro. In this study, we investigated the effects of CTGF/Hcs24 on the proliferation and differentiation of rabbit articular cartilage (RAC) cells in vitro. RAC cells transduced by recombinant adenoviruses generating mRNA for CTGF/Hcs24 synthesized more proteoglycan than the control cells. Also, treatment of RAC cells with recombinant CTGF/Hcs24 (rCTGF/Hcs24) increased DNA and proteoglycan syntheses in a dose-dependent manner. Northern blot analysis revealed that the rCTGF/Hcs24 stimulated the gene expression of type II collagen and aggrecan core protein, which are markers of chondrocyte maturation, in both RGC and RAC cells. However, the gene expression of type X collagen, a marker of hypertrophic chondrocytes, was stimulated by rCTGF/Hcs24 only in RGC cells, but not in RAC cells. Oppositely, gene expression of tenascin-C, a marker of articular chondrocytes, was stimulated by rCTGF/Hcs24 in RAC cells, but not in RGC cells. Moreover, rCTGF/Hcs24 effectively increased both alkaline phosphatase (ALPase) activity and matrix calcification of RGC cells, but not of RAC cells. These results indicate that CTGF/Hcs24 promotes the proliferation and differentiation of articular chondrocytes, but does not promote their hypertrophy or calcification. Taken together, the data show that CTGF/Hcs24 is a direct growth and differentiation factor for articular cartilage, and suggest that it may be useful for the repair of articular cartilage.

To clarify the mechanism of cartilage degradation induced by mechanical stress, we investigated the influence of cyclic tension force (CTF) on the metabolism of cultured chondrocytes. The chondrocytes were exposed to CTF using a Flexercell strain unit. Five or 15 kPa of high frequency CTF significantly inhibited the syntheses of DNA, proteoglycan, collagen, and protein. Fifteen kPa of high frequency CTF induced the expression of interleukin-1 (IL-1), matrix metalloproteinase (MMP)-2 and -9 mRNA, and increased the production of pro- and active-MMP-9. The degradation of proteoglycan was inhibited by and MMP inhibitor, indicating that MMPs are involved in the degradation of proteoglycans induced by high frequency CTF. Moreover, reducing the frequency of CTF from high to low decreased the inhibition of proteoglycan synthesis. These findings suggest that the CTF frequency is one of the key determinants of chondrocyte metabolism. Low magnitude CTF, whether high or low frequency, did not cause the gene expression of cartilage degradation factors, suggesting that this CTF magnitude causes only minor changes in the cartilage matrix. High magnitude and frequency CTF caused the gene expression of IL-1 and MMP-9, followed by increases in the production of MMP-2 and -9 proteins, suggesting that excessive and continuous cyclic mechanical stress induces the production of IL-1 and MMP-9, resulting in cartilage degradation.

GEE analysis showed that smoking was a risk factor for early implant failure, and several risk factors were identified for late implant failure.