Abrasion arthroplasty increases mesenchymal stem cell content of postoperative joint effusions.

BACKGROUND: Abrasion arthroplasty (AAP) is a procedure by which intrinsic cartilage healing is believed to be stimulated. Although clinically accepted for degenerative and traumatic cartilage lesions scientific evidence at a molecular level that proves the effect of AAP is scarce. METHOD: Mononuclear cells were extracted from postoperative joint effusions 21.5 h post AAP and simple debridement of cartilage lesions. Luminex, ELISA and FACS experiments were performed. Immunohistochemical stainings of cell cultures for cartilage markers were used to confirm the findings. RESULTS: Postoperative joint effusions after AAP showed increased contents of Mononuclear cells compared to Arthroscopic Chondroplasty (ACP). BMP-4 and IGF were increased in AAP as complared to ACP. Mononuclear cells isolated after AAP express the MSC markers CD 73, CD 105, CD 90, CD 44 and are CD34 negative. Chondrogenic differentiation was demonstrated by positive staining for Sox9, collagen II, proteoglycan, chondroitin-4-sulfate. CONCLUSION: Our results support the clinical application of AAP as a procedure that enhances cartilage repair as an alternative to far more complex procedures that have gained popularity. Furthermore the data presented supports clinical investigations that recommend not to use suction drainage as by this procedure a considerable amount of the regeneratory potential of postoperative joint effusions might be extracted.

Endostatin/collagen XVIII--an inhibitor of angiogenesis--is expressed in cartilage and fibrocartilage.

UNLABELLED: Aim of the study was to get a deeper insight in the mechanisms regulating avascularity of cartilaginious tissues. In the center of our interest was the expression of the anti-angiogenic fragment of collagen XVIII and its potency to inhibit angiogenesis. We observed a strong endostatin/collagen XVIII production in articular and fibrocartilage and an inhibitory potency concerning the VEGF-signalling pathway. INTRODUCTION: Cartilaginous tissue is mainly avascular and shows a limited intrinsic capacity for healing. Aim of this study was to investigate the expression of the antiangiogenic peptide endostatin/collagen XVIII in cartilage and fibrocartilage. RESULTS: In fetal epiphyseal cartilage of humans high endostatin/collagen XVIII levels could be detected by ELISA whereas significantly lower levels were found in articular cartilage of adults. In the fibrocartilaginous tissue of the menisci, there was no significant difference in the endostatin/collagen XVIII concentrations between samples of fetuses and adults. But in the menisci of adults, endostatin/collagen XVIII concentrations were higher in the internal avascular two thirds of the meniscus whereas in the fetal menisci higher endostatin/collagen XVIII concentrations were found in the external third. Endostatin/collagen XVIII immunostaining of rat articular cartilage shows that endostatin/collagen XVIII downregulation starts soon after birth. In fetal cartilage and fibrocartilage of rats and humans, endostatin/collagen XVIII could be immunostained in the extracellular matrix and in the pericellular matrix of endothelial cells, fibrochondrocytes and chondrocytes. In adult cells, weak endostatin/collagen XVIII immunostaining was restricted to the pericellular matrix of fibrochondrocytes and chondrocytes. The detection of endostatin/collagen XVIII could be verified by in situ hybridization. Chondrocytes in vitro released measurable amounts of endostatin/collagen XVIII into culture supernatants. Stimulation of chondrocytes with EGF, as an example of a growth factor, or dexamethasone had no influence on endostatin/collagen XVIII expression. Endostatin inhibited VEGF-induced phosphorylation of MAPK in chondrocytes. CONCLUSIONS: The spatial and temporal expression of endostatin/collagen XVIII in cartilaginous tissue and its potency regarding inactivation of VEGF signalling suggests that this antiangiogenic factor is important not only for the development but also for the maintenance of avascular zones in cartilage and fibrocartilage. EXPERIMENTAL PROCEDURES: We analyzed the spatial and temporal expression of endostatin/collagen XVIII--an endogenous angiogenesis inhibiting factor--in cartilage and fibrocartilage of humans and rats by immunohistochemical and biochemical (ELISA) methods and by in situ hybridization. To elucidate possible factors responsible for the induction or suppression of endostatin/collagen XVIII in cartilaginous tissues, chondrocytes (cell line C28/I2) were exposed to EGF and dexamethason. To study the possible interaction of endostatin/collagen XVIII with angiogenic factors, the immortalized human chondrocytes (C28/I2) have been incubated with VEGF and the phosphorylation of the MAPK Erk 1/2 (extracellular-regulated kinases), a known signal transduction pathway for VEGF has been determined under the influence of endostatin.