BACKGROUNDThere is a difficulty in evaluating the in vivo functionality of individual chondrocytes, and there is much heterogeneity among cartilage affected by osteoarthritis (OA). In this study, in vitro cultured chondrocytes harvested from varying stages of degeneration were studied as a projective model to further understand the pathogenesis of osteoarthritis.

METHODSCartilage of varying degeneration of end-stage OA was harvested, while cell yield and matrix glycosaminoglycan (GAG) content were measured. Cell morphology, proliferation, and gene expression of collagen type I, II, and X, aggrecan, matrix metalloproteinase 13 (MMP-13), and ADAMTS5 of the acquired chondrocytes were measured during subsequent in vitro culture.

RESULTSBoth the number of cells and the GAG content increased with increasing severity of OA. Cell spreading area increased and gradually showed spindle-like morphology during in vitro culture. Gene expression of collagen type II, collagen type X as well as GAG decreased with severity of cartilage degeneration, while expression of collagen type I increased. Expression of MMP-13 increased with severity of cartilage degeneration, while expression of ADAMTS-5 remained stable. Expression of collagen type II, X, GAG, and MMP-13 substantially decreased with in vitro culture. Expression of collagen type I increased with in vitro cultures, while expression of ADAMTS 5 remained stable.

CONCLUSIONSExpression of functional genes such as collagen type II and GAG decreased during severe degeneration of OA cartilage and in vitro dedifferentiation. Gene expression of collagen I and MMP-13 increased with severity of cartilage degeneration.

ADAM Proteins ; ADAMTS5 Protein ; Cartilage ; pathology ; Cell Differentiation ; genetics ; physiology ; Cells, Cultured ; Chondrocytes ; metabolism ; Collagen Type II ; genetics ; Collagen Type X ; genetics ; Glycosaminoglycans ; metabolism ; Humans ; Matrix Metalloproteinase 13 ; genetics ; Osteoarthritis ; genetics ; pathology

OBJECTIVETo establish a model of chondrocyte degeneration in vitro.

METHODSChondrocytes were isolated from articular cartilages of newly born SD rats by digestion with typeⅡ collagenase. The chondrocytes were cultured with H-DMEM medium containing 10%FBS, 50 ng/mL IL-1β+10%FBS, 2.5% rat serum and 5% rat serum, respectively; and the chondrocytes at passage one were used in the experiments. The morphology changes were investigated under phase contrast microscope after chondrocytes were treated with rat serum and IL-1β. Proliferation of chondrocytes was detected by MTT method. The protein expression levels of PCNA, typeⅡ collagen and MMP-13 were examined by Western blotting. The levels of ADAMTS5, MMP-9, Aggrecan and SOX-9 mRNA were detected by real-time PCR.

RESULTSThe cell morphology was changed from polygon to spindle in both rat serum groups and IL-1β group, and the proliferation of chondrocytes in these groups was much higher than that in control group. The results showed that the expression levels of typeⅡ collagen, Aggrecan and SOX-9 decreased while the expression levels of MMP-13, MMP-9 and ADMATS5 were up-regulated in rat serum and IL-1β-treated groups compared with control group.

CONCLUSIONThe results indicate that rat serum can induce chondrocyte degeneration and may be used for osteoarthritis model in vitro.

ADAM Proteins ; metabolism ; ADAMTS5 Protein ; Aggrecans ; metabolism ; Animals ; Cartilage, Articular ; cytology ; Cells, Cultured ; Chondrocytes ; pathology ; Collagen Type II ; metabolism ; Disease Models, Animal ; Interleukin-1beta ; pharmacology ; Matrix Metalloproteinase 13 ; metabolism ; Matrix Metalloproteinase 9 ; metabolism ; Osteoarthritis ; pathology ; Proliferating Cell Nuclear Antigen ; metabolism ; RNA, Messenger ; Rats ; Rats, Sprague-Dawley ; SOX9 Transcription Factor ; metabolism ; Serum ; Up-Regulation