A “coupled” subchondral bone-articular cartilage tissue culture system for the study of cartilage proteoglycan metabolism

Bone tissue cultures: an in vitro model for the evaluation of bone defect healing after L-arginine and L-lysine administration

The development of new therapeutic strategies and innovative biomaterials for the muscoloskeletal system, stresses the need for researchers to have reliable, easy, less time-consuming and ethical experimental models. The aim of the present study was to characterise an in vitro model of cultured rat femora and test the possibility of using this model in dynamic studies on bone healing. 24 femurs were explanted after 12 rats were killed for other experimental protocols. A standard bone defect was created in the distal femoral condyles and femurs were cultured in GBJb medium. Arginine and lysine were administered daily in the Arg-Lys group. The other femurs were left untreated (Control group). At 1, 7, 14 and 21 days, alkaline phosphatase activity, nitric oxide and calcium were measured on the supernatant. At 21 days, femurs were embedded in polymethylmethacrylate for histomorphometry and microhardness evaluation of the newly formed bone. The current results showed that it was possible to study bone healing in vitro by using cultured bones from adult animals. A process for bone healing was observed also in untreated bones. Moreover, the structural analysis of the cultured bone showed that it had characteristics similar to those of the femurs, when they were embedded in resin immediately after animal sacrifice. The effect of Arg and Lys confirmed data of a previous study, where a faster healing of bone defect and fracture was observed in rabbits after Arg and Lys administration.

Anionic glycoconjugates from differentiated and dedifferentiated cultures of bovine articular chondrocytes: modulation by TGF-beta

Primary, high density bovine articular chondrocyte (BAC) cultures, stimulated with transforming growth factor-beta-1, elaborated a high molecular weight anionic glycoconjugate, kDa 540, which does not contain glycosaminoglycan chains (Chan and Anastassiades, 1996). The effect of exogenously added transforming growth factor-beta-1 on the elaboration of the high molecular weight glycoconjugate and of proteoglycans was studied during dedifferentiation of the chondrocytes, utilizing a serial subculture technique under anchorage-dependent conditions, up to four subcultures. The high molecular weight glycoconjugate was detected in the media of all growth-factor-stimulated chondrocyte subcultures, as well as stimulated primary cultures, but not in unstimulated primary cultures or subcultures. By contrast, a large proteoglycan, was only secreted by primary cultures and first subcultures, whether treated with transforming growth factor-beta-1 or untreated. This proteoglycan contained mostly chondroitin sulfate chains, whose hydrodynamic size was increased by the addition of transforming growth factor-beta-1. Further, the pattern of the proteoglycans appearing in the media of subcultures 2-4 was influenced by the addition of transforming growth factor-beta-1, so that while these control subcultures elaborated both the large and small chondroitin sulfate proteoglycans, the equivalent stimulated subcultures elaborated only intermediate sized chondroitin sulfate proteoglycan(s). These results suggest that while dedifferentiation of articular chondrocytes, achieved by subculturing, strongly modulates the effect of exogenously added transforming growth factor-beta-1 on the type of proteoglycan elaborated, the process of dedifferentiation does not influence the transforming-growth-factor-beta-dependent synthesis of the high molecular weight anionic glycoconjugate.