Establishment of a clonal bipotent chondroprogenitor cell line from adult mouse to provide a new tool for the elucidation of chondrogenesis in adult animal.
A clonal cell line CL-1 was established from tibia of adult mouse. Differentiation of CL-1 was characterized in monolayer culture. Effects of growth factors (TGF-beta(1), IGF-I, bFGF) and hormones (all trans retinoic acid, 1 alpha.25(OH)(2)D(3), PTH (1-34)) on the growth and differentiation of CL-1 were examined. Bipotency of CL-1 in vivo was examined by transplantation into SCID mice.
CL-1 formed alcian blue (pH1.0) positive nodules spontaneously. The nodules were mineralized in the presence of ascorbic acid and beta-glycerophosphate. CL-1 differentiated also into oil red O positive adipocytes spontaneously. CL-1 cells expressed specific genes of chondrocytes (collagen type II, X, aggrecan) and adipocytes (PPAR-gamma(2), aP(2)). Hyaline cartilage and adipose tissue formation was observed also in subcutaneously transplanted CL-1 cells into SCID mice. These data demonstrate that CL-1 has bipotency either in vitro or in vivo. TGF-beta(1)suppressed growth of CL-1 and induced dominant chondrogenesis accompanied with marked suppression of adipogenesis in 10% FCS. IGF-I stimulated both growth (in 3% FCS) and differentiation of CL-1 into both lineages (in 10% FCS). 1 alpha.25(OH)(2)D(3)and all trans retinoic acid acted as negative regulators on proliferation and differentiation of CL-1 in 10% FCS.
CL-1 will be a useful tool for the understanding of chondrogenesis in adult animal. Furthermore, CL-1 can be also a powerful tool for screening of the chondrogenic agent.