Cartilage-derived morphogenetic protein-1 and cartilage-derived morphogenetic protein-2 are present in ligament fibroblasts and lead to chondrogenic differentiation
© The Author(s) 2003
Published: 12 September 2003
The enhancement of tissue repair by growth factor stimulation is of potential therapeutic interest. Given the importance of cartilage-derived morphogenetic protein (CDMP)-1 and CDMP-2 in ligament formation and repair, we studied the effects of these growth factors on the proliferation and metabolism of ligament fibroblasts as well as their osteogenic/chondrogenic differentiation potential.
Ligament fibroblasts were obtained from 3-month-old calves, plated as monolayers or micromass cultures and stimulated with CDMPs. The expression of the indicated growth factors was assessed either by RT-PCR or by Western immunoblotting. The presence of their respective type I and type II receptors, as well as lineage-related markers were investigated in stimulated and unstimulated cells by RT-PCR and by northern blotting. The biosynthesis of matrix proteoglycans was assessed by [35S]sulfate incorporation in monolayers. Alcian-blue staining as well as toluidin-blue was performed in micromass cultures. The cell proliferation rate was measured by the use of [3H]thymidine incorporation.
The presence of CDMP-1 and CDMP-2 was detected on mRNA as well as on the protein level. Type I and type II receptors were endogenously expressed in unstimulated ligament fibroblasts. The growth factors stimulated cell proliferation as measured by [3H]thymidine incorporation and total proteoglycan synthesis as assessed by [35S] incorporation. Alcian-blue and toluidin-blue staining showed the differentiation into chondrocytes in the growth-factor-treated ligament fibroblasts. Moreover, transcription analysis of stimulated ligament fibroblasts demonstrated an upregulation of chondrogenic markers (aggrecan, collagen type II, type IX and type X) but not of osteogenic markers.
CDMP-1 and CDMP-2 induce matrix synthesis and cell proliferation in cells derived from bovine ligament. The expression of chondrocyte markers suggests that adult cells from ligaments and tendons have the capability of differentiation into chondrocytes under the influence of CDMPs. Given our current dilemma in the treatment of osteoarthritis, CDMP-1 and CDMP-2 could therefore contribute an interesting therapeutic molecule for osteoarthritis.