INTRINSIC-PROPERTIES OF ACL AND MCL CELLS AND THEIR RESPONSES TO GROWTH-FACTORS

Different intrinsic properties of the constituent cells of the anterio r cruciate Ligament (ACL) and medial collateral ligament (MCL) have be en proposed to be one of the factors in the differential repair mechan isms. We have found that the outgrowth of cells from rabbit ACL explan ts was slower than from MCL explants after 10 d. Growth curves of ACL and MCL cultures at both Passage numbers 2 and 6 showed a slower rate of proliferation of ACL cells than MCL cells (P < 0.005). The prolifer ative response of rabbit ACL and MCL cells to b-FGF and TGF-beta was a lso investigated. Both b-FGF and TGF-beta had no significant effect on cell proliferation of ACL and MCL cultures after 48 h. However, TGF-b eta did have an inhibitory effect on thymidine incorporation, especial ly at concentrations greater than 1 ng . ml(-1), while b-FGF stimulate d thymidine incorporation in ACL and MCL in a dose-dependent manner. D ifferences in the cell morphology of the ACL and MCL cells grown in cu lture were seen also. Cells from Passages 3-6 demonstrated these diffe rences more prominently, and phalloidin staining for actin showed that ACL cells appeared to have more intracellular actin fibers.