INTRACELLULAR CALCIUM RESPONSE OF ACL AND MCL LIGAMENT FIBROBLASTS TOFLUID-INDUCED SHEAR-STRESS

This study examines the real time intracellular calcium concentration, [Ca2+](i), response of canine medial collateral ligament (MCL) and an terior cruciate ligament (ACL) fibroblasts subjected to a fluid-induce d shear stress of 25 dynes/cm2(.) In experiments using a modified Hank s' Balanced Salt Solution (HBSS) perfusate, both cell types demonstrat ed a significant increase in peak [Ca2+](i) compared to respective no- flow controls, the response of MCL fibroblasts being nearly 2-fold gre ater than that of ACL fibroblasts. In studies where the cells were bat hed in a medium of HBSS supplemented with 2% newborn bovine serum (NBS ) and then introduced to flow with the same medium, ACL fibroblasts re sponded nearly 3-fold greater than MCL fibroblasts. Neomycin (10 mM), thapsigarigin (1 mu M) and Ca2+-free media supplemented with EGTA (1 m M) were able to inhibit significantly the [Ca2+](i) response to flow w ith HBSS in both fibroblasts. Thapsigargin also blocked the NBS flow r esponse in both cell types, while neomycin and Ca2+-free media signifi cantly inhibited the ACL response. Our findings demonstrate that ACL a nd MCL cells are not the same. These differences may be related to the disparate healing capacity of the ACL and MCL observed clinically. (C ) 1997 Elsevier Science Inc.