Retraction of Thrombin-Induced Fibrin by Rhabdomyosarcoma BA 1112 Cultured Cells

The capacity to induce fibrin retraction has been considered a specific property of platelets until recently, when Niewiarowski et al. (Proc. Soc. Exp, Biol. Med. 140, 1199, 1972) observed fibrin retraction induced by human fibroblasts. As a part of a larger study on the interactions of cultured cells with fibrin, we have investigated the ability of the following cell lines to retract fibrin: KB (human oral epidermoid carcinoma); HeLa (human cervix carcinoma); Chang Liver (human, normal epithelium; Chang Conjunctiva (human normal epithelium); NCTC clone 929 (L) (fibroblasts from C3H/AN mice) and BA 1112 (rhabdomyosarcoma developed on WAG/Rji inbred rats). Cells were cultured in Eagle’s MEM, in Hank’s blanced salt solution plus 10% calf serum, removed from the flasks by trypsin treatment and resuspended at a concentration of 2 × 10⁶/ml in Tyrode-albumin solution, containing Ca⁺⁺ and Mg⁺⁺. Human citrated platelet-poor plasma was clotted in a test tube at 37° C by thrombin in the presence of either the cell suspensions or buffer. Only BA 1112 cells were able to retract fibrin; the presence of Ca⁺⁺, cellular integrity and random distribution in the sample were required for this activity. BA 1112 cells were able to modify the structuration of thrombin-induced fibrin as indicated by the marked increase of the maximal amplitude of thrombelastogram. BA 1112-induced fibrin retraction was inhibited by PGE₁ and by some pyrimido-pyrimidine derivatives, not by apsirin. No retraction occurred when reptilase instead of thrombin was used as the clotting agent, even if the cells were preincubated with ADP. These results suggest that BA 1112 cells have a susceptibility to thrombin similar to that of platelets; this hypothesis is interesting in view of the muscular origin of these cells.

(Supported by Grant NIH-PHRB-10RO1 CA 12764–01.)