IN-VITRO GENERATION OF EQUINE OSTEOCLASTS FROM BONE-MARROW CELLS USING A NOVEL CULTURE SYSTEM

We report on preliminary results of a novel in vitro culture system de signed to generate equine osteoclasts in large numbers. Osteoclast gen eration, as determined by the expression of tartrate resistant acid ph osphatase (TRAP) and ability to resorb bone, was enhanced in equine bo ne marrow cultures supplemented with fibroblastic cell (L929) conditio ned medium (L929-CM). Bone marrow was collected from a total of 12 hor ses and ponies and TRAP-positive cells with bone resorbing ability wer e generated in significant numbers in the last seven. TRAP-positive mo nonuclear cells appeared after three days in culture and steadily incr eased in number and size up to seven days when multinuclear TRAP-posit ive cells starred to appear. L929-CM caused a significant increase in the number of TRAP-positive mononuclear cells generated after four and seven days, after which time the number of TRAP-positive cells decrea sed. The development of this in vitro system provides a reproducible m eans of generating large numbers of equine osteoclasts necessary for t he study of bone remodelling and endochondral ossification in the hors e.