Equine osteoclast-like cells generated in vitro demonstrate similar characteristics to directly isolated mature osteoclasts

We report on novel methods to isolate osteoclasts (OC s) and generate osteoclast-like cells (OCL s) from the bone and bone marrow of the equine femur. OC s were successfully isolated from bone scrapings taken from the endosteal surface of the femurs of three horses. OCL s were generated from bone marrow cells taken from the same animals. The validity of using the formation of OCL s as a method for studying OC differentiation and activity was confirmed by the similar characteristics of these two cells. In particular, they both were multinuclear, expressed the enzyme tartrate resistant acid phosphatase and the vitronectin receptor. Most importantly, both were able to resorb bone as demonstrated by the formation of extensive resorption pits when cultured on dentine slices.The generation of OCL s from bone marrow obtained from the equine femur can therefore be used to study equine OC differentiation and for studies requiring the generation of large numbers of these cells. OC s isolated directly from the same bones may be used to examine the effect of a variety of factors on bone resorption in vitro and to continually reaffirm the validity of using OCL s for large-scale studies on OC biology. Such research is essential for improved understanding of bone turnover and endochondral ossification in the horse.