Study of osteogenesis with castor oil polymer/calcium carbonate in equine bone tissue: histological and immunochemical evaluation

Abstract

The major challenge for orthopedic surgery is repair of fractures with bone gap. Moreover, perfect alignment of the fragments, especially in horses and when there is loss of bone fragments that generates discontinuity, decrease stabilization and results. On these cases, the use of bone substitutes must be considered for success in osteosynthesis. An experimental bone defect was created in the right and left third metacarpal bone of six adult horses. One defect was randomly selected for treatment with biopolymer (polymer limb) while the contralateral defect was left untreated (control limb). Bone biopsies were collected from the mature bone/biopolymer interface or the new bone/mature bone (polymer and control limbs respectively) 120 days after surgery using a 0.5 cm trephine saw. Study of biological behavior of the equine species to the polymer were performed. Collected material was processed, with a rate fixed in paraformaldehyde (sample for immunohistochemical and histochemical tests - IHC and HQ) and another aliquot was fixed in paraformaldehyde-based solution and glutaraldehyde (sample transmission electron microscopy - TEM). Tissue biopsy samples were decalcified with EDTA. IHC sample, after decalcification, will be embedded in paraffin to perform IHC testing of gene expression of Runx-2 and TRAP staining to identify osteoclasts. TEM sample, after decalcification, will be embedded in Spurr epoxy resin to be examined in a transmission electron microscope. Aim of this study is evaluate cell type inside the biomaterial and the interface of biomaterial with pre-existing bone arrangement. In addition to identifying the gene expression of osteoblastic activity in the newly formed tissue in biopsy of third metacarpal bone following implantation of a castor oil/calcium carbonate biopolymer in horses. By this analysis it will be possible to confirm the osteogenic profile of newly formed tissue in the presence of biomaterial, which will allow its indication for use as a bone substitute in horses. (AU)