Bone Marrow Derived Stem Cells versus Hydroxyapatite Nanopowder in Bone Regeneration of Albino Rats (Histological and Immunohistochemical study)

Abstract

Bone is a highly vascularized, innervated and mineralized connective tissue, which is structured in lamellae of calcified osteoid matrix. Bone comprises ofabout 67% inorganic and 33% organic material. The mineral component consists of calcium and phosphate in the form of hydroxyapatitecrystals. The organic material formed mainly of 90% type I collagen fibers lying in about 5% ground substance of non-collagenous proteins and osteogenic cells. Bone marrow stroma contains multipotential nonhematopoietic progenitor cells capable of differentiating into various tissues of mesenchymal origin.Bone marrow mesenchymal stem cells may differentiate into tissue cells in order to restore lost morphology as well as function and to secrete a wide spectrum of bioactive factors that help to create a repair environment through their antiapoptotic effects, immunoregulatory function and the stimulation of endothelial progenitor cell proliferation. Bioceramics(hydroxyappatite) have been extensively researched for use in engineered bone grafts. Nowadays HA is widely used in biomedical applications, including matrices to control drug release and material engineering of bone tissues based on the chemical similarities between HA and inorganic component of bone matrix,osteoconduction and bioresorptionproperties. So the aim of this study was todetect and compare the role of bone marrow derived mesenchymal stem cells and hydroxyapatite nanopowder in bone regeneration of bony defects in albino ratsand to be evaluated through: • Histological and immunohistochemical examination. • Histomorphometrical and statistical analysis. Eighty four adult male albino rats weighing between 150-200 grams were used in this study. Linear incision was performed to expose the bone surface of the middle third of the lateral surface of the right tibia. A monocortical bone defect was created by round dental approximately 3mm in diameter. Duringthe surgical operation the albino rats were into three main groups, twenty eight rats in each group as follows: 1-Control untreatedgroup (C G):In which the bone defectswere left untreated. 2-Bone marrow derivedmesenchymal stem cellstreatedgroup (BMSC):In which (BMSCs) were injected inside the bone defects. 3-Hydroxyapatite nanopowder treated group (HAp): In which hydroxyapatite nanopowder was applied inside the bone defect till its filling. Each group was further subdivided into four subgroups, seven rats in each as follows: Subgroup I:In which ratswere sacrificed one week postoperatively. Subgroup II:In which rats were sacrificed two weeks postoperatively. Subgroup III:In which rats were sacrificed three weeks postoperatively. Subgroup IV:In which rats were sacrificed four weeks postoperatively. At the end of the experimental period of each subgroup, rats were sacrificed and tibiae were dissected and fixed, then decalcifiedand prepared for paraffin embedding. Finally the sections were stained by hematoxylin and eosin,Masson trichrome andanti osteonectin for examination under light microscope. Histomorphometrical and statistical analysis were carriedfor each positive Masson trichrome and anti osteonectin stained section.