Increased internal porosity and surface area of hydroxyapatite accelerates healing and compensates for low bone marrow mesenchymal stem cell concentrations in critically-sized bone defects

Abstract

For clinical treatment of skeletal defects, osteoinductive scaffolds must have the ability to conform to the unique geometry of the injury site without sacrificing biologically favorable properties, including porosity. This investigation seeks to combine the osteoinductive properties of porous hydroxyapatite (HA) scaffolds with the beneficial handling characteristics of granules or putties, while evaluating the effects of mesenchymal stem cell (MSC) concentration on the composite grafts' ability to regenerate bone in vivo. The results demonstrate that porous HA granules regenerate significantly larger volumes of bone compared to non-porous HA. Increased MSC concentrations in autologous bone marrow aspirate (BMA) contributed to greater bone regeneration. This effect was most predominant with non-porous HA. While the extent of bone regeneration using non-porous HA was strongly correlated with MSC concentration of the marrow, porous HA microparticles combined with autologous BMA were successful in faster treatment of critically-sized bone defects and with less dependence on the MSC concentration than non-porous HA.