Growth factors produced by bone marrow stromal cells on nanoroughened titanium-aluminum-vanadium surfaces program distal MSCs into osteoblasts via BMP2 signaling

Abstract

Statement of Clinical Significance: There remains the need to develop materials and surfaces that can increase the rate of implant osseointegration. Though osteoanabolic agents, like bone morphogenetic protein (BMP), can provide signaling for osteogenesis, the appropriate design of implants can also produce an innate cellular response that may reduce or eliminate the need to use additional agents to stimulate bone formation. Studies show that titanium implant surfaces that mimic the physical properties of osteoclast resorption pits regulate cellular responses of bone marrow stromal cells (MSCs) by altering cell morphology, transcriptomes, and local factor production to increase their differentiation into osteoblasts without osteogenic media supplements required for differentiation of MSCs on tissue culture polystyrene (TCPS). The goal of this study was to determine how cells in contact with biomimetic implant surfaces regulate the microenvironment around these surfaces in vitro. Two different approaches were used. First, unidirectional signaling was assessed by treating human MSCs grown on TCPS with conditioned media from MSC cultures grown on Ti6Al4V biomimetic surfaces. In the second set of studies, bidirectional signaling was assessed by coculturing MSCs grown on mesh inserts that were placed into culture wells in which MSCs were grown on the biomimetic Ti6Al4V substrates. The results show that biomimetic Ti6Al4V surface properties induce MSCs to produce factors within 7 days of culture that stimulate MSCs not in contact with the surface to exhibit an osteoblast phenotype via endogenous BMP2 acting in a paracrine signaling manner.

Keywords: biomimetic; bone-implant interface; osteoblasts; spine; titanium.