Building Osteogenic Microenvironments With Strontium-Substituted Calcium Phosphate Ceramics

Abstract

Bioceramics have experienced great development over the past 50 years. Modern bioceramics are designed to integrate bioactive ions within ceramic granules to trigger living tissue regeneration. Preclinical and clinical studies have shown that strontium is a safe and effective divalent metal ion for preventing osteoporosis, which has led to its incorporation in calcium phosphate-based ceramics. The local release of strontium ions during degradation results in moderate concentrations that trigger osteogenesis with few systemic side effects. Moreover, strontium has been proven to generate a favorable immune environment and promote early angiogenesis at the implantation site. Herein, the important aspects of strontium-enriched calcium phosphate bioceramics (Sr-CaPs), and how Sr-CaPs affect the osteogenic microenvironment, are described.

Keywords: biomaterials; bone regeneration; calcium phosphate ceramics; microenvironment; strontium substitution.

FIGURE 1

Schematic demonstrating the microenvironment of the host bone-implant interface. The degradation-precipitation reactions of bioactive Sr-CaPs modulate local ion concentrations and influence peripheral physiological processes, including ① hMSC osteogenic differentiation, ② immune responses such as macrophage polarization to M2, and ③ revascularization processes.

FIGURE 2

Hypothesis for osteogenic microenvironments of SrCaPs. The local ionic environment not only stimulates the osteoblastic differentiation of bMSCs but interacts with the inflammatory cells and vascular endothelial cells.