Cellular interactions and gene expression analysis of two equine-derived bone graft materials: an in vitro study

Bone grafting is a surgical procedure that involves the use of bone tissue or bone substitutes to repair damaged bone. In dentistry and maxillofacial surgery, bone graft substitutes from various sources are commonly used. Given their critical role in clinical outcomes, it is essential to thoroughly investigate the biological and mechanical properties of these materials.

In this in vitro study, we evaluated the biological properties of two equine-derived bone graft substitutes in comparison to β-tricalcium phosphate. The materials included one equine-derived graft containing hydrolyzed type I collagen and another containing preserved type I collagen. To assess their biological performance, we analyzed cell viability, adhesion, osteogenic differentiation, and the expression of genes involved in bone remodeling.

All graft substitutes demonstrated similarly good biocompatibility. However, in the β-tricalcium phosphate group, intergranular tissue fibers or extracellular matrix were absent both before and after osteogenic differentiation. In contrast, cells cultured on the equine-derived graft containing hydrolyzed type I collagen exhibited intergranular tissue fibers and matrix, while those on the graft containing preserved type I collagen showed intergranular tissue fibers, individual cells, and matrix. Gene expression analysis suggested that β-tricalcium phosphate may undergo faster resorption kinetics compared to the equine-derived grafts, which were associated with gene expression patterns indicative of enhanced bone formation.

Our results suggest that both hydrolyzed and preserved type I collagen support bone matrix deposition more effectively than β-tricalcium phosphate, with preserved collagen demonstrating superior performance. From a clinical perspective, preserved collagen appears to be the optimal choice for larger or less contained bone defects, as it promotes faster cell repopulation and may lead to more rapid remodeling with the patient's own vital bone. In contrast, hydrolyzed collagen seems to elicit a slower cellular response and may be better suited for smaller, localized defects where immediate biological activity is less critical. Further research is essential to guide clinicians in selecting the most appropriate bone graft substitute based on the specific clinical context.