β‐TCP/Collagen Composite Scaffolds Facilitate Bone Remodeling in Vertebral Plate Fusion

ABSTRACT

β‐tricalcium phosphate (β‐TCP) is widely used as a bone substitute because of its biocompatibility, osteoconductivity, and biodegradability; however, its brittleness and limited adaptability to irregular bone surfaces may restrict its performance in spinal fusion. This study aimed to evaluate whether a β‐TCP/collagen composite scaffold could enhance osteogenesis and promote sustained bone remodeling in a sheep lumbar interlaminar fusion model. β‐TCP/collagen composite scaffolds and β‐TCP scaffolds were compared in vitro using MC3T3‐E1 osteogenic precursor cells. Cell adhesion, proliferation, apoptosis, extracellular matrix mineralization, and osteogenic differentiation were assessed by scanning electron microscopy, CCK‐8 assay, flow cytometry, alizarin red staining, alkaline phosphatase staining, RT‐qPCR, and western blotting. In vivo, β‐TCP and β‐TCP/collagen scaffolds were implanted into the L3–L4 and L4–L5 interlaminar spaces, respectively, in a self‐controlled sheep model. Bone formation and remodeling were evaluated by X‐ray, micro‐CT, and Van Gieson staining at 3, 5, and 8 months after surgery. The β‐TCP/collagen scaffold showed a porous collagen‐containing structure that supported greater MC3T3‐E1 cell spreading and pseudopod extension than β‐TCP alone. Cell proliferation on the β‐TCP/collagen scaffold was significantly increased from day 3, whereas apoptosis remained low in all groups, with apoptotic cells accounting for less than 5%. Alizarin red and alkaline phosphatase staining showed more pronounced extracellular matrix mineralization in the β‐TCP/collagen group. RT‐qPCR and western blotting further demonstrated enhanced expression of osteogenic markers in the β‐TCP/collagen group compared with β‐TCP alone. In the sheep lumbar interlaminar fusion model, radiological, and histological analyses showed more sustained new bone formation and more organized trabecular remodeling in the β‐TCP/collagen group. The β‐TCP/collagen composite scaffold enhanced osteogenic activity in vitro and promoted more sustained bone remodeling in a sheep lumbar interlaminar fusion model compared with β‐TCP alone. These findings suggest that β‐TCP/collagen scaffolds may provide a clinically relevant biomaterial strategy for posterior spinal fusion, although further studies are needed to clarify the mechanisms underlying scaffold‐mediated vascularized bone remodeling.