Alkaline phosphatase-induced mineral deposition to anchor collagen fibrils to a solid surface

Reconstruction of tendon and ligament tissues requires proper attachment of the tissue-engineered construct to surrounding tissues. A problem of reconstructing collagen-rich tissues is that an in vitro engineered collagenous network containing fibroblasts will contract and detach from a solid surface. In vivo anchorage of soft connective tissues to mineralized tissues like bones and teeth is accomplished by embedding collagen fibrils into mineralized layers. Mineralization is partially the result of local activity of the enzyme alkaline phosphatase (ALP). In this study, we tested whether ALP-induced mineral deposition at the interface between a collagen gel and a polystyrene or polyetheretherketone (PEEK) surface could prevent gel detachment from the surface. Coating of culture wells with intestinal ALP prevented detachment of gels harbored with human periodontal ligament (PDL) fibroblasts in the presence of its substrate beta-glycerophosphate. Mineral deposition was observed predominantly at the interface of collagen gel and well surface. The contractile properties of fibroblasts were not influenced by either ALP, beta-glycerophosphate or both. The presence of ALP on a solid surface and providing its substrate to allow mineral deposition can prevent detachment of collagen matrices. Our findings provide a tool to induce attachment of fibrillar collagen to a solid surface; an approach that seems useful for reconstruction of load-bearing tissues and attachment of ligaments to implants.