Cross-linking of collagen I by tissue transglutaminase provides a promising biomaterial for promoting bone healing

Transglutaminases (TGs) stabilize proteins by the formation of epsilon(gamma-glutamyl)lysine cross-links. Here, we demonstrate that the cross-linking of collagen I (COL I) by tissue transglutaminase (TG2) causes an alteration in the morphology and rheological properties of the collagen fibers. Human osteoblasts (HOB) attach, spread, proliferate, differentiate and mineralize more rapidly on this cross-linked matrix compared to native collagen. When seeded on cross-linked COL I, HOB are more resistant to the loss of cell spreading by incubation with RGD containing peptides and with alpha 1, alpha 2 and beta 1 integrin blocking antibodies. Following adhesion on cross-linked collagen, HOB show increased phosphorylation of the focal adhesion kinase, and increased expression of beta 1 and beta 3 integrins. Addition of human bone morphogenetic protein to HOB seeded on TG2 cross-linked COL I enhanced the expression of the differentiation marker bone alkaline phosphatase when compared to cross-linked collagen alone. In summary, the use of TG2-modified COL I provides a promising new scaffold for promoting bone healing.