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. Author manuscript; available in PMC: 2013 Jun 12.
Published in final edited form as: Biomaterials. 2009 Jan 20;30(10):1898–1909. doi: 10.1016/j.biomaterials.2008.12.053

Figure 8. Model describing the effects of integrin-binding peptides on osseointegration of HA implants.

Figure 8

A) Integrin activation by adsorbed proteins, such as FN and VN, plays a key role in MSC adhesion, survival and osteoblastic differentiation. When RGD is present on the HA surface, we hypothesize that integrins such as αvβ3 bind the RGD rather than full-length FN or VN, leading to poor cell adhesion and survival. Collagen-binding integrins such as α2β1 would not likely be engaged with ligand, given that minimal amounts of collagen I would adsorb to the HA surface from blood (given that fibrillar collagen I is not abundant in blood). The combination of weak signaling from RGD-dependent integrins (e.g. αvβ3, α5β1, αIIbβ3), and a lack of signaling from collagen-selective integrins, is proposed to contribute to poor implant integration. B) Conversely, the presence of either DGEA or P15 on the HA surface provides a ligand for collagen-selective integrins that, upon activation, initiate signaling mechanisms promoting osteoblastic differentiation. As well, RGD-dependent integrins would engage the native FN, VN or Fbg adsorbed from blood, resulting in strong adhesive and survival signaling. Collectively, signaling from these multiple integrin species is hypothesized to enhance osseointegration of HA biomaterials.