Fibroblast Attachment to Titanium Implants via Integrins: A Two Step Process

Objectives: Titanium implants effectively replace missing teeth. Surface modifications have been used to enhance implant osteointegration. Despite these innovations, little is known about how cells interact with modified titanium surfaces. This study aims to examine how mesenchymal cells attached to modified titanium surfaces.
Methods: Human periodontal ligament (PDL) and gingival fibroblasts were evaluated for their ability to survive and attach to three different commercially available implants; Dual thermo-etched titanium, hydroxyapatite coated dual transition surface and moderately rough titanium oxide layer with high crystallinity and a high phosphorus content. Cell attachment to modified titanium surfaces were examined for enhancement using serum proteins and inhibition using anti-integrin or anti-extracellular matrix molecule (ECM) antibodies.
Results: Cells attached to modified titanium implant surfaces in a time dependent manner over 24 hours, with no significant difference between the surface modifications examined. Cell attachment was dependent upon the presence of serum in the growth media. Serum is known to contain several ECM proteins, including; fibronection, fibrinogen, and vitronectin. Integrin β1 antibodies significantly inhibited cell attachment, while αVβ3 antibodies did not. Fibronectin/RGD dependent integrin receptor antibodies (αV and α5) inhibited early attachment (before 8 hours). In contrast, collagen dependent integrin receptor antibodies (α1 and α2) inhibited only later attachment (after 8 hours). Finally, laminin dependent integrin receptor antibodies (α3 and α6) failed to significantly inhibit cell attachment. In addition, fibronectin (and to a lesser extent fibrinogen) antibodies inhibited early cell attachment, while collagen Type I antibodies inhibited later attachment.
Conclusions: Cell attachments to titanium surfaces are at least partially modulated by integrin receptors via ECM proteins coating the titanium surfaces. Cell attachment can be broken down into 2 phases: (1) mediated by serum fibronectin/fibrinogen for the first 8 hours, and (2) mediated by collagens produced by the mesenchymal cells between 8 and 24 hours.