Biomaterials 28 (2007) 2281–2293 Comparative response of epithelial cells and osteoblasts to microfabricated tapered pit topographies in vitro and in vivo Douglas W. Hamilton, Babak Chehroudi, Donald M. Brunette à Department of Oral, Biological and Medical Sciences, University of British Columbia, 2199 Wesbrook Mall, Vancouver, BC, Canada V6T 1Z3 Received 31 October 2006; accepted 23 January 2007 Available online 2 February 2007 Abstract Microfabricated tapered pits in vivo can stimulate connective tissue and bone attachment to percutaneous devices, secondarily preventing epithelial migration, and promoting long-term implant survival. Epithelial cells, which form a seal with a dental implant, acting as a barrier, and osteoblasts, which form bone, can come into contact with the same implant topography. To investigate whether the phenotypic characteristics of each cell type influenced cell response to micro-topography, we compared the response of the two cell types to the same dimensions of tapered pits, in vitro, and in vivo. Increased spreading, mature FAs, and restricted migration characterized individual PLE cell response to tapered pits. In contrast, osteoblasts were highly migratory, formed smaller, punctate adhesions and mineralized. Epithelial sheets formed from high-density PLE cultures demonstrated that tapered pits did not inhibit migration of the PLE sheets in vitro, similar to in vivo observations. In vitro, PLE sheet migration correlated with increases in vinculin, tyrosine phosphorylation, cytokeratin and ERK 1/2 phosphorylation. The findings of this study show that tapered pits stimulate osteoblast mineral deposition in vitro and in vivo, but do not prevent epithelial sheet migration. In vitro results suggest that epithelial sheet migration could involve altered FA mediated signal transduction. r 2007 Elsevier Ltd. All rights reserved. Keywords: Substratum topography; Dental implant; Osteoblasts; Epithelium; Osseointegration; Epithelial downgrowth 1. Introduction Upon placement in the jaw, a dental implant must successfully interface with at least three distinct cell populations, osteoblasts (bone), fibroblasts (connective tissue), and epithelium [1,2], at different regions along the long axis of the implant. Each cell type is specialized to perform a specific physiological function. Osteoblasts secrete matrix and mineral to form bone, and fibroblasts produce collagen rich connective tissue, with both tissues helping to anchor the implant. Epithelial cells attach at the dorsal interface of the tissue and implant, ideally forming a tight seal between the tissue and the implant surface. Inappropriate, as well as inadequate, adhesion of these three cell populations has been implicated in poor implant survival [2–5]. Failure of bone and connective tissue to form a tight seal to the implant can result in epithelial downgrowth, which can lead to deep pocket formation as well as possible avulsion of the implant, whereas an inadequate epithelial seal can lead to infection [3,6–8]. Therefore, identifying the surface features that enhance bone and connective tissue attachment to the implant, whilst, discouraging epithelial downward migration would be advantageous for optimizing implant longevity [2,3,7,9]. Advances in implant design have often focused on altering the micro-topography and chemistry of the implant surface [2,10–12]. In particular, implant surface topography has been identified as a potent modulator of bone and connective tissue attachment in vivo, as well as showing success in inhibiting epithelial downgrowth [4,6,7]. Chehroudi et al. [4], identified that both grooved substrata and tapered pits (TPs) could promote connective tissue attachment in vivo, which in turn reduced the level of epithelial downgrowth [4]. However, not all groove depths formed an absolute barrier to epithelial downward migra- tion, and inhibition of this downgrowth for times greater than 2 weeks seemed related more to the level of ARTICLE IN PRESS www.elsevier.com/locate/biomaterials 0142-9612/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2007.01.026 à Corresponding author. Tel.: +604 822 2994; fax: +604 822 3562. E-mail address: brunette@interchange.ubc.ca (D.M. Brunette).