Superposition of nanostructures on microrough titanium–aluminum–vanadium alloy surfaces results in an altered integrin expression profile in osteoblasts

Abstract

Recent studies of new surface modifications that superimpose well-defined nanostructures on microrough implants, thereby mimicking the hierarchical complexity of native bone, report synergistically enhanced osteoblast maturation and local factor production at the protein level compared to growth on surfaces that are smooth, nanorough, or microrough. Whether the complex micro/nanorough surfaces enhance the osteogenic response by triggering similar patterns of integrin receptors and their associated signaling pathways as with well-established microrough surfaces, is not well understood. Human osteoblasts (hOBs) were cultured until confluent for gene expression studies on tissue culture polystyrene (TCPS) or on titanium alloy (Ti6Al4V) disks with different surface topographies: smooth, nanorough, microrough, and micro/nanorough surfaces. mRNA expression of osteogenesis-related markers such as osteocalcin (BGLAP) and bone sialoprotein (BSP), bone morphogenetic protein 2 (BMP2), BMP4, noggin (NOG) and gremlin 1 (GREM1) were all higher on microrough and micro/nanorough surfaces, with few differences between them, compared to smooth and nanorough groups. Interestingly, expression of integrins α1 and β2, which interact primarily with collagens and laminin and have been commonly associated with osteoblast differentiation on microrough Ti and Ti6Al4V, were expressed at lower levels on micro/nanorough surfaces compared to microrough ones. Conversely, the av subunit, which binds ligands such as vitronectin, osteopontin, and bone sialoprotein among others, had higher expression on micro/nanorough surfaces concomitantly with regulation of the β3 mRNA levels on nanomodified surfaces. These results suggest that the maturation of osteoblasts on micro/nanorough surfaces may be occurring through different integrin engagement than those established for microrough-only surfaces.

Participation of integrin β3 in osteoblast differentiation induced by titanium with nano or microtopography

“…Here, the integrin β3 silencing resulted in a concomitant decrease of the integrin αv gene expression only in cells cultured on nanotopography. Corroborating this finding and our observation of the key role of integrin β3 in the osteogenic induction of Ti with nanotopography, it has been shown that the integrin αvβ3 complex is upregulated on nanostructured surfaces …”

Bioactive treatment promotes osteoblast differentiation on titanium materials fabricated by selective laser melting technology

“…There have been many studies describing various nanostructures on titanium materials, and most of them have reported positive effects on osteoblast proliferation 39) . The superposition of nanoscale structures (pore diameter ranged between 20 nm and 180 nm) on a microrough surface (Sa=2.20) has been reported to provide the original surface with additional benefits including the enhancement of osteogenic gene expression 46) and modification of the expression profile of integrin subunits 47) of osteoblasts. Wettability has also been identified as an important factor affecting the control of osteogenic cell differentiation 48,49) .…”

Coordinated regulation of mesenchymal stem cell differentiation on microstructured titanium surfaces by endogenous bone morphogenetic proteins

“…However, others have found that Noggin suppression resulted in poorer BMP2-induced osteogenesis [43]. The ultimate outcome may also be influenced by surface nanotopography [44], the response of other cell types around the implant to BMP2, and prove to be context-dependent. Moreover, a number of mechanisms may be responsible for an apparent BMP2 enhancement when MSCs are cultured on microtextured Ti, including the expression of microRNAs that influence BMP2 pathways [45–47].…”