TGF‐β activity in acid bone lysate adsorbs to titanium surface

Abstract

Objectives Osteoblasts lay down new bone on implant surfaces. The underlying cellular mechanism and the spatio‐temporal mode of action, however, remain unclear. It can be proposed that growth factors released upon acidification by osteoclasts adsorb to the implant surface and control the early stages of osseointegration. Methods To simulate bone lysis by osteoclasts, titanium discs were exposed to acid bone lysate (ABL) followed by vigorous washing and seeding of oral fibroblasts. The expression of TGF‐β target genes interleukin 11 (IL11) and NADPH oxidase 4 (NOX4) was evaluated by reverse transcriptase polymerase chain reaction and IL11 ELISA. TGF‐β signaling activation was assessed via Smad2/3 immunofluorescence. The impact of ABL on osteogenic differentiation was determined with murine ST2 mesenchymal stromal cells. Results We report here that ABL‐conditioned titanium discs, independent of turned or rough surface, increased the expression of IL11 and NOX4. This increase was blocked by the TGF‐β receptor 1 antagonist SB431542. Further support for the TGF‐β signaling activation came from the translocation of Smad2/3 into the nucleus of oral fibroblasts. Moreover, titanium discs exposed to ABL decreased alkaline phosphatase and osteopontin in ST2 cells. Conclusions These in vitro findings suggest that titanium can adsorb TGF‐β from ABLs. The data provide a strong impetus for studies on the protein adsorption on implant surfaces in vitro and in vivo, specifically for growth factors including bone‐derived TGF‐β during successful and failed osseointegration.

TGFβ activity released from platelet-rich fibrin adsorbs to titanium surface and collagen membranes

“…Furthermore, we showed that PRF-derived TGF-β activity also adsorbs to titanium surfaces. This accords with our earlier observations, which showed that the bone-derived TGF-β activity binds to titanium surfaces 20 . Considering that PRF increases implant stability of dental implants at early stages 5,8 , PRF-derived TGF-β activity may play a critical role in the early phases of osseointegration 20 .…”

“…This was confirmed by using two independent TGF-β receptor kinase inhibitors thereby blocking the expression of IL11, NOX4 and PRG4. The activation of the Smad2/3 canonical signalling pathway by PRF corroborated our findings, which are in line with previous research on bone-derived TGF-β 20,23 . However, it is unlikely that TGF-β is the only growth factor in PRF lysates capable of inducing a cellular response.…”

“…Since PRF has been widely used during implant placement to boost osseointegration 5 we examined first whether the PRF-activity absorbs to titanium surfaces. Gingival fibroblasts were seeded onto titanium discs as previously described 20 . Titanium surfaces exposed to PRF followed by vigorous washings with buffered saline caused a robust gene expression of IL11, NOX4, and PRG4 in gingival fibroblasts (Fig.…”

“…PRF-derived growth factors such as TGF-β have been identified to adsorb to biomaterials including titanium 19,20 and collagen membranes 21,22 . The biological role of this binding nevertheless remains to be elucidated.…”

“…Thus, and since PRF is frequently combined with the aforementioned biomaterials, the question arises whether PRF-derived growth factors that cause the major changes in gene expression -adsorb to these biomaterials. We have therefore included a series of experiments, similar to our previous research with acid bone lysates 20,23 . In order to mimic a clinical situation in an in vitro setting, we examined whether the growth factors released by PRF activates mesenchymal cells bound to the respective biomaterials.…”