Role of extracellular signal-regulated kinases (ERKs) on osteoblast and adipoblast phenotype expression of mesenchymal stem cells cultured on titanium with nanotopography

Abstract

Titanium (Ti) with nanotopography enhances bone formation in close contact with the implant surface, which is essential for osseointegration. Ti osseointegration may be affected by imbalances between osteogenic and adipogenic differentiation related to aging and diseases such as osteoporosis. The differentiation of bone marrow mesenchymal stem cells (BMMSCs) into either osteoblasts or adipoblasts is regulated by critical transcription factors runt-related transcription factor 2 (Runx2) and peroxide proliferator-activated receptor gamma (PPAR³), respectively. It has been shown that extracellular signal-regulated kinases (ERKs), specifically ERK 1/2, members of the mitogen-activated protein kinases (MAPKs) family, act as a switch for the reciprocal regulation of osteogenesis and adipogenesis by modulating Runx2 and PPAR³ expression and/or activity. Considering this, it is possible to hypothesize that the positive effect of Ti surfaces with nanotopography on osteogenesis is, at least partially, due to a modulation of ERK/Runx2/PPAR³ interactions and a consequent balance between osteoblast and idioblast phenotype expression of BMMSCs. To test this hypothesis, rat BMMSCs will be cultured in osteogenic and adipogenic medium on Ti surfaces with nanotopography and machined (untreated, control) for periods of up to 17 days, in the presence or absence of an inhibitor (PD98059) signaling pathway ERKs. The following parameters will be assessed: 1) gene expression of ERK1/2, Runx2, and PPAR³ in osteogenic and adipogenic cultures on day 10; 2) mineralized matrix formation by Alizarin red S staining at day 17 days in osteogenic cultures and 3) Oil red O Staining at day 17 in adipogenic cultures.(AU)