Insights into the osteoblast precursor differentiation towards mature osteoblasts induced by continuous BMP-2 signaling

Abstract

SummaryMature osteoblasts are the cells responsible for bone formation and are derived from precursor osteoblasts. However, the mechanisms that control this differentiation are poorly understood. In fact, unlike the majority of organs in the body, which are composed of “soft” tissue from which cells can easily be isolated and studied, the “hard” mineralized tissue of bone has made it difficult to study the function of bone cells. Here, we established an in vitro model that mimics this differentiation under physiological conditions. We obtained mature osteoblasts and characterized them on the basis of the following parameters: the strong expression of osteoblastic markers, such as Runx2 and Col-I; the achievement of specific dimensions (the cell volume increases 26-fold compared to the osteoblast precursors); and the production of an abundant extracellular matrix also called osteoid. We demonstrated that the differentiation of osteoblast precursors into mature osteoblasts requires the continuous activation of Bone Morphogenetic Protein (BMP) receptors, which we established with the immobilization of a BMP-2mimetic peptide on a synthetic matrix mimicking in vivo microenvironment. Importantly, we demonstrated that the organization of the F-actin network and acetylated microtubules of the cells were modified during the differentiation process. We showed that the perturbation of the F-actin cytoskeleton organization abolished the differentiation process. In addition, we demonstrated that expression of the Runx2 gene is required for this differentiation. These findings demonstrate the retro-regulation of cytoplasmic and genic components due to the continuous induction of BMP-2 and also provide more detailed insights into the correct signaling of BMPs for cell differentiation in bone tissue.

Microtubule actin crosslinking factor 1 promotes osteoblast differentiation by promoting β‐catenin/TCF1/Runx2 signaling axis

“…Besides, cytoskeleton reorganization affects osteoblastic differentiation (Yourek, Hussain, & Mao, ). The perturbation of the F‐actin cytoskeleton organization abolished the osteoblast differentiation process (Zouani, Rami, Lei, & Durrieu, ) and transient dynamic actin cytoskeletal reorganization stimulated osteoblastic differentiation (Higuchi, Nakamura, Yoshikawa, & Itoh, ). Wang et al, have shown that cytoskeleton reorganization is involved in lanthanum‐promoted both osteoblast proliferation and differentiation (Wang, Huang, Zhang, & Wang, ).…”

The role of COX-2 in mediating the effect of PTEN on BMP9 induced osteogenic differentiation in mouse embryonic fibroblasts

“…Besides these, the microenvironment are also important for osteogenic differentiation [35,36]. BMPs belong to the TGF- b super-family and are considered to have critical roles not only in bone development [8,37] BMP9, also known as growth differentiation factor 2 (GDF2), has been reported as the most potential member of BMPs to promote osteogenic differentiation in MPCs [9], which can be used as an efficacious factor in tissue engineering together with suitable biomaterials for bone regeneration.…”

Membrane Nanowaves in Single and Collective Cell Migration

“…In the first example, we have developed a differentiation model and have characterized differentiated cells by using this superresolution wide-field optical profilometry microscopy technique. We have induced cell swelling and have demonstrated that the cell fixation method (which also involves gold or titanium deposition) does not alter the surface topography to any significant degree thus ruling out any artifacts [32], [44]. In a second example, we have developed another nanotopographical model for stem cell differentiation and have analyzed cell adhesion and collective cell organization by using the same superresolution technique.…”