Facile distribution of an alkaline microenvironment improves human bone marrow mesenchymal stem cell osteogenesis on a titanium surface through the ITG/FAK/ALP pathway

Purpose

Osseointegration at the titanium surface-bone interface is one of the key factors affecting the success rate of dental implants. However, the titanium surface always forms a passive oxide layer and impacts bone marrow–derived mesenchymal stem cell (BMSC) osteogenic differentiation after exposure to the atmosphere, which further leads to poor osseointegration. Given that wet storage helps prevent titanium aging and that weakly alkaline conditions stimulate BMSC osteogenic differentiation, the aim of the present study was to explore whether sodium bicarbonate, a well-known hydrogen ion (pH) buffer, forms an alkaline microenvironment on titanium surfaces to promote BMSC osteogenic differentiation.

Material and methods

In this work, sand-blasted and acid-etched (SLA) titanium discs were soaked in 20 mM, 50 mM, 100 mM, and 200 mM sodium bicarbonate at room temperature for 5 min without rinsing. The influence of this surface modification on BMSC adhesion, proliferation, and osteogenic differentiation was measured. Additionally, cellular osteogenic differentiation–associated signaling pathways were evaluated.

Results

We showed that titanium discs treated with sodium bicarbonate created an extracellular environment with a higher pH for BMSCs than the normal physiological value for 5 days, strongly promoting BMSC osteogenic differentiation via the activation of integrin-focal adhesion kinase-alkaline phosphatase (Itg-FAK-ALP). In addition, the proliferation and adhesion of BMSCs were increased after alkaline treatment. These cellular effects were most significant with 100 mM sodium bicarbonate.

Conclusion

The results indicated that the titanium surface treated with sodium bicarbonate improved BMSC osteogenic differentiation mainly by creating an alkaline microenvironment, which further activated the Itg-FAK-ALP signaling pathway.

Clinical relevance

Surfaces modified with 100 mM sodium bicarbonate had the highest initial pH value and thus showed the greatest potential to improve BMSC performance on titanium surfaces, identifying a novel conservation method for dental implants.

Positive role of calcium phosphate ceramics regulated inflammation in the osteogenic differentiation of mesenchymal stem cells

Recently, researches have confirmed the crucial role of inflammatory response in Ca-P ceramic-induced osteogenesis, however, the underlying mechanism has not yet been fully understood. In this study, BCP and β-TCP ceramics were used as material models to investigate the effect of physicochemical properties on inflammatory response in vitro. The results showed that BCP and β-TCP could support macrophages attachment, proliferation, and spreading favorably, as well as promote gene expressions of inflammatory related cytokines (IL-1, IL-6, MCP-1, and TNF-α) and growth factors (TGF-β, FGF, PDGF, VEGF, IGF, and EGF). BCP showed a facilitating function on the gene expressions earlier than β-TCP. Further coculture experiments performed in vitro demonstrated that the CMs containing various increased cytokines for macrophages pre-culture could significantly promote MSCs osteogenic differentiation, which was confirmed by the gene expressions of osteogenic specific markers and the intracellular OCN product accumulation under the stimulation of BCP and β-TCP ceramics. Further evidence was found from the formation of mineralized nodules in BCM and TCM. In addition, this study showed a concise relationship between Ca-P ceramic induced inflammation and its osteoinductivity that the increased cytokines and growth factors from macrophages could promote MSCs osteogenic differentiation.

A critical review of multifunctional titanium surfaces: New frontiers for improving osseointegration and host response, avoiding bacteria contamination

Evolution of metal implants progressively shifted the focus from adequate mechanical strength to improved biocompatibility and absence of toxicity and, finally, to fast osseointegration. Recently, new frontiers and challenges of Ti implants have been addressed to improvement of bioactivity, fighting of bacterial infection and biofilm formation, as well as modulation of inflammation. This is closely related to the clinical demand of multifunctional implants able to simultaneously have a number of specific responses with respect to body fluids, cells (osteoblasts, fibroblasts, macrophages) and pathogenic agents (bacteria, viruses). This complex system of multiple biological stimuli and surface responses is a major arena of the current research on biomaterials and biosurfaces. This review covers the strategies explored to this purpose since 2010 in the case of Ti and Ti alloys, considering that the number of related papers doubled about in the last seven years and no review has comprehensively covered this engaging research area yet. The different approaches followed for producing multifunctional Ti-based surfaces involve the use of thick and thin inorganic coatings, chemical surface treatments, and functionalization strategies coupled with organic coatings.

STATEMENT OF SIGNIFICANCE

According to the clinical demand of multifunctional implants able to simultaneously have a number of specific responses with respect to body fluids, cells and pathogenic agents, new frontiers of Ti implants have been addressed to improvement of bioactivity, fighting of bacterial infection and biofilm formation, as well as modulation of inflammation. Literature since 2010 is here reviewed. Several strategies for getting bioactive and antibacterial actions on Ti surfaces have been suggested, but they still need to be optimized with respect to several concerns. A further step will be to combine on the same surface a proven ability of modulation of inflammatory response. The achievement of multifunctional surfaces able to modulate inflammation and to promote osteogenesis is a grand challenge.

Enhanced osteoblast adhesion on amino-functionalized titanium surfaces through combined plasma enhanced chemical vapor deposition (PECVD) method

A combined PECVD method has been developed to introduce amino-groups onto titanium implants for the better improvement of osseointegration.