Search

Lipoteichoic acid (LTA) and lipopolysaccharide (LPS) are cell wall components of Gram-positive and Gram-negative bacteria, respectively. Notably, oral microflora consists of a variety of bacterial species, and osteomyelitis of the jaw caused by dental infection presents with symptoms of bone resorption and osteosclerosis. However, the effects of LTA and LPS on osteogenic differentiation have not yet been clarified. We examined the effects of LTA and LPS on osteoblasts and found that LTA alone promoted alizarin red staining at low concentrations and inhibited it at high concentrations. Additionally, gene expression of osteogenic markers (ALP, OCN, and OPG) were enhanced at low concentrations of LTA. High concentrations of LPS suppressed calcification potential, and the addition of low concentrations of LTA inhibited calcification suppression, restoring the gene expression levels of suppressed bone differentiation markers (ALP, BSP, and OCN). Moreover, the suppression of p38, a signaling pathway associated with bone differentiation, had opposing effects on gene-level expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), suggesting that mixed LTA and LPS infections have opposite effects on bone differentiation through concentration gradients, involving inflammatory markers (TNF-α and IL-6) and the p38 pathway.

Mesenchymal Stem Cells (MSCs) are pluripotent cells that can be differentiated as osteoblasts, adipocytes, myocytes or chondrocytes depending on the culture condition. However, MSCs are known to lose their differentiation potency after long-term culture. Development of a new cell culture method to maintain their stemness is required for successful application of MSCs. Here, we revealed that low-intensity pulsed ultrasound (LIPUS) stimulation was useful for maintaining the MSC stemness as LIPUS inhibited the loss of osteogenic differentiation potency of osteo-progenitor cells induced by serial subculture. LIPUS also increased the transcriptional and phosphorylation level of Nanog, a crucial stem cell marker gene in a MSC cell line. We also found that LIPUS induced the secretion of extracellular adenosine triphosphate (ATP) in MSC. The treatments of the conditioned medium from LIPUS-stimulated MSC and exogenous ATP promoted Nanog expression. Thus, LIPUS may maintain the long-term differentiation potency of MSCs and osteo-progenitor cells by induction in Nanog transcript level and phosphorylation.

Mesenchymal Stem Cells (MSCs) are pluripotent cells with the capability of self-renewal. It has been established that MSCs can transform into osteoblasts, adipocytes or chondrocytes depending on the culture condition. Regenerative medicine is considered to become an essential therapy in the field of