Low-Intensity Pulsed Ultrasound Stimulation Enhances Heat-Shock Protein 90 and Mineralized Nodule Formation in Mouse Calvaria-Derived Osteoblasts

Abstract

Low-intensity pulsed ultrasound (LIPUS) has demonstrated its positive effects on osteogenic differentiation of mesenchymal stem cells and the proliferation and differentiation of osteoblasts, negative effects on osteoclast growth, and promotion of angiogenesis, leading to improvement of the tissue perfusion. Heat-shock proteins (HSPs) are initially identified as molecules encouraged and expressed by heat stress or chemical stress to cells and involved in the balance between differentiation and apoptosis of osteoblasts. However, it remains unclear if the effect of LIPUS on osteoblast differentiation could involve HSP expression and contribution. In this study, mouse calvarial osteoblasts were exposed to LIPUS at a frequency of 3.0 MHz by 30 mW/cm 2 for 15 min or to 42°C heat shock for 20 min at day 3 of cell culture and examined for osteogenesis with pursuing induction of HSP27, HSP70, and HSP90. LIPUS as well as heat shock initially upregulated HSP90 and phosphorylation of Smad1 and Smad5, encouraging cell viability and proliferation at 24 h, enhancing mineralized nodule formation stronger by LIPUS after 10 days. However, HSP27, associated with BMP2-stimulated p38 mitogen-activated protein kinase during osteoblast differentiation, was downregulated by both stimulations at this early time point. Notably, these two stimuli maintained Smad1 phosphorylation with mineralized nodule formation even under BMP2 signal blockage. Therefore, LIPUS might be a novel inducer of osteoblastic differentiation through a noncanonical signal pathway. In conclusion, LIPUS stimulation enhanced cell viability and proliferation as early as 24 h after treatment, and HSP90 was upregulated, leading to dense mineralization in the osteoblast cell culture after 10 days.

Whole-brain low-intensity pulsed ultrasound therapy markedly improves cognitive dysfunctions in mouse models of dementia - Crucial roles of endothelial nitric oxide synthase

“…Although the total number of Iba-1-positive microglia decreased by LIPUS, phagocytosis was rather enhanced in the LIPUS-treated group. Besides, Hsp 90, which is known to inhibit aggregation of Ab [28], was enhanced by LIPUS in the present study, a consistent finding of the previous study [29]. Hsp 90 is promptly recruited by endothelial stimulation of shear stress induced by ultrasonic waves, and enhances eNOS activation [30].…”

“…In the present study, the expression of APP and BACE-1 were significantly decreased by the LIPUS therapy, and Ab was significantly reduced in triton-soluble fraction and histological assessment. Regarding the mechanism of unchanged TBS soluble Ab levels, Ab is known to dissolve in a monomer form at concentrations lower than 3 mM, whereas it aggregates at concentrations higher than 3 mM [29]. In the present study, although the total amount of Ab was actually decreased by LIPUS treatment, more amount of Ab was produced than the amount that could dissolve in extracellular fluid.…”

Osteoking improves OP rat by enhancing HSP90‑β expression

“…By contrast, an HSP90-β inhibitor inhibited tumor growth through apoptosis, inducing cell cycle arrest and downregulating target proteins (38,39). In addition, HSP90-β has been demonstrated to regulate bone metabolism (40).…”

Low‐intensity pulsed ultrasound accelerates nerve regeneration following inferior alveolar nerve transection in rats

“…Recent studies have reported that exposure to low‐intensity pulsed ultrasound (LIPUS) accelerates tissue regeneration as a result of enhanced blood circulation, resulting in an acceleration of wound or fracture healing and induction of angiogenesis . Numerous phenomenological studies have shown that a variety of cellular events occur in injured tissues following exposure to LIPUS.…”