ABSTRACT
Large-conductance Ca2+-activated K+ (BKCa) channels, activated by stress, exhibit mechanosensitivity and are involved in stress-regulated cellular function. For different types of cells, they will have different expression and activity changes due to their BKCa channels responding to different stress patterns. Correspondingly, the mechanism underling channel activation behaves differently, which is activated by the elevation in Ca2+ concentration or changes in membrane bilayer and cytoskeleton. In this review, the research progress in mechanosensitivity of BKCachannels was summarized from 3 aspects, including its molecular structure basis, manifestation and stress activation mechanism.
ABSTRACT
Cells are exposed to mechanical stress, such as fluid shear stress (FSS), mechanical strain, hydrostatic pressure in vivo. FSS is considered to be the most important stress during bone homeostasis and remodeling. At present, most studies are mainly about the FSS effect on osteocytes and osteoblasts. However, the effects of FSS on bone mesenchymal stem cell (BMSCs) are not fully understood. BMSCs are of great significance in bone reconstruction and clinical treatment, so researchers increasingly focus on the response of BMSCs to FSS. The response of BMSCs to FSS depends on the alteration of cytoskeleton, matrix stiffness and elasticity, osteogenic signaling pathways and so on. In this review paper, the recent researches about the mechanotransduction mechanism of FSS, and its effect on differentiation and function of BMSCs are summarized, so as to provide new insights for studying construction of tissue engineered bone and treatment of bone diseases.
ABSTRACT
Objective To explore the relation between prostaglandin E2(PGE2) and the mechanosensitivity of osteoblasts and to analyze its action mechanism in cellular level .Methods Osteoblasts cell line MC3T3-E1 cells were performed the pre-treatment by using 16 ,16-dimethyl prostaglandin E2(dmPGE2) .Then the regulating effect of PGE2 on intracellular calcium ion signal was ob-served;the activator agent and inhibitor of the protein kinase A (PKA) signal path were adopted to detect the participating effect of the PKA signal path in the regulating process .Results Compared with the blank treatment group ,dmPGE2 pre-treatment signifi-cantly increased the calcium ion signal intensity induced by hypotonic swelling stimulation in MC 3T3-E1 cells .This effect of dmPGE2 was mimicked by 8-bromo-cAMP(8br-cAMP) ,an activator of PKA pathway ;but blocked by PKI ,an inhibitor of PKA pathway .Conclusion dmPGE2 is able to up-regulate the calcium response induced by hypotonic swelling stimulation by activating PKA pathway ,which provides an important cellular mechanism for explaining PGE2′s anabolic effect in bone tissue .
ABSTRACT
Mechanical stress imposed by physical exercise is known to play an important role in increasing bone mass and preventing osteoporosis. As repetitional loadings may diminish mechano-sensitivity of bone cell, understanding shifts in mechano-sensitivity is important for making an effective training program for bones. The primary purpose of this study was to investigate bone responses when rats performed 400 repetitions of jump exercise in total using different training programs over 40 days. The secondary purpose was to clarify whether loading magnitude affects the results. This study comprised two experiments (EX1, EX2). In each experiment, 60 female Wistar rats (10-weeks-old) were divided into 1 sedentary group and 4 exercise groups. The 4 exercise groups were exercised with 10 jumps every day (10 jumps/day), 20 jumps every other day (20 jumps/2 days), 50 jumps every 5 days (50 jumps/5 days) or 100 jumps every 10 days (100 jumps/10 days). Jump height was set at 40 cm in EX1 and 30 cm in EX2. After 40 days, the 10 jumps/day, 20 jumps/2 days and 50 jumps/5 days groups in EX1 and EX2 showed significantly greater bone mass and strength compared to each sedentary group, although differences in training effects between these 3 groups were little. The 100 jumps/10 days group in EX1 also showed significantly greater bone mass and strength compared to the sedentary group, but the training effect was less. The 100 jumps/10 days group in EX2 did not show significantly greater bone mass and strength compared to the sedentary group. These results suggest that exercise everyday or every other day is not always necessary for bone development.