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Substrate rigidity regulates Ca2+ oscillation via RhoA pathway in stem cells.

ABSTRACT: Substrate rigidity plays crucial roles in regulating cellular functions, such as cell spreading, traction forces, and stem cell differentiation. However, it is not clear how substrate rigidity influences early cell signaling events such as calcium in living cells. Using highly sensitive Ca(2+) biosensors based on fluorescence resonance energy transfer (FRET), we investigated the molecular mechanism by which substrate rigidity affects calcium signaling in human mesenchymal stem cells (HMSCs). Spontaneous Ca(2+) oscillations were observed inside the cytoplasm and the endoplasmic reticulum (ER) using the FRET biosensors targeted at subcellular locations in cells plated on rigid dishes. Lowering the substrate stiffness to 1 kPa significantly inhibited both the magnitudes and frequencies of the cytoplasmic Ca(2+) oscillation in comparison to stiffer or rigid substrate. This Ca(2+) oscillation was shown to be dependent on ROCK, a downstream effector molecule of RhoA, but independent of actin filaments, microtubules, myosin light chain kinase, or myosin activity. Lysophosphatidic acid, which activates RhoA, also inhibited the frequency of the Ca(2+) oscillation. Consistently, either a constitutive active mutant of RhoA (RhoA-V14) or a dominant negative mutant of RhoA (RhoA-N19) inhibited the Ca(2+) oscillation. Further experiments revealed that HMSCs cultured on gels with low elastic moduli displayed low RhoA activities. Therefore, our results demonstrate that RhoA and its downstream molecule ROCK may mediate the substrate rigidity-regulated Ca(2+) oscillation, which determines the physiological functions of HMSCs.

SUBMITTER: Kim TJ

PROVIDER: S-EPMC2592496 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature

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Substrate rigidity regulates Ca2+ oscillation via RhoA pathway in stem cells.

Kim Tae-Jin TJ Seong Jihye J Ouyang Mingxing M Sun Jie J Lu Shaoying S Hong Jun Pyu JP Wang Ning N Wang Yingxiao Y

Journal of cellular physiology 20090201 2

Substrate rigidity plays crucial roles in regulating cellular functions, such as cell spreading, traction forces, and stem cell differentiation. However, it is not clear how substrate rigidity influences early cell signaling events such as calcium in living cells. Using highly sensitive Ca(2+) biosensors based on fluorescence resonance energy transfer (FRET), we investigated the molecular mechanism by which substrate rigidity affects calcium signaling in human mesenchymal stem cells (HMSCs). Spo ...[more]

PMID: 18844232

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Project description:Abstract Background Melatonin (MEL), an endogenous hormone, has been widely investigated in neurological diseases. Microglia (MG), a resident immunocyte localizing in central nervous system is reported to play important functions in the animal model of temporal lobe epilepsy (TLE). Some evidence showed that MEL influenced activation of MG, but the detailed model of action that MEL plays in remains uncertain. Methods In this study, we established a model of TLE in mice by stereotactic injection of kainic acid (KA). We treated the mice with MEL. Lipopolysaccharide, ROCK2‐knockdown (ROCK‐KD) and ‐overexpression (ROCK‐OE) of lentivirus‐treated cells were used in cell experiments to simulate an in vitro inflammatory model. Results The results of electrophysiological tests showed that MEL reduced frequency and severity of seizure. The results of behavioral tests indicated MEL improved cognition, learning, and memory ability. Histological evidences demonstrated a significant reduction of neuronal death in the hippocampus. In vivo study showed that MEL changed the polarization status of MG from a proinflammatory M1 phenotype to an anti‐inflammatory M2 phenotype by inversely regulating the RhoA/ROCK signaling pathway. In cytological study, we found that MEL had a significant protective effect in LPS‐treated BV‐2 cells and ROCK‐KD cells, while the protective effect of MEL was significantly attenuated in ROCK‐OE cells. Conclusion MEL played an antiepileptic role in the KA‐induced TLE modeling mice both in behavioral and histological levels, and changed MG polarization status by regulating the RhoA/ROCK signaling pathway. 1. Melatonin (MEL) reduces frequency and severity of seizure. 2. MEL regulates the ROCK2 signaling pathway rather than ROCK1 to promote microglial polarization toward an anti‐inflammatory direction. 3. RhoA/ROCK2 signaling pathway might be a potential mechanism in the status epilepticus modeling mice. Highlights • Melatonin (MEL) reduces frequency and severity of seizure.• MEL regulates the ROCK2 signaling pathway rather than ROCK1 to promote microglial polarization toward an anti‐inflammatory direction.• RhoA/ROCK2 signaling pathway may be important in the temporal lobe epilepsy modeling mice.

Project description:BackgroundHeat shock protein B7 (HSPB7), which belongs to small heat shock protein family, has been reported to be involved in diverse biological processes and diseases. However, whether HSPB7 regulates osteogenic differentiation of human adipose derived stem cells (hASCs) remains unexplored.MethodsThe expression level of HSPB7 during the osteogenesis of hASCs was examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analysis. Lentivirus transfection was used to knock down or overexpress HSPB7, which enabled us to investigate the effect of HSPB7 on osteogenic differentiation of hASCs. U0126 and extracellular signal-regulated protein kinase 1/2 (ERK1/2) siRNA were used to identify the mechanism of the HSPB7/ERK1/2 axis in regulating osteogenic differentiation of hASCs. Moreover, ectopic bone formation in nude mice and osteoporosis mice model was used to investigate the effect of HSPB7 on osteogenesis in vivo.ResultsIn this study, we found the expression of HSPB7 was significantly downregulated during the osteogenic differentiation of hASCs. HSPB7 knockdown remarkably promoted osteogenic differentiation of hASCs, while HSPB7 overexpression suppressed osteogenic differentiation of hASCs both in vitro and in vivo. Moreover, we discovered that the enhancing effect of HSPB7 knockdown on osteogenic differentiation was related to the activation of extracellular signal-regulated protein kinase (ERK) signaling pathway. Inhibition of ERK signaling pathway with U0126 or silencing ERK1/2 effectively blocked the stimulation of osteogenic differentiation induced by HSPB7 knockdown. Additionally, we found that HSPB7 expression was markedly increased in mouse bone marrow mesenchymal stem cells (mBMSCs) from the osteoporotic mice which suggested that HSPB7 might be utilized as a potential target in the development of effective therapeutic strategies to treat osteoporosis and other bone diseases.ConclusionTaken together, these findings uncover a previously unrecognized function of HSPB7 in regulating osteogenic differentiation of hASCs, partly via the ERK signaling pathway.

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Substrate rigidity regulates Ca2+ oscillation via RhoA pathway in stem cells.

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Substrate rigidity regulates Ca2+ oscillation via RhoA pathway in stem cells.

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