The role of calcium signalling in the chondrogenic response of mesenchymal stem cells to hydrostatic pressure

Abstract

The objective of this study was to elucidate the role of calcium (Ca ++) signalling in the chondrogenic response of mesenchymal stem cells (MSCs) to hydrostatic pressure (HP). MSCs were seeded into agarose hydrogels, subjected to HP or kept in free swelling conditions, and cultured either with or without pharmacological inhibitors of Ca ++ mobility and downstream targets. Chelating free Ca ++ , inhibiting voltage-gated calcium channels, and depleting intracellular calcium stores suppressed the beneficial effect of HP on chondrogenesis, indicating that Ca ++ mobility may play an important role in the mechanotransduction of HP. However, inhibition of stretch-activated calcium channels in the current experiment yielded similar results to the control group, suggesting that mechanotransduction of HP is distinct from loads that generate cell deformations. Inhibition of the downstream targets calmodulin, calmodulin kinase II, and calcineurin all knocked down the effect of HP on chondrogenesis, implicating these targets in MSCs response to HP. All of the pharmacological inhibitors that abolished the chondrogenic response to HP also maintained a punctate vimentin organisation in the presence of HP, as opposed to the mechanoresponsive groups where the vimentin structure became more diffuse. These results suggest that Ca ++ signalling may transduce HP via vimentin adaptation to loading.

Determinants of stem cell lineage differentiation toward chondrogenesis versus adipogenesis

“…Moreover, transient Ca 2+ exposure (5 mM) enhanced chondrogenesis while subsequent exposures to elevated Ca 2+ (5 mM) suppressed chondrogenic differentiation [154]. Calcium channels, which are regulated by physical stimuli, such as hydrostatic pressure, electrical stimulation and pulse electromagnetic fields, seemed to play a crucial role in chondrogenic differentiation of MSCs [154][155][156]. Voltage operated calcium channels, transient receptor potential channels and purinergic receptors have been reported to be regulated by physical stimuli [150,151,157,158].…”

Enhancement of mesenchymal stem cell chondrogenesis with short-term low intensity pulsed electromagnetic fields

“…Appropriately applied mechanical stimulation positively influences MSC-induced chondrogenic differentiation, ECM deposition and the mechanical properties of the generated cartilage 17 – 20 . At the cellular level the transduction of mechanical signals (mechanotransduction) involves their conversion into biochemical responses, often with the assistance of mechanosensitive calcium channels 21 – 24 . Electromagnetic field (EMF)-stimulation has been shown to promote cell differentiation via the modulation of extracellular calcium entry via plasma membrane-embedded cation channels 25 – 27 , raising the intriguing possibility that EMFs may be recruiting related pathways.…”

“…Here, we systematically characterized the effects of PEMF exposure over MSC chondrogenic differentiation by varying the field amplitude, exposure duration and dosage with an emphasis on determining the briefest and lowest amplitude electromagnetic exposure to render a developmental outcome. Given that both mechanical stimuli and calcium entry 21 , 22 influences chondrogenic differentiation, we investigated the ability of PEMF exposure to influence calcium homeostasis during early induction of MSCs into the chondrogenic lineage, in particular that attributed to the Transient Receptor Potential (TRP) family of cation-permeable channels, which has been broadly implicated in cellular mechanotransduction 23 , 44 . We show that brief and single exposures to low amplitude PEMFs were most effective at stimulating MSC chondrogenesis.…”

The Role of Physical Stimuli on Calcium Channels in Chondrogenic Differentiation of Mesenchymal Stem Cells

“…This collection of ion channels in chondrocytes is required for the efficient extracellular matrix (ECM) turnover and homeostasis. Chelating free Ca 2+ , inhibiting voltage-gated calcium channels, and depleting intracellular calcium stores suppressed the beneficial effect of hydrostatic pressure on chondrogenesis, indicating that Ca 2+ mobility might play an important role in the mechanotransduction of mechanical pressure [ 33 , 34 ]. During chondrogenic differentiation of MSCs, intracellular Ca 2+ is known to be involved in wide range of Ca 2+ sensitive signaling pathways, including various protein kinase systems, which may enable distinct gene expression profiles via differential activation of key transcription factors (NFAT, CREB, etc.…”