Synergistically regulated spontaneous calcium signaling is attributed to cartilaginous extracellular matrix metabolism

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Abstract
Ca2+ has been recognized as a key molecule for chondrocytes, however, the role and mechanism of spontaneous [Ca 2+] i signaling in cartilaginous extracellular matrix (ECM) metabolism regulation are unclear. Here we found that spontaneous Ca 2+ signal of in‐situ porcine chondrocytes was [Ca 2+] o dependent, and mediated by [Ca 2+] i store release. T‐type voltage‐dependent calcium channel (T‐VDCC) mediated [Ca 2+] o influx was associated with decreased cell viability and expression levels of ECM deposition genes. Further analysis revealed that chondrocytes expressed both inositol 1,4,5‐trisphosphate receptor (InsP3R) and Orai isoforms. Inhibition of endoplasmic reticulum (ER) Ca 2+ release and store‐operated calcium entry significantly abolished spontaneous [Ca 2+] i signaling of in‐situ chondrocytes. Moreover, blocking ER Ca 2+ release with InsP3R inhibitors significantly upregulated ECM degradation enzymes production, and was accompanied by decreased proteoglycan and collagen type II intensity. Taken together, our data provided evidence that spontaneous [Ca 2+] i signaling of in‐situ porcine chondrocytes was tightly regulated by [Ca 2+] o influx, InsP3Rs mediated [Ca 2+] i store release, and Orais mediated calcium release‐activated calcium channels activation. Both T‐VDCC mediated [Ca 2+] o influx and InsP3Rs mediated ER Ca 2+ release were found crucial to cartilaginous ECM metabolism through distinct regulatory mechanisms.
Funding Information
  • China Postdoctoral Science Foundation (2018M633690)
  • Chongqing Postdoctoral Science Foundation (Xm2017078)
  • National Natural Science Foundation of China (81572107, 31800784)

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