Altered Expression of ORAI and STIM Isoforms in Activated Human Cardiac Fibroblasts

Area of Science:

• Cardiovascular Biology
• Cellular Physiology
• Molecular Medicine

Background:

• Cardiac fibrotization, characterized by fibroblast activation and extracellular matrix accumulation, leads to cardiac stiffness in various heart diseases.
• The precise cellular mechanisms driving fibrotization remain incompletely understood, though calcium signaling pathways are implicated.
• Store-operated calcium entry (SOCE), mediated by STIM and Orai proteins, is a critical calcium influx pathway.

Purpose of the Study:

• To investigate the role of selected SOCE-associated genes in human cardiac fibroblast (HCF) activation.
• To evaluate the impact of cardiovascular overload stimuli (phenylephrine, isoprenaline) on SOCE gene expression and collagen production in HCFs.
• To determine if altered calcium homeostasis via SOCE contributes to fibroblast activation in pathological contexts.

Main Methods:

• Human cardiac fibroblast (HCF) cell culture was treated with phenylephrine and isoprenaline to simulate cardiovascular overload.
• Soluble collagen content in the cell medium was measured to assess fibroblast activation.
• Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to determine mRNA levels of STIM and Orai genes.

Main Results:

• Treatment with phenylephrine and isoprenaline led to increased expression of the Orai2 isoform.
• A significant change in the Orai1/Orai3 expression ratio was observed.
• The expression of the STIM2 isoform was also found to increase under simulated stress conditions.

Conclusions:

• The findings suggest enhanced activation of the SOCE mechanism in cardiac fibroblasts under stress conditions.
• Altered calcium homeostasis through the SOCE pathway may play a crucial role in fibroblast activation during pathological cardiac remodeling.
• This study supports the hypothesis that SOCE is a key player in cardiac fibrotization and the development of cardiac stiffness.