Downregulation of miR-542-3p contributes to apoptosis resistance in dermal fibroblasts from systemic sclerosis patients via Survivin overexpression.


 Downregulation of miR-542-3p contributes to apoptosis resistance in dermal fibroblasts from systemic sclerosis patients via Survivin overexpression: Systemic sclerosis (SSc) is characterized by excessive production of collagens by fibroblasts that leads to vast fibrosis. Resistance to apoptosis is one of the possible underlying mechanisms of fibrosis in these patients. Survivinis involved in inhibition of apoptosis and aberrantly functions in SSc. Since dysregulation of survivin-targeting microRNAs (miRNAs) has frequently been observed in cancer and some autoimmune disorders, this study aimed to investigate their expression status in dermal fibroblasts from SSc patients. DiffuseSSc patients were selected according to American College of Rheumatology criteria. Isolated fibroblasts from 10 SSc and 10 healthy skin biopsies were cultured. After examining purity of the cells, mRNA and miRNAs extraction was performed followed by complementary DNA (cDNA) synthesis. Relative expressions ofsurvivin mRNA, miR-16-5p, miR-320a, miR-218-5p, miR-708-5p and miR-542-3p were analyzed using real time PCR. Survivin mRNA expression was significantly 1.85-fold upregulated in fibroblasts from SSc patients compared with healthy controls (p=0.046). Among the studied miRNAs, miR-542-3p expression was significantly decreased (p=0.033), while enhanced expression of miR-708-5p was observed in SSc fibroblasts (p=0.05) in comparison to healthy subjects. Downregulation of miR-542-3p significantly correlated with survivin overexpression (r=˗0.45, p=0.049). Downregulation of miR-542-3p that is correlated with higher surviving expression levels might be a possible cause of apoptosis resistance in SSc fibroblasts, hence providing a new understanding of the disease pathogenesis.

INTRODUCTION; Downregulation of miR-542-3p contributes to apoptosis resistance

Systemic sclerosis (scleroderma, SSc) is an autoimmune fibrotic disorder that mostly affects the skin and internal organs with a progressive course and fatal outcome. 1,2 Although the exact etiology of SSc has not been characterized, it has been proposed that environmental factors through epigenetic bridge cause disease in genetically predisposed individuals. 3,4 Clinical manifestations of SSc include various vascular dysfunctions, immune abnormalities, and fibrosis, mediated by various molecules and pathways. 5,6 After tissue injury, fibroblasts tilt homeostasis towards producing collagens and differentiating into myofibroblasts.

In opposition to normal wound healing, which is terminated by tissue contraction and cell apoptosis, unknown stimuli keep fibroblasts activated with decreased susceptibility to apoptosis. Afterwards, excessive collagen production by these long-lived cells causes fibrosis in the affected tissues.

specific mediators

One of the specific mediators that is responsible fo apoptosis resistance is the inhibitor of apoptosis (IAP) protein family. IAP proteins are essential for cell survival by targeting caspase enzymes as central mediators in apoptosis pathways. Survivin (also known as BIRC5) is an IAP member and plays a dual role in promoting cell cycle and inhibiting apoptosis.

The critical role of survivin in cell division is inferred from its sharp expression at Gap2/Mitosis (G2/M) phases due to inactivation of a cell cycle regulator called cycli dependent kinase (Cdk) 4. Although the underlying mechanisms are unclear, studies have shown the apoptosis-regulating role of survivin.15Survivinhas gained much attention in SSc research16,17and previously unpublished data by our lab along with another findings pointed out to the higher survivin expression in these patients.

MicroRNAs; Downregulation of miR-542-3p contributes to apoptosis resistance

MicroRNAs (miRNAs) are small (about 22 nucleotides) noncoding RNAs that regulate their target mRNAs post-transcriptionally through degradation or translational repression. They exert their effects by binding to complementary sequences in 3′-untranslated regions (3′-UTR) of mRNAs. 19miRNAs have vastly been surveyed in autoimmunity. 4,20,21 Among the transcription factors, signaling molecules and ligands as well as other regulatory mechanisms of surviving expression, 22the role of miRNAs in survivin modulation has received increasing attention in the field of cancer23 and several critical survivin-targeting miRNAs have been identified to date.

The role of miR-218 in survivin regulation has been reported in lung, breast, and nasopharyngeal cancers.

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