Mechanical strain induces a pro-fibrotic phenotype in human mitral valvular interstitial cells through RhoC/ROCK/MRTF-A and Erk1/2 signaling pathways

Abstract

The mitral valve is a complex multilayered structure populated by fibroblast-like cells, valvular interstitial cells (VIC) which are embedded in an extracellular matrix (ECM) scaffold and are submitted to the mechanical deformations affecting valve at each heartbeat, for an average of 40 million times per year. Myxomatous mitral valve (MMV) is the most frequent heart valve disease characterized by disruption of several valvular structures due to alterations of their ECM preventing the complete closure of the valve resulting in symptoms of prolapse and regurgitation. VIC and their ECM exhibit reciprocal dynamic processes between the mechanical signals issued from the ECM and the modulation of VIC phenotype responsible for ECM homeostasis of the valve. Abnormal perception and responsiveness of VIC to mechanical stress may induce an inappropriate adaptative remodeling of the valve progressively leading to MMV. To investigate the response of human VIC to mechanical strain and identify the molecular mechanisms of mechano-transduction in these cells, a cyclic equibiaxial elongation of 14% at the cardiac frequency of 1.16 Hz was applied to VIC by using a Flexercell-4000 T™ apparatus for increasing time (from 1 h to 8 h). We showed that cyclic stretch induces an early (1 h) and transient over-expression of TGFβ2 and αSMA. CTGF, a profibrotic growth factor promoting the synthesis of ECM components, was strongly induced after 1 and 2 h of stretching and still upregulated at 8 h. The mechanical stress-induced CTGF up-regulation was dependent on RhoC, but not RhoA, as demonstrated by siRNA-mediated silencing approaches, and further supported by evidencing RhoC activation upon cell stretching and suppression of cell response by pharmacological inhibition of the effector ROCK1/2. It was also dependent on the MEK/Erk1/2 pathway which was activated by mechanical stress independently of RhoC and ROCK. Finally, mechanical stretching induced the nuclear translocation of myocardin related transcription factor-A (MRTF-A) which forms a transcriptional complex with SRF to promote the expression of target genes, notably CTGF. Treatment of stretched cultures with inhibitors of the identified pathways (ROCK1/2, MEK/ Erk1/2, MRTF-A translocation) blocked CTGF overexpression and abrogated the increased MRTF-A nuclear translocation. CTGF is up-regulated in many pathological processes involving mechanically challenged organs, promotes ECM accumulation and is considered as a hallmark of fibrotic diseases. Pharmacological targeting of MRTF-A by newly developed inhibitors may represent a relevant therapy for MMV.

The distinct roles of myosin IIA and IIB under compression stress in nucleus pulposus cells

“…50 Another study demonstrated that mechanical strain induced the nuclear translocation of MRTF-A and a pro-fibrotic phenotype in human mitral valvular interstitial cells. 51 A recent study revealed that NP cells in stiff substrate appeared spread and fibrotic shape opposed to the round shape in soft matrix. 52 In addition, matrix stiffness increased nu- The RhoA/ROCK pathway is known to act as a prominent player in mechanical signals and remodelling of the actomyosin F I G U R E 5 Distinct effects of myosin IIA or IIB knockdown on compression stress-induced human NP cells senescence.…”

MicroRNA‑199a‑5p suppresses cell proliferation, migration and invasion by targeting ITGA3 in colorectal cancer

“…The genome profile stability serves a crucial role in the maintenance of human health. Emerging evidence has indicated that the dysregulation of gene expression occurs in multiple diseases, such as cardiovascular disease ( 1 ), Parkinson's disease ( 2 ) and malignant tumors ( 3 , 4 ). Colorectal cancer (CRC) is a common malignant disease of the gastrointestinal tract; the incidence and mortality of CRC has been steadily declining for the past two decades ( 5 ), with an exception of younger adults (<50 years), which is possibly related to an increase in cancer screening and improved therapeutic modalities ( 5 ).…”

Cyclic Stretch Induces Vascular Smooth Muscle Cells to Secrete Connective Tissue Growth Factor and Promote Endothelial Progenitor Cell Differentiation and Angiogenesis

“…It has been shown that mechanical stretching increased the amount of CTGF secretion in anterior cruciate ligamentderived cells (Miyake et al, 2011), indicating that CTGF is a mechano-sensitive molecule. Blomme et al reported that valvular interstitial cells showed the significant upregulation of CTGF at 1.15 Hz (heart frequency) and 14% elongation mechanical stretch, which was promoted through RhoC and MEK/Erk signaling pathways (Blomme et al, 2019). Additionally, in our previous study, we found that pathological cyclic stretch induces vascular remodeling by promoting VSMC proliferation via the miR-19b-3p/CTGF pathway (Wang et al, 2019).…”