Abbreviations
AngII: angiotensin II
Col: collagen
CTGF: connective tissue growth factor
CVF: collagen volume fraction
ECM: extracellular matrix
EZH2: enhancer of zeste homolog 2
GAPDH: glyceraldehyde-3-phosphate dehydrogenase
H&E: hematoxylin-eosin
LD: lumen diameter
miR: microRNA
MT: media thickness
MuT: mutant-type
OD: optical density
PBS: phosphate buffered saline
PCNA: proliferating cell nuclear antigen
p-Smad3: phospho-Smad3
qRT-PCR: quantitative real-time PCR
rAAV: recombinant adeno-associated virus
SBP: systolic blood pressure
SHR: spontaneously hypertensive rat
siRNA: small interfering RNA
VR: vascular remodeling
VSMC: vascular smooth muscle cell
WKY: Wistar Kyoto rat
Introduction
Vascular remodeling (VR) persists throughout the course of hypertension and is characterized by chronic, continuous, and complex changes in vascular structure and abnormalities in vascular functions (Hayashiet al. , 2009; Lemarie et al. , 2010; Zhang et al. , 2019). VR, as an important indicator of the progression of hypertension, is closely related to the severity and prognosis of the disease (Mulvany, 2012; Magnussen, 2017; Brown et al. , 2018). Angiotensin II (AngII)-induced dysfunction of vascular smooth muscle cells (VSMCs) plays a critical role in hypertensive VR (Das et al. , 2018), but the potential molecular mechanisms remain poorly understood. Therefore, study of new therapeutic targets for hypertensive VR and exploring potential molecular mechanisms are of benefit.
MicroRNAs (miRs) are highly conserved, small non-coding RNAs that modulate the function of VSMCs, such as their proliferation, differentiation, and migration (Chen et al. , 2018a; Chen et al. , 2018b; Wang et al. , 2019a; Wang et al. , 2019b). Moreover, miR expression is highly related to vascular remodeling and angiogenesis (Henn et al. , 2019). Cai et al. found that miR-24 attenuated VR under diabetic conditions (Cai et al. , 2019). Downregulation of miR‐224 aggravated VR in acute coronary syndrome (Xu et al. , 2019). MiR-1 overexpression mitigated pulmonary VR, thereby protecting against the progression of pulmonary hypertension (Sysol et al. , 2018).
MiR-26a, a highly conserved post-transcriptional regulator, can inhibit the proliferation and migration of VSMCs after vascular injury (Tanet al. , 2017) and protect VSMCs against oxidative stress (Penget al. , 2018). Thus, miR-26a may be a therapeutic target for vascular dysfunction. Moreover, the serum level of mir-26a was found altered in patients with hypertension (Yang et al. , 2018). However, the role and molecular mechanisms of miR-26a in hypertensive VR need to be clarified.
Our research aimed to elucidate the role of miR-26a in hypertensive VR and to reveal the potential miR-dependent mechanisms. We present evidence that miR-26a plays a protective role in hypertensive VR. AngII-activated Smad3 inhibited miR-26a expression, which in turn promoted Smad3 activation by targeting Smad4, thereby forming a Smads/miR-26a positive feedback loop and further downregulating miR-26a. Downregulation of miR-26 further led to VR by promoting connective tissue growth factor (CTGF) expression and the enhancer of zeste homolog 2 (EZH2) /p21 pathway.
Materials and Methods