Aging-associated changes in microRNA expression profile of internal anal sphincter smooth muscle: Role of microRNA-133a

Abstract

A comprehensive genomic and proteomic, computational, and physiological approach was employed to examine the (previously unexplored) role of microRNAs (miRNAs) as regulators of internal anal sphincter (IAS) smooth muscle contractile phenotype and basal tone. miRNA profiling, genome-wide expression, validation, and network analyses were employed to assess changes in mRNA and miRNA expression in IAS smooth muscles from young vs. aging rats. Multiple miRNAs, including rno-miR-1, rno-miR-340-5p, rno-miR-185, rno-miR-199a-3p, rno-miR-200c, rno-miR-200b, rno-miR-31, rno-miR-133a, and rno-miR-206, were found to be upregulated in aging IAS. qPCR confirmed the upregulated expression of these miRNAs and downregulation of multiple, predicted targets (Eln, Col3a1, Col1a1, Zeb2, Myocd, Srf, Smad1, Smad2, Rhoa/Rock2, Fn1, Tagln v2, Klf4, and Acta2) involved in regulation of smooth muscle contractility. Subsequent studies demonstrated an aging-associated increase in the expression of miR-133a, corresponding decreases in RhoA, ROCK2, MYOCD, SRF, and SM22α protein expression, RhoA-signaling, and a decrease in basal and agonist [U-46619 (thromboxane A analog)]-induced increase in the IAS tone. Moreover, in vitro transfection of miR-133a caused a dose-dependent increase of IAS tone in strips, which was reversed by anti-miR-133a. Last, in vivo perianal injection of anti-miR-133a reversed the loss of IAS tone associated with age. This work establishes the important regulatory effect of miRNA-133a on basal and agonist-stimulated IAS tone. Moreover, reversal of age-associated loss of tone via anti-miR delivery strongly implicates miR dysregulation as a causal factor in the aging-associated decrease in IAS tone and suggests that miR-133a is a feasible therapeutic target in aging-associated rectoanal incontinence.

Mitochondrial (Dys) Function in Inflammaging: Do MitomiRs Influence the Energetic, Oxidative, and Inflammatory Status of Senescent Cells?

“…Thus, it has been hypothesized that SA-miRs and mtDNA-targeting mitomiRs play a major role in the mitochondrial dysfunction observed in both cellular senescence and the inflammaging process [ 94 ]. Notably, among all mitomiRs targeting mitochondrial genome, a subset of miRs has been associated to inflammatory processes, that is, miR-130a-3p [ 95 ] or to both inflammation and aging, that is, let-7b [ 96 , 97 ], miR-146a-5p [ 98 ], miR-181c-5p [ 99 , 100 ], miR-133a [ 101 , 102 ], and miR-1 [ 103 , 104 ].…”

Role of differentially expressed microRNA-139-5p in the regulation of phenotypic internal anal sphincter smooth muscle tone

“…Strips were transfected with miRNA-139-5p as per 29 . Briefly, the IAS tissue strips were transferred into 2-ml muscle baths containing KPS that was continuously perfused with carbogen (95% O 2  + 5% CO 2 ).…”

“…Likewise, studies in rat IAS and mouse stomach have shown that miRNA-133a downregulates RhoA in aging- and diabetes-associated decrease in the respective smooth muscles’ contractility 29, 30 . It is well known that, in the smooth muscle contractility, ROCK, specifically ROCK2 is an important downstream target of RhoA and is expressed markedly higher in the tonic tissues such as the IAS 11, 12, 31–33 .…”

Mitochondrial MicroRNAs in Aging and Neurodegenerative Diseases

“…While low levels of mir-133a may cause exercise intolerance, high levels of mir-133a are also deleterious and are seen in heart failure patients [ 115 ]. Furthermore, miR-133a is upregulated in aged internal anal sphincter muscles, which has been found to restore tonicity to the muscle fibers [ 116 ].…”