MicroRNA-21 in Glomerular Injury.
Authors Lai JY, Luo J, O'Connor C, Jing X, Nair V, Ju W, Randolph A, Ben-Dov IZ, Matar
RN, Briskin D, Zavadil J, Nelson RG, Tuschl T, Brosius FC, Kretzler M, Bitzer M
Submitted By Markus Bitzer on 9/4/2014
Status Published
Journal Journal of the American Society of Nephrology : JASN
Year 2014
Date Published 8/21/2014
Volume : Pages Not Specified : Not Specified
PubMed Reference 25145934
Abstract TGF-ß1 is a pleotropic growth factor that mediates glomerulosclerosis and
podocyte apoptosis, hallmarks of glomerular diseases. The expression of
microRNA-21 (miR-21) is regulated by TGF-ß1, and miR-21 inhibits apoptosis in
cancer cells. TGF-ß1-transgenic mice exhibit accelerated podocyte loss and
glomerulosclerosis. We determined that miR-21 expression increases rapidly in
cultured murine podocytes after exposure to TGF-ß1 and is higher in kidneys of
TGF-ß1-transgenic mice than wild-type mice. miR-21-deficient TGF-ß1-transgenic
mice showed increased proteinuria and glomerular extracellular matrix deposition
and fewer podocytes per glomerular tuft compared with miR-21 wild-type
TGF-ß1-transgenic littermates. Similarly, miR-21 expression was increased in
streptozotocin-induced diabetic mice, and loss of miR-21 in these mice was
associated with increased albuminuria, podocyte depletion, and mesangial
expansion. In cultured podocytes, inhibition of miR-21 was accompanied by
increases in the rate of cell death, TGF-ß/Smad3-signaling activity, and
expression of known proapoptotic miR-21 target genes p53, Pdcd4, Smad7, Tgfbr2,
and Timp3. In American-Indian patients with diabetic nephropathy (n=48),
albumin-to-creatinine ratio was positively associated with miR-21 expression in
glomerular fractions (r=0.6; P<0.001) but not tubulointerstitial fractions
(P=0.80). These findings suggest that miR-21 ameliorates TGF-ß1 and
hyperglycemia-induced glomerular injury through repression of proapoptotic
signals, thereby inhibiting podocyte loss. This finding is in contrast to
observations in murine models of tubulointerstitial kidney injury but consistent
with findings in cancer models. The aggravation of glomerular disease in
miR-21-deficient mice and the positive association with albumin-to-creatinine
ratio in patients with diabetic nephropathy support miR-21 as a feedback
inhibitor of TGF-ß signaling and functions.

Investigators with authorship
Markus BitzerUniversity of Michigan
Frank BrosiusUniversity of Arizona
Matthias KretzlerUniversity of Michigan