Research paves the way for the use of MSCs for therapeutic delivery of miRNA targeted at kidney disease

The advancement of microRNA (miRNA) therapies has been hampered by difficulties in delivering miRNA to the injured kidney in a robust and sustainable manner. Using bioluminescence imaging in mice with unilateral ureteral obstruction (UUO), researchers at Monash University report that mesenchymal stem cells (MSCs), engineered to overexpress miRNA-let7c, selectively homed to damaged kidneys and upregulated miR-let7c gene expression, compared to non-targeting control (NTC)-MSCs. In vitro analysis confirmed the transfer of miR-let7c from miR-let7c-MSCs occurred via secreted exosomal uptake, visualized in NRK52E cells using cyc3-labeled pre-miRNA-transfected MSCs with/without the exosomal inhibitor, GW4869. The upregulated expression of fibrotic genes in NRK52E cells induced by TGF-β1 was repressed following the addition of isolated exosomes or indirect co-culture of miR-let7c-MSCs, compared to NTC-MSCs. Furthermore, the co-transfection of NRK52E cells using the 3’UTR of TGF-βR1 confirmed that miR-let7c attenuates TGF-β1-driven TGF-βR1 gene expression.

(a) Flow cytometry and fluorescence microscopy for GFP+ expression showed the transfection efficiency of MSCs with miR-let7c, that were karyotypically normal.  (b) Successful  transduction  of  MSCs  with  miR-NTC  was  demonstrated  by  fluorescence microscopy  and  flow  cytometry.  The transfected cells also displayed karyotypically normality.      (c)   MSC   displayed   multilineage   differentiation   potential in   vitro, differentiating  into  osteocytes, evidenced  by  osteocalcin  staining  (magnification  x200), adipocytes   indicated   by   the   presence   of   lipid   droplets   stained   with   Oil   Red-O (magnification  x400)  and  chondrocytes  shown  by  the presence  of  aggrecan  staining (magnification x200). (d) In addition to displaying a normal morphology, the transduced MSCs, miR-let7c-MSC displayed a normal proliferative ability.  Abbreviations:  GFP, green  fluorescent  protein,  NTC,  non-targeting  control;  MSCs,  mesenchymal  stem  cells. Scale bars: Panel B = 100µm.

Taken together, the effective anti-fibrotic function of engineered MSCs are able to selectively transfer miR-let7c to damaged kidney cells, and will pave the way for the use of MSCs for therapeutic delivery of miRNA targeted at kidney disease.