Functional microRNA library screening identifies the hypoxamir miR-24 as a potent regulator of smooth muscle cell proliferation and vascularization.
Smooth muscle cells (SMCs) are key components within the vasculature. Dependent on the stimulus, SMC can either be in a proliferative (synthetic) or differentiated state. Alterations of SMC phenotype also appear in several disease settings, further contributing to disease progression.


OBJECTIVE
Here, we asked whether microRNAs (miRNAs, miRs), which are strong posttranscriptional regulators of gene expression, could alter SMC proliferation. Results and Innovation: Employing a robotic-assisted high-throughput screening method using miRNA libraries, we identified hypoxia-regulated miR-24 as a master regulator of SMC proliferation. Proteome profiling showed a strong miR-24-dependent impact on cellular stress-associated factors, overall resulting in reduced stress resistance. In vitro, synthetic miR-24 overexpression had detrimental effects on SMC functional capacity inducing apoptosis, migration defects, enhanced autophagy, and loss of contractile marker genes. Impaired SMC function was mediated in part by the herein identified direct target gene heme oxygenase 1. Ex vivo, miR-24 was shown to inhibit the development of vasculature in a model of engineered heart tissue.


CONCLUSIONS
Collectively, we report the identification of the hypoxamir-24 as an inhibitor of SMC proliferation, contributing to loss of vascularization.
1 Institute of Molecular and Translational Therapeutic Strategies (IMTTS) , Hannover Medical School, Hannover, Germany .
Jan
J
Fiedler
Andrea
A
Stöhr
Shashi Kumar
SK
Gupta
Dorothee
D
Hartmann
Angelika
A
Holzmann
Annette
A
Just
Arne
A
Hansen
Denise
D
Hilfiker-Kleiner
Thomas
T
Eschenhagen
Thomas
T
Thum
D000818:Animals; D001011:Aorta / Q000166:cytology; D001483:Base Sequence; D001665:Binding Sites; D049109:Cell Proliferation; D002478:Cells, Cultured; D004794:Enzyme Repression; D015723:Gene Library; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D018919:Neovascularization, Physiologic; D034622:RNA Interference; D046509:Tissue Culture Techniques
C543845:MIRN24 microRNA, human; D035683:MicroRNAs; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1