miR‐145 transgenic mice develop cardiopulmonary complications leading to postnatal death

BACKGROUND: Both downregulation and elevation of microRNA miR‐145 has been linked to an array of cardiopulmonary phenotypes, and a host of studies suggest that it is an important contributor in governing the differentiation of cardiac and vascular smooth muscle cell types. METHODS AND RESULTS: To better understand the role of elevated miR‐145 in utero within the cardiopulmonary system, we utilized a transgene to overexpress miR‐145 embryonically in mice and examined the consequences of this lineage‐restricted enhanced expression. Overexpression of miR‐145 has detrimental effects that manifest after birth as overexpressor mice are unable to survive beyond postnatal day 18. The miR‐145 expressing mice exhibit respiratory distress and fail to thrive. Gross analysis revealed an enlarged right ventricle, and pulmonary dysplasia with vascular hypertrophy. Single cell sequencing of RNA derived from lungs of control and miR‐145 transgenic mice demonstrated that miR‐145 overexpression had global effects on the lung with an increase in immune cells and evidence of leukocyte extravasation associated with vascular inflammation. CONCLUSIONS: These data provide novel findings that demonstrate a pathological role for miR‐145 in the cardiopulmonary system that extends beyond its normal function in governing smooth muscle differentiation.