238 - miR-17~92 Cluster Haploinsufficiency Causes Pulmonary Hypertension without Pulmonary-Vascular Pruning

Poster Number: 238
Publication Number: 238.222

Ashley Kimble, Northwestern University, Ann and Robert H. Lurie Children's Hospital of Chicago, CHICAGO, IL, United States; Russell Moskal, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, United States; Greg B. Waypa, Northwestern University The Feinberg School of Medicine, Chicago, IL, United States; Mary E. Robbins, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, United States

Background: Bronchopulmonary dysplasia (BPD) causes significant morbidity and mortality in premature infants.  Pulmonary hypertension is often associated with BPD, but underlying mechanisms are not well understood.  We have previously reported that microRNA (miR)-17~92 expression is severely attenuated in human patients who died with BPD and in a murine model of BPD.  Murine global deletion of miR-17~92 results in fatal neonatal respiratory failure from pulmonary hypoplasia and ventricular septal defects.  This cluster is predicted to regulate many genes implicated in cellular proliferation, including Pten.  The effect of miR-17~92 haploinsufficiency (HI) on pulmonary vascular and cardiovascular function during murine aging has not been characterized.

Objective: The following studies test the hypothesis that miR-17~92 HI causes pulmonary hypertension reminiscent of a BPD-like phenotype.

Design/Methods: miR-17~92flox/flox and Tg-Sox2Cre mice were mated to produce HI (Tg-Sox2Cre/miR-17~92+/flox) and control (C: miR-17~92+/flox) offspring.  Hearts were dissected; right ventricle (RV) was separated from the left ventricle and septum (LV+S) (n=5-10/group).  von Willebrand factor stained slides were used to analyze small non-muscular vessel count and area using ImageQuant Pro (n=3-6/group).  Medial wall thickness (MWT) was measured on small muscularized pulmonary arteries using ImageJ (n=3/group).  Right Ventricular Systolic Pressure (RVSP), measured by Millar, assessed cardiovascular function (n=2-4/group).  Pten quantified by Western blot on whole heart homogenates was normalized to Β-actin (n=4/group).  Data was analyzed by unpaired t-test.  Significance is noted at p < 0.05.

Results: The Fulton’s index, a ratio of RV to LV+S weights, was significantly different between HI vs C (0.274 vs 0.241) at P14; however, no difference was present between groups for vessel counts or MWT.  RVSP was increased in HI vs C at P28 (17.6 vs 12.6 mmHg) and P56 (23.8 vs 15.9 mmHg).  Pten is similar between HI and C (1.00 vs 0.90) at P14 and P28. Conclusion(s): Our data reveals that miR-17~92 HI causes right ventricular hypertrophy and increased RVSP, consistent with pulmonary hypertension; however, common mechanisms of decreased pulmonary vessel counts, increased MWT or Pten induced cellular proliferation are not present.  This suggests the loss of miR-17~92 may impact cardiovascular development differently than what has previously been reported in other pulmonary hypertension models.  Therefore, our next steps will be investigating the effects of cluster deletion on cardiac myocyte function.
Ashley Kimble CVKimble, Ashley_CV_01.04.2022.pdf