Cardiosphere-derived exosomal microRNAs for cardiac repair in pediatric dilated cardiomyopathy: preclinical and safety lead-in phase 1 clinical studies
Authors: Hirai K , Baba K , Ohtsuki S , Oh H 
Published: November 2020

Abstract

Introduction
Stem cell therapies have been shown to improve cardiac function; however, therapeutic potential of cardiosphere-derived cells (CDCs) in dilated cardiomyopathy (DCM) and the underlying mechanisms of paracrine effectors include CDC-secreted exosomes (CDCex) mediating cardiac repair remain unknown. Purpose- We aimed to evaluate the safety and therapeutic efficacy of CDCs in swine model of DCM and translate the preclinical results into children with DCM.

Methods
As a preclinical study, female Yorkshire pigs (n=15) were treated by intracoronary administration of microspheres (1.0×104 particles) to develop diffuse cardiac dysfunction and animals were randomly assigned to receive placebo or 9.0×106 CDC injection pretreated by DMSO or exosome inhibitor (EI; GW4869). CDCex-derived microRNAs (miRs) profile was assessed and ventricular ejection fraction (EF) was evaluated before and 1 month after cell infusion. In safety lead-in clinical trial, 5 patients with DCM (&lt;18 years) with reduced EF (&lt;40%) were prospectively enrolled to receive CDC infusion. The primary endpoint was to assess safety, and the secondary outcome measure was change in cardiac function over 12 months.

Results
Compared with placebo control, DMSO-treated CDC infusion resulted in improved cardiac function with decrease in myocardial fibrosis (18.2±4.1% versus; 9.5±3.6%; P&lt;0.001) and enhanced cardiomyocyte cycling (Ki67: 27.2±3.6/106 myocytes versus 43.9±6.0/106 myocytes; P=0.002) and neovascularization (von Willebrand factor: 644.8±84.3/mm2 versus 820.7±159.7/mm2; P=0.01) at 1 month. miR expression analysis showed that CDCex were highly enriched with miR-126, miR-132, miR-146a, miR-181b, miR-210, and miR-451. Inhibition of CDCex-derived miRs production by EI pretreatment did not affect CDC viability but rendered CDC ineffective in functional improvement (ΔEF: +5.4%±2.0% versus −1.0%±2.1%; P=0.002). One-year follow-up of clinical trial was completed in 5 patients with favorable profile and preliminary efficacy outcomes. Echocardiographic measurements revealed that CDC infusion increased EF from baseline to 12 months of follow up (28.5±10.7% versus 33.0±11.1%; P=0.038) in accordance with reduced native T1 mapping (1041.6±60.4 ms versus 984.8±39.3 ms; P=0.025). CDCex-derived miRs profiles from patients demonstrated that several miRs were exclusively enriched in CDCs but human cardiac fibroblasts included miR-126, miR-132, miR-146a, miR-181b, and miR-210. Notably, miR-146a expression levels were positively correlated with the reduction in myocardial fibrosis 12 months after CDC infusion (Δnative T1: r=0.896, P=0.040).

Conclusions
Intracoronary delivery of CDCs is safe and improves cardiac function through CDCex-derived miRs secretion in swine model of DCM. The safety lead-in results in patients warrant further assessment of clinical benefits and highlight miR-146a as a major paracrine mediator of CDC's antifibrotic function for clinical therapeutics.

Funding Acknowledgement
Type of funding source: Public grant(s) – National budget only. Main funding source(s): Research Project for Practical Application of Regenerative Medicine (16bk0104052h0001, 17bk0104052h0002, 18bk0104052h0003) by the Japan Agency for Medical Research and Development