Theranostics 2019; 9(15):4324-4341. doi:10.7150/thno.32734

Research Paper

Regulatory T-cells regulate neonatal heart regeneration by potentiating cardiomyocyte proliferation in a paracrine manner

Jiatao Li1,2, Kevin Y. Yang1, Rachel Chun Yee Tam1, Vicken W. Chan1, Hui Yao Lan2,3, Shohei Hori4, Bin Zhou5, Kathy O. Lui1,2✉

1. Department of Chemical Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
2. Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
3. Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
4. Laboratory of Immunology and Microbiology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Japan
5. The State Key Laboratory of Cell Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China

Abstract

The neonatal mouse heart is capable of transiently regenerating after injury from postnatal day (P) 0-7 and macrophages are found important in this process. However, whether macrophages alone are sufficient to orchestrate this regeneration; what regulates cardiomyocyte proliferation; why cardiomyocytes do not proliferate after P7; and whether adaptive immune cells such as regulatory T-cells (Treg) influence neonatal heart regeneration have less studied.

Methods: We employed both loss- and gain-of-function transgenic mouse models to study the role of Treg in neonatal heart regeneration. In loss-of-function studies, we treated mice with the lytic anti-CD25 antibody that specifically depletes Treg; or we treated FOXP3DTR with diphtheria toxin that specifically ablates Treg. In gain-of-function studies, we adoptively transferred hCD2+ Treg from NOD.Foxp3hCD2 to NOD/SCID that contain Treg as the only T-cell population. Furthermore, we performed single-cell RNA-sequencing of Treg to uncover paracrine factors essential for cardiomyocyte proliferation.

Results: Unlike their wild type counterparts, NOD/SCID mice that are deficient in T-cells but harbor macrophages fail to regenerate their injured myocardium at as early as P3. During the first week of injury, Treg are recruited to the injured cardiac muscle but their depletion contributes to more severe cardiac fibrosis. On the other hand, adoptive transfer of Treg results in mitigated fibrosis and enhanced proliferation and function of the injured cardiac muscle. Mechanistically, single-cell transcriptomic profiling reveals that Treg could be a source of regenerative factors. Treg directly promote proliferation of both mouse and human cardiomyocytes in a paracrine manner; and their secreted factors such as CCL24, GAS6 or AREG potentiate neonatal cardiomyocyte proliferation. By comparing the regenerating P3 and non-regenerating P8 heart, there is a significant increase in the absolute number of intracardiac Treg but the whole transcriptomes of these Treg do not differ regardless of whether the neonatal heart regenerates. Furthermore, even adult Treg, given sufficient quantity, possess the same regenerative capability.

Conclusion: Our results demonstrate a regenerative role of Treg in neonatal heart regeneration. Treg can directly facilitate cardiomyocyte proliferation in a paracrine manner.

Keywords: CD4+ regulatory T-cells, heart regeneration, cardiomyocyte proliferation, cardiac fibrosis, macrophages, single-cell RNA-seq

This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/). See http://ivyspring.com/terms for full terms and conditions.
How to cite this article:
Li J, Yang KY, Tam RCY, Chan VW, Lan HY, Hori S, Zhou B, Lui KO. Regulatory T-cells regulate neonatal heart regeneration by potentiating cardiomyocyte proliferation in a paracrine manner. Theranostics 2019; 9(15):4324-4341. doi:10.7150/thno.32734. Available from http://www.thno.org/v09p4324.htm