Specific ablation of CD4⁺ T-cells promotes heart regeneration in juvenile mice

Abstract

Unlike adult cardiomyocytes, neonatal cardiomyocytes can readily proliferate that contributes to a transient regenerative potential after myocardial injury in mice. We have recently reported that CD4 + regulatory T-cells promote this process; however, the role of other CD4 + T-cell subsets as well as CD8 + T-cells in postnatal heart regeneration has been less studied. Methods: by comparing the regenerating postnatal day (P) 3 and the non-regenerating P8 heart after injury, we revealed the heterogeneity of CD4 + and CD8 + T-cells in the myocardium through single cell analysis. We also specifically ablated CD4 + and CD8 + T-cells using the lytic anti-CD4 and -CD8 monoclonal antibodies, respectively, in juvenile mice at P8 after myocardial injury. Results : we observe significantly more CD4 + FOXP3 - conventional T-cells in the P8 heart when compared to that of the P3 heart within a week after injury. Surprisingly, such a difference is not seen in CD8 + T-cells that appear to have no function as their depletion does not reactivate heart regeneration. On the other hand, specific ablation of CD4 + T-cells contributes to mitigated cardiac fibrosis and increased cardiomyocyte proliferation after injury in juvenile mice. Single-cell transcriptomic profiling reveals a pro-fibrotic CD4 + T-cell subset in the P8 but not P3 heart. Moreover, there are likely more Th1 and Th17 cells in the P8 than P3 heart. We further demonstrate that cytokines of Th1 and Th17 cells can directly reduce the proliferation and increase the apoptosis of neonatal cardiomyocytes. Moreover, ablation of CD4 + T-cells can directly or indirectly facilitate the polarization of macrophages away from the pro-fibrotic M2-like signature in the juvenile heart. Nevertheless, ablation of CD4 + T-cells alone does not offer the same protection in the adult heart after myocardial infarction, suggesting a developmental change of immune cells including CD4 + T-cells in the regulation of age-related mammalian heart repair. Conclusions : our results demonstrate that ablation of CD4 + but not CD8 + T-cells promotes heart regeneration in juvenile mice; and CD4 + T-cells play a distinct role in the regulation of heart regeneration and repair during development.

LPA3-mediated lysophosphatidic acid signaling promotes postnatal heart regeneration in mice

“…It is believed that cardiomyocyte proliferation contributes to mammalian heart growth largely during the embryonic period, and cardiomyocyte enlargement is thought to be responsible for growth after birth. However, accumulating evidence has demonstrated that cardiomyocytes still have proliferative potential even after birth 8 - 12 . Since we found that LPA 1 and LPA 3 significantly peaked during the early postnatal period and decreased rapidly thereafter, which coincides with the loss of the heart's regenerative potential, the role of LPA signaling in cardiomyocyte proliferation and heart regeneration after birth was elucidated in this study.…”

An emerging role of regulatory T-cells in cardiovascular repair and regeneration

“…In addition to the immunomodulation of macrophages, Treg can also suppress the pro-inflammatory response of other activated cells such as effector CD4 + and CD8 + T cells. Intriguingly, a recent study shows a developmentally distinct role of CD4 + T cells in heart repair and regeneration 73 . CD4 + T cells inhibit heart regeneration in the juvenile mice but promote heart repair in the adult mice 73 .…”

“…Intriguingly, a recent study shows a developmentally distinct role of CD4 + T cells in heart repair and regeneration 73 . CD4 + T cells inhibit heart regeneration in the juvenile mice but promote heart repair in the adult mice 73 . Unlike the CD4 + T cells, CD8 + T cells are found unresponsive to heart injury in the juvenile mice 73 .…”

“…CD4 + T cells inhibit heart regeneration in the juvenile mice but promote heart repair in the adult mice 73 . Unlike the CD4 + T cells, CD8 + T cells are found unresponsive to heart injury in the juvenile mice 73 . The pro-inflammatory cytokines of Th1 (e.g.…”

Immune Cell Therapies to Improve Regeneration and Revascularization of Non-Healing Wounds

“…Several studies highlighted the detrimental role of CD4 + and CD8 + lymphocytes in tissue regeneration and revascularization. For instance, CD4 + cell ablation promotes heart regeneration [ 126 ] and both CD4 + [ 127 ] and CD8 + [ 128 ] blockade improves angiogenesis in diabetic mice. Yet, their functional role in skin regeneration is controversial, as indicated by numerous studies reporting conflicting results, and a clear discrimination of the specific role of circulating and resident lymphocytes is often missing.…”