Wednesday, April 20, 2016

Type 2 immunity contributes to ECM scaffold-guided muscle tissue regeneration

Few days back Science published a short study suggesting that muscle regeneration post surgical-injury required type 2 immune response orchestrated by adaptive TH2 cells.

For this study the authors applied three different tissue-derived extracellular matrix (ECM) scaffolds to surgically-injured muscle tissue: (1) particulate collagen, (2) bone–derived tissue ECM scaffold (B-ECM), (3) cardiac muscle–derived tissue ECM scaffold (C-ECM). Gene expression profiling of sorted T cells harvested from muscle tissue 1 week post-injury showed up-regulation of IL-4, a canonical TH2 cytokine (also IL-17, but the authors did not discuss its significance).

Next, authors found that up-regulation IL-4 in injured tissue was abolished in RAG-KO mice that lack adaptive immune cells, indicating the role of adaptive TH2 cells in this process.

The role of TH2 cells in orchestrating type II immune environment was also shown by analysis of CD206+ myeloid cells (a mannose receptor and classical M2 marker) from injured tissue in RAG-KO, IL4ra−/− mice that cannot receive signals from IL-4, or Rictor−/− CD4+ T cells (T-Rictr−/−, TH2-deficient).

Finally, the authors showed that functionally-competent TH2 cells were necessary for wound healing and recovery of muscle functionality in response to cardiac muscle–derived tissue ECM scaffold.

In summary, this short study reveals a complex nature of type 2 immunity. Earlier studies showed that type 2 immunity is [in addition] involved in allergy/asthma, immune response to worms, thermoregulation / lean body metabolism. Now we can to this list tissue regeneration as well.

David Usharauli

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