Type 2 for Tissue Regeneration

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Science  12 Apr 2013:
Vol. 340, Issue 6129, pp. 123
DOI: 10.1126/science.340.6129.123-c

Although we classically think of the immune system as important for warding off foreign invaders, once the invaders are squashed, it sticks around to help pick up the pieces. The specific mechanisms by which the immune system supports tissue repair can differ from tissue to tissue and overall are not very well understood. Heredia et al. investigate this in the context of skeletal muscle injury and specifically look at the role of type 2 immunity, which has previously been implicated in tissue repair. The signature type 2 cytokines interleukin (IL)–4 and –13 were up-regulated in response to skeletal muscle injury in mice, and the use of genetically modified mice demonstrated that signaling through the IL-4 receptor was required for muscle repair. Surprisingly, the primary source of IL-4 was eosinophils, not macrophages, which had been shown previously to infiltrate damaged tissue and make IL-4. Within damaged tissues, fibro/adipogenic progenitor cells, which have the potential to give rise to either fibroblasts or adipocytes, responded to IL-4 and were induced to support myogenesis rather than differentiating into adipocytes. Moreover, they were necessary for the clearance of necrotic debris.

Cell 10.1016/j.cell.2013.02.053 (2013).

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