Removing a key muscle-scar cell changes fat and scar after rotator cuff tears in mice

In two mouse injury models, depleting fibroadipogenic progenitors reduced scarring in both but affected fat buildup and function only in the rotator cuff tear model.

Abstract editorial illustration accompanying the article: Removing a key muscle-scar cell changes fat and scar after rotator cuff tears in mice

Editorial illustration — not from the study.

Fibroadipogenic progenitors (FAPs) are resident muscle cells that can become fat or scar-forming cells after injury. They are also thought to help muscle regrow, but their roles in different injury settings are not well defined.

Using a FAP-depletion mouse approach, researchers examined two injury models relevant to muscle and tendon disorders: a rotator cuff tear model affecting the supraspinatus and infraspinatus tendons and a nerve, and a volumetric muscle loss model in the tibialis anterior muscle. They then measured muscle changes and function six weeks after surgery.

Key results in two models

In the rotator cuff tear model, depleting FAPs significantly attenuated muscle atrophy and improved fibrosis, fat infiltration, and global shoulder function.

In the tibialis anterior volumetric muscle loss model, FAP depletion significantly decreased muscle fibrosis, but did not change fat infiltration or functional outcomes.

Why the cell role differs

The findings suggest that FAPs can contribute differently to muscle degeneration and recovery depending on the injury context. This helps explain why the same cell population may be linked to both repair and poor tissue changes after damage.

Evidence and study limits

This is an animal study using a specific FAP-depletion strategy in two injury models in mice, with functional testing and histology six weeks after surgery. Limitations include uncertainty about how the results translate to human rotator cuff tears and muscle loss, and the abstract does not report how many animals were included in each group or other detailed outcomes beyond the stated trends.

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