Background:

Glucocorticoids (GCs) injections are commonly used to relieve pain and improve function in patients with multiple shoulder disability, they cause detrimental effects on the rotator cuff tendons. Adipose stem cell-derived exosomes (ASC-Exos) reportedly recover impaired tendon matrix metabolism by maintaining tissue homeostasis. It is unclear whether additional ASC-Exos treatment overrides the detrimental effects of GCs without interfering with their anti-inflammatory effects.

Methods:

: The in vitro studies included inflammatory analysis and cytoprotective analysis. In the inflammatory analysis, rat raw cells were treated with saline, GCs, or GCs + ASC-Exos and evaluated regarding cellular proliferation, migration, and secretion of inflammatory-related cytokines. In the cytoprotective analysis, rat tenocytes were treated with saline, GCs, or GCs + ASC-Exos and evaluated regarding cellular proliferation, migration, senescence, apoptosis, and transcription of tenocytic genes. In the in vivo studies, a subacromial injection of saline, GCs, or GCs + ASC-Exos was performed in a chronic injured-intact rotator cuff rat model. Histological and biomechanical analysis were performed 1 week to evaluate the protective effect of ASC-Exos against GCs-induced detriments on injured-intact in rotator cuffs.

Results:

: In the in vitro inflammatory analysis, GCs treatment significantly decreased the proliferation, migration, and secretion of pro-inflammatory cytokines in raw cells, and increased the secretion of anti-inflammatory cytokines; additional ASC-Exos treatment further significantly decreased the secretion of pro-inflammatory cytokines and increased the secretion of anti-inflammatory cytokines, while restoring GCs-suppressed cellular proliferation and migration. In the in vitro cytoprotective analysis, GCs treatment significantly decreased the proliferation, migration, and transcription of tenocytic matrix molecules of tenocytes, and significantly increased their senescence, apoptosis, and transcription of ROS and tenocytic degradative enzymes; additional ASC-Exos treatment significantly improved the GCs-suppressed cellular proliferation, migration, and transcription of tenocytic matrix molecules, transcription of tenocytic degradative enzyme inhibitors, and significantly decreased the GCs-induced cell senescence, apoptosis, and transcription of ROS and tenocytic degradative enzymes. In the in vivo studies, an additional ASC-Exos injection restored the impaired histological and biomechanical properties owing to GCs administration.

Conclusion:

ASC-Exos may exert a stronger anti-inflammatory effect in combination with GCs, and override their detrimental effects on the rotator cuff.