Table 3.

Animal studies; animal studies with the specific aim to investigate the pathophysiology of frozen shoulder

Author	Year	Study Design	Method used for analysis	Most relevant findings
Watson [50]	2011	animal model (rats)	RT-PCR	TGF-β1 gene transfer induced a fibrotic condition comparable to frozen shoulder patients with similar expression levels of ECM proteins, MMPs, adhesion- and collagen proteins
Xue [51]	2016	animal model (rats) + cell culture	RT-PCR and gene silencing with a lentivirus	Smad4 silencing can suppress chronic inflammation and fibrosis in joint tissue by inhibiting the TGF-β/Smad pathway
Blessing [52]	2019	animal model (rats) + cell culture	immunohistochemistry	Local delivery of Relaxin-2 downregulates type I collagen and α-smooth muscle actin production

CHL coracohumeral ligament, RI rotator interval RT-PCR real time polymerase chain reaction, TGF-β transforming growth factor beta, ECM extracellular matrix, MMP matrix metalloproteinase, α-SMA α - smooth muscle actin