Background: A growing number of studies have demonstrated that mesenchymal stem cells (MSCs) can effectively regulate the progression of multiple autoimmune diseases and can respond positively to mechanical stimulation by ultrasound in an in vitro setting to improve transplantation efficacy.
Objective: The aim of this study was to activate hUC-MSCs by pretreatment with low-intensity focused pulsed ultrasound (LIFPUS) in an in vitro environment and transplant them into a rat model of EAT via tail vein. To investigate the efficacy and potential mechanism of action of hUC-MSCs in the treatment of EAT.
Methods: In this study, 40 female lewis rats were divided into control, EAT, hUC-MSCs treatment and LIFPUS pretreatment transplantation group. EAT models were established by subcutaneous multi-point injection of PTG+Freund's adjuvant, and the primary hUC-MSCs were treated with different gradients of LIFPUS irradiation or sham irradiation in an in vitro environment and screened by Western Blot (WB), flow cytology cycle analysis, and cellular immunofluorescence to find the optimal treatment parameters for LIFPUS to promote cell proliferation. After tail vein injection of different pretreatment groups of hUC-MSCs, Homing sites of hUC-MSCs in vivo, circulating autoantibody expression levels and local thyroid histopathological changes were assessed by enzyme-linked immunosorbent assay (ELISA), spleen index, tissue hematoxylin-eosin (HE) staining and immunohistochemistry. The expression levels of apoptotic proteins Bcl-2, Bax and endoplasmic reticulum stress-related proteins Chop and EIF2α in thyroid tissue were also examined by WB.
Results: LIFPUS can effectively stimulate hUC-MSCs in vitro to achieve the most optimal proliferative and secretory activity. In the EAT model, hUC-MSCs can effectively reduce thyroid cell apoptosis, improve thyroid function and reduce excessive accumulation of autoimmune antibodies in the body. in comparison, the LIFPUS pretreatment group showed a more favorable treatment outcome. Further experiments demonstrated that hUC-MSCs transplantation may effectively inhibit the apoptotic state of thyroid follicles and follicular epithelial cells by down-regulating the unfolded protein reaction (UPR) of the PERK pathway, thus providing a therapeutic effect for AIT.
Conclusion: hUC-MSCs can effectively reverse the physiological function of EAT thyroid tissue and reduce the accumulation of circulating antibodies in the body. in comparison, hUC-MSCs under LIFPUS pretreatment showed more desirable therapeutic potential. hUC-MSCs transplanted under LIFPUS pretreatment may be a new class of safe therapeutic modality for the treatment of AIT.
Keywords: Mesenchymal stem cells, experimental autoimmune thyroiditis, low intensity focused pulsed ultrasound, cell cycle, apoptosis, thyroid function.