Background/Purpose: Interstitial lung disease (ILD) is a serious condition characterized by inflammation and fibrosis in the lung interstitium. The important subtypes of ILD include idiopathic pulmonary fibrosis (IPF) and connective tissue disease-associated ILD (CTD-ILD). The main histopathological pattern observed in IPF and Rheumatoid arthritis-ILD (RA-ILD) is usual interstitial pneumonia (UIP), and if left untreated, the prognosis is unfavorable. Recently, cell-based mesenchymal stem cells (MSCs) can improve lung fibrosis through anti-apoptotic effect by immunomodulation, protein expression regulation, and mitochondria transfer. However, this ability decreases with passage in adult tissue-derived MSC. But Embryonic stem cell, called DW-MSCs, maintains a constant their ability even after repeated passage culture. Therefore, we evaluated whether DW-MSC can improve lung fibrosis in IPF and RA-ILD, and to identify the mechanism of improvement.

Methods: A total of 1.0 x 10⁶ DW-MSCs were injected into mice via the tail vein either 4 or 7 days after intratracheal administration of bleomycin and collagen induction. The therapeutic effect was analyzed by evaluation the lung tissue fibrosis scores, and α-SMA expression through western blot and immunohistochemistry. The immune cell modulation of DW-MSCs was evaluated by analyzing immune cells in lung tissue using flow cytometry analysis. The Damaged AECs protection of DW-MSCs was investigated by inducing apoptosis in A549 cells with CoCl₂ and confirming trough TUNEL assay, cell viability and the expression level of Bcl-2 and Bcl-2 associated X (Bax) through western blot. Lastly, we co-cultured DW-MSCs and hypoxia-induced AECs to confirm the transfer of mitochondria through tunneling nanotubes (TNTs) of DW-MSCs using fluorescence microscopy.

Results: DW-MSCs attenuates Bleomycin-induced and Collagen-induced pulmonary fibrosis. The therapeutic efficacy of DW-MSCs was found to be comparable to Nintedanib. DW-MSCs showed improvements in the fibrosis score, reduced α-SMA expression, and regulated fibrosis relate gene expression. Furthermore, DW-MSCs exhibited immunomodulatory effects by influencing B cells during the early phase and promoting an increase in regulatory T cells while decreasing Th17 cells during the late phase. Additionally, DW-MSCs demonstrated the ability to inhibit apoptosis in damaged AECs and down-regulate apoptosis-related proteins. Moreover, DW-MSCs enhanced cell viability and mitochondrial respiration in damaged epithelial cells by facilitating the transfer of mitochondria through tunneling nanotubes.

Conclusion: Our study provides compelling evidence for the therapeutic potential of DW-MSCs in improving IPF and RA-ILD. A single administration, DW-MSCs exhibit beneficial effects on AECs injury, inflammation, and fibrosis. These effects are achieved through the protection of AECs by inhibiting apoptosis, facilitating mitochondrial transfer, and exerting immunomodulatory and anti-fibrotic effects. Additionally, their high clinical applicability is an added advantage as their efficacy remains constant across various passages. Therefore, DW-MSCs can be considered an ideal candidate for ILD treatment in the future.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/human-embryonic-stem-cell-derived-mesenchymal-stem-cells-attenuates-experimental-pulmonary-fibrosis-through-mitochondria-transfer-mediated-anti-apoptotic-and-immunomodulatory-effects/