Overexpression of Decorin Optimizes the Treatment Efficacy of Umbilical Cord Mesenchymal Stem Cells in Bleomycin‐Induced Pulmonary Fibrosis in Rats

Idiopathic pulmonary fibrosis (IPF) is a long-term, diffuse pulmonary parenchyma lesion that primarily affects middle-aged and older adults. It is characterized by pulmonary interstitial fibrosis of unknown cause. The death rate upon diagnosis is higher than that of many other cancer types. Mesenchymal stem cell (MSC) treatment of organ fibrosis is a hot topic in preclinical and clinical research because it effectively treats IPF. In recent years, decorin (DCN) has been regarded as a critical mediator for its anti-inflammatory and antifibrotic effects. The purpose of this study was to generate human umbilical cord MSCs (HUC-MSCs) that overexpress DCN and to investigate the safety, mechanism, and effectiveness of using these cells to cure pulmonary fibrosis caused by bleomycin (BLM). First, lentiviral (LV) particles carrying the therapeutic DCN gene (LV-DCN) and control LV particles were created and transfected using the plasmid vector GV208 to create a viral solution for infecting HUC-MSCs. These solutions were used to create a DCN overexpression cell line and an MSC-Con. cell line infected with the control lentivirus. Intratracheal injection of BLM was used to establish a rat model of pulmonary fibrosis. On the second day following modeling, different treatments were administered, and the body weight and survival status of the rats were noted. The relevant tests were performed on days 15 and 29 following modeling. The results demonstrated that the overexpression of DCN did not affect the properties of HUC-MSCs and that these cells were effective in treating IPF. MSC-Con. and MSC-DCN reduced systemic inflammation by reducing serum interleukin (IL) 1<i>β</i>. Both cell types successfully treated pulmonary fibrosis in rats, as demonstrated by hematoxylin and eosin (HE) and Masson staining. MSC-DCN showed better efficacy due to lower mortality, higher weight gain, less alveolar inflammation, and less fibrosis. The safety of venous transplantation with MSCs was established by HE staining of the heart, liver, spleen, and kidney, as well as serum lactate dehydrogenase (LDH), creatinine (CRE), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) levels. Immunohistochemical (IHC) staining of CD68 and CD206 in lung tissue and in vitro experiments on THP-1-induced M2 macrophage polarization and transforming growth factor-beta 1 (TGF-<i>β</i>1)-induced MRC-5 fibrosis indicated that MSC-DCN may mitigate lung inflammation by altering macrophage recruitment and polarization and inhibiting TGF-<i>β</i>1 expression to reduce fibrous hyperplasia and collagen deposition, thereby improving the treatment of BLM-induced IPF.