Acute respiratory distress syndrome (ARDS) in COVID‐19 is associated with high mortality. Mesenchymal stem cells are known to exert immunomodulatory and anti‐inflammatory effects and could yield beneficial effects in COVID‐19 ARDS. The objective of this study was to determine safety and explore efficacy of umbilical cord mesenchymal stem cell (UC‐MSC) infusions in subjects with COVID‐19 ARDS. A double‐blind, phase 1/2a, randomized, controlled trial was performed. Randomization and stratification by ARDS severity was used to foster balance among groups. All subjects were analyzed under intention to treat design. Twenty‐four subjects were randomized 1:1 to either UC‐MSC treatment (n = 12) or the control group (n = 12). Subjects in the UC‐MSC treatment group received two intravenous infusions (at day 0 and 3) of 100 ± 20 × 106 UC‐MSCs; controls received two infusions of vehicle solution. Both groups received best standard of care. Primary endpoint was safety (adverse events [AEs]) within 6 hours; cardiac arrest or death within 24 hours postinfusion). Secondary endpoints included patient survival at 31 days after the first infusion and time to recovery. No difference was observed between groups in infusion‐associated AEs. No serious adverse events (SAEs) were observed related to UC‐MSC infusions. UC‐MSC infusions in COVID‐19 ARDS were found to be safe. Inflammatory cytokines were significantly decreased in UC‐MSC‐treated subjects at day 6. Treatment was associated with significantly improved patient survival (91% vs 42%, P = .015), SAE‐free survival (P = .008), and time to recovery (P = .03). UC‐MSC infusions are safe and could be beneficial in treating subjects with COVID‐19 ARDS.

Background Hypoxia is a major cause of beta cell death and dysfunction after transplantation. The aim of this study was to investigate the effect of exosomes derived from mesenchymal stem cells (MSCs) on beta cells under hypoxic conditions and the potential underlying mechanisms. Methods Exosomes were isolated from the conditioned medium of human umbilical cord MSCs and identified by WB, NTA, and transmission electron microscopy. Beta cells (βTC-6) were cultured in serum-free medium in the presence or absence of exosomes under 2% oxygen conditions. Cell viability and apoptosis were analysed with a CCK-8 assay and a flow cytometry-based annexin V-FITC/PI apoptosis detection kit, respectively. Endoplasmic reticulum stress (ER stress) proteins and apoptosis-related proteins were detected by the WB method. MiRNAs contained in MSC exosomes were determined by Illumina HiSeq, and treatment with specific miRNA mimics or inhibitors of the most abundant miRNAs was used to reveal the underlying mechanism of exosomes. Results Exosomes derived from MSC-conditioned culture medium were 40–100 nm in diameter and expressed the exosome markers CD9, CD63, CD81, HSP70, and Flotillin 1, as well as the MSC markers CD73, CD90, and CD105. Hypoxia significantly induced beta cell apoptosis, while MSC exosomes remarkably improved beta cell survival. The WB results showed that ER stress-related proteins, including GRP78, GRP94, p-eIF2α and CHOP, and the apoptosis-related proteins cleaved caspase 3 and PARP, were upregulated under hypoxic conditions but were inhibited by MSC exosomes. Moreover, the p38 MAPK signalling pathway was activated by hypoxia and was inhibited by MSC exosomes. The Illumina HiSeq results show that MSC exosomes were rich in miR-21, let-7 g, miR-1246, miR-381, and miR-100. After transfection with miRNA mimics, the viability of beta cells under hypoxia was increased significantly by miR-21 mimic, and the p38 MAPK and ER stress-related proteins in beta cells were downregulated. These changes were reversed after exosomes were pretreated with miR-21 inhibitor. Conclusions Exosomes derived from MSCs could protect beta cells against apoptosis induced by hypoxia, largely by carrying miR-21, alleviating ER stress and inhibiting p38 MAPK signalling. This result indicated that MSC exosomes might improve encapsulated islet survival and benefit diabetes patients.

DNA polymerase kappa (POLkappa) is a low fidelity translesional DNA polymerase implicated in spontaneous and DNA damage-induced mutagenesis. We have previously shown that POLkappa was frequently overexpressed in human lung cancer tissues as compared with their matched non-tumorous tissue counterpart. In the present study, we found a close correlation between elevated POLkappa expression and p53 inactivation in lung cancer tissues. To investigate whether POLK expression might be regulated by p53, we have determined the transcriptional initiation site of POLK gene and examined its promoter activity in A549, H358-129, and PC-3 human lung cancer cell lines. Wild-type p53, but not a mutant p53 (R273H) devoid of the DNA-binding activity, strongly inhibited POLK promoter activity in these cells. In addition, POLK promoter exhibited a significantly higher activity in p53-/- murine embryo fibroblasts (MEF) than in p53+/- and p53+/+ MEF. These results link p53 status with POLkappa expression and suggest that loss of p53 function may in part contribute to the observed POLkappa upregulation in human lung cancers.

No abstract