Intravenous infusion has been used as the method of cell delivery in many preclinical studies as well as in some early clinical trials. Among its advantages are broad distribution, ability to handle a large-volume infusion, and ease of access. Progenitor cells used in cell-based therapy act through their secretomes, rather than their ability to differentiate into lineage-specific cell type. Since not all progenitor cells have similar secretome potency, the innate abilities of the secretome of cells used in clinical trials will obviously dictate their effectiveness. We previously found that cardiac neonatal mesenchymal stromal cells (nMSCs) are more effective in repairing the infarcted myocardium compared to adult mesenchymal stromal cells (aMSCs) due to their robust secretome (Sharma et al Circulation Research 120:816-834, 2017). In this study, we explored the efficacy of intravenous (IV) delivery of nMSCs for myocardial recovery. Six-week-old male Brown Norway rats underwent acute MI by ligation of the left anterior descending artery, followed by IV infusion of cell dose 5 × 106 nMSCs/rat body weight (kg) or saline on days 0 and 5. We found that cardiac parameters in the rodent ischemia model improved 1 month after nMSCs infusion, and the result is comparable with the intramyocardial injection of nMSCs. Tracking the infused cells in target organ revealed that their movement after IV delivery was mediated by the cell surface receptor CD44. Systemic injection of nMSCs stimulated immunomodulatory responses specifically by increasing FoxP3+ T-regulatory cell influenced anti-inflammatory macrophages (M2) in heart. These data demonstrate that nMSCs promote immunogenic tolerance via CD44-driven T-reg/M2 stimulation that helps nMSCs for longer viability in the injured myocardium for better functional recovery. Our data also demonstrate a rationale for a clinical trial of IV infusion of nMSCs to promote cardiac function improvement in the ischemic patients.
© 2024. The Author(s).

JOURNAL/nrgr/04.03/01300535-202410000-00027/figure1/v/2024-02-06T055622Z/r/image-tiff Spinal cord injury is a disabling condition with limited treatment options. Multiple studies have provided evidence suggesting that small extracellular vesicles (SEVs) secreted by bone marrow mesenchymal stem cells (MSCs) help mediate the beneficial effects conferred by MSC transplantation following spinal cord injury. Strikingly, hypoxia-preconditioned bone marrow mesenchymal stem cell-derived SEVs (HSEVs) exhibit increased therapeutic potency. We thus explored the role of HSEVs in macrophage immune regulation after spinal cord injury in rats and their significance in spinal cord repair. SEVs or HSEVs were isolated from bone marrow MSC supernatants by density gradient ultracentrifugation. HSEV administration to rats via tail vein injection after spinal cord injury reduced the lesion area and attenuated spinal cord inflammation. HSEVs regulate macrophage polarization towards the M2 phenotype in vivo and in vitro. MicroRNA sequencing and bioinformatics analyses of SEVs and HSEVs revealed that miR-146a-5p is a potent mediator of macrophage polarization that targets interleukin-1 receptor-associated kinase 1. Reducing miR-146a-5p expression in HSEVs partially attenuated macrophage polarization. Our data suggest that HSEVs attenuate spinal cord inflammation and injury in rats by transporting miR-146a-5p, which alters macrophage polarization. This study provides new insights into the application of HSEVs as a therapeutic tool for spinal cord injury.
Copyright © 2024 Copyright: © 2024 Neural Regeneration Research.

Oxidative stress and apoptosis of neurons significantly contribute to the pathophysiological cascade of spinal cord injury (SCI). However, the role of hypoxic-preconditioned mesenchymal stem cell-derived small extracellular vesicles (H-sEVs) in promoting SCI repair remains unclear. Hence, the present study aims to investigate the regulatory effects of H-sEVs on neuronal oxidative stress and apoptotic responses following SCI.
The administration of H-sEVs of SCI rats was assessed using behavioral evaluations such as Basso-Beattie-Bresnahan (BBB) scores, neuroelectrophysiological monitoring, and Catwalk gait analysis. Indices of oxidative stress (including superoxide dismutase [SOD], total antioxidant capacity [T-AOC], and malondialdehyde [MDA]) were measured. Neuronal survival was evaluated through Nissl staining, while the expression level of sirtuin 1 (SIRT1) was examined using immunohistochemical staining. Additionally, histological evaluation of lesion size was performed using hematoxylin-eosin (HE) staining. Tunel cell apoptosis staining and analysis of apoptosis-associated proteins (B-cell lymphoma-2 [Bcl2] and BCL2-Associated X [Bax]) were conducted through immunofluorescence staining and western blot, respectively. Furthermore, the model of oxidative stress was established using PC12 cells, and apoptosis levels were assessed via flow cytometry and western blot analysis. Importantly, to ascertain the critical role of SIRT1, we performed SIRT1 knockout experiments in PC12 cells using lentivirus transfection, followed by western blot.
Using those behavioral evaluations, we observed significant functional improvement after H-sEVs treatment. Nissl staining revealed that H-sEVs treatment promoted neuronal survival. Moreover, we found that H-sEVs effectively reduced oxidative stress levels after SCI. HE staining demonstrated that H-sEVs could reduce lesion area. Immunohistochemical analysis revealed that H-sEVs enhanced SIRT1 expression. Furthermore, Tunel cell apoptosis staining and western blot analysis of apoptosis-related proteins confirmed the anti-apoptotic effects of H-sEVs. The PC12 cells were used to further substantiate the neuroprotective properties of H-sEVs by significantly inhibiting neuronal death and attenuating oxidative stress. Remarkably, SIRT1 knockout in PC12 cells reversed the antioxidant stress effects induced by H-sEVs treatment. Additionally, we elucidated the involvement of the downstream Nrf2/HO-1 signaling pathway.
Our study provides valuable insights into the effects of H-sEVs on neuronal oxidative stress and apoptosis after SCI. These findings underscore the potential clinical significance of H-sEVs-based therapies for SCI.
Copyright © 2024 Rao, Xie, Liang, Yang, Chen, Zhou, Xu, Lin, Lin, Wang, Wang and Chen.

Renal ischaemia reperfusion (I/R) triggers a cascade of events including oxidative stress, apoptotic body and microparticle (MP) formation as well as an acute inflammatory process that may contribute to organ failure. Macrophages are recruited to phagocytose cell debris and MPs. The tyrosine kinase receptor MerTK is a major player in the phagocytosis process. Experimental models of renal I/R events are of major importance for identifying I/R key players and for elaborating novel therapeutical approaches. A major aim of our study was to investigate possible involvement of MerTK in renal I/R. We performed our study on both natural mutant rats for MerTK (referred to as RCS) and on wild type rats referred to as WT. I/R was established by of bilateral clamping of the renal pedicles for 30' followed by three days of reperfusion. Plasma samples were analysed for creatinine, aspartate aminotransferase (ASAT), lactate dehydrogenase (LDH), kidney injury molecule -1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) levels and for MPs. Kidney tissue damage and CD68-positive cell requirement were analysed by histochemistry. monocyte chemoattractant protein-1 (MCP-1), myeloperoxidase (MPO), inducible nitric oxide synthase (iNOS), and histone 3A (H3A) levels in kidney tissue lysates were analysed by western blotting. The phagocytic activity of blood-isolated monocytes collected from RCS or WT towards annexin-V positive bodies derived from cultured renal cell was assessed by fluorescence-activated single cell sorting (FACS) and confocal microscopy analyses. The renal I/R model for RCS rat described for the first time here paves the way for further investigations of MerTK-dependent events in renal tissue injury and repair mechanisms.

Mammary epithelial progenitors are the normal cell-of-origin of breast cancer. We previously defined a population of p27+ quiescent hormone-responsive progenitor cells in the normal human breast whose frequency associates with breast cancer risk. Here, we describe that deletion of the Cdkn1b gene encoding the p27 cyclin-dependent kinase inhibitor in the estrogen-induced mammary tumor-susceptible ACI rat strain leads to a decrease in the relative frequencies of Cd49b+ mammary luminal epithelial progenitors and pregnancy-related differentiation. We show by comprehensive gene expression profiling of purified progenitor and differentiated mammary epithelial cell populations that p27 deletion has the most pronounced effects on luminal progenitors. Cdkn1b-/- females have decreased fertility, but rats that are able to get pregnant had normal litter size and were able to nurse their pups implying that loss of p27 in ACI rats does not completely abrogate ovarian function and lactation. Reciprocal mammary gland transplantation experiments indicate that the p27-loss-induced changes in mammary epithelial cells are not only caused by alterations in their intrinsic properties, but are likely due to altered hormonal signaling triggered by the perturbed systemic endocrine environment observed in Cdkn1b-/- females. We also observed a decrease in the frequency of mammary epithelial cells positive for progesterone receptor (Pr) and FoxA1, known direct transcriptional targets of the estrogen receptor (Erα), and an increase in phospho-Stat5 positive cells commonly induced by prolactin (Prl). Characterization of genome-wide Pr chromatin binding revealed distinct binding patterns in mammary epithelial cells of Cdkn1b+/+ and Cdkn1b-/- females and enrichment in genes with known roles in Notch, ErbB, leptin, and Erα signaling and regulation of G1-S transition. Our data support a role for p27 in regulating the pool size of hormone-responsive luminal progenitors that could impact breast cancer risk.