Aging impairs beige adipocyte differentiation of mesenchymal stem cells via the reduced expression of Sirtuin 1.

In the body, different types of adipose tissue perform different functions, with brown and beige adipose tissues playing unique roles in dissipating energy. Throughout life, adipocytes are regenerated from progenitors, and this process is impaired by aging. One of the progenitors of adipocytes are mesenchymal stem cells (MSCs), which have recently become a promising tool for stem cell therapy. However, whether or not aging impairs the brown/beige adipocyte differentiation of adipose tissue-derived MSCs (AT-MSCs) remains unclear. In the present study, we isolated AT-MSCs from two different age groups of donors (infants and elderly subjects) and examined the effects of aging on the AT-MSC brown/beige adipocyte differentiation ability. We found that none of the AT-MSCs expressed Myf5, which indicated the beige (not brown) differentiation ability of cells. Of note, an inverse correlation was noted between the beige adipocyte differentiation ability and age, with AT-MSCs derived from elderly donors showed the most severely reduced function due to induced cellular senescence. The impaired expression of Sirtuin 1 (Sirt1) and Sirt3 proved to be responsible for the induction of senescence in elderly AT-MSCs; however, only Sirt1 was directly involved in the regulation of beige adipocyte differentiation. The overexpression of Sirt1 impaired the p53/p21 pathway, thereby preventing elderly AT-MSCs from entering senescence and restoring the beige differentiation ability. Thus, our study represents the important role of Sirt1 and senescence in the regulation of beige adipocyte differentiation during aging.

Hypoxia promotes the phenotypic change of aldehyde dehydrogenase activity of breast cancer stem cells.

Stable breast cancer cell (BCC) lines are valuable tools for the identification of breast cancer stem cell (BCSC) phenotypes that develop in response to several stimuli as well as for studying the basic mechanisms associated with the initiation and maintenance of BCSCs. However, the characteristics of individual, BCC-derived BCSCs varies and these cells show distinct phenotypes depending on the different BCSC markers used for their isolation. Aldehyde dehydrogenase (ALDH) activity is just such a recognized biomarker of BCSCs with a CD44+ /CD24- phenotype. We isolated BCSCs with high ALDH activity (CD44+ /CD24- /Aldefluorpos ) from a primary culture of human breast cancer tissue and observed that the cells had stem cell properties compared to BCSCs with no ALDH activity (CD44+ /CD24- /Aldefluorneg ). Moreover, we found Aldefluorpos BCSCs had a greater hypoxic response and subsequent induction of HIF-1α expression compared to the Aldefluorneg BCSCs. We also found that knocking down HIF-1α, but not HIF-2α, in Aldefluorpos BCSCs led to a significant reduction of the stem cell properties through a decrease in the mRNA levels of genes associated with the epithelial-mesenchymal transition. Indeed, HIF-1α overexpression in Aldefluorneg BCSCs led to Slug and Snail mRNA increase and the associated repression of E-cadherin and increase in Vimentin. Of note, prolonged hypoxic stimulation promoted the phenotypic changes of Aldefluorneg BCSCs including ALDH activity, tumorigenesis and metastasis, suggesting that hypoxia in the tumor environment may influence BCSC fate and breast cancer clinical outcomes.

SDF-1 improves wound healing ability of glucocorticoid-treated adipose tissue-derived mesenchymal stem cells.

Glucocorticoids cause the delayed wound healing by suppressing inflammation that is required for wound healing process. Adipose tissue-derived mesenchymal stem cells (AT-MSCs) play an important role for wound healing by their cytokine productions including stromal derived factor 1 (SDF-1). However, it has not been clear how glucocorticoids affect the wound healing ability of AT-MSCs. In this study, we found that glucocorticoid downregulated SDF-1 expression in AT-MSCs. In addition, glucocorticoid-treated AT-MSCs induced less migration of inflammatory cells and impaired wound healing capacity compared with glucocorticoid-untreated AT-MSCs. Of note, prostaglandin E2 (PGE2) synthesis-related gene expression was downregulated by glucocorticoid and PGE2 treatment rescued not only SDF-1 expression in the presence of glucocorticoid but also their wound healing capacity in vivo. Furthermore, we found SDF-1-overexpressed AT-MSCs restored wound healing capacity even after treatment of glucocorticoid. Consistent with the results obtained from glucocorticoid-treated AT-MSCs, we found that AT-MSCs isolated from steroidal osteonecrosis donors (sAT-MSCs) who received chronic glucocorticoid therapy showed less SDF-1 expression and impaired wound healing capacity compared with traumatic osteonecrosis donor-derived AT-MSCs (nAT-MSCs). Moreover, the SDF-1 level was also reduced in plasma derived from steroidal osteonecrosis donors compared with traumatic osteonecrosis donors. These results provide the evidence that concomitant application of AT-MSCs with glucocorticoid shows impaired biological modulatory effects that induce impaired wound healing.

GATA2 is critical for the maintenance of cellular identity in differentiated mast cells derived from mouse bone marrow.

GATA2 plays a crucial role for the mast cell fate decision. We herein demonstrate that GATA2 is also required for the maintenance of the cellular identity in committed mast cells derived from mouse bone marrow (BMMCs). The deletion of the GATA2 DNA binding domain (GATA2ΔCF) in BMMCs resulted in a loss of the mast cell phenotype and an increase in the number of CD11b- and/or Ly6G/C-positive cells. These cells showed the ability to differentiate into macrophage- and neutrophil-like cells but not into eosinophils. Although the mRNA levels of basophil-specific genes were elevated, CD49b, a representative basophil marker, never appeared on these cells. GATA2 ablation led to a significant upregulation of C/EBPα, and forced expression of C/EBPα in wild-type BMMCs phenocopied the GATA2ΔCF cells. Interestingly, simultaneous deletion of the Gata2 and Cebpa genes in BMMCs restored the aberrant increases of CD11b and Ly6G/C while retaining the reduced c-Kit expression. Chromatin immunoprecipitation assays indicated that GATA2 directly binds to the +37-kb region of the Cebpa gene and thereby inhibits the RUNX1 and PU.1 binding to the neighboring region. Upregulation of C/EBPα following the loss of GATA2 was not observed in cultured mast cells derived from peritoneal fluid, whereas the repression of c-Kit and other mast cell-specific genes were observed in these cells. Collectively, these results indicate that GATA2 maintains cellular identity by preventing Cebpa gene activation in a subpopulation of mast cells, whereas it plays a fundamental role as a positive regulator of mast cell-specific genes throughout development of this cell lineage.

FOXA1 expression affects the proliferation activity of luminal breast cancer stem cell populations.

The expression of estrogen receptor is the key in most breast cancers (BC) and binding of estrogen receptor to the genome correlates to Forkhead protein (FOXA1) expression. We herein assessed the correlation between the cancer stem cell (CSC) population and FOXA1 expression in luminal BC. We established luminal BC cells derived from metastatic pleural effusion and analyzed the potency of CSC and related factors with established luminal BC cell lines. We also confirmed that mammosphere cultures have an increased aldehyde dehydrogenase-positive population, which is one of the CSC markers, compared with adherent culture cells. Using a quantitative PCR analysis, we found that mammosphere forming cells showed a higher expression of FOXA1 and stemness-related genes compared with adherent culture cells. Furthermore, the growth activity and colony-forming activity of 4-hydroxytamoxifen-treated BC cells were inhibited in a mammosphere assay. Interestingly, 4-hydroxytamoxifen-resistant cells had significantly increased FOXA1 gene expression levels. Finally, we established short hairpin RNA of FOXA1 (shFOXA1) MCF-7 cells and investigated the relationship between self-renewal potential and FOXA1 expression. As a result, we found no significant difference in the number of mammospheres but decreased colony formation in shFOXA1 MCF-7 cells compared with control. These results suggest that the expression of FOXA1 appears to be involved in the proliferation of immature BC cells rather than the induction of stemness-related genes and self-renewal potency of CSCs.

Microvesicles enhance the mobility of human diabetic adipose tissue-derived mesenchymal stem cells in vitro and improve wound healing in vivo.

Microvesicles (MVs) derived from mesenchymal stem cells showed the ability to alter the cell phenotype and function. We previously demonstrated that type 2 diabetic adipose tissue-derived mesenchymal stem cells (dAT-MSCs) increase in cell aggregation and adhesion in vitro and impair wound healing in vivo. However, the characterization and function of MVs derived from human non-diabetic AT-MSCs (nAT-MSCs) remain unknown. In this study, we characterized nAT-MSC-derived MVs and their function after the transfection of dAT-MSCs with MVs using the scratch assay and a flap mouse model. We found that human nAT-MSC-derived MVs expressed MSC-surface markers and improved dAT-MSC functions by altering the expression of genes associated with cell migration, survival, inflammation, and angiogenesis as well as miR29c and miR150. Remarkably, the transfection of dAT-MSCs with nAT-MSC-derived MVs improved their migration ability in vitro and wound healing ability in a flap mouse model. These results demonstrate a promising opportunity to modify the function of dAT-MSCs for therapeutic stem cell application in diabetic patients.

Microvesicles derived from Alde-Low EPCs support the wound healing capacity of AT-MSCs.

Mesenchymal stem cells (MSCs) are defined as multipotent cells that can give rise to various kinds of differentiated mesenchymal cells, and are thus considered to be useful for clinical therapy. However, the big hurdles of MSC therapy are the inability of MSCs to reach the appropriate tissues or sites with high efficiency and engraftment after transplantation. In this study, we investigated how adipose tissue-derived MSCs (AT-MSCs) improve their homing ability after intravenous injection. We previously found that human endothelial progenitor cells with low aldehyde dehydrogenase activity (Alde-Low EPCs) are suitable for the treatment of ischemic tissues. In addition, we demonstrated that microvesicles (MVs) derived from Alde-Low EPCs possessed the ability to improve the homing ability of non-functional Alde-High EPCs, resulting in wound healing. We initially transfected MVs derived from Alde-Low EPCs (EMVs) to human AT-MSCs, which were originally unable to cure ischemic tissues by intravenous transplantation. Remarkably, AT-MSC transfected EMVs dramatically repaired the ischemic skin flap compared with AT-MSC derived-MV (MMVs) transfected AT-MSCs or control AT-MSCs. We then found that the expression of CXCR4, an important chemokine receptor for cell migration, was highly elevated in EMV-transfected AT-MSCs. Moreover, AT-MSCs transfected with EMVs, but not control AT-MSCs, migrated to wound sites after intravenous injection. Consequently, CD45(+) inflammatory cells were successfully recruited at the wound sites after the injection of EMV-transfected AT-MSCs. These results demonstrate that EMVs are a useful source to improve the homing ability and wound healing ability of MSCs at the wound sites.

Hypoxia-inducible factor-3α promotes angiogenic activity of pulmonary endothelial cells by repressing the expression of the VE-cadherin gene.

The variants of the hypoxia-inducible factor-3α gene HIF-3α and NEPAS are known to repress the transcriptional activities driven by HIF-1α and HIF-2α. Although NEPAS has been shown to play an important role in vascular remodeling during lung development, little is known about the roles of HIF-3α in adult lung function. Here, we examined pulmonary endothelial cells (ECs) isolated from wild-type (WT) and HIF-3α functional knockout (KO) mice. The expression levels of angiogenic factors (Flk1, Ang2 and Tie2) were significantly greater in the HIF-3α KO ECs than those in the WT ECs irrespective of oxygen tension. However, the HIF-3α KO ECs showed impaired proliferative and angiogenic activities. The impaired EC function was likely due to the excess vascular endothelial (VE)-cadherin, an inhibitor of Flk1/PI3 kinase/Akt signaling, as treatment of the cells to a neutralizing antibody partly restored the phenotype of the HIF-3α KO ECs. Importantly, we found that the mRNA levels of HIF-2α and Ets-1 were significantly increased by HIF-3α ablation. Given that both factors are known to activate the VE-cadherin gene, the transcriptional repression of these factors by HIF-3α might be important for silencing the irrelevant expression of the VE-cadherin gene. Collectively, these data show novel and unique roles of HIF-3α for angiogenic gene regulation in pulmonary ECs.

In vivo retinal and choroidal hypoxia imaging using a novel activatable hypoxia-selective near-infrared fluorescent probe.

PURPOSE: Retinal hypoxia plays a crucial role in ocular neovascular diseases, such as diabetic retinopathy, retinopathy of prematurity, and retinal vascular occlusion. Fluorescein angiography is useful for identifying the hypoxia extent by detecting non-perfusion areas or neovascularization, but its ability to detect early stages of hypoxia is limited. Recently, in vivo fluorescent probes for detecting hypoxia have been developed; however, these have not been extensively applied in ophthalmology. We evaluated whether a novel donor-excited photo-induced electron transfer (d-PeT) system based on an activatable hypoxia-selective near-infrared fluorescent (NIRF) probe (GPU-327) responds to both mild and severe hypoxia in various ocular ischemic diseases animal models. METHODS: The ocular fundus examination offers unique opportunities for direct observation of the retina through the transparent cornea and lens. After injection of GPU-327 in various ocular hypoxic diseases of mouse and rabbit models, NIRF imaging in the ocular fundus can be performed noninvasively and easily by using commercially available fundus cameras. To investigate the safety of GPU-327, electroretinograms were also recorded after GPU-327 and PBS injection. RESULT: Fluorescence of GPU-327 increased under mild hypoxic conditions in vitro. GPU-327 also yielded excellent signal-to-noise ratio without washing out in vivo experiments. By using near-infrared region, GPU-327 enables imaging of deeper ischemia, such as choroidal circulation. Additionally, from an electroretinogram, GPU-327 did not cause neurotoxicity. CONCLUSIONS: GPU-327 identified hypoxic area both in vivo and in vitro.

Impaired expression of HIF-2α induces compensatory expression of HIF-1α for the recovery from anemia.

Erythropoiesis is strongly influenced by the interactions between stromal cells and erythroid progenitors, as well as by a key regulatory factor, erythropoietin (EPO). We previously generated mice with a knockdown mutation of Hif-2α (referred to as kd/kd) and found that these kd/kd mice exhibited normocytic anemia, even though the EPO expression was not severely affected. However, the VCAM-1 expression in spleen endothelial cells (EC), which is regulated by HIF-2α, was impaired, resulting in defective erythroid maturation. A deficiency of HIF-2α clearly led to pancytopenia. However, the critical level of HIF-2α required for erythropoiesis has not yet been elucidated. In this study, we generated HIF-2α knockdown/knockout heterozygous mice (kd/null). Strikingly, anemia was observed in the kd/null mice, but the red blood cell indices were significantly improved compared to those of kd/kd mice. In the spleens of kd/null mice, higher HIF-1α activity and expansion of the red pulp area were observed compared to those of kd/kd mice. Importantly, EC isolated from kd/null spleens showed high expression of VEGF receptors, FLK-1 and FLT-1, which are regulated by HIF-1α instead of HIF-2α under hypoxic conditions. We also found higher expression of phosphorylated ERK and higher proliferative activity in the EC isolated from kd/null mice compared to those from kd/kd mice. While the HIF-2α expression was diminished, HIF-1α bound to the HRE region in the promoters of genes that are normally regulated by HIF-2α. These results suggest that there is a compensatory pathway involving HIF-1α that regulates the expression of some HIF-2α target genes.

Deficiency of NOX1/nicotinamide adenine dinucleotide phosphate, reduced form oxidase leads to pulmonary vascular remodeling.

OBJECTIVE: Involvement of reactive oxygen species derived from nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase has been documented in the development of hypoxia-induced model of pulmonary arterial hypertension (PAH). Because the PAH-like phenotype was demonstrated in mice deficient in Nox1 gene (Nox1(-/Y)) raised under normoxia, the aim of this study was to clarify how the lack of NOX1/NADPH oxidase could lead to pulmonary pathology. APPROACH AND RESULTS: Spontaneous enlargement and hypertrophy of the right ventricle, accompanied by hypertrophy of pulmonary vessels, were demonstrated in Nox1(-/Y) 9 to 18 weeks old. Because an increased number of α-smooth muscle actin-positive vessels were observed in Nox1(-/Y), pulmonary arterial smooth muscle cells (PASMCs) were isolated and characterized by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. In Nox1(-/Y) PASMCs, the number of apoptotic cells was significantly reduced without any change in the expression of endothelin-1, and hypoxia-inducible factors HIF-1α and HIF-2α, factors implicated in the pathogenesis of PAH. A significant decrease in a voltage-dependent K(+) channel, Kv1.5 protein, and an increase in intracellular potassium levels were demonstrated in Nox1(-/Y) PASMCs. When a rescue study was performed in Nox1(-/Y) crossed with transgenic mice overexpressing rat Nox1 gene, impaired apoptosis and the level of Kv1.5 protein in PASMCs were almost completely recovered in Nox1(-/Y) harboring the Nox1 transgene. CONCLUSIONS: These findings suggest a critical role for NOX1 in cellular apoptosis by regulating Kv1.5 and intracellular potassium levels. Because dysfunction of Kv1.5 is among the features demonstrated in PAH, inactivation of NOX1/NADPH oxidase may be a causative factor for pulmonary vascular remodeling associated with PAH.

Establishment of erythroleukemic GAK14 cells and characterization of GATA1 N-terminal domain.

GATA1 is a transcription factor essential for erythropoiesis and megakaryopoiesis. It has been found that Gata1 gene knockdown heterozygous female (Gata1(G1.05/+)) mice spontaneously develop erythroblastic leukemias. In this study, we have generated a novel Gata1 knockdown erythroblastic cell line, designated GAK14, from the leukemia cells in the Gata1(G1.05/+) mice. Although GAK14 cells maintain immature phenotype on OP9 stromal cells in the presence of erythropoietin and stem cell factor, the cells produce Gr-1-, Mac1-, B220-, CD3e- or CD49b-positive hematopoietic cells when co-cultured with DAS104-8 feeder cells. However, GAK14 cells did not produce erythroid and megakaryocytic lineages, perhaps due to the absence of GATA1. Indeed, GAK14 cells became capable of differentiating into mature erythroid cells when complemented with full-length GATA1 and co-cultured with fetal liver-derived FLS5 stromal cells. This differentiation potential was impaired when GATA1 lacking the N-terminal domain was complemented. The N-terminal domain is known to contribute to the pathogenesis of transient abnormal myelopoiesis and acute megakaryoblastic leukemia related to Down syndrome. These results thus showed that GAK14 cells will serve as a powerful tool for dissecting domain function of GATA1 and that the GATA1 N-terminal domain is essential for the erythroid differentiation of GAK14 cells.

GATA factor switching from GATA2 to GATA1 contributes to erythroid differentiation.

Transcription factor GATA2 is highly expressed in hematopoietic stem cells and progenitors, whereas its expression declines after erythroid commitment of progenitors. In contrast, the start of GATA1 expression coincides with the erythroid commitment and increases along with the erythroid differentiation. We refer this dynamic transition of GATA factor expression to as the 'GATA factor switching'. Here, we examined contribution of the GATA factor switching to the erythroid differentiation. In Gata1-knockdown embryos that concomitantly express Gata2-GFP reporter, high-level expression of GFP reporter was detected in accumulated immature hematopoietic cells with impaired differentiation, demonstrating that GATA1 represses Gata2 gene expression in hematopoietic progenitors in vivo. We have conducted chromatin immunoprecipitation (ChIP) on microarray analyses of GATA2 and GATA1, and results indicate that the GATA1-binding sites widely overlap with the sites pre-occupied by GATA2 before the GATA1 expression. Importantly, erythroid genes harboring GATA boxes bound by both GATA1 and GATA2 tend to be expressed in immature erythroid cells, whereas those harboring GATA boxes to which GATA1 binds highly but GATA2 binds only weakly are important for the mature erythroid cell function. Our results thus support the contention that preceding binding of GATA2 helps the following binding of GATA1 and thereby secures smooth expression of the transient-phase genes.

Functional endothelial progenitor cells selectively recruit neurovascular protective monocyte-derived F4/80(+) /Ly6c(+) macrophages in a mouse model of retinal degeneration.

Retinitis pigmentosa is a group of inherited eye disorders that result in profound vision loss with characteristic retinal neuronal degeneration and vasculature attenuation. In a mouse model of retinitis pigmentosa, endothelial progenitor cells (EPC) from bone marrow rescued the vasculature and photoreceptors. However, the mechanisms and cell types underlying these protective effects were uncertain. We divided EPC, which contribute to angiogenesis, into two subpopulations based on their aldehyde dehydrogenase (ALDH) activity and observed that EPC with low ALDH activity (Alde-Low) had greater neuroprotection and vasoprotection capabilities after injection into the eyes of an rd1 mouse model of retinitis pigmentosa compared with EPC with high ALDH activity (Alde-High). Of note, Alde-Low EPC selectively recruited F4/80(+) /Ly6c(+) monocyte-derived macrophages from bone marrow into retina through CCL2 secretion. In addition, the mRNA levels of CCR2, the neurotrophic factors TGF-ß1 and IGF-1, and the anti-inflammatory mediator interleukin-10 were higher in migrated F4/80(+) /Ly6c(+) monocyte-derived macrophages as compared with F4/80(+) /Ly6c(-) resident retinal microglial cells. These results suggest a novel therapeutic approach using EPC to recruit neuroprotective macrophages that delay the progression of neural degenerative disease.

Oxidative stress retards vascular development before neural degeneration occurs in retinal degeneration rd1 mice.

PURPOSE: To investigate the role of reactive oxygen species (ROS) in retinal development during the early postnatal stage of rd1 mice. METHODS: Development of the three retinal vascular layers of C57BL/6 J (WT) and C3H/HeN (rd1) mice was evaluated from 9th postnatal day (P9) to P21. Retinal ROS production was semi-quantitatively measured using dihydroethidium fluorescence. Mice were treated with intraperitoneal injections of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL) at a dose of 275 mg/kg body weight, and PBS as the control from P3 to P8. RESULTS: Rd1 mice showed retardation of retinal vascular development in the deep layer at P9. No significant difference was observed in the outer nuclear layer thickness of rd1 and WT mice. ROS production in the outer nuclear layer of rd1 mice was significantly higher than that in the outer nuclear layer of WT mice at P9, P13, and P17 (P < .05). TEMPOL facilitated the development of the deep vascular layer when compared with injection of PBS. CONCLUSIONS: Retardation of retinal vascular development is observed in rd1 mice; ROS is partially responsible for this finding. When using rd1 mice, we should be aware of this difference in comparison to other retinal degeneration animal models and human pathophysiological changes.

Extracellular Vesicles Derived from Type 2 Diabetic Mesenchymal Stem Cells Induce Endothelial Mesenchymal Transition under High Glucose Conditions Through the TGFß/Smad3 Signaling Pathway.

Type 2 diabetes mellitus (T2DM) is associated with endothelial dysfunction, which results in delayed wound healing. Mesenchymal stem cells (MSCs) play a vital role in supporting endothelial cells (ECs) and promoting wound healing by paracrine effects through their secretome-containing extracellular vesicles. We previously reported the impaired wound healing ability of adipose tissue-derived MSC from T2DM donors; however, whether extracellular vesicles isolated from T2DM adipose tissue-derived MSCs (dEVs) exhibit altered functions in comparison to those derived from healthy donors (nEVs) is still unclear. In this study, we found that nEVs induced EC survival and angiogenesis, whereas dEVs lost these abilities. In addition, under high glucose conditions, nEV protected ECs from endothelial-mesenchymal transition (EndMT), whereas dEV significantly induced EndMT by activating the transforming growth factor-ß/Smad3 signaling pathway, which impaired the tube formation and in vivo wound healing abilities of ECs. Interestingly, the treatment of dEV-internalized ECs with nEVs rescued the induced EndMT effects. Of note, the internalization of nEV into T2DM adipose tissue-derived MSC resulted in the production of an altered n-dEV, which inhibited EndMT and supported the survival of T2DM db/db mice from severe wounds. Taken together, our findings suggest the role of dEV in endothelial dysfunction and delayed wound healing in T2DM by the promotion of EndMT. Moreover, nEV treatment can be considered a promising candidate for cell-free therapy to protect ECs in T2DM.

Extracellular vesicles derived from SARS-CoV-2 M-protein-induced triple negative breast cancer cells promoted the ability of tissue stem cells supporting cancer progression.

Introduction: SARS-CoV-2 infection increases the risk of worse outcomes in cancer patients, including those with breast cancer. Our previous study reported that the SARS-CoV-2 membrane protein (M-protein) promotes the malignant transformation of triple-negative breast cancer cells (triple-negative BCC). Methods: In the present study, the effects of M-protein on the ability of extracellular vesicles (EV) derived from triple-negative BCC to regulate the functions of tissue stem cells facilitating the tumor microenvironment were examined. Results: Our results showed that EV derived from M-protein-induced triple-negative BCC (MpEV) significantly induced the paracrine effects of adipose tissue-derived mesenchymal stem cells (ATMSC) on non-aggressive BCC, promoting the migration, stemness phenotypes, and in vivo metastasis of BCC, which is related to PGE2/IL1 signaling pathways, in comparison to EV derived from normal triple-negative BCC (nEV). In addition to ATMSC, the effects of MpEV on endothelial progenitor cells (EPC), another type of tissue stem cells, were examined. Our data suggested that EPC uptaking MpEV acquired a tumor endothelial cell-like phenotype, with increasing angiogenesis and the ability to support the aggressiveness and metastasis of non-aggressive BCC. Discussion: Taken together, our findings suggest the role of SARS-CoV-2 M-protein in altering the cellular communication between cancer cells and other non-cancer cells inside the tumor microenvironment via EV. Specifically, M-proteins induced the ability of EV derived from triple-negative BCC to promote the functions of non-cancer cells, such as tissue stem cells, in tumorigenesis.

Impairment of HIF-2α Expression Induced the Compensatory Overexpression of the HIF-1α/SDF-1 Axis to Promote Wound Healing.

Glucocorticoids are common anti-inflammatory factors; however, they have been reported to have side effects that delay the wound healing process. In a previous study, we found that mesenchymal stem cells isolated from the adipose tissue of patients with long-term glucocorticoid treatment (sAT-MSC) showed impaired wound healing ability due to the downregulation of SDF-1. In this study, we aimed to clarify the mechanisms by which SDF-1 is regulated in sAT-MSC by focusing on the roles of hypoxia-inducible factors (HIFs). Our data suggested that sAT-MSC showed impairment of HIF-1α and the upregulation of HIF-2α. Notably, HIF-2α impairment resulted in the compensatory overexpression of HIF-1α and its target gene SDF-1, which improved the wound healing ability of sAT-MSC. In addition, using knockdown/knockout heterozygous HIF-2α kd/null mice (kd/null), the functions of HIF-2α in the ischemic wound healing process were clarified. With a 50% reduction in the expression of HIF-2α, kd/null mice showed significantly induced wound healing effects, which are involved in the promotion of the inflammatory phase. Specifically, kd/null mice showed the compensatory overexpression of HIF-1α, which upregulated the expression of SDF-1 and enhanced the recruitment of inflammatory cells, such as neutrophils. Our study highlighted the novel function of HIF-2α in the inflammation phase of the wound healing process through the HIF-1α/SDF-1 axis, suggesting that the physiological state of the impaired expression of HIF-2α is a new concept for wound therapy.

A subpopulation of endothelial progenitor cells with low aldehyde dehydrogenase activity attenuates acute ischemic brain injury in rats.

Previous studies have examined the therapeutic effect of endothelial progenitor cells (EPCs) during the chronic phase of cerebral infarction in rats; however, few studies have investigated the effects of EPCs during the acute phase of infarction. In this study, we evaluated the therapeutic effect of EPCs with low aldehyde dehydrogenase activity (Alde-Low EPCs) in rats with acute cerebral infarction, and our results provide insight that may help to identify a therapeutic mechanism of EPCs for acute cerebral infarction. The administration of Alde-Low EPCs into rats with acute cerebral infarction results in the accumulation and migration of the Alde-Low EPCs into the infarct area and the subsequent decrease of infarct volume. Moreover, we found that the stromal cell-derived factor-1 (SDF-1) and CXC chemokine receptor 4 (CXCR4) signaling pathway may regulate the accumulation of Alde-Low EPCs. The transplantation of Alde-Low EPCs may represent a potential treatment strategy for acute cerebral infarction.