Mesenchymal stem cell extracellular vesicles mitigate vascular permeability and injury in the small intestine and lung in a mouse model of hemorrhagic shock and trauma.

BACKGROUND: Hemorrhagic shock and trauma (HS/T)-induced gut injury may play a critical role in the development of multi-organ failure. Novel therapies that target gut injury and vascular permeability early after HS/T could have substantial impacts on trauma patients. In this study, we investigate the therapeutic potential of human mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (MSC EVs) in vivo in HS/T in mice and in vitro in Caco-2 human intestinal epithelial cells. METHODS: In vivo, using a mouse model of HS/T, vascular permeability to a 10-kDa dextran dye and histopathologic injury in the small intestine and lungs were measured among mice. Groups were (1) sham, (2) HS/T + lactated Ringer's (LR), (3) HS/T + MSCs, and (4) HS/T + MSC EVs. In vitro, Caco-2 cell monolayer integrity was evaluated by an epithelial cell impedance assay. Caco-2 cells were pretreated with control media, MSC conditioned media (CM), or MSC EVs, then challenged with hydrogen peroxide (H2O2). RESULTS: In vivo, both MSCs and MSC EVs significantly reduced vascular permeability in the small intestine (fluorescence units: sham, 456 ± 88; LR, 1067 ± 295; MSC, 765 ± 258; MSC EV, 715 ± 200) and lung (sham, 297 ± 155; LR, 791 ± 331; MSC, 331 ± 172; MSC EV, 303 ± 88). Histopathologic injury in the small intestine and lung was also attenuated by MSCs and MSC EVs. In vitro, MSC CM but not MSC EVs attenuated the increased permeability among Caco-2 cell monolayers challenged with H2O2. CONCLUSION: Mesenchymal stem cell EVs recapitulate the effects of MSCs in reducing vascular permeability and injury in the small intestine and lungs in vivo, suggesting MSC EVs may be a potential cell-free therapy targeting multi-organ dysfunction in HS/T. This is the first study to demonstrate that MSC EVs improve both gut and lung injury in an animal model of HS/T.

µ-Lat: A mouse model to evaluate human immunodeficiency virus eradication strategies.

A critical barrier to the development of a human immunodeficiency virus (HIV) cure is the lack of a scalable animal model that enables robust evaluation of eradication approaches prior to testing in humans. We established a humanized mouse model of latent HIV infection by transplanting "J-Lat" cells, Jurkat cells harboring a latent HIV provirus encoding an enhanced green fluorescent protein (GFP) reporter, into irradiated adult NOD.Cg-Prkdcscid Il2rgtm1Wjl /SzJ (NSG) mice. J-Lat cells exhibited successful engraftment in several tissues including spleen, bone barrow, peripheral blood, and lung, in line with the diverse natural tissue tropism of HIV. Administration of tumor necrosis factor (TNF)-α, an established HIV latency reversal agent, significantly induced GFP expression in engrafted cells across tissues, reflecting viral reactivation. These data suggest that our murine latency ("µ-Lat") model enables efficient determination of how effectively viral eradication agents, including latency reversal agents, penetrate, and function in diverse anatomical sites harboring HIV in vivo.

Regulation of endothelial cell permeability by platelet-derived extracellular vesicles.

BACKGROUND: Platelet (Plt)-derived extracellular vesicles (Plt-EVs) have hemostatic properties similar to Plts. In addition to hemostasis, Plts also function to stabilize the vasculature and maintain endothelial cell (EC) barrier integrity. We hypothesized that Plt-EVs would inhibit vascular EC permeability, similar to fresh Plts. To investigate this hypothesis, we used in vitro and in vivo models of vascular endothelial compromise and bleeding. METHODS: In the vitro model, Plt-EVs were isolated by ultracentrifugation and characterized for Plt markers and particle size distribution. Effects of Plts and Plt-EVs on endothelial barrier function were assessed by transendothelial electrical resistance measurements and histological analysis of endothelial junction proteins. Hemostatic potential of Plt-EVs and Plts was assessed by multiple electrode Plt aggregometry. Using an in vivo model, the effects of Plts and Plt-EVs on vascular permeability and bleeding were assessed in non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice by an established Miles assay of vascular permeability and a tail snip bleeding assay. RESULTS: In the in vitro model, Plt-EVs displayed exosomal size distribution and expressed Plt-specific surface markers. Platelets and Plt-EVs decreased EC permeability and restored EC junctions after thrombin challenge. Multiplate aggregometry revealed that Plt-EVs enhanced thrombin receptor-activating peptide-mediated aggregation of whole blood, whereas Plts enhanced thrombin receptor-activating peptide-, arachidonic acid-, collagen-, and adenosine diphosphate-mediated aggregation. In the in vivo model, Plt-EVs are equivalent to Plts in attenuating vascular endothelial growth factor (VEGF)-A-induced vascular permeability and uncontrolled blood loss in a tail snip hemorrhage model. CONCLUSION: Our study is the first to report that Plt-EVs might provide a feasible product for transfusion in trauma patients to attenuate bleeding, inhibit vascular permeability, and mitigate the endotheliopathy of trauma.

Identification and characterization of a rich population of CD34+ mesenchymal stem/stromal cells in human parotid, sublingual and submandibular glands.

Mesenchymal stem/stromal cells (MSCs) play crucial roles in maintaining tissue homeostasis during physiological turnovers and injuries. Very little is known about the phenotype, distribution and molecular nature of MSCs in freshly isolated human salivary glands (SGs) as most reports have focused on the analysis of cultured MSCs. Our results demonstrate that the cell adhesion molecule CD34 was widely expressed by the MSCs of human major SGs, namely parotid (PAG), sublingual (SLG) and submandibular (SMG) glands. Further, gene expression analysis of CD34+ cells derived from fetal SMGs showed significant upregulation of genes involved in cellular adhesion, proliferation, branching, extracellular matrix remodeling and organ development. Moreover, CD34+ SMG cells exhibited elevated expression of genes encoding extracellular matrix, basement membrane proteins, and members of ERK, FGF and PDGF signaling pathways, which play key roles in glandular development, branching and homeostasis. In vitro CD34+ cell derived SG-MSCs revealed multilineage differentiation potential. Intraglandular transplantation of cultured MSCs in immunodeficient mice led to their engraftment in the injected and uninjected contralateral and ipsilateral glands. Engrafted cells could be localized to the stroma surrounding acini and ducts. In summary, our data show that CD34+ derived SG-MSCs could be a promising cell source for adoptive cell-based SG therapies, and bioengineering of artificial SGs.

StemRegenin 1 selectively promotes expansion of Multipotent Hematopoietic Progenitors derived from Human Embryonic Stem Cells.

Human embryonic stem cell (hESC)-derived hematopoietic stem/progenitor cells hold tremendous potential as alternative cell sources for the treatment of various hematological diseases, drug discovery and toxicological screening. However, limited number of hematopoietic stem/progenitor cells generated from the differentiation of hESCs hinders their downstream applications. Here, we show that aryl hydrocarbon receptor antagonist StemRegenin 1 (SR1) selectively promotes expansion of hESC-derived lin-CD34+ hematopoietic progenitors in a concentration-dependent manner. The colony-forming cell (CFC) activity was found to be enriched in the CD34+ cells that were expanded with SR1; however, these cells have less colony-forming activity as compared to unexpanded cells (1,338 vs. 7 of CD34+ cells to form 1 colony, respectively). Interestingly, SR1 showed a bipotential effect on the proliferation of CD34 negative population, that is low dose of SR1 (1 µM) enhanced cell proliferation, whereas it was repressed at higher doses (>5 µM). In summary, our results suggest that SR1 has the potential to facilitate expansion of hESC-derived lin-CD34+ hematopoietic progenitors, which further retain the potential to form multilineage hematopoietic colonies.

Wnt signaling inhibitor FH535 selectively inhibits cell proliferation and potentiates imatinib-induced apoptosis in myeloid leukemia cell lines.

Wnt signaling pathway plays a major role in leukemogenesis of myeloid leukemia. Aberrancy in its regulation results in hyperactivity of the pathway contributing to leukemia propagation and maintenance. To investigate effects of Wnt pathway inhibition in leukemia, we used human leukemia cell lines (i.e., K562, HL60, THP1, and Jurkat) and several Wnt inhibitors, including XAV939, IWP2 and FH535. Our results showed that leukemia cell lines (>95 % cells) had increased endogenous levels of ß-catenin as compared to mononuclear cells from healthy donors (0 %). Among the tested inhibitors, FH535 demonstrated a markedly suppressive effect (IC50 = 358 nM) on mRNA levels of ß-catenin target genes (LEF1, CCND1, and cMYC). In addition, FH535 significantly potentiated imatinib-induced apoptosis. Evaluation of erythrocyte and megakaryocyte lineage using flow cytometry demonstrated that the potentiation mechanism is independent of the developmental stage, and is more likely due to crosstalk between other pathways and ß-catenin. FH535 also displayed antiproliferative properties in other cell lines used in this study. In summary, FH535 showed significantly high antiproliferative effects at submicromolar dosages, and additionally enhanced imatinib-induced apoptosis in human leukemia cell lines. Our results highlight its potential antileukemic promise when used in conjunction with other conventional therapeutic regimens.

Identification of the hemogenic endothelial progenitor and its direct precursor in human pluripotent stem cell differentiation cultures.

Hemogenic endothelium (HE) has been recognized as a source of hematopoietic stem cells (HSCs) in the embryo. Access to human HE progenitors (HEPs) is essential for enabling the investigation of the molecular determinants of HSC specification. Here, we show that HEPs capable of generating definitive hematopoietic cells can be obtained from human pluripotent stem cells (hPSCs) and identified precisely by a VE-cadherin(+)CD73(-)CD235a/CD43(-) phenotype. This phenotype discriminates true HEPs from VE-cadherin(+)CD73(+) non-HEPs and VE-cadherin(+)CD235a(+)CD41a(-) early hematopoietic cells with endothelial and FGF2-dependent hematopoietic colony-forming potential. We found that HEPs arise at the post-primitive-streak stage of differentiation directly from VE-cadherin-negative KDR(bright)APLNR(+)PDGFRα(low/-) hematovascular mesodermal precursors (HVMPs). In contrast, hemangioblasts, which are capable of forming endothelium and primitive blood cells, originate from more immature APLNR(+)PDGFRα(+) mesoderm. The demarcation of HEPs and HVMPs provides a platform for modeling blood development from endothelium with a goal of facilitating the generation of HSCs from hPSCs.

Analysis of the WISP3 gene in Indian families with progressive pseudorheumatoid dysplasia.

Progressive pseudorheumatoid dysplasia (PPD) is a progressive skeletal syndrome characterized by stiffness, swelling and pain in multiple joints with associated osteoporosis in affected patients. Radiographically, the predominant features resemble a spondyloepiphyseal dysplasia. Mutations in the WISP3 gene are known to cause this autosomal recessive condition. To date, only a limited number of studies have looked into the spectrum of mutations causing PPD. We report on clinical features and WISP3 mutations in a large series of Indian patients with this rare skeletal dysplasia. Families with at least one member showing clinical and radiologic features of PPD were recruited for the study. Symptoms, signs and radiographic findings were documented in 35 patients from 25 unrelated families. Swelling of small joints of hands and contractures are the most common presenting features. Mutation analysis was carried out by bidirectional sequencing of the WISP3 gene in all 35 patients. We summarize the clinical features of 35 patients with PPD and report on 11 different homozygous mutations and one instance of compound heterozygosity. Eight (c.233G>A, c.340T>C, c.348C>A, c.433T>C, c.682T>C, c.802T>G, c.947_951delAATTT, and c.1010G>A) are novel mutations and three (c.156C>A, c.248G>A, and c.739_740delTG) have been reported previously. One missense mutation (c.1010G>A; p.Cys337Tyr) appears to be the most common in our population being seen in 10 unrelated families. This is the largest cohort of patients with PPD in the literature and the first report from India on mutation analysis of WISP3. We also review all the mutations reported in WISP3 till date.

Generation of mature hematopoietic cells from human pluripotent stem cells.

A number of malignant and non-malignant hematological disorders are associated with the abnormal production of mature blood cells or primitive hematopoietic precursors. Their capacity for continuous self-renewal without loss of pluripotency and the ability to differentiate into adult cell types from all three primitive germ layers make human embryonic stem cells and induced pluripotent stem cells (hiPSCs) attractive complementary cell sources for large-scale production of transfusable mature blood cell components in cell replacement therapies. The generation of patient-specific hematopoietic stem/precursor cells from iPSCs by the regulated manipulation of various factors involved in reprograming to ensure complete pluripotency, and developing innovative differentiation strategies for generating unlimited supply of clinically safe, transplantable, HLA-matched cells from hiPSCs to outnumber the inadequate source of hematopoietic stem cells obtained from cord blood, bone marrow and peripheral blood, would have a major impact on the field of regenerative and personalized medicine leading to translation of these results from bench to bedside.