Prostaglandin E2 Induces YAP1 and Agrin Through EP4 in Neonatally-Derived Islet-1+ Stem Cells.

Prostaglandin E2 (PGE2) has recently gained attention in the field of regenerative medicine because of the beneficial effects of this molecule on stem cell proliferation and migration. Furthermore, PGE2 has the ability to mitigate immune rejection and fibrosis. In the colon and kidney, PGE2 induces YAP1, a transcription factor critical for cardiac regeneration. Establishing a similar connection in stem cells that can be transplanted in the heart could lead to the development of more effective therapeutics. In this report, we identify the effects of PGE2 on neonatal Islet-1+ stem cells. These stem cells synthesize PGE2, which functions by stimulating the transcription of the extracellular matrix protein Agrin. Agrin upregulates YAP1. Consequently, both YAP1 and Agrin are induced by PGE2 treatment. Our study shows that PGE2 upregulated the expression of both YAP1 and Agrin in Islet-1+ stem cells through the EP4 receptor and stimulated proliferation using the same mechanisms. PGE2 administration further elevated the expression of stemness markers and the matrix metalloproteinase MMP9, a key regulator of remodeling in the extracellular matrix post-injury. The expression of PGE2 in neonatal Islet-1+ cells is a factor which contributes to improving the functional efficacy of these cells for cardiac repair.

Neonatal Cardiovascular-Progenitor-Cell-Derived Extracellular Vesicles Activate YAP1 in Adult Cardiac Progenitor Cells.

New stem cell and extracellular-vesicle-based therapies have the potential to improve outcomes for the increasing number of patients with heart failure. Since neonates have a significantly enhanced regenerative ability, we hypothesized that extracellular vesicles isolated from Islet-1+ expressing neonatal human cardiovascular progenitors (CPCs) will induce transcriptomic changes associated with improved regenerative capability when co-cultured with CPCs derived from adult humans. In order to test this hypothesis, we isolated extracellular vesicles from human neonatal Islet-1+ CPCs, analyzed the extracellular vesicle content using RNAseq, and treated adult CPCs with extracellular vesicles derived from neonatal CPCs to assess their functional effect. AKT, ERBB, and YAP1 transcripts were elevated in adult CPCs treated with neonatal CPC-derived extracellular vesicles. YAP1 is lost after the neonatal period but can stimulate cardiac regeneration. Our results demonstrate that YAP1 and additional transcripts associated with improved cardiovascular regeneration, as well as the activation of the cell cycle, can be achieved by the treatment of adult CPCs with neonatal CPC-derived extracellular vesicles. Progenitor cells derived from neonates secrete extracellular vesicles with the potential to stimulate and potentially improve functional effects in adult CPCs used for cardiovascular repair.

Transcriptomic Effects on the Mouse Heart Following 30 Days on the International Space Station.

Efforts to understand the impact of spaceflight on the human body stem from growing interest in long-term space travel. Multiple organ systems are affected by microgravity and radiation, including the cardiovascular system. Previous transcriptomic studies have sought to reveal the changes in gene expression after spaceflight. However, little is known about the impact of long-term spaceflight on the mouse heart in vivo. This study focuses on the transcriptomic changes in the hearts of female C57BL/6J mice flown on the International Space Station (ISS) for 30 days. RNA was isolated from the hearts of three flight and three comparable ground control mice and RNA sequencing was performed. Our analyses showed that 1147 transcripts were significantly regulated after spaceflight. The MAPK, PI3K-Akt, and GPCR signaling pathways were predicted to be activated. Transcripts related to cytoskeleton breakdown and organization were upregulated, but no significant change in the expression of extracellular matrix (ECM) components or oxidative stress pathway-associated transcripts occurred. Our results indicate an absence of cellular senescence, and a significant upregulation of transcripts associated with the cell cycle. Transcripts related to cellular maintenance and survival were most affected by spaceflight, suggesting that cardiovascular transcriptome initiates an adaptive response to long-term spaceflight.

Identification of SALL4 Expressing Islet-1+ Cardiovascular Progenitor Cell Clones.

The utilization of cardiac progenitor cells (CPCs) has been shown to induce favorable regenerative effects. While there are various populations of endogenous CPCs in the heart, there is no consensus regarding which population is ideal for cell-based regenerative therapy. Early-stage progenitor cells can be differentiated into all cardiovascular lineages, including cardiomyocytes and endothelial cells. Identifying an Islet-1+ (Isl-1+) early-stage progenitor population with enhanced stemness, multipotency and differentiation potential would be beneficial for the development of novel regenerative therapies. Here, we investigated the transcriptome of human neonatal Isl-1+ CPCs. Isl-1+ human neonatal CPCs exhibit enhanced stemness properties and were found to express Spalt-like transcription factor 4 (SALL4). SALL4 plays a role in embryonic development as well as proliferation and expansion of hematopoietic progenitor cells. SALL4, SOX2, EpCAM and TBX5 are co-expressed in the majority of Isl-1+ clones isolated from neonatal patients. The pre-mesendodermal transcript TFAP2C was identified in select Isl-1, SALL4, SOX2, EpCAM and TBX5 expressing clones. The ability to isolate and expand pre-mesendodermal stage cells from human patients is a novel finding that holds potential value for applications in regenerative medicine.

MicroRNA Expression in the Infarcted Heart Following Neonatal Cardiovascular Progenitor Cell Transplantation in a Sheep Model of Stem Cell-Based Repair.

Myocardial infarctions affect approximately 735,000 people annually in the United States and have a substantial impact on quality of life. Neonates have an enhanced capability of repairing cardiovascular damage, while adults do not. The mechanistic basis for this age-dependent difference in regenerative capacity remains unknown. Recent studies have shown that microRNAs (miRNAs) play a significant role in regulating the regenerative ability of cardiovascular cells. This report defines the alterations in miRNA expression within the cardiovascular repair zone of infarcted sheep hearts following intracardiac injection of neonatal islet-1+ cardiovascular progenitor cells. Sheep were infarcted via left anterior descending coronary artery ligation. After 3 to 4 weeks of infarction, sheep neonatal islet-1+ cardiovascular progenitor cells were injected into the infarcted area for repair. Cell-treated sheep were euthanized 2 months following cell injection, and their hearts were harvested for the analysis of miRNA and gene expression within the cardiovascular repair zone. Ten miRNAs were differentially regulated in vivo, including miR-99, miR-100, miR-302a, miR-208a, miR-665, miR-1, miR-499a, miR-34a, miR-133a, and miR-199a. These miRNAs promote stemness, cell division, and survival. Several signaling pathways are regulated by these miRNAs, including Hippo, Wnt, and Erythroblastic Leukemia Viral Oncogene B (ERBB). Transcripts encoding Wnt, ERBB, and Neuregulin 1 (NRG1) were elevated in vivo in the infarct repair zone. Wnt5a signaling and ERBB/NRG1 transcripts contribute to activation of Yes-Associated Protein 1. MiRNAs that impact proliferation, cell survival, and signaling pathways that promote regeneration were induced during cardiovascular repair in the sheep model. This information can be used to design new approaches for the optimization of miRNA-based treatments for the heart.

Long-Term Hypoxia Maintains a State of Dedifferentiation and Enhanced Stemness in Fetal Cardiovascular Progenitor Cells.

Early-stage mammalian embryos survive within a low oxygen tension environment and develop into fully functional, healthy organisms despite this hypoxic stress. This suggests that hypoxia plays a regulative role in fetal development that influences cell mobilization, differentiation, proliferation, and survival. The long-term hypoxic environment is sustained throughout gestation. Elucidation of the mechanisms by which cardiovascular stem cells survive and thrive under hypoxic conditions would benefit cell-based therapies where stem cell survival is limited in the hypoxic environment of the infarcted heart. The current study addressed the impact of long-term hypoxia on fetal Islet-1+ cardiovascular progenitor cell clones, which were isolated from sheep housed at high altitude. The cells were then cultured in vitro in 1% oxygen and compared with control Islet-1+ cardiovascular progenitor cells maintained at 21% oxygen. RT-PCR, western blotting, flow cytometry, and migration assays evaluated adaptation to long term hypoxia in terms of survival, proliferation, and signaling. Non-canonical Wnt, Notch, AKT, HIF-2α and Yap1 transcripts were induced by hypoxia. The hypoxic niche environment regulates these signaling pathways to sustain the dedifferentiation and survival of fetal cardiovascular progenitor cells.

Genome Sequence of JangDynasty, a Newly Isolated Mycobacteriophage.

JangDynasty is a bacteriophage that infects Mycobacterium smegmatis mc2155. It has a genome length of 70,883 bp, with 124 predicted open reading frames (ORFs), 42 of which have known functions. JangDynasty belongs to cluster O, and like other cluster O phages, it is a siphovirus with a prolate capsid.