Pulse exposure of haematopoietic grafts to prostaglandin E2 in vitro facilitates engraftment and recovery

OBJECTIVES: The aim of this study was to evaluate the effects of prostaglandin E(2) (PGE(2) ) on haematopoietic stem cell (HSC) function and determine its mechanism of action. MATERIALS AND METHODS: HSC were exposed to PGE(2) for 2 h and effects on their homing, engraftment and self-renewal evaluated in vivo. Effects of PGE(2) on HSC cell cycle, CXCR4 expression and migration to SDF-1α were analysed in vitro. Apoptosis was evaluated by examination of survivin expression and active caspase-3 levels. RESULTS: Equivalent haematopoietic reconstitution was demonstrated using 4-fold fewer PGE(2) -treated cells compared to controls. Multilineage reconstitution was stable on secondary transplantation, indicating that PGE(2) affects long-term repopulating HSC (LT-HSC) and that enhanced chimaerism of PGE(2) -pulsed cells results from their initial treatment. PGE(2) increased CXCR4 expression on mouse and human HSC, increased their migration to SDF-1αin vitro and enhanced in vivo marrow homing 2-fold, which was blocked by a CXCR4 receptor antagonist. PGE(2) pulse exposure reduced apoptosis of mouse and human HSC, with increase in endogenous caspase inhibitor survivin, and concomitant decrease in active caspase-3. Two-fold more HSC entered the cell cycle and proliferated within 24 h after PGE(2) pulse exposure. CONCLUSIONS: These studies demonstrate that short-term PGE(2) exposure enhances HSC function and supports the concept of utility of PGE(2) as an ex vivo strategy to improve function of haematopoietic grafts, particularly those where HSC numbers are limited

Cardiac and Renal Delayed Effects of Acute Radiation Exposure: Organ Differences in Vasculopathy, Inflammation, Senescence and Oxidative Balance

We have previously shown significant pathology in the heart and kidney of murine hematopoietic-acute radiation syndrome (H-ARS) survivors of 8.7-9.0 Gy total-body irradiation (TBI). The goal of this study was to determine temporal relationships in the development of vasculopathy and the progression of renal and cardiovascular delayed effects of acute radiation exposure (DEARE) at TBI doses less than 9 Gy and to elucidate the potential roles of senescence, inflammation and oxidative stress. Our results show significant loss of endothelial cells in coronary arteries by 4 months post-TBI (8.53 or 8.72 Gy of gamma radiation). This loss precedes renal dysfunction and interstitial fibrosis and progresses to abnormalities in the arterial media and adventitia and loss of coronary arterioles. Major differences in radiation-induced pathobiology exist between the heart and kidney in terms of vasculopathy progression and also in indices of inflammation, senescence and oxidative imbalance. The results of this work suggest a need for different medical countermeasures for multiple targets in different organs and at various times after acute radiation injury to prevent the progression of DEARE

Chemokine expression in renal ischemia/reperfusion injury is most profound during the reparative phase

Chemokines are important players in the migration of leukocytes to sites of injury and are also involved in angiogenesis, development and wound healing. In this study, we performed microarray analyses to identify chemokines that play a role during the inflammatory and repair phase after renal ischemia/reperfusion (I/R) injury and investigated the temporal relationship between chemokine expression, leukocyte accumulation and renal damage/repair. C57Bl/6 mice were subjected to unilateral ischemia for 45 min and sacrificed 3 h, 1 day and 7 days after reperfusion. From ischemic and contralateral kidney, RNA was isolated and hybridized to a microarray. Microarray results were validated with quantitative real-time reverse transcription–PCR (QRT–PCR) on RNA from an independent experiment. (Immuno)histochemical analyses were performed to determine renal damage/repair and influx of leukocytes. Twenty out of 114 genes were up-regulated at one or more reperfusion periods. All these genes were up-regulated 7 days after I/R. Up-regulated genes included CC chemokines MCP-1 and TARC, CXC chemokines KC and MIP-2α, chemokine receptors Ccr1 and Cx3cr1 and related genes like matrix metalloproteinases. Microarray data of 1 and 7 days were confirmed for 17 up-regulated genes by QRT–PCR. (Immuno)histochemical analysis showed that the inflammatory and repair phase after renal I/R injury take place after, respectively, 1 and 7 days. Interestingly, chemokine expression was highest during the repair phase. In addition, expression profiles showed a biphasic expression of all up-regulated CXC chemokines coinciding with the early inflammatory and late repair phase. In conclusion, we propose that temporal expression of chemokines is a crucial factor in the regulation of renal I/R injury and repair

Differential Stem and Progenitor Cell Trafficking by Prostaglandin E2

SUMMARY To maintain lifelong production of blood cells, hematopoietic stem cells (HSC) are tightly regulated by inherent programs and extrinsic regulatory signals received from their microenvironmental niche. Long-term repopulating HSC (LT-HSC) reside in several, perhaps overlapping, niches that produce regulatory molecules/signals necessary for homeostasis and increased output following stress/injury 1–5. Despite significant advances in specific cellular or molecular mechanisms governing HSC/niche interactions, little is understood about regulatory function within the intact mammalian hematopoietic niche. Recently, we and others described a positive regulatory role for Prostaglandin E2 (PGE2) on HSC function ex vivo 6,7. While exploring the role of endogenous PGE2 we unexpectedly observed hematopoietic egress after nonsteroidal anti-inflammatory drug (NSAID) treatment. Surprisingly, this was independent of the SDF-1/CXCR4 axis. Stem and progenitor cells were found to have differing mechanisms of egress, with HSC transit to the periphery dependent on niche attenuation and reduction in the retentive molecule osteopontin (OPN). Hematopoietic grafts mobilized with NSAIDs had superior repopulating ability and long-term engraftment. Treatment of non-human primates and healthy human volunteers confirmed NSAID-mediated egress in higher species. PGE2 receptor knockout mice demonstrated that progenitor expansion and stem/progenitor egress resulted from reduced EP4 receptor signaling. These results not only uncover unique regulatory roles for EP4 signaling in HSC retention in the niche but also define a rapidly translatable strategy to therapeutically enhance transplantation

A Single Radioprotective Dose of Prostaglandin E2 Blocks Irradiation-Induced Apoptotic Signaling and Early Cycling of Hematopoietic Stem Cells

Ionizing radiation exposure results in acute and delayed bone marrow suppression. Treatment of mice with 16,16-dimethyl prostaglandin E2 (dmPGE2) prior to lethal ionizing radiation (IR) facilitates survival, but the cellular and molecular mechanisms are unclear. In this study we show that dmPGE2 attenuates loss and enhances recovery of bone marrow cellularity, corresponding to a less severe hematopoietic stem cell nadir, and significantly preserves long-term repopulation capacity and progenitor cell function. Mechanistically, dmPGE2 suppressed hematopoietic stem cell (HSC) proliferation through 24 h post IR, which correlated with fewer DNA double-strand breaks and attenuation of apoptosis, mitochondrial compromise, oxidative stress, and senescence. RNA sequencing of HSCs at 1 h and 24 h post IR identified a predominant interference with IR-induced p53-downstream gene expression at 1 h, and confirmed the suppression of IR-induced cell-cycle genes at 24 h. These data identify mechanisms of dmPGE2 radioprotection and its potential role as a medical countermeasure against radiation exposure

Stromal‐Derived Factor‐1α (CXCL12) Levels Increase in Periodontal Disease

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142300/1/jper0845.pd

Past, present, and future efforts to enhance the efficacy of cord blood hematopoietic cell transplantation

Cord blood (CB) has been used as a viable source of hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) in over 35,000 clinical hematopoietic cell transplantation (HCT) efforts to treat the same variety of malignant and non-malignant disorders treated by bone marrow (BM) and mobilized peripheral blood (mPB) using HLA-matched or partially HLA-disparate related or unrelated donor cells for adult and children recipients. This review documents the beginning of this clinical effort that started in the 1980's, the pros and cons of CB HCT compared to BM and mPB HCT, and recent experimental and clinical efforts to enhance the efficacy of CB HCT. These efforts include means for increasing HSC numbers in single CB collections, expanding functional HSCs ex vivo, and improving CB HSC homing and engraftment, all with the goal of clinical translation. Concluding remarks highlight the need for phase I/II clinical trials to test the experimental procedures that are described, either alone or in combination

Uncovering the multifaceted roles played by neutrophils in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a life-saving procedure used for the treatment of selected hematological malignancies, inborn errors of metabolism, and bone marrow failures. The role of neutrophils in alloHSCT has been traditionally evaluated only in the context of their ability to act as a first line of defense against infection. However, recent evidence has highlighted neutrophils as key effectors of innate and adaptive immune responses through a wide array of newly discovered functions. Accordingly, neutrophils are emerging as highly versatile cells that are able to acquire different, often opposite, functional capacities depending on the microenvironment and their differentiation status. Herein, we review the current knowledge on the multiple functions that neutrophils exhibit through the different stages of alloHSCT, from the hematopoietic stem cell (HSC) mobilization in the donor to the immunological reconstitution that occurs in the recipient following HSC infusion. We also discuss the influence exerted on neutrophils by the immunosuppressive drugs delivered in the course of alloHSCT as part of graft-versus-host disease (GVHD) prophylaxis. Finally, the potential involvement of neutrophils in alloHSCT-related complications, such as transplant-associated thrombotic microangiopathy (TA-TMA), acute and chronic GVHD, and cytomegalovirus (CMV) reactivation, is also discussed. Based on the data reviewed herein, the role played by neutrophils in alloHSCT is far greater than a simple antimicrobial role. However, much remains to be investigated in terms of the potential functions that neutrophils might exert during a highly complex procedure such as alloHSCT