Mitigation of Lethal Radiation Syndrome in Mice by Intramuscular Injection of 3D Cultured Adherent Human Placental Stromal Cells

Xenogenic Application of Human Placenta-Derived Mesenchymal Stromal Cells in a Porcine Large Animal Model

In animal models, cell therapies for different diseases or injuries have been very successful. Preclinical studies with cells aiming at a stroke, heart attack, and other emergency situations were promising but sometimes failed translation in clinical situations. We, therefore, investigated if human placenta-derived mesenchymal stromal cells can be injected in pigs without provoking rejection to serve as a xenogenic transplantation model to bridge preclinical animal studies to more promising future preclinical studies. Male human placenta-derived mesenchymal stromal cells were isolated, expanded, and characterized by flow cytometry, in vitro differentiation, and quantitative reverse-transcription polymerase chain reaction to prove their nature. Such cells were injected into the sphincter muscle of the urethrae of female pigs under visual control by cystoscopy employing a Williams needle. The animals were observed over 7 days of follow-up. Reactions of the host to the xenogeneic cells were explored by monitoring body temperature, and inflammatory markers including IL-1ß, CRP, and haptoglobin in blood. After sacrifice on day 7, infiltration of inflammatory cells in the tissue targeted was investigated by histology and immunofluorescence. DNA of injected human cells was detected by PCR. Upon injection in vascularized porcine tissue, human placenta-derived mesenchymal stromal cells were tolerated, and systemic inflammatory parameters were not elevated. DNA of injected cells was detected in situ 7 days after injection, and moderate local infiltration of inflammatory cells was observed. The therapeutic potential of human placenta-derived mesenchymal stromal cells can be explored in porcine large animal models of injury or disease. This seems a promising strategy to explore technologies for cell injections in infarcted hearts or small organs and tissues in therapeutically relevant amounts requiring large animal models to yield meaningful outcomes.

Regulation of Immune Checkpoint Antigen CD276 (B7-H3) on Human Placenta-Derived Mesenchymal Stromal Cells in GMP-Compliant Cell Culture Media

Therapies utilizing autologous mesenchymal cell delivery are being investigated as anti-inflammatory and regenerative treatments for a broad spectrum of age-related diseases, as well as various chronic and acute pathological conditions. Easily available allogeneic full-term human placenta mesenchymal stromal cells (pMSCs) were used as a potential pro-regenerative, cell-based therapy in degenerative diseases, which could be applied also to elderly individuals. To explore the potential of allogeneic pMSCs transplantation for pro-regenerative applications, such cells were isolated from five different term-placentas, obtained from the dissected maternal, endometrial (mpMSCs), and fetal chorion tissues (fpMSCs), respectively. The proliferation rate of the cells in the culture, as well as their shape, in vitro differentiation potential, and the expression of mesenchymal lineage and stem cell markers, were investigated. Moreover, we studied the expression of immune checkpoint antigen CD276 as a possible modulation of the rejection of transplanted non-HLA-matched homologous or even xeno-transplanted pMSCs. The expression of the cell surface markers was also explored in parallel in the cryosections of the relevant intact placenta tissue samples. The expansion of pMSCs in a clinical-grade medium complemented with 5% human platelet lysate and 5% human serum induced a significant expression of CD276 when compared to mpMSCs expanded in a commercial medium. We suggest that the expansion of mpMSCs, especially in a medium containing platelet lysate, elevated the expression of the immune-regulatory cell surface marker CD276. This may contribute to the immune tolerance towards allogeneic pMSC transplantations in clinical situations and even in xenogenic animal models of human diseases. The endurance of the injected comparably young human-term pMSCs may promote prolonged effects in clinical applications employing non-HLA-matched allogeneic cell therapy for various degenerative disorders, especially in aged adults.

Mitigation of acute radiation syndrome (ARS) with human umbilical cord blood

PURPOSE

The growing concern over potential unintended nuclear accidents or malicious activities involving nuclear/radiological devices cannot be overstated. Exposure to whole-body doses of radiation can result in acute radiation syndrome (ARS), colloquially known as "radiation sickness," which can severely damage various organ systems. Long-term health consequences, such as cancer and cardiovascular disease, can develop many years post-exposure. Identifying effective medical countermeasures and devising a strategic medical plan represents an urgent, unmet need. Various clinical studies have investigated the therapeutic use of umbilical cord blood (UCB) for a range of illnesses, including ARS. The objective of this review is to thoroughly discuss ARS and its sub-syndromes, and to highlight recent findings regarding the use of UCB for radiation injury. UCB, a rich source of stem cells, boasts numerous advantages over other stem cell sources, like bone marrow, owing to its ease of collection and relatively low risk of severe graft-versus-host disease. Preclinical studies suggest that treatment with UCB, and often UCB-derived mesenchymal stromal cells (MSCs), results in improved survival, accelerated hematopoietic recovery, reduced gastrointestinal tract damage, and mitigation of radiation-induced pneumonitis and pulmonary fibrosis. Interestingly, recent evidence suggests that UCB-derived exosomes and their microRNAs (miRNAs) might assist in treating radiation-induced damage, largely by inhibiting fibrotic pathways.

CONCLUSION

UCB holds substantial potential as a radiation countermeasure, and future research should focus on establishing treatment parameters for ARS victims.

Alleviation of Severe Skin Insults Following High-Dose Irradiation with Isolated Human Fetal Placental Stromal Cells

Skin exposure to high-dose irradiation, as commonly practiced in radiotherapy, affects the different skin layers, causing dry and wet desquamation, hyperkeratosis fibrosis, hard to heal wounds and alopecia and damaged hair follicles. Fetal tissue mesenchymal stromal cells (f-hPSC) were isolated from excised human fetal placental tissue, based on their direct migration from the tissue samples to the tissue dish. The current study follows earlier reports on for the mitigation of acute radiation syndrome following whole body high-dose exposure with remotely injected f-hPSC. Both the head only and a back skin flap of mice were irradiated with 16 &18 Gy, respectively, by 6MeV clinical linear accelerator electron beam. In both locations, the irradiated skin areas developed early and late radiation induced skin damages, including cutaneous fibrosis, lesions, scaring and severe hair follicle loss and reduced hair pigmentation. Injection of 2 × 106 f-hPSC, 3 and 8 weeks following 16 Gy head irradiation, and 1 and 4 weeks following the 18 Gy back skin only irradiation, resulted in significantly faster healing of radiation induced damages, with reduction of wet desquamation as measured by surface moisture level and minor recovery of the skin viscoelasticity. Detailed histological morphometry showed a clear alleviation of radiation induced hyperkeratosis in f-hPSC treated mice, with significant regain of hair follicles density. Following 16 Gy head irradiation, the hair follicles density in the scalp skin was reduced significantly by almost a half relative to the controls. A nearly full recovery of hair density was found in the f-hPSC treated mice. In the 18 Gy irradiated back skin, the hair follicles density dropped in a late stage by ~70% relative to naïve controls. In irradiated f-hPSC treated mice, it was reduced by only ~30% and was significantly higher than the non-treated group. Our results suggest that local injections of xenogeneic f-hPSC could serve as a simple, safe and highly effective non-autologous pro-regenerative treatment for high-dose radiation induced skin insults. We expect that such treatment could also be applied for other irradiated organs.

Pre-Administration of PLX-R18 Cells Protects Mice from Radiation-Induced Hematopoietic Failure and Lethality

Acute Radiation Syndrome (ARS) is a syndrome involving damage to multiple organs caused by exposure to a high dose of ionizing radiation over a short period of time; even low doses of radiation damage the radiosensitive hematopoietic system and causes H-ARS. PLacenta eXpanded (PLX)-R18 is a 3D-expanded placenta-derived stromal cell product designated for the treatment of hematological disorders. These cells have been shown in vitro to secrete hematopoietic proteins, to stimulate colony formation, and to induce bone marrow migration. Previous studies in mice showed that PLX-R18 cells responded to radiation-induced hematopoietic failure by transiently secreting hematopoiesis related proteins to enhance reconstitution of the hematopoietic system. We assessed the potential effect of prophylactic PLX-R18 treatment on H-ARS. PLX-R18 cells were administered intramuscularly to C57BL/6 mice, −1 and 3 days after (LD70/30) total body irradiation. PLX R18 treatment significantly increased survival after irradiation (p < 0.0005). In addition, peripheral blood and bone marrow (BM) cellularity were monitored at several time points up to 30 days. PLX-R18 treatment significantly increased the number of colony-forming hematopoietic progenitors in the femoral BM and significantly raised peripheral blood cellularity. PLX-R18 administration attenuated biomarkers of bone marrow aplasia (EPO, FLT3L), sepsis (SAA), and systemic inflammation (sP-selectin and E-selectin) and attenuated radiation-induced inflammatory cytokines/chemokines and growth factors, including G-CSF, MIP-1a, MIP-1b, IL-2, IL-6 and MCP-1, In addition, PLX-R18 also ameliorated radiation-induced upregulation of pAKT. Taken together, prophylactic PLX-R18 administration may serve as a protection measure, mitigating bone marrow failure symptoms and systemic inflammation in the H-ARS model.

Therapeutic effects of placenta derived-, umbilical cord derived-, and adipose tissue derived-mesenchymal stem cells in chronic Helicobacter pylori infection: comparison and novel mechanisms

Supported with significant rejuvenating and regenerating actions of mesenchymal stem cells (MSCs) in various gastrointestinal diseases including Helicobacter pylori (H. pylori)-associated gastric diseases, we have compared these actions among placenta derived-MSCs (PD-MSCs), umbilical cord derived-MSCs (UC-MSCs), and adipose tissue derived-MSCs (AD-MSCs) and explored contributing genes implicated in rejuvenation of H. pylori-chronic atrophic gastritis (CAG) and tumorigenesis. In this study adopting H. pylori-initiated, high salt diet-promoted gastric carcinogenesis model, we have administered three kinds of MSCs around 15-18 weeks in H. pylori infected C57BL/6 mice and sacrificed at 24 and 48 weeks, respectively, in order to either assess the rejuvenating capability or anti-tumorigenesis. At 24 weeks, MSCs all led to significantly mitigated atrophic gastritis, for which significant inductions of autophagy, preservation of tumor suppressive 15-PGDH, attenuated apoptosis, and efficient efferocytosis was imposed with MSCs administration during atrophic gastritis. At 48 weeks, MSCs administered during H. pylori-associated atrophic gastritis afforded significant blocking the progression of CAG, as evidenced with statistically significant reduction in H. pylori-associated gastric tumor (p<0.05) accompanied with significant decreases in IL-1β, COX-2, STAT3, and NF-κB. Combined together with the changes of stanniocalcin-1 (STC-1), thrombospondin-1 (TSP-1), and IL-10 known as biomarkers reflecting stem cell activities at 48 weeks after H. pylori, PD-MSCs among MSCs afforded the best rejuvenating action against H. pylori-associated CAG via additional actions of efferocytosis, autophagy, and anti-apoptosis at 24 weeks. In conclusion, MSCs, especially PD-MSCs, exerted rejuvenating actions against H. pylori-associated CAG via anti-mutagenesis of IL-10, CD-36, ATG5 and cancer suppressive influences of STC-1, TSP-1, and 15-PGDH.

Therapeutic approach of adipose-derived mesenchymal stem cells in refractory peptic ulcer

Peptic ulcer is one of the most common gastrointestinal tract disorders worldwide, associated with challenges such as refractory morbidity, bleeding, interference with use of anticoagulants, and potential side effects associated with long-term use of proton pump inhibitors. A peptic ulcer is a defect in gastric or duodenal mucosa extending from muscularis mucosa to deeper layers of the stomach wall. In most cases, ulcers respond to standard treatments. However, in some people, peptic ulcer becomes resistant to conventional treatment or recurs after initially successful therapy. Therefore, new and safe treatments, including the use of stem cells, are highly favored for these patients. Adipose-derived mesenchymal stem cells are readily available in large quantities with minimal invasive intervention, and isolation of adipose-derived mesenchymal stromal stem cells (ASC) produces large amounts of stem cells, which are essential for cell-based and restorative therapies. These cells have high flexibility and can differentiate into several types of cells in vitro. This article will investigate the effects and possible mechanisms and signaling pathways of adipose tissue-derived mesenchymal stem cells in patients with refractory peptic ulcers.

Human umbilical cord mesenchymal stem cell transplantation restores hematopoiesis in acute radiation disease

OBJECTIVE

Nuclear technology has been widely used in military and civilian fields, and radiotherapy is an effective and common form of treatment for cancer. However, acute radiation disease caused by high doses of radiation is a serious complication. The aim of this study was to investigate the chance of mitigating radiation-triggered hematopoiesis failure using human umbilical cord mesenchymal stem cell (HUCMSC) transplantation.

METHODS

Umbilical cords were obtained from three full-term female neonatus through cesarean section at Xinqiao Hospital. Bone marrow mesenchymal stem cells (BMSCs) were cultivated as depicted before. Briefly, monocytes were collected from bone marrow blood by means of density separation columns. An acute radiation disease mouse model was established to compare the restoration effect of HUCMSCs and BMSCs transplanted via the tail vein. The hematopoietic stem cell transplantation (HSCT) mouse model was obtained through bone marrow cell transplantation (BMCT) from C57BL/6 mice (H-2b, donor) to female CB6F1 mice (H-2b×d, recipient) after irradiation. The mice were divided into five groups, including control (saline), irradiated (radiation), bone marrow (HSCT, transplanted 1×10⁶ BM cells), HUCMSC (transplanted a mixture of 1×10⁶ HUCMSCs and 1×10⁶ BM cells), and BMSC group (transplanted a mixture of 1×10⁶ BMSCs and 1×10⁶ BM cells). The blood condition results were used to test the radiation-induced inflammatory reaction, and bone marrow pathological staining (H&E) was used to determine the radiation-induced bone marrow hematopoiesis failure.

RESULTS

After radiation, HUCMSC transplantation significantly improved the survival rate. By analyzing the blood condition test, colony formation, and bone marrow pathology, it was found that the HUCMSC group demonstrated significant functional improvements in terms of the recovery from hematopoiesis failure and reduction of inflammatory reaction.

CONCLUSIONS

HUCMSCs have more advantages over BMSCs in restoring and promoting the recovery of radiation-induced hematopoietic damage, thus having a new therapeutic potential for patients with acute radiation disease.

Acute Radiation-Induced Hematopoietic Depletion Does Not Alter the Onset or Severity of Pneumonitis in Mice

Survival from partial-body irradiation (PBI) may be limited by the development of the late lung injury response of pneumonitis. Herein we investigated the hypothesis that acute hematopoietic depletion alters the onset and severity of lung disease in a mouse model. To establish depletion, C3H/HeJ mice received 8 Gy PBI with shielding of only the tibiae, ankles and feet. One week after irradiation, blood lymphocyte and neutrophil counts were each significantly reduced (P < 0.04) in these mice compared to levels in untreated controls or in mice receiving 16 Gy to the whole thorax only. All 8 Gy PBI mice survived to the experimental end point of 16 weeks postirradiation. To determine whether the hematopoietic depletion affects lung disease, groups of mice received 8 Gy PBI plus 8 Gy whole-thorax irradiation (total lung dose of 16 Gy) or 16 Gy whole-thorax irradiation only. The weight loss, survival to onset of respiratory distress (P = 0.17) and pneumonitis score (P = 0.96) of mice that received 8 Gy PBI plus 8 Gy whole-thorax irradiation were not significantly different from those of mice receiving 16 Gy whole-thorax irradiation only. Mice in respiratory distress from PBI plus whole-thorax irradiation had significantly reduced (P = 0.02) blood monocyte counts compared to levels in distressed, whole-thorax irradiated mice, and symptomatic pneumonitis was associated with increased blood neutrophil counts (P = 0.04) relative to measures from irradiated, non-distressed mice. In conclusion, survivable acute hematopoietic depletion by partial-body irradiation did not alter the onset or severity of lethal pneumonitis in the C3H/HeJ mouse model.

Allogenic Use of Human Placenta-Derived Stromal Cells as a Highly Active Subtype of Mesenchymal Stromal Cells for Cell-Based Therapies

The application of mesenchymal stromal cells (MSCs) from different sources, including bone marrow (BM, bmMSCs), adipose tissue (atMSCs), and human term placenta (hPSCs) has been proposed for various clinical purposes. Accumulated evidence suggests that the activity of the different MSCs is indirect and associated with paracrine release of pro-regenerative and anti-inflammatory factors. A major limitation of bmMSCs-based treatment for autologous application is the limited yield of cells harvested from BM and the invasiveness of the procedure. Similar effects of autologous and allogeneic MSCs isolated from various other tissues were reported. The easily available fresh human placenta seems to represent a preferred source for harvesting abundant numbers of human hPSCs for allogenic use. Cells derived from the neonate tissues of the placenta (f-hPSC) can undergo extended expansion with a low risk of senescence. The low expression of HLA class I and II on f-hPSCs reduces the risk of rejection in allogeneic or xenogeneic applications in normal immunocompetent hosts. The main advantage of hPSCs-based therapies seems to lie in the secretion of a wide range of pro-regenerative and anti-inflammatory factors. This renders hPSCs as a very competent cell for therapy in humans or animal models. This review summarizes the therapeutic potential of allogeneic applications of f-hPSCs, with reference to their indirect pro-regenerative and anti-inflammatory effects and discusses clinical feasibility studies.

Therapeutic Applications of Stem Cells and Extracellular Vesicles in Emergency Care: Futuristic Perspectives

Regenerative medicine (RM) is an interdisciplinary field that aims to repair, replace or regenerate damaged or missing tissue or organs to function as close as possible to its physiological architecture and functions. Stem cells, which are undifferentiated cells retaining self-renewal potential, excessive proliferation and differentiation capacity into offspring or daughter cells that form different lineage cells of an organism, are considered as an important part of the RM approaches. They have been widely investigated in preclinical and clinical studies for therapeutic purposes. Extracellular vesicles (EVs) are the vital mediators that regulate the therapeutic effects of stem cells. Besides, they carry various types of cargo between cells which make them a significant contributor of intercellular communication. Given their role in physiological and pathological conditions in living cells, EVs are considered as a new therapeutic alternative solution for a variety of diseases in which there is a high unmet clinical need. This review aims to summarize and identify therapeutic potential of stem cells and EVs in diseases requiring acute emergency care such as trauma, heart diseases, stroke, acute respiratory distress syndrome and burn injury. Diseases that affect militaries or societies including acute radiation syndrome, sepsis and viral pandemics such as novel coronavirus disease 2019 are also discussed. Additionally, featuring and problematic issues that hamper clinical translation of stem cells and EVs are debated in a comparative manner with a futuristic perspective. Graphical Abstract.

Allogeneic adipose-derived stem cells mitigate acute radiation syndrome by the rescue of damaged bone marrow cells from apoptosis

Acute radiation syndrome (ARS) is the radiation toxicity that can affect the hematopoietic, gastrointestinal, and nervous systems upon accidental radiation exposure within a short time. Currently, there are no effective and safe approaches to treat mass population exposure to ARS. Our study aimed to evaluate the therapeutic potential of allogeneic adipose‐derived stem cells (ASCs) for total body irradiation (TBI)‐induced ARS and understand the underlying mitigation mechanism. We employed 9.25 Gy TBI dose to C57BL/6 mice and studied the effect of allogeneic ASCs on mice survival and regeneration of the hematopoietic system. Our results indicate that intraperitoneal‐injected ASCs migrated to the bone marrow, rescued hematopoiesis, and improved the survival of irradiated mice. Our transwell coculture results confirmed the migration of ASCs to irradiated bone marrow and rescue hematopoietic activity. Furthermore, contact coculture of ASCs improved the survival and hematopoiesis of irradiated bone marrow in vitro. Irradiation results in DNA damage, upregulation of inflammatory signals, and apoptosis in bone marrow cells, while coculture with ASCs reduces apoptosis via activation of DNA repair and the antioxidation system. Upon exposure to irradiated bone marrow cells, ASCs secrete prosurvival and hematopoietic factors, such as GM‐CSF, MIP1α, MIP1β, LIX, KC, 1P‐10, Rantes, IL‐17, MCSF, TNFα, Eotaxin, and IP‐10, which reduces oxidative stress and rescues damaged bone marrow cells from apoptosis. Our findings suggest that allogeneic ASCs therapy is effective in mitigating TBI‐induced ARS in mice and may be beneficial for clinical adaptation to treat TBI‐induced toxicities. Further studies will help to advocate the scale‐up and adaptation of allogeneic ASCs as the radiation countermeasure.

Use of MSCs and MSC-educated macrophages to mitigate hematopoietic acute radiation syndrome

Purpose of Review

Innovative and minimally toxic treatment approaches are sorely needed for the prevention and treatment of hematopoietic acute radiation syndrome (H-ARS). Cell therapies have been increasingly studied for their potential use as countermeasures for accidental and intentional ionizing radiation exposures which can lead to fatal ARS. Mesenchymal stem/stromal cells (MSCs) are a cell therapy that have shown promising results in preclinical studies of ARS, and are being developed in clinical trials specifically for H-ARS. MSCs, MSC-educated macrophages (MEMs) and MSC-exosome educated macrophages (EEMs) all have the potential to be used as adoptive cell therapies for H-ARS. Here we review how MSCs have been reported to mitigate inflammation from radiation injury while also stimulating hematopoiesis during ARS.

Recent findings

We discuss emerging work with immune cell subsets educated by MSCs, including MEMs and EEMs, in promoting hematopoiesis in xenogeneic models of ARS. We also discuss the first placental-derived MSC product to enter phase I trials, PLX-R18, and the challenges faced by bringing MSC and other cell therapies into the clinic for treating ARS.

Summary

Although MSCs, MEMs and EEMs are potential cell therapy candidates in promoting hematopoietic HRS, challenges persist in translational clinical development of these products to the clinic. Whether any of these cellular therapies will be sufficient as stand-alone therapies to mitigate H-ARS or if they will be a bridging therapy that insures survival until a curative allogeneic hematopoietic stem cell transplant can be performed are the key questions that will have to be answered.

Alleviation of acute radiation-induced bone marrow failure in mice with human fetal placental stromal cell therapy

Purpose

Selected placental mesenchymal stromal cells isolated from the fetal mesenchymal placental tissues (f-hPSCs) were tested as cell therapy of lethal acute radiation syndrome (ARS) with bone marrow regeneration and induced extramedullary hematopoiesis.

Methods and materials

f-hPSCs were isolated from the chorionic plate of human placentae and further expanded in regular culture conditions. 2 × 10⁶ f-hPSCs were injected on days 1 and 4 to 8-Gy total body irradiated (TBI) C3H mice, both intramuscularly and subcutaneously. Pre-splenectomized TBI mice were used to test the involvement of extramedullary spleen hematopoiesis in the f-hPSC-induced hematopoiesis recovery in the TBI mice. Weight and survival of the mice were followed up within the morbid period of up to 23 days following irradiation. The role of hematopoietic progenitors in the recovery of treated mice was evaluated by flow cytometry, blood cell counts, and assay of possibly relevant growth factors.

Results and conclusions

The survival rate of all groups of TBI f-hPSC-treated mice at the end of the follow-up was dramatically elevated from < 10% in untreated to ~ 80%, with a parallel regain of body weight, bone marrow (BM) recovery, and elevated circulating progenitors of blood cell lineages. Blood erythropoietin levels were elevated in all f-hPSC-treated mice. Extramedullary splenic hematopoiesis was recorded in the f-hPSC-treated mice, though splenectomized mice still had similar survival rate. Our findings suggest that the indirect f-hPSC life-saving therapy of ARS may also be applied for treating other conditions with a failure of the hematopoietic system and severe pancytopenia.

Mesenchymal Stromal Cells and Exosomes: Progress and Challenges

Due to their robust immunomodulatory capabilities, mesenchymal stem/stromal cells (MSCs) have been used as a cellular therapy for a number of human diseases. Part of the mechanism of action of MSCs is the production of extracellular vesicles (EVs) that contain proteins, nucleic acids, and lipids that transmit signals to recipient cells that change their biologic behavior. This review briefly summarizes the development of MSCs as a treatment for human diseases as well as describes our present understanding of exosomes; how they exert their effects on target cells, and how they are differentiated from other EVs. The current treatment paradigm for acute radiation syndrome (ARS) is discussed, and how MSCs and MSC derived exosomes are emerging as treatment options for treating patients after radiation exposure. Other conditions such as graft-versus-host disease and cardiovascular disease/stroke are discussed as examples to highlight the immunomodulatory and regenerative capacity of MSC-exosomes. Finally, a consideration is given to how these cell-based therapies could possibly be deployed in the event of a catastrophic radiation exposure event.

Pharmacological management of ionizing radiation injuries: current and prospective agents and targeted organ systems

Introduction: There is a limited array of currently available medicinals that are useful for either the prevention, mitigation or treatment of bodily injuries arising from ionizing radiation exposure.Area covered: In this brief article, the authors review those pharmacologic agents that either are currently being used to counter the injurious effects of radiation exposure, or those that show promise and are currently under development.Expert opinion: Although significant, but limited progress has been made in the development and fielding of safe and effective pharmacotherapeutics for select types of acute radiation-associated injuries, additional effort is needed to broaden the scope of drug development so that overall health risks associated with both short- and long-term injuries in various organ systems can be reduced and effectively managed. There are several promising radiation countermeasures that may gain regulatory approval from the government in the near future for use in clinical settings and in the aftermath of nuclear/radiological exposure contingencies.

Isolation and expansion of high yield of pure mesenchymal stromal cells from fresh and cryopreserved placental tissues

The injection of placental stromal cells isolated from fetal human tissues (f-hPSC) was reported to indirectly induce tissue regeneration in different animal models. A procedure of f-hPSC isolation from fragments of both selected fresh or cryopreserved bulk placental neonate tissues is proposed, based on their high migratory potential,. The fragments of the desired fetal placental tissues are adhered to a culture dish by traces of diluted fibrin and covered with culture medium. Spontaneous migration of pure f-hPSC from the tissue fragments to the cell culture dishes is followed by their rapid expansion by numerous passages. The isolated f-hPSC express typical mesenchymal surface antigens, including CD29, CD105, CD166 and CD146, with negative expression of white blood cell lineage and endothelial cells markers. Optimal yields of f-hPSC cultures can also be obtained from tissue samples cryopreserved in medium composed of 10% dimethyl sulfoxide (M₂SO) and 50% fetal calf serum. Slightly better yields are obtained with media supplemented with 1% human albumin. Medium with 5% M₂SO and/or 0.25 mg/ml PEG yielded inferior results. The f-hPSC from fresh or cryopreserved tissues express similar cell markers and growth kinetics. The proposed isolation protocol may also be applied for high yield isolation of stromal cells from fresh and cryopreserved tissue of other organs.

Placenta-Derived Adherent Stromal Cell Therapy for Hematopoietic Disorders: A Case Study of PLX-R18

The ephemeral placenta provides a noncontroversial source of young, healthy cells of both maternal and fetal origin from which cell therapy products can be manufactured. The 2 advantages of using live cells as therapeutic entities are: (a) in their environmental-responsive, multifactorial secretion profile and (b) in their activity as a “slow-release drug delivery system,” releasing secretions over a long time frame. A major difficulty in translating cell therapy to the clinic involves challenges of large-scale, robust manufacturing while maintaining product characteristics, identity, and efficacy. To address these concerns early on, Pluristem developed the PLacental eXpanded (PLX) platform, the first good manufacturing practice–approved, 3-dimensional bioreactor-based cell growth platform, to enable culture of mesenchymal-like adherent stromal cells harvested from the postpartum placenta. One of the products produced by Pluristem on this platform is PLX-R18, a product mainly comprising placental fetal cells, which is proven in vivo to alleviate radiation-induced lethality and to enhance hematopoietic cell counts after bone marrow (BM) failure. The identified mechanism of action of PLX-R18 cells is one of the cell-derived systemic pro-hematopoietic secretions, which upregulate endogenous secretions and subsequently rescue BM and peripheral blood cellularity, thereby boosting survival. PLX-R18 is therefore currently under study to treat both the hematopoietic syndrome of acute radiation (under the US Food and Drug Administration [FDA]’s Animal Rule) and the incomplete engraftment after BM transplantation (in a phase I study). In the future, they could potentially address additional hematological indications, such as aplastic anemia, myelodysplastic syndrome, primary graft failure, and acute or chronic graft versus host disease.

Rescue from lethal acute radiation syndrome (ARS) with severe weight loss by secretome of intramuscularly injected human placental stromal cells

BACKGROUND

Most current cell-based regenerative therapies are based on the indirect induction of the affected tissues repair. Xenogeneic cell-based treatment with expanded human placenta stromal cells, predominantly from fetal origin (PLX-RAD cells), were shown to mitigate significantly acute radiation syndrome (ARS) following high dose irradiation in mice, with expedited regain of weight loss and haematopoietic function. The current mechanistic study explores the indirect effect of the secretome of PLX-RAD cells in the rescue of the irradiated mice.

METHODS

The mitigation of the ARS was investigated following two intramuscularly (IM) injected 2 × 10⁶ PLX-RAD cells, 1 and 5 days following 7.7 Gy irradiation. The mice survival rate and their blood or bone marrow (BM) cell counts were followed up and correlated with multiplex immunoassay of a panel of related human proteins of PLX-RAD derived secretome, as well as endogenous secretion of related mouse proteins. PLX-RAD secretome was also tested in vitro for its effect on the induction of the migration of BM progenitors.

RESULTS

A 7.7 Gy whole body mice irradiation resulted in ~25% survival by 21 days. Treatment with two IM injections of 2 × 10⁶ PLX-RAD cells on days 1 and 5 after irradiation mitigated highly significantly the subsequent lethal ARS, with survival rate increase to nearly 100% and fast regain of the initial weight loss (P < 0,0001). This was associated with a significant faster haematopoiesis recovery from day 9 onwards (P < 0.01). Nine out of the 65 human proteins tested were highly significantly elevated in the mouse circulation, peaking on days 6-9 after irradiation, relative to negligible levels in non-irradiated PLX-RAD injected mice (P < 0.01). The highly elevated proteins included human G-CSF, GRO, MCP-1, IL-6 and lL-8, reaching >500 pg/mL, while MCP-3, ENA, Eotaxin and fractalkine levels ranged between ~60-160pg/mL. The detected radiation-induced PLX-RAD secretome correlated well with the timing of the fast haematopoiesis regeneration. The radiation-induced PLX-RAD secretome seemed to reinforce the delayed high levels secretion of related mouse endogenous cytokines, including GCSF, KC, MCP-1 and IL-6. Additional supportive in vitro studies also confirmed the ability of cultured PLX-RAD secretome to induce accelerated migration of BM progenitors.

CONCLUSIONS

A well-regulated and orchestrated secretion of major pro-regenerative BM supporting secretome in high dose irradiated mice, treated with xenogeneic IM injected PLX-RAD cells, can explain the observed mitigation of ARS. This seemed to coincide with faster haematopoiesis regeneration, regain of severe weight loss and the increased survival rate. The ARS-related stress signals activating the IM injected PLX-RAD cells for the remote secretion of the relevant human proteins deserve further investigation.

Posttransplant Intramuscular Injection of PLX-R18 Mesenchymal-Like Adherent Stromal Cells Improves Human Hematopoietic Engraftment in A Murine Transplant Model

Late-term complications of hematopoietic cell transplantation (HCT) are numerous and include incomplete engraftment. One possible mechanism of incomplete engraftment after HCT is cytokine-mediated suppression or dysfunction of the bone marrow microenvironment. Mesenchymal stromal cells (MSCs) elaborate cytokines that nurture or stimulate the marrow microenvironment by several mechanisms. We hypothesize that the administration of exogenous MSCs may modulate the bone marrow milieu and improve peripheral blood count recovery in the setting of incomplete engraftment. In the current study, we demonstrated that posttransplant intramuscular administration of human placental derived mesenchymal-like adherent stromal cells [PLacental eXpanded (PLX)-R18] harvested from a three-dimensional in vitro culture system improved posttransplant engraftment of human immune compartment in an immune-deficient murine transplantation model. As measured by the percentage of CD45⁺ cell recovery, we observed improvement in the peripheral blood counts at weeks 6 (8.4 vs. 24.1%, p < 0.001) and 8 (7.3 vs. 13.1%, p < 0.05) and in the bone marrow at week 8 (28 vs. 40.0%, p < 0.01) in the PLX-R18 cohort. As measured by percentage of CD19⁺ cell recovery, there was improvement at weeks 6 (12.6 vs. 3.8%) and 8 (10.1 vs. 4.1%). These results suggest that PLX-R18 may have a therapeutic role in improving incomplete engraftment after HCT.

Cholinergic and cytoprotective signaling cascades mediate the mitigative effect of erythropoietin on acute radiation syndrome

The present investigation aimed to evaluate the radiomitigative efficacy of the recombinant human erythropoietin (EPO) against acute radiation syndrome (ARS) in a rat model. Rats were irradiated with a single sublethal dose of γ-radiation (7 Gy; total body irradiation; TBI) on the 1st day of experimental course, then received EPO (5000 IU/kg; i.p.) 24 h after irradiation, and rats were observed for 30 days of survival analysis. Administration of EPO improved 30-day survival, alleviated TBI-induced myelosuppression and pancytopenia, by augmenting lymphocytes and other white blood cells in the peripheral blood of rats, while bone marrow and spleen cellularity were restored. EPO post-exposure treatment alleviated hepatotoxicity biomarkers and restored splenic function. EPO abrogated radiation-induced oxidative stress through the upregulation of the cholinergic anti-inflammatory nicotinic acetylcholine receptor (α-7-nAChR) and the pro-survival Janus kinase-2 and signal transducers and activators of transcription JAK-2/STAT-3 signaling mediated via enhancing nuclear factor erythroid-2 related factor-2 (Nrf-2) cytoprotective machinery in liver and spleen of irradiated rats. Moreover, EPO treatment prevented hepatic and splenic apoptosis. The present study establishes the implication of α-7-nAChR-JAK-2/STAT-3-Nrf-2 signaling cascade in the radiomitigative potential of EPO against ARS.

Cellular Therapies for Treatment of Radiation Injury: Report from a NIH/NIAID and IRSN Workshop

In recent years, there has been increasing concern over the possibility of a radiological or nuclear incident occurring somewhere in the world. Intelligence agencies frequently report that terrorist groups and rogue nations are seeking to obtain radiological or nuclear weapons of mass destruction. In addition, there exists the real possibility that safety of nuclear power reactors could be compromised by natural (such as the tsunami and subsequent Fukushima accident in Japan in March, 2011) or accidental (Three Mile Island, 1979 and Chernobyl, 1986) events. Although progress has been made by governments around the world to prepare for these events, including the stockpiling of radiation countermeasures, there are still challenges concerning care of patients injured during a radiation incident. Because the deleterious and pathological effects of radiation are so broad, it is desirable to identify medical countermeasures that can have a beneficial impact on several tissues and organ systems. Cellular therapies have the potential to impact recovery and tissue/organ regeneration for both early and late complications of radiation exposure. These therapies, which could include stem or blood progenitor cells, mesenchymal stromal cells (MSCs) or cells derived from other tissues (e.g., endothelium or placenta), have shown great promise in treating other nonradiation injuries to and diseases of the bone marrow, skin, gastrointestinal tract, brain, lung and heart. To explore the potential use of these therapies in the treatment of victims after acute radiation exposure, the National Institute of Allergy and Infectious Diseases co-sponsored an international workshop in July, 2015 in Paris, France with the Institut de Radioprotection et de Sûreté Nucléaire. The workshop included discussions of data available from testing in preclinical models of radiation injury to different organs, logistics associated with the practical use of cellular therapies for a mass casualty incident, as well as international regulatory requirements for authorizing such drug products to be legally and readily used in such incidents. This report reviews the data presented, as well as key discussion points from the meeting.

The efficacy of human placenta-derived mesenchymal stem cells on radiation enteropathy along with proteomic biomarkers predicting a favorable response

BACKGROUND

Radiation enteropathy is a common complication in patients with abdominopelvic cancer, but no treatment has yet been established. Stem cell therapy may be a viable therapeutic option because intestinal stem cells are highly vulnerable to ionizing radiation (IR) and stem cell loss explains its intractability to general treatment. Here, we investigated either prophylactic or therapeutic efficacy of human placenta-derived mesenchymal stem cells (hPDSCs) against radiation enteropathy and could identify biomarkers predicting a favorable response to stem cell therapy.

METHODS

We challenged a radiation-induced enteropathy model with hPDSCs. After sacrifice, we checked the gross anatomy of small intestine, histology gross, and analyzed that, accompanied with molecular changes implicated in this model.

RESULTS

hPDSCs significantly improved the outcome of mice induced with either radiation enteropathy or lethal radiation syndrome (P < 0.01). hPDSCs exerted inhibitory actions on inflammatory cytokines, the re-establishment of epithelium homeostasis was completed with increasing endogenous restorative processes as assessed with increased levels of proliferative markers in the hPDSCs group, and a significant inhibition of IR-induced apoptosis. The preservation of cells expressing lysozyme, and Musashi-1 were significantly increased in the hPDSC treatment group. Both preventive and therapeutic efficacies of hPDSCs were noted against IR-induced enteropathy. Label-free quantification was used to identify biomarkers which predict favorable responses after hPDSC treatment, and finally glutathione S-transferase-mu type, interleukin-10, and peroxiredoxin-2 were validated as proteomic biomarkers predicting a favorable response to hPDSCs in radiation enteropathy.

CONCLUSIONS

hPDSCs may be a useful prophylactic and therapeutic cell therapy for radiation enteropathy.

Placental Stromal Cell Therapy for Experimental Autoimmune Encephalomyelitis: The Role of Route of Cell Delivery

Multiple sclerosis (MS) is an immune‐mediated disease of the central nervous system (CNS) with no effective treatment available for the chronic‐progressive stage. Cell therapy is a promising therapeutic approach for attenuating the immune‐mediated CNS process. Isolated and expanded human placental stromal cells (hPSCs) possess potent immunomodulatory and trophic properties, making them a good candidate for MS therapy. We examined the potential of hPSC therapy in preventing the onset or attenuating the course of established disease in a murine MS model of myelin oligodendrocyte glycoprotein‐induced experimental autoimmune encephalomyelitis. We examined the feasibility of hPSC systemic delivery by intramuscular (i.m.) implantation rather than the commonly used intravenous injection, which is dose‐limiting and carries the risk of pulmonary obstruction. Our findings showed significant attenuation of the disease only when hPSCs were injected directly to the central nervous system. Intramuscular implanted hPSCs survived at the site of injection for at least 2 months and elicited extensive local immune responses. Intramuscular hPSC implantation before disease onset caused a delay in the appearance of clinical signs and reduced the severity of a relapse induced by repeated challenge with the autoantigen. Intramuscular implantation after disease onset did not affect its course. Thus, pathological analysis of CNS tissue did not show inhibition of neuroinflammation in i.m. hPSC‐implanted mice. Moreover, no apparent effect was seen on the proliferative response of peripheral lymph node cells in these animals. We conclude that to maximize their therapeutic potential in MS, hPSCs should be delivered directly to the affected CNS. Stem Cells Translational Medicine2017;6:1286–1294

The healing effect of bone marrow-derived stem cells in acute radiation syndrome

Objectives:

To determine the effect of bone marrow-derived mesenchymal stem cells (BMSCs) on regeneration of bone marrow and intestinal tissue and survival rate in experimental mice with acute radiation syndrome (ARS).

Methods:

Forty mice were randomly divided into two equal groups of A receiving no BMSC transplantation and B receiving BMSCs. BMSCs were isolated from the bone marrow and cultured in DMEM media. Both groups were irradiated with 10 Gy (dose rate 0.28 Gy/ min) ⁶⁰CO during 35 minutes with a field size of 35×35 for all the body area. Twenty-four hours after γ irradiation, 150×10³ cells of passage 5 in 150 µl medium were injected intravenously into the tail. Animals were euthanized one and two weeks after cell transplantation. They were evaluated histologically for any changes in bone marrow and intestinal tissues. The survival rate in mice were also determined.

Results:

A significant increase for bone marrow cell count and survival rate were observed in group B in comparison to group A. Histological findings denoted to a healing in sample tissues.

Conclusion:

BMSCs could significantly reduce the side effects of ARS and increase the survival rate and healing in injured tissue. As such their transplantation may open a window in treatment of patients with ARS.

γ-Tocotrienol as a Promising Countermeasure for Acute Radiation Syndrome: Current Status

The hazard of ionizing radiation exposure due to nuclear accidents or terrorist attacks is ever increasing. Despite decades of research, still, there is a shortage of non-toxic, safe and effective medical countermeasures for radiological and nuclear emergency. To date, the U.S. Food and Drug Administration (U.S. FDA) has approved only two growth factors, Neupogen (granulocyte colony-stimulating factor (G-CSF), filgrastim) and Neulasta (PEGylated G-CSF, pegfilgrastim) for the treatment of hematopoietic acute radiation syndrome (H-ARS) following the Animal Efficacy Rule. Promising radioprotective efficacy results of γ-tocotrienol (GT3; a member of the vitamin E family) in the mouse model encouraged its further evaluation in the nonhuman primate (NHP) model. These studies demonstrated that GT3 significantly aided the recovery of radiation-induced neutropenia and thrombocytopenia compared to the vehicle controls; these results particularly significant after exposure to 5.8 or 6.5 Gray (Gy) whole body γ-irradiation. The stimulatory effect of GT3 on neutrophils and thrombocytes (platelets) was directly and positively correlated with dose; a 75 mg/kg dose was more effective compared to 37.5 mg/kg. GT3 was also effective against 6.5 Gy whole body γ-irradiation for improving neutrophils and thrombocytes. Moreover, a single administration of GT3 without any supportive care was equivalent, in terms of improving hematopoietic recovery, to multiple doses of Neupogen and two doses of Neulasta with full supportive care (including blood products) in the NHP model. GT3 may serve as an ultimate radioprotector for use in humans, particularly for military personnel and first responders. In brief, GT3 is a promising radiation countermeasure that ought to be further developed for U.S. FDA approval for the ARS indication.

Combined mitigation of the gastrointestinal and hematopoietic acute radiation syndromes by an LPA2 receptor-specific nonlipid agonist

Pharmacological mitigation of injuries caused by high-dose ionizing radiation is an unsolved medical problem. A specific nonlipid agonist of the type 2 G protein coupled receptor for lysophosphatidic acid (LPA2) 2-[4-(1,3-dioxo-1H,3H-benzoisoquinolin-2-yl)butylsulfamoyl]benzoic acid (DBIBB) when administered with a postirradiation delay of up to 72 hr reduced mortality of C57BL/6 mice but not LPA2 knockout mice. DBIBB mitigated the gastrointestinal radiation syndrome, increased intestinal crypt survival and enterocyte proliferation, and reduced apoptosis. DBIBB enhanced DNA repair by augmenting the resolution of γ-H2AX foci, increased clonogenic survival of irradiated IEC-6 cells, attenuated the radiation-induced death of human CD34(+) hematopoietic progenitors and enhanced the survival of the granulocyte/macrophage lineage. DBIBB also increased the survival of mice suffering from the hematopoietic acute radiation syndrome after total-body irradiation. DBIBB represents a drug candidate capable of mitigating acute radiation syndrome caused by high-dose γ-radiation to the hematopoietic and gastrointestinal system.

High incidence of contaminating maternal cell overgrowth in human placental mesenchymal stem/stromal cell cultures: a systematic review

Placenta is a readily accessible translationally advantageous source of mesenchymal stem/stromal cells (MSCs) currently used in cryobanking and clinical trials. MSCs cultured from human chorion have been widely assumed to be fetal in origin, despite evidence that placental MSCs may be contaminated with maternal cells, resulting in entirely maternally derived MSC cultures. To document the frequency and determinants of maternal cell contamination in chorionic MSCs, we undertook a PRISMA-compliant systematic review of publications in the PubMed, Medline, and Embase databases (January 2000 to July 2013) on placental and/or chorionic MSCs from uncomplicated pregnancies. Of 147 studies, only 26 (18%) investigated fetal and/or maternal cell origin. After excluding studies that did not satisfy minimal MSC criteria, 7 of 15 informative studies documented MSC cultures as entirely fetal, a further 7 studies reported cultured human chorionic MSC populations to be either maternal (n=6) or mixed (n=1), whereas 1 study separately cultured pure fetal and pure maternal MSC from the same placenta. Maternal cell contamination was associated with term and chorionic membrane samples and greater passage number but was still present in 30% of studies of chorionic villous MSCs. Although most studies assume fetal origin for MSCs sourced from chorion, this systematic review documents a high incidence of maternal-origin MSC populations in placental MSC cultures. Given that fetal MSCs have more primitive properties than adult MSCs, our findings have implications for clinical trials in which knowledge of donor and tissue source is pivotal. We recommend sensitive methods to quantitate the source and purity of placental MSCs.

Effect of Gender on the Radiation Sensitivity of Murine Blood Cells

Space travel beyond the Earth's protective magnetosphere risks exposing astronauts to ionizing radiation, such as that generated during a solar particle event (SPE). Ionizing radiation has well documented effects on blood cells and it is generally assumed that these effects contribute to the hematopoietic syndrome (HS), observed in animals and humans, following exposure to total body irradiation (TBI). The purpose of the current study was to assess the role of gender on the effects of gamma radiation on blood cells. C3H/HeN mice were irradiated with a ¹³⁷Cs gamma source. Radiation had similar effects on white blood cells (WBCs), lymphocytes, and granulocytes in male and female C3H/HeN mice, while red blood cell (RBC) counts and hematocrit values remained stable following radiation exposure. Non-irradiated male mice had 13% higher platelet counts, compared with their female counterparts, and showed enhanced recovery of platelets on day 16 following radiation exposure. Hence, gender differences influence the response of platelets to TBI exposure.