Placenta-derived Stromal Cells Research Articles

Intramuscular Administration of Placenta-Derived Stromal Cells Enhances Survival of Rhesus Macaque Monkeys Exposed to Total Body Irradiation

Placenta-derived stromal cells named PLX-R18 have been shown in-vitro to secrete pro-hematopoiesis proteins, induce bone marrow migration, and promote colony formation. Murine in-vivo studies indicated that placental cells are capable of reducing lethality from the Hematopoietic Sub-syndrome of Acute Radiation Syndrome (HS-ARS).A NIAID-supported pilot study with non-human primate (NHP) rhesus macaque monkeys was conducted with the objective to characterize the effect of PLX-R18 on HS-ARS, including survival and hematological parameters in irradiated NHP. 62 male and female rhesus macaque monkeys were divided into irradiated and non-irradiated cohorts. Non-irradiated or irradiated NHPs were treated with three intramuscular doses of PLX-R18 at 1 and 5 days post irradiation, or with placebo control. All doses of PLX-R18 improved outcome of irradiated NHPs relative to placebo (dose of 4, 10 and 20M cells/kg increased survival by 33.3, 35.7 and 16.7% respectively).A tendency towards earlier recovery of blood lineages was evident in all doses tested, particularly, for the two lower doses. The 4 million cells/kg dose of PLX-R18 reduced the duration of critical neutropenia, thrombocytopenia, and anemia (NEUT< 0.1x10^9/L, PLT< 10x10^9/L, HGB< 65 g/L) by 1.5, 1.5, and 0.7 days respectively. Importantly, NHP results recapitulate findings from mouse studies with respect to non-irradiated animals in that hematological parameters are minimally affected.Taken together, all doses of PLX-R18 positively affected survival rates and multiple hematological parameters of HS-ARS in rhesus monkeys and had no negative effects in either irradiated or non-irradiated monkeys. This supports the intended development of PLX-R18 as a treatment for HS-ARS. DisclosuresSher:Pluristem LTD: Employment, Equity Ownership. Prezma:Pluristem LTD: Employment, Equity Ownership. Fuchs-Telem:Pluristem LTD: Employment, Equity Ownership. Shraga- Heled:Pluristem LTD: Employment, Equity Ownership. Authier:CiToxLAB: Employment. Chang:SRI International: Employment. Ascah:CiToxLAB: Employment. Bakke:SRI International: Employment. Gahagen:SRI International: Employment. Ofir:Pluristem LTD: Employment, Equity Ownership.

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.

Placenta-Expanded Stromal Cell Therapy in a Rodent Model of Simulated Weightlessness.

Long duration spaceflight poses potential health risks to astronauts during flight and re-adaptation after return to Earth. There is an emerging need for NASA to provide successful and reliable therapeutics for long duration missions when capability for medical intervention will be limited. Clinically relevant, human placenta-derived therapeutic stromal cells (PLX-PAD) are a promising therapeutic alternative. We found that treatment of adult female mice with PLX-PAD near the onset of simulated weightlessness by hindlimb unloading (HU, 30 d) was well-tolerated and partially mitigated decrements caused by HU. Specifically, PLX-PAD treatment rescued HU-induced thymic atrophy, and mitigated HU-induced changes in percentages of circulating neutrophils, but did not rescue changes in the percentages of lymphocytes, monocytes, natural killer (NK) cells, T-cells and splenic atrophy. Further, PLX-PAD partially mitigated HU effects on the expression of select cytokines in the hippocampus. In contrast, PLX-PAD failed to protect bone and muscle from HU-induced effects, suggesting that the mechanisms which regulate the structure of these mechanosensitive tissues in response to disuse are discrete from those that regulate the immune- and central nervous system (CNS). These findings support the therapeutic potential of placenta-derived stromal cells for select physiological deficits during simulated spaceflight. Multiple countermeasures are likely needed for comprehensive protection from the deleterious effects of prolonged spaceflight.

Human Placenta-Derived Stromal Cells Rescue Mice from Radiation-Induced Bone Marrow Failure: A Cytof-Based Mechanistic Analysis

Acute Radiation Syndrome (ARS) is a set of health effects involving damage to multiple organs caused by exposure to high dose ionizing radiation over a short period of time. Even low doses damage the radio-sensitive hematopoietic system (causing H-ARS). We probed the mechanism of action by which a 3D-expanded placenta-derived stromal cell product designated for the treatment of hematological disorders alleviates symptoms in the H-ARS mouse model. These cells have been shown in vitro to secrete hematopoietic proteins, stimulate colony formation, and induce bone marrow (BM) migration.Previous studies show that cells administered intramuscularly to C3H/HeN and C57BL/6 mice, 1 and 5 days after (LD70/30) total body irradiation, rescue radio-induced weight loss, survival, and peripheral blood (PB) and BM cellularity. The injected cells transiently secrete haematopoiesis related proteins to enhance reconstitution of the hematopoietic system and further induce endogenous cells to secrete a panel of cytokines.Analysis of PB and BM taken from the experimental endpoint (day 23) of cell-treated irradiated mice indicated rescue of blood lineages to levels near those of naïve mice.CyTOF analysis of BM cells indicated that in the myeloid lineage, the percentages of neutrophils and monocytes were consistently higher in cell-treated irradiated mice than in naïve mice (2.6±0.08 fold for neutrophils and 1.4±0.1 fold for monocytes). There was also a 1.5±0.5 fold increase in the percentage of the lymphoid lineage pDCs and a 2.8±0.9 fold reduction in the percentage of T cells in the BM of the treated compared to naïve mice. On the other hand, the percentage of B cells and NK cells were more similar when compared to naïve mice (1.2±0.4 fold for B cells and 1.1±0.2 fold for NK cells).Neutrophils and monocytes were also elevated in the PB of cell-treated irradiated mice (1.3±0.09 fold for neutrophils and 1.7±0.2 fold for monocytes), and within the monocyte population, percentages of classical and non-classical monocytes were essentially identical to naïve mice (0.97±0.05 fold for classical and 1.1±0.1 fold for non-classical). In cell-treated mice, B cells showed evidence of active recovery from pro-B to the immature stage of development when compared to naïve mice (4.4±0.7 fold increase for pro-B cells in BM and 5.5±0.8 fold increase for immature B cells in blood). In addition, CD8+ effector memory T cells showed a 1.9±0.3 fold increase in treated compared to naïve mice.The effect of placenta-derived stromal cells on human BM migration in vitro was also analyzed by CyTOF. Results indicated that the stromal cell product may induce significant maturation of early-stage neutrophils to late-stage neutrophils and significantly enhance the migration of neutrophils 17.9±1.4 fold compared to control. Active induction of migration of monocytes (2.4±0.0004 fold), eosinophils (2.6±0.1 fold), and endothelial cells (2.1±0.2 fold) was also observed.A number of these beneficial effects may be ascribed to cytokines known to be secreted by the cell product in high concentration. IL-8 and osteopontin are highly chemotactic toward neutrophils and MCP1 is highly chemotactic toward monocytes. These cytokines may contribute to the observed migration of human BM neutrophils and monocytes in vitro as well as to the increased percentage of neutrophils and monocytes in the blood of the cell-treated irradiated mice. In addition, cytokines known to be involved in neutrophil granulopoiesis, i.e. SCF, G-CSF, GM-CSF, IL-3 and IL-6, are present in the secretome of the cell product and may contribute to the observed maturation of early-stage neutrophils in human BM.Taken together, placenta-derived stromal cells have the capacity to alleviate symptoms of BM failure in the H-ARS model and rescue multiple blood lineages via a complex mechanism of action based on the secretion of multiple proteins acting on multiple hematopoietic lineages. Due to this combined mechanism of action involving the induction of cell migration, proliferation and differentiation, as well as an adaptive secretion profile based on the changing environment within the animal, placenta-derived cells are able to rescue from BM failure multiple cell lineages of the hematopoietic system to near-normal levels. DisclosuresAllen:Pluristem: Employment. Sher:Pluristem: Employment. Rekhes:Pluristem: Employment. Pinzur:Pluristem: Employment. Prezma:Pluristem: Employment. Gorodetsky:Pluristem: Consultancy. Volk:Pluristem: Consultancy. Aberman:Pluristem: Employment. Ofir:Pluristem: Employment.

Human placenta-derived stromal cells decrease inflammation, placental injury and blood pressure in hypertensive pregnant mice.

Pre-eclampsia, the development of hypertension and proteinuria or end-organ damage during pregnancy, is a leading cause of both maternal and fetal morbidity and mortality, and there are no effective clinical treatments for pre-eclampsia aside from delivery. The development of pre-eclampsia is characterized by maladaptation of the maternal immune system, excessive inflammation and endothelial dysfunction. We have reported that detection of extracellular RNA by the Toll-like receptors (TLRs) 3 and 7 is a key initiating signal that contributes to the development of pre-eclampsia. PLacental eXpanded (PLX-PAD) cells are human placenta-derived, mesenchymal-like, adherent stromal cells that have anti-inflammatory, proangiogenic, cytoprotective and regenerative properties, secondary to paracrine secretion of various molecules in response to environmental stimulation. We hypothesized that PLX-PAD cells would reduce the associated inflammation and tissue damage and lower blood pressure in mice with pre-eclampsia induced by TLR3 or TLR7 activation. Injection of PLX-PAD cells on gestational day 14 significantly decreased systolic blood pressure by day 17 in TLR3-induced and TLR7-induced hypertensive mice (TLR3 144-111 mmHg; TLR7 145-106 mmHg; both P<0.05), and also normalized their elevated urinary protein:creatinine ratios (TLR3 5.68-3.72; TLR7 5.57-3.84; both P<0.05). On gestational day 17, aortic endothelium-dependent relaxation responses improved significantly in TLR3-induced and TLR7-induced hypertensive mice that received PLX-PAD cells on gestational day 14 (TLR3 35-65%; TLR7 37-63%; both P<0.05). In addition, markers of systemic inflammation and placental injury, increased markedly in both groups of TLR-induced hypertensive mice, were reduced by PLX-PAD cells. Importantly, PLX-PAD cell therapy had no effects on these measures in pregnant control mice or on the fetuses. These data demonstrate that PLX-PAD cell therapy can safely reverse pre-eclampsia-like features during pregnancy and have a potential therapeutic role in pre-eclampsia treatment.

Age Does Matter: A Pilot Comparison of Placenta-Derived Stromal Cells for in utero Repair of Myelomeningocele Using a Lamb Model

Introduction: Fetal amniotic membranes (FM) have been shown to preserve spinal cord histology in the fetal sheep model of myelomeningocele (MMC). This study compares the effectiveness of placenta-derived mesenchymal stromal cells (PMSCs) from early-gestation versus term-gestation placenta to augment FM repair to improve distal motor function in a sheep model. Methods: Fetal lambs (n = 4) underwent surgical MMC creation followed by repair with FM patch with term-gestation PMSCs (n = 1), FM with early-gestation PMSCs (n = 1), FM only (n = 1), and skin closure only (n = 1). Histopathology and motor assessment was performed. Results: Histopathologic analysis demonstrated increased preservation of spinal cord architecture and large neurons in the lamb repaired with early-gestation cells compared to all others. Lambs repaired with skin closure only, FM alone, and term-gestation PMSCs exhibited extremely limited distal motor function; the lamb repaired with early-gestation PMSCs was capable of normal ambulation. Discussion: This pilot study is the first in vivo comparison of different gestational-age placenta-derived stromal cells for repair in the fetal sheep MMC model. The preservation of large neurons and markedly improved motor function in the lamb repaired with early-gestation cells suggest that early-gestation placental stromal cells may exhibit unique properties that augment in utero MMC repair to improve paralysis.

Cardioprotection by placenta-derived stromal cells in a murine myocardial infarction model

BackgroundAutologous cells for cell therapy of ischemic cardiomyopathy often display age- and disease-related functional impairment, whereas an allogenic immunotolerant cell product would allow off-the-shelf application of uncompromised donor cells. We investigated the cardiac regeneration potential of a novel, clinical-grade placenta-derived human stromal cell product (PLX-PAD). MethodsPLX-PAD cells derived from human donor placentas and expanded in a three-dimensional bioreactor system were tested for surface marker expression, proangiogenic, anti-inflammatory, and immunomodulatory properties in vitro. In BALB/C mice, the left anterior descending artery was ligated and PLX-PAD cells (n = 10) or vehicle (n = 10) were injected in the infarct border zone. Four weeks later, heart function was analyzed by two-dimensional and M-mode echocardiography. Scar size, microvessel density, extracellular matrix composition, myocyte apoptosis, and PLX-PAD cell retention were studied by histology. ResultsIn vitro, PLX-PAD cells displayed both proangiogenesis and anti-inflammatory properties, represented by the secretion of both vascular endothelial growth factor and angiopoietin-1 that was upregulated by hypoxia, as well as by the capacity to suppress T-cell proliferation and augment IL-10 secretion when co-cultured with peripheral blood mononuclear cells. Compared with control mice, PLX-PAD-treated hearts had better contractile function, smaller infarct size, greater regional left ventricular wall thickness, and less apoptosis after 4 wk. PLX-PAD stimulated both angiogenesis and arteriogenesis in the infarct border zone, and periostin expression was upregulated in PLX-PAD-treated hearts. ConclusionsClinical-grade PLX-PAD cells exert beneficial effects on ischemic myocardium that are associated with improved contractile function, and may be suitable for further evaluation aiming at clinical pilot trials of cardiac cell therapy.

Abundant expression and hemimethylation of C19MC in cell cultures from placenta-derived stromal cells

MicroRNAs of the chromosome 19 microRNA cluster (C19MC) are known to be abundantly expressed in the placenta. Their genes are located on the long arm of chromosome 19 and seem to be part of a large imprinted region. Although the data available so far suggest important functions in the placenta, no data are available on their general expression patterns in cultures of placenta-derived mesenchymal stromal cells (PDMSC). Surprisingly, qRT-PCR on tissue cultures from first-trimester and term placenta mesenchymal stromal cells showed an abundant expression of the cluster members miR-517a-3p, miR-519a-3p, and miR-520c-3p. Accordingly, analyses of methylation patterns suggested that these cells had escaped methylation and epigenetic silencing, respectively, of the paternal allele. This was confirmed by the results of treatment of chorionic villous stromal cells by the demethylating agent 5-Aza-2′-deoxycytidine. Our results offer clear evidence that, in contrast to what is suggested in previous papers, members of C19MC are highly expressed in PDMSC indicating that their placenta-specific functions are not restricted to the trophoblast.