Development of adult pluripotent stem cell therapies for ischemic injury and disease

Human multipotent adult progenitor cells effectively reduce graft-vs-host disease while preserving graft-vs-leukemia activity

Graft‐vs‐host disease (GvHD) limits successful outcomes following allogeneic blood and marrow transplantation (allo‐BMT). We examined whether the administration of human, bone marrow‐derived, multipotent adult progenitor cells (MAPCs™) could regulate experimental GvHD. The immunoregulatory capacity of MAPC cells was evaluated in vivo using established murine GvHD models. Injection of MAPC cells on day +1 (D1) and +4 (D4) significantly reduced T‐cell expansion and the numbers of donor‐derived, Tumor Necrosis Factor Alpha (TNFα) and Interferon Gamma (IFNγ)‐producing, CD4+ and CD8+ cells by D10 compared with untreated controls. These findings were associated with reductions in serum levels of TNFα and IFNγ, intestinal and hepatic inflammation and systemic GvHD as measured by survival and clinical score. Biodistribution studies showed that MAPC cells tracked from the lung and to the liver, spleen, and mesenteric nodes within 24 hours after injection. MAPC cells inhibited mouse T‐cell proliferation in vitro and this effect was associated with reduced T‐cell activation and inflammatory cytokine secretion and robust increases in the concentrations of Prostaglandin E2 (PGE2) and Transforming Growth Factor Beta (TGFβ). Indomethacin and E‐prostanoid 2 (EP2) receptor antagonism both reversed while EP2 agonism restored MAPC cell‐mediated in vitro T‐cell suppression, confirming the role for PGE2. Furthermore, cyclo‐oxygenase inhibition following allo‐BMT abrogated the protective effects of MAPC cells. Importantly, MAPC cells had no effect on the generation cytotoxic T lymphocyte activity in vitro, and the administration of MAPC cells in the setting of leukemic challenge resulted in superior leukemia‐free survival. Collectively, these data provide valuable information regarding the biodistribution and regulatory capacity of MAPC cells, which may inform future clinical trial design.

The Delivery of Multipotent Adult Progenitor Cells to Extended Criteria Human Donor Livers Using Normothermic Machine Perfusion

Background: Pre-clinical research with multi-potent adult progenitor cells (MAPC® cells, Multistem, Athersys Inc., Cleveland, Ohio) suggests their potential as an anti-inflammatory and immunomodulatory therapy in organ transplantation. Normothermic machine perfusion of the liver (NMP-L) has been proposed as a way of introducing therapeutic agents into the donor organ. Delivery of cellular therapy to human donor livers using this technique has not yet been described in the literature. The primary objectives of this study were to develop a technique for delivering cellular therapy to human donor livers using NMP-L and demonstrate engraftment. Methods: Six discarded human livers were perfused for 6 h at 37°C using the Liver Assist (Organ Assist, Groningen). 50 × 106 CMPTX-labeled MAPC cells were infused directly into the right lobe via the hepatic artery (HA, n = 3) or portal vein (PV, n = 3) over 20 min at different time points during the perfusion. Perfusion parameters were recorded and central and peripheral biopsies were taken at multiple time-points from both lobes and subjected to standard histological stains and confocal microscopy. Perfusate was analyzed using a 35-plex multiplex assay and proteomic analysis. Results: There was no detrimental effect on perfusion flow parameters on infusion of MAPC cells by either route. Three out of six livers met established criteria for organ viability. Confocal microscopy demonstrated engraftment of MAPC cells across vascular endothelium when perfused via the artery. 35-plex multiplex analysis of perfusate yielded 13 positive targets, 9 of which appeared to be related to the infusion of MAPC cells (including Interleukin's 1b, 4, 5, 6, 8, 10, MCP-1, GM-CSF, SDF-1a). Proteomic analysis revealed 295 unique proteins in the perfusate from time-points following the infusion of cellular therapy, many of which have strong links to MAPC cells and mesenchymal stem cells in the literature. Functional enrichment analysis demonstrated their immunomodulatory potential. Conclusion: We have demonstrated that cells can be delivered directly to the target organ, prior to host immune cell population exposure and without compromising the perfusion. Transendothelial migration occurs following arterial infusion. MAPC cells appear to secrete a host of soluble factors that would have anti-inflammatory and immunomodulatory benefits in a human model of liver transplantation.

Treatment evaluation of acute stroke for using in regenerative cell elements (TREASURE) trial: Rationale and design

Rationale MultiStem® (HLM051) is one of the promising allogenic cell products for acute ischemic stroke with strong evidence. A previous phase 2 randomized, double-blind, placebo-controlled, multicenter dose-escalation trial showed the safety of MultiStem® for acute ischemic stroke, with a time window beyond that of rt-PA and endovascular thrombectomy. We aim to obtain stronger evidence and to show the efficacy of the MultiStem® for treatment of ischemic stroke. Sample size Estimated sample size is 220 (110 patients per group), which has 90% power at 5% significance level. Methods and design TREASURE is a randomized, double-blind, placebo-controlled, multicenter phase 2/3 trial. The trial will be done at 31 medical centers in Japan. Patients with acute ischemic stroke including motor or speech deficit defined by a National Institution of Health Stroke Scale (NIHSS) score of 8-20 at baseline will be randomized 1:1 to receive a single intravenous infusion of MultiStem® or placebo within 18-36 h of stroke onset. Study outcomes Primary outcome in this study is the proportion of patients with an excellent outcome at day 90 defined by the functional assessment. Trial registration ClinicalTrials.gov (NCT02961504). Conclusion The TREASURE trial will provide a novel treatment option and expand the therapeutic window for patients with stroke if the results are positive.

Mesenchymal Stem and Progenitor Cells in Regeneration: Tissue Specificity and Regenerative Potential

It has always been an ambitious goal in medicine to repair or replace morbid tissues for regaining the organ functionality. This challenge has recently gained momentum through considerable progress in understanding the biological concept of the regenerative potential of stem cells. Routine therapeutic procedures are about to shift towards the use of biological and molecular armamentarium. The potential use of embryonic stem cells and invention of induced pluripotent stem cells raised hope for clinical regenerative purposes; however, the use of these interventions for regenerative therapy showed its dark side, as many health concerns and ethical issues arose in terms of using these cells in clinical applications. In this regard, adult stem cells climbed up to the top list of regenerative tools and mesenchymal stem cells (MSC) showed promise for regenerative cell therapy with a rather limited level of risk. MSC have been successfully isolated from various human tissues and they have been shown to offer the possibility to establish novel therapeutic interventions for a variety of hard-to-noncurable diseases. There have been many elegant studies investigating the impact of MSC in regenerative medicine. This review provides compact information on the role of stem cells, in particular, MSC in regeneration.

Multipotent adult progenitor cells on an allograft scaffold facilitate the bone repair process

Multipotent adult progenitor cells are a recently described population of stem cells derived from the bone marrow stroma. Research has demonstrated the potential of multipotent adult progenitor cells for treating ischemic injury and cardiovascular repair; however, understanding of multipotent adult progenitor cells in orthopedic applications remains limited. In this study, we evaluate the osteogenic and angiogenic capacity of multipotent adult progenitor cells, both in vitro and loaded onto demineralized bone matrix in vivo, with comparison to mesenchymal stem cells, as the current standard. When compared to mesenchymal stem cells, multipotent adult progenitor cells exhibited a more robust angiogenic protein release profile in vitro and developed more extensive vasculature within 2 weeks in vivo. The establishment of this vascular network is critical to the ossification process, as it allows nutrient exchange and provides an influx of osteoprogenitor cells to the wound site. In vitro assays confirmed the multipotency of multipotent adult progenitor cells along mesodermal lineages and demonstrated the enhanced expression of alkaline phosphatase and production of calcium-containing mineral deposits by multipotent adult progenitor cells, necessary precursors for osteogenesis. In combination with a demineralized bone matrix scaffold, multipotent adult progenitor cells demonstrated enhanced revascularization and new bone formation in vivo in an orthotopic defect model when compared to mesenchymal stem cells on demineralized bone matrix or demineralized bone matrix–only control groups. The potent combination of angiogenic and osteogenic properties provided by multipotent adult progenitor cells appears to create a synergistic amplification of the bone healing process. Our results indicate that multipotent adult progenitor cells have the potential to better promote tissue regeneration and healing and to be a functional cell source for use in orthopedic applications.

Development of Synthetic and Natural Materials for Tissue Engineering Applications Using Adipose Stem Cells

Adipose stem cells have prominent implications in tissue regeneration due to their abundance and relative ease of harvest from adipose tissue and their abilities to differentiate into mature cells of various tissue lineages and secrete various growth cytokines. Development of tissue engineering techniques in combination with various carrier scaffolds and adipose stem cells offers great potential in overcoming the existing limitations constraining classical approaches used in plastic and reconstructive surgery. However, as most tissue engineering techniques are new and highly experimental, there are still many practical challenges that must be overcome before laboratory research can lead to large-scale clinical applications. Tissue engineering is currently a growing field of medical research; in this review, we will discuss the progress in research on biomaterials and scaffolds for tissue engineering applications using adipose stem cells.

Immunophenotypic comparison of heterogenous non-sorted versus sorted mononuclear cells from human umbilical cord blood: a novel cell enrichment approach

Human umbilical cord blood (hUCB) has been the preferred source of stem cells for the treatment of haematological malignancies and genetic disorders. This is primarily due to its non-invasiveness, high accessibility with relative ease of isolation. Still failures do prevail due to its heterogeneity and lesser frequency of MSC identified in UCB. This study, thus, employs a cell enrichment technology to improve its therapeutic efficacy. This was achieved by immunophenotypic comparison of stem cells isolated from the heterogenous non-sorted mononuclear cells (MNCs), linage depleted (Lin+ and Lin-) fractions obtained from magnetic activated cell sorter (MACS) and sorted MNCs obtained by fluorescent activated cell sorter (FACS). The markers under consideration were CD29, CD44, CD34, CD45, CD133, CD90 and CD117. FACS sorted MNCs were rich in naive stem cell population, whereas non-sorted MNCs and lineage depleted fractions were found to be rich in progenitors. Thus, we suggest that a combination therapy of both sorted population might serve as an alternative valuable tool in treating haematologic/genetic disorders. However, further research on cell enrichment technology might give a clue for improved cell based therapy in regenerative medicine.

A double-blind placebo-controlled clinical evaluation of MultiStem for the treatment of ischemic stroke

BACKGROUND

There is growing interest in neurorestorative and reparative therapies after acute stroke. MultiStem is an allogeneic cell therapy treatment comprising a population of multipotent adherent bone marrow cells that has shown safety in clinical trials of myocardial infarction and graft vs. host disease, as well as preclinical evidence of activity in stroke and other neurological damage models. MultiStem is now being evaluated in a clinical trial in patients that have suffered an ischemic stroke, in which the product is administered intravenously 24-36 h after the ischemic event.

METHODS

The Phase 2 randomized, double-blind, placebo-controlled, multicenter dose-escalation trial will consist of three treatment cohorts, including a placebo group, and two treatment groups involving dose tiers of either 400 million or 1200 million cells per patient. Patients will be treated at 24-36 h after stroke. The two primary objectives are to determine the highest well-tolerated and safe single dose of MultiStem up to a maximum of 1200 million total cells in subjects with ischemic stroke and to determine the efficacy of MultiStem on functional outcome in subjects with stroke as measured by the modified Rankin Scale at 90 days. Patients will also be evaluated using the National Institutes of Health Stroke Scale and Barthel Index. The study will explore other aspects including, uniquely, the measurement of spleen size after stroke by magnetic resonance imaging or computed tomography imaging.

CONCLUSIONS AND FUTURE DIRECTION

If MultiStem is safe and there is a signal of efficacy, a late stage phase IIb-III trial is planned.

Lineage depletion of stromal vascular fractions isolated from human adipose tissue: a novel approach towards cell enrichment technology

The therapeutic rationale for tissue repair and regeneration using stem cells is at its infancy and needs advancement in understanding the role of individual component's innate capability. As stem cells of adipose tissue reside in a more heterogeneous population of stromal vascular fractions, cell separation or sorting becomes an eminent step towards revealing their unique properties. This study elucidates the comparative efficacy of lineage depleted adipose derived stromal vascular fraction (SVF) and their innate ability using magnetic activated cell sorter (MACS). To this end, isolated SVF from human adipose tissue was lineage depleted according to the manufacturer's instructions using specific antibody cocktail through MACS. The enriched lineage negative (lin-) and lineage positive (lin+) cell fractions were cultured, phenotypically characterized for the panel of cell surface markers using flowcytometry and subjected to osteoblastic and adipogenic differentiation. The expression profile obtained for lin- cells was CD34-/CD45-/HLADR-/CD49d-/CD140b-/CD31-/CD90+/CD105+/CD73+/CD54+/CD166+/CD117- when compared to Lin+ cells expressing CD34+/CD45+/HLADR-/CD49d-/CD140b+/CD31-/CD90+/CD105+/CD73+/CD54+/CD166+/CD117+ (CD-cluster of differentiation). These results, thus, advances our understanding on the inherent property of the individual cell population. Furthermore, both the fractions exhibited mesodermal lineage differentiation capacity. To conclude, this research pursuit rationalized the regenerative therapeutic applicability of both lin- and lin+ cultures of human adipose tissue for disorders of mesodermal, haematological and vascular origin.

Multipotent adult progenitor cell-loaded demineralized bone matrix for bone tissue engineering

Multipotent adult progenitor cells (MAPCs) from bone marrow have been shown to be capable of forming bone, cartilage and other connective tissues. In addition, MAPCs differentiate into lineages that are different from their germ layers of origin. Previous studies showed the ability of MAPCs to improve cardiac function and control allogenic-reactive responses associated with acute graft versus host disease. In the current study, we evaluated the ability of MAPCs to produce bone matrix on demineralized bone allograft substrates. Specifically, MAPCs expressed alkaline phosphatase, produced extracellular matrix proteins and deposited calcium-containing mineral on demineralized bone matrices. Furthermore, the addition of MAPCs on demineralized bone matrix (DBM) scaffolds enhanced osteoinductivity of the carrier in a rat ectopic pouch model. These results demonstrated the potential of MAPCs as a new approach for bone repair in tissue-engineering applications.

Mesenchymal stem cells: a revolution in therapeutic strategies of age-related diseases

The great evolutionary biologist Theodosius Dobzhansky once said: "Nothing in biology makes sense except in the light of evolution". Aging is a complex biological phenomenon and the factors governing the process of aging and age-related diseases are only beginning to be understood, oxidative stress, telomere shortening in DNA components and genetic changes were shown to be the mainly regulating mechanisms during the recent decades. Although a considerable amount of both animal and clinical data that demonstrate the extensive and safe use of mesenchymal stromal cells (MSCs) is available, the precise summarization and identification of MSCs in age-related diseases remains a challenge. Along this line, this review discussed several typical age-related diseases for which MSCs have been proved to confer protection and put forward a hypothesis for the association among MSCs and age-related diseases from an evolutionary perspective. Above all, we hope further and more research efforts could be aroused to elucidate the role and mechanisms that MSCs involved in the age-related diseases.

Development of a surrogate angiogenic potency assay for clinical-grade stem cell production

BACKGROUND AIMS

Clinical results from acute myocardial infarction (AMI) patients treated with MultiStem®, a large-scale expanded adherent multipotent progenitor cell population (MAPC), have demonstrated a strong safety and benefit profile for these cells. The mechanism of benefit with MAPC treatment is a result, in part, of its ability to induce neovascularization through trophic support. Production of clinical-grade stem cell products requires the development of lot-release criteria based on potency assays that directly reflect the fundamental mechanistic pathway underlying the therapeutic response to verify manufacturing process consistency and product potency.

METHODS AND RESULTS

Using an in vitro endothelial tube formation assay, a potency assay has been developed that reflects MAPC pro-angiogenic activity. Serum-free conditioned media collected from MAPC culture induced endothelial tube formation. A proteomic survey of angiogenic factors produced by the cells in vitro revealed candidate factors linked to angiogenic potency. Three cytokines, chemokine (C-X-C motif) ligand 5 (CXCL5), interleukin 8 (IL-8) and vascular endothelial growth factor (VEGF), were required for this angiogenic activity. Depletion of any of these factors from the media prevented tube formation, while adding back increasing amounts of these cytokines into the depleted serum-free conditioned media established the lower limits of each of the cytokines required to induce angiogenesis.

CONCLUSIONS

A necessary threshold of angiogenic factor expression was established using an in vitro angiogenesis assay. By correlating the levels of the cytokines required to induce tube formation in vitro with levels of the factors found in the spent media from manufacturing production runs, detection of these factors was identified as a surrogate potency assay with defined pass/fail criteria.

Genetically engineered mesenchymal stem cells as a proposed therapeutic for Huntington's disease

There is much interest in the use of mesenchymal stem cells/marrow stromal cells (MSC) to treat neurodegenerative disorders, in particular those that are fatal and difficult to treat, such as Huntington's disease. MSC present a promising tool for cell therapy and are currently being tested in FDA-approved phase I-III clinical trials for many disorders. In preclinical studies of neurodegenerative disorders, MSC have demonstrated efficacy, when used as delivery vehicles for neural growth factors. A number of investigators have examined the potential benefits of innate MSC-secreted trophic support and augmented growth factors to support injured neurons. These include overexpression of brain-derived neurotrophic factor and glial-derived neurotrophic factor, using genetically engineered MSC as a vehicle to deliver the cytokines directly into the microenvironment. Proposed regenerative approaches to neurological diseases using MSC include cell therapies in which cells are delivered via intracerebral or intrathecal injection. Upon transplantation, MSC in the brain promote endogenous neuronal growth, encourage synaptic connection from damaged neurons, decrease apoptosis, reduce levels of free radicals, and regulate inflammation. These abilities are primarily modulated through paracrine actions. Clinical trials for MSC injection into the central nervous system to treat amyotrophic lateral sclerosis, traumatic brain injury, and stroke are currently ongoing. The current data in support of applying MSC-based cellular therapies to the treatment of Huntington's disease is discussed.

Safety and feasibility of third-party multipotent adult progenitor cells for immunomodulation therapy after liver transplantation--a phase I study (MISOT-I)

BACKGROUND

Liver transplantation is the definitive treatment for many end-stage liver diseases. However, the life-long immunosuppression needed to prevent graft rejection causes clinically significant side effects. Cellular immunomodulatory therapies may allow the dose of immunosuppressive drugs to be reduced. In the current protocol, we propose to complement immunosuppressive pharmacotherapy with third-party multipotent adult progenitor cells (MAPCs), a culture-selected population of adult adherent stem cells derived from bone marrow that has been shown to display potent immunomodulatory and regenerative properties. In animal models, MAPCs reduce the need for pharmacological immunosuppression after experimental solid organ transplantation and regenerate damaged organs.

METHODS

Patients enrolled in this phase I, single-arm, single-center safety and feasibility study (n = 3-24) will receive 2 doses of third-party MAPCs after liver transplantation, on days 1 and 3, in addition to a calcineurin-inhibitor-free "bottom-up" immunosuppressive regimen with basiliximab, mycophenolic acid, and steroids. The study objective is to evaluate the safety and clinical feasibility of MAPC administration in this patient cohort. The primary endpoint of the study is safety, assessed by standardized dose-limiting toxicity events. One secondary endpoint is the time until first biopsy-proven acute rejection, in order to collect first evidence of efficacy. Dose escalation (150, 300, 450, and 600 million MAPCs) will be done according to a 3 + 3 classical escalation design (4 groups of 3-6 patients each).

DISCUSSION

If MAPCs are safe for patients undergoing liver transplantation in this study, a phase II/III trial will be conducted to assess their clinical efficacy.

Efficacy and Durability in Direct Labeling of Mesenchymal Stem Cells Using Ultrasmall Superparamagnetic Iron Oxide Nanoparticles with Organosilica, Dextran, and PEG Coatings

We herein report a comparative study of mesenchymal stem cell (MSC) labeling using spherical superparamagnetic iron oxide (SPIO) nanoparticles containing different coatings, namely, organosilica, dextran, and poly(ethylene glycol) (PEG). These nanomaterials possess a similar SPIO core size of 6–7 nm. Together with their coatings, the overall sizes are 10–15 nm for all SPIO@SiO₂, SPIO@dextran, and SPIO@PEG nanoparticles. These nanoparticles were investigated for their efficacies to be uptaken by rabbit bone marrow-derived MSCs without any transfecting agent. Experimentally, both SPIO@SiO₂ and SPIO@PEG nanoparticles could be successfully uptaken by MSCs while the SPIO@dextran nanoparticles demonstrated limited labeling efficiency. The labeling durability of SPIO@SiO₂ and SPIO@PEG nanoparticles in MSCs after three weeks of culture were compared by Prussian blue staining tests. SPIO@SiO₂ nanoparticles demonstrated more blue staining than SPIO@PEG nanoparticles, rendering them better materials for MSCs labeling by direct uptake when durable intracellullar retention of SPIO is desired.

Mesenchymal stem cells for the treatment of neurodegenerative disease

Mesenchymal stem cells/marrow stromal cells (MSCs) present a promising tool for cell therapy, and are currently being tested in US FDA-approved clinical trials for myocardial infarction, stroke, meniscus injury, limb ischemia, graft-versus-host disease and autoimmune disorders. They have been extensively tested and proven effective in preclinical studies for these and many other disorders. There is currently a great deal of interest in the use of MSCs to treat neurodegenerative diseases, in particular for those that are fatal and difficult to treat, such as Huntington's disease and amyotrophic lateral sclerosis. Proposed regenerative approaches to neurological diseases using MSCs include cell therapies in which cells are delivered via intracerebral or intrathecal injection. Upon transplantation into the brain, MSCs promote endogenous neuronal growth, decrease apoptosis, reduce levels of free radicals, encourage synaptic connection from damaged neurons and regulate inflammation, primarily through paracrine actions. MSCs transplanted into the brain have been demonstrated to promote functional recovery by producing trophic factors that induce survival and regeneration of host neurons. Therapies will capitalize on the innate trophic support from MSCs or on augmented growth factor support, such as delivering brain-derived neurotrophic factor or glial-derived neurotrophic factor into the brain to support injured neurons, using genetically engineered MSCs as the delivery vehicles. Clinical trials for MSC injection into the CNS to treat traumatic brain injury and stroke are currently ongoing. The current data in support of applying MSC-based cellular therapies to the treatment of neurodegenerative disorders are discussed.

Multipotent adult progenitor cells prevent macrophage-mediated axonal dieback and promote regrowth after spinal cord injury

Macrophage-mediated axonal dieback presents an additional challenge to regenerating axons after spinal cord injury. Adult adherent stem cells are known to have immunomodulatory capabilities, but their potential to ameliorate this detrimental inflammation-related process has not been investigated. Using an in vitro model of axonal dieback as well as an adult rat dorsal column crush model of spinal cord injury, we found that multipotent adult progenitor cells (MAPCs) can affect both macrophages and dystrophic neurons simultaneously. MAPCs significantly decrease MMP-9 (matrix metalloproteinase-9) release from macrophages, effectively preventing induction of axonal dieback. MAPCs also induce a shift in macrophages from an M1, or "classically activated" proinflammatory state, to an M2, or "alternatively activated" antiinflammatory state. In addition to these effects on macrophages, MAPCs promote sensory neurite outgrowth, induce sprouting, and further enable axons to overcome the negative effects of macrophages as well as inhibitory proteoglycans in their environment by increasing their intrinsic growth capacity. Our results demonstrate that MAPCs have therapeutic benefits after spinal cord injury and provide specific evidence that adult stem cells exert positive immunomodulatory and neurotrophic influences.

Durable mesenchymal stem cell labelling by using polyhedral superparamagnetic iron oxide nanoparticles

Small polyhedral superparamagnetic iron oxide (SPIO) nanoparticles (<10 nm) coated with a thin layer of silica were prepared (SPIO@SiO(2) and SPIO@SiO(2)-NH(2)). Surface modification of the small polyhedral silica-coated SPIO nanoparticles with amines led to substantially higher mesenchymal stem cell (MSC) labelling efficiency without the use of additional transfecting agents. Therefore, amine surface-modified nanoparticles (SPIO@ SiO(2)-NH(2)) appeared to be the preferred candidate for MSC labelling. In vitro studies demonstrated that controlled labelling of SPIO@SiO(2) and SPIO@SiO(2)-NH(2) did not cause MSC death or proliferation inhibition. MSCs labelled with SPIO@SiO(2)-NH(2) nanoparticles retained differentiation potential and showed osteogenic, adipogenic and chondrogenic differentiations. The noncytotoxic polyhedral SPIO@SiO(2)-NH(2) nanoparticle-labelled MSCs were successfully implanted in rabbit brain and erector spinae muscle, and demonstrated long-lasting, durable MRI labelling efficacy after 8-12 weeks.

Comparison of the response of human embryonic stem cells and their differentiated progenies to oxidative stress

OBJECTIVE

To investigate effects of oxidative stress on human embryonic stem cells (hESC) and their spontaneously differentiated fibroblastic progenies (at passage 5).

BACKGROUND DATA

In ischemic disease models, high levels of free radicals and reactive oxygen species are critical factors in decreasing survivability and engraftment of transplanted/transfused cells. Hence, it is imperative to characterize response of hESC and their differentiated progenies to oxidative stress.

METHODS

Oxidative stress was induced either by (i) varying durations (0 to 40 min) of photodynamic treatment (diode laser, 664 nm, 30 mW) in the presence of 10 microM methylene blue as a photosensitizer, or by (ii) exposure to varying concentrations of hydrogen peroxide (0 to 50 microM) for a fixed duration of 40 min. Additionally, the effects of heat shock and mild oxidative stress preconditioning on oxidative stress response was also investigated.

RESULTS

Consistently higher survivability (MTT assay) of hESC was observed compared to their differentiated fibroblastic progenies, upon exposure to equivalent levels of oxidative stress. Further experiments demonstrated that heat-shock pretreatment (42 degrees C for 90 min) did not enhance the resistance of either hESC or their differentiated progenies to oxidative stress (photodynamic treatment), but in fact had a slightly detrimental effect on their survivability upon subsequent exposure to oxidative stress. Similarly, preconditioning of both undifferentiated hESC and their differentiated progenies with low levels of oxidative stress also did not enhance cellular survivability upon subsequent exposure to much higher levels of oxidative stress induced by photodynamic treatment.

CONCLUSIONS

Undifferentiated hESC are intrinsically more resistant to oxidative stress compared to their spontaneously differentiated fibroblastic progenies.

Regenerative stromal cell therapy in allogeneic hematopoietic stem cell transplantation: current impact and future directions

Regenerative stromal cell therapy (RSCT) has the potential to become a novel therapy for preventing and treating acute graft-versus-host disease (GVHD) in the allogeneic hematopoietic stem cell transplant (HSCT) recipient. However, enthusiasm for using RSCT in allogeneic HSCT has been tempered by limited clinical data and poorly defined in vivo mechanisms of action. As a result, the full clinical potential of RSCT in supporting hematopoietic reconstitution and as treatment for GVHD remains to be determined. This manuscript reviews the immunomodulatory activity of regenerative stromal cells in preclinical models of allogeneic HSCT, and emphasizes an emerging literature suggesting that microenvironment influences RSC activation and function. Understanding this key finding may ultimately define the proper niche for RSCT in allogeneic HSCT. In particular, mechanistic studies are needed to delineate the in vivo effects of RSCT in response to inflammation and injury associated with allogeneic HSCT, and to define the relevant sites of RSC interaction with immune cells in the transplant recipient. Furthermore, development of in vivo imaging technology to correlate biodistribution patterns, desired RSC effect, and clinical outcome will be crucial to establishing dose-response effects and minimal biologic dose thresholds needed to advance translational treatment strategies for complications like GVHD.

Pre-clinical safety testing supporting clinical use of allogeneic multipotent adult progenitor cells

BACKGROUND

Successful clinical development of novel cellular therapeutics requires the evaluation of clinical acute toxicity endpoints in scoring patient adverse events (AE) contributing to dose-limiting toxicity (DLT) for establishment of the maximum-tolerated dose (MTD). However, many clinical pathology parameters are not routinely evaluated in pre-clinical safety testing. The objective of this pre-clinical study was to investigate thoroughly the acute toxicity of single- and multiple-dose administrations of allogeneic multipotent adult progenitor cells (MultiStem), which represent a class of stromal stem cells with therapeutic potential.

METHODS

MultiStem were tested as an adjunct treatment in a rat myeloablative hematopoietic stem cell transplantation (HSCT) model for impact on clinical parameters, clinical chemistry, hematology, immunology and histopathology parameters. Animals received MultiStem in a single dose of 12.5 million cells/kg on day 2 after HSCT or in five infusions at this dose on days 2, 9, 16, 23 and 30. Controls received phosphate-buffered saline injections and all animals were killed on day 37.

RESULTS

There were no significant differences between tests and controls regarding evaluation of respiratory distress upon infusion, clinical assessment and hematology and clinical chemistry analysis. Gross necropsy and histopathology analysis showed no organ profile alterations. There was no significant evidence for allogeneic antibody production or T-cell sensitization upon MultiStem infusion.

DISCUSSION

These studies demonstrate the safety of administration of allogeneic stromal stem cells in repeat dosing regimens in bone marrow transplant settings, and define pre-clinical safety testing standards relevant to the development of cellular therapeutics using allogeneic adherent adult stem cells.

Horse bone marrow mesenchymal stem cells express embryo stem cell markers and show the ability for tenogenic differentiation by in vitro exposure to BMP-12

Background

Mesenchymal stem cells (MSCs) have been recently investigated for their potential use in regenerative medicine. MSCs, in particular, have great potential, as in various reports they have shown pluripotency for differentiating into many different cell types. However, the ability of MSCs to differentiate into tendon cells in vitro has not been fully investigated.

Results

In this study, we show that equine bone marrow mesenchymal stem cells (BM-MSCs), defined by their expression of markers such as Oct4, Sox-2 and Nanog, have the capability to differentiate in tenocytes. These differentiated cells express tendon-related markers including tenomodulin and decorin. Moreover we show that the same BM-MSCs can differentiate in osteocytes, as confirmed by alkaline phosphatase and von Kossa staining.

Conclusion

As MSCs represent an attractive tool for tendon tissue repair strategies, our data suggest that bone marrow should be considered the preferred MSC source for therapeutic approaches.

Bone marrow transplantation: new approaches to immunosuppression and management of acute graft-versus-host disease

PURPOSE OF REVIEW

Acute graft-versus-host disease (GVHD) significantly limits the application and the success of allogeneic hematopoietic stem cell transplantation (HSCT). Novel therapies that target the aberrant immune response underlying GVHD are reviewed with particular emphasis on immunomodulatory agents currently incorporated into clinical trials. In addition, regenerative stromal cellular therapy (RSCT) is discussed as an emerging form of novel GVHD therapy.

RECENT FINDINGS

Knowledge for transplant immunology, particularly as it relates to underlying pathophysiology of GVHD, has dramatically increased over the last decade. As a result, new immunomodulatory therapies have been used to treat steroid-refractory GVHD. However, their success has been limited by their lack of clinical experience during HSCT as well as by their associated toxicity profiles. RSCT uniquely offers the potential to enhance donor-derived hematopoiesis and immunity and to ameliorate adverse sequelae associated with GVHD.

SUMMARY

An exciting era incorporating the use of cellular therapeutics during HSCT has arrived. As the experience and understanding for cellular therapies, in general, and RSCT, in particular, increases, so too will their success in benefiting the HSCT recipient beyond limitations of current pharmaceutical agents.

Enrichment of putative stem cells from adipose tissue using dielectrophoretic field-flow fractionation

We have applied the microfluidic cell separation method of dielectrophoretic field-flow fractionation (DEP-FFF) to the enrichment of a putative stem cell population from an enzyme-digested adipose tissue derived cell suspension. A DEP-FFF separator device was constructed using a novel microfluidic-microelectronic hybrid flex-circuit fabrication approach that is scaleable and anticipates future low-cost volume manufacturing. We report the separation of a nucleated cell fraction from cell debris and the bulk of the erythrocyte population, with the relatively rare (<2% starting concentration) NG2-positive cell population (pericytes and/or putative progenitor cells) being enriched up to 14-fold. This work demonstrates a potential clinical application for DEP-FFF and further establishes the utility of the method for achieving label-free fractionation of cell subpopulations.

Therapeutic pathways of adult stem cell repair

The use of adult stem cells as therapeutic agents to treat disease has become increasingly prevalent. During the last decade, isolated and expanded stem and progenitor cells have demonstrated the capacity to differentiate into multiple cell types. Early optimism that in vitro differentiation capacity would translate into in vivo tissue regeneration has lessened and identifying the mechanisms that underlie the benefit of stem cell repair is an emerging area of investigation. This review considers several of the pathways and mechanisms required for adult stem cell repair. These mechanisms include the mobilization and the homing of stem cells to sites of injury, immunomodulatory effect of stem cells, and the association of stem cells with increased vascularization of injured tissue. These data suggest that the unique properties of adult stem cells can be utilized to treat a wide variety of diseases that cannot be treated with existing pharmacological agents, and prompt new paradigms for the bio-pharmacokinetics of biological expressed by efficacious stem cells.

Direct delivery of syngeneic and allogeneic large-scale expanded multipotent adult progenitor cells improves cardiac function after myocardial infarct

BACKGROUND

Multipotent adult progenitor cells (MAPC) comprise interesting candidates for myocardial regeneration because of a broad differentiation ability and immune privilege. We aimed to compare the improvement of cardiac function by syngeneic and allogeneic MAPC produced on a large scale using a platform optimized from MAPC research protocols.

METHODS

Myocardial infarction was induced in Lewis rats by direct left anterior descending ligation followed immediately by direct injection into the infarct border zone of either Sprague-Dawley or Lewis MAPC from large-scale expansions. Echocardiography was performed to evaluate improvement in cardiac function, and immunohistochemistry was performed to identify MAPC within the infarct zone.

RESULTS

Significant increases were observed in functional performance in animals transplanted with expanded MAPC compared with saline controls, with no significant differences between the syngeneic and allogeneic groups. Immunostaining demonstrated significant engraftment of expanded MAPC at 1 day after acute myocardial infarction, with <10% of either syngeneic or allogeneic cells remaining at 6 weeks. At this point there was no evidence of myocardial regeneration. However, a significant increase in vascular density within the infarct zone in MAPC-transplanted animals was observed, and MAPC were found to produce high levels of VEGF in culture.

DISCUSSION

These findings support a model in which delivery of expanded MAPC following acute myocardial infarction results in improvement in cardiac function because of paracrine effects resulting in vascular density increases, as well as potentially other trophic effects, supporting newly injured cardiac myocytes. Thus transplantation with MAPC may represent a promising therapeutic strategy with application in the stimulation of neovascularization in ischemic heart disease.