Bone Marrow-derived Hematopoietic Stem Cells Research Articles

The NIH and the Regenerative Medicine Field

Stem cells come in many flavors. The scientific distinction to make between these cells is not whether they are embryonic, fetal, adult or cadaveric, but rather the properties of the particular stem cell that is harvested for use. For example, a bone marrow-derived hematopoietic stem cell is the best choice for marrowrelated disease, but adult neural stem cells are not. Similarly, an adult limbal stem cell is great for repairing a cornea, but a mesenchymal stem cell (MSC) from the same adult is not the best choice. Nor is a fetal MSC, or even a MSC derived from a pluripotent stem cell [1]. Rather, the utility of the cell depends on the tissue it came from and its functional properties. This has been borne out by numerous clinical studies with adult stem cells. Applying this again to MSCs, these look very promising for treating limb ischemia or graft-versus-host disease, as this appears to be their normal function in the adult. However, MSCs have not been useful in forming neurons in the brain or cardiac muscle in the heart, as this is not their normal function, and this has been borne out by studies carried out by responsible proponents of adult stem cell therapy. Embryonic and fetal cells in general are more immature than adult cells and take much longer to mature, even when transplanted. They are not generally preferred, unless there is no useful adult source or their numbers are limited. Thus, despite the fact that fetal neural stem cells take longer to mature, we consider them for therapy over adult cells when adult stem cells are not available in the numbers required for therapy. The NIH, therefore, has focused on funding the best science and – in terms of translation – the best cell for a particular disease

Monitoring the glioma tropism of bone marrow-derived progenitor cells by 2-photon laser scanning microscopy and positron emission tomography

Intracerebral experimental gliomas attract intravenously injected murine or human bone marrow-derived hematopoietic progenitor and stem cells (HPC) in vitro, ex vivo, and in vivo, indicating that these progenitor cells might be suitable vehicles for a cell-based delivery of therapeutic molecules to malignant gliomas. With regard to therapeutic application, it is important to investigate cell fates in vivo (i.e., the time-dependent intratumoral and systemic distribution after intravenously injection). Conventional histological analysis has limitations in this regard because longitudinal monitoring is precluded. Here, we used 2-photon laser scanning microscopy (2PLSM), positron emission tomography (PET), and MRI to study the fate of intravenously injected HPC carrying fluorescence, bioluminescence, and PET reporter genes in glioma-bearing mice. Our 2PLSM-based monitoring studies revealed that HPC homing to intracerebral experimental gliomas occurred already within the first 6 h and was most efficient within the first 24 h after intravenous injection. The highest PET signals were detected in intracerebral gliomas, whereas the tracer uptake in other organs, notably spleen, lung, liver, and muscle, remained at background levels. The results have important implications for designing schedules for therapeutic cell-based anti-glioma approaches. Moreover, the PET reporter-based imaging technique will allow noninvasive monitoring of cell fate in future cell-based therapeutic antiglioma approaches.

Generation of CD2+CD8+NK Cells from c-kit+Bone Marrow Cells in Porcine

Natural killer (NK) cells provide one of the initial barriers of cellular host defense against pathogens, in particular intracellular pathogens. Because bone marrow-derived hematopoietic stem cells (HSCs), lymphoid protenitors, can give rise to NK cells, NK ontogeny has been considered to be exclusively lymphoid. Here, we show that porcine c-kit+ bone marrow cells (c-kit+ BM cells) develop into NK cells in vitro in the presence of various cytokines [interleukin (IL)-2, IL-7, IL-15, IL-21, stem cell factor (SCF), and fms-like tyrosine kinase-3 ligand (FLT3L)]. Adding hydrocortisone (HDC) and stromal cells greatly increases the frequency of c-kit+ BM cells that give rise to CD2+CD8+ NK cells. Also, intracellular levels of perforin, granzyme B, and NKG2D were determined by RT-PCR and western blotting analysis. It was found that of perforin, granzyme B, and NKG2D levels significantly were increased in cytokine-stimulated c-kit+ BM cells than those of controls. And, we compared the ability of the cytotoxicity of CD2+CD8+ NK cells differentiated by cytokines from c-kit+ BM cells against K562 target cells for 28 days. Cytokines-induced NK cells as effector cells were incubated with K562 cells as target in a ratio of 100:1 for 4 h once a week. In results, CD2+CD8+ NK cells induced by cytokines and stromal cells showed a significantly increased cytotoxicity 21 days later. Whereas, our results indicated that c-kit+ BM cells not pretreated with cytokines have lower levels of cytotoxicity. Taken together, this study suggests that cytokines-induced NK cells from porcine c-kit+ BM cells may be used as adoptive transfer therapy if the known obstacles to xenografting (e.g. immune and non-immune problems) were overcome in the future.

A target for antiangiogenic therapy: Vascular endothelium derived from glioblastoma

Glioblastoma is the most frequent primary brain tumor in the adult, accounting for 53.8% of all gliomas (http://www.cbtrus.org), and it is one of the most deadly among all human tumors. Despite aggressive treatment at diagnosis, consisting of resection followed by radiation with concurrent and subsequent adjuvant chemotherapy with temozolomide, the tumor almost invariably recurs or progresses, with a patient median survival of 14.6 mo (1). The hallmark of glioblastoma that distinguishes it from all of the other glial tumors is microvascular proliferation in conjunction with necrosis. Therefore, treatment with antiangiogenic agents holds great promise to block the growth of this most vascularized tumor. The best-known antiangiogenic agents are inhibitors of VEGF-A, an indispensable angiogenic factor during developmental organogenesis and growth of numerous tumors. However, treatment with bevacizumab, a neutralizing antibody to VEGF-A, at relapse only confers transient benefit and a marginal increase in survival, indicating at tumor progression a VEGF-independent angiogenic mechanism of glioblastoma resistance (2). Several mechanisms have been implicated in angiogenesis. One is the sprouting of capillaries from preexisting blood vessels by endothelial proliferation (3). Another is the cooption of preexisting blood vessels by tumor cells, leading to expression of angiopoietin-2 by those vessels’ endothelial cells and tumor cell proliferation, followed later by involution of preexisting vessels in the core of the tumor, massive tumor cell apoptosis, organization of remaining tumor cells into pseudopalisading that resides around areas of necrosis, and tumor rescue at the margins by angiogenesis (4, 5). Expression of HIF-1α and up-regulation of VEGF-A have been identified in hypoxic perinecrotic pseudopalisading tumor cells (4–6). Hypoxia induces elevated levels of VEGF-A (6) and VEGF-A receptors that appear up-regulated in tumor endothelial cells but not in normal brain (7). Another mechanism is the release of angiogenic factors by the tumor that recruit bone marrow-derived endothelial progenitors, hematopoietic stem and progenitor cells that participate in vessel formation (8–10). In PNAS, Soda, Verma, and colleagues reveal a new paradigm for glioblastoma angiogenesis whose main contribution is transdifferentiation of glioblastoma cells into endothelial cells (11) (Fig. 1). Notably, these tumor-derived endothelial cells (TDECs) are refractory to inhibition of both VEGF-A and basic fibroblast growth factor (bFGF, FGF-2) pathways. By mapping GFP+ p53-deficient glioblastoma established in glial-specific Cre mice (GFAP-Cre) (12), Soda et al. find that tumor cells can directly transdifferentiate into CD31+CD34+ endothelial cells that lack VEGF-A receptors (VEGFR), constituting over 20% of total CD31+CD34+ tumor endothelial population. These TDECs are capable of forming patent vessels. Moreover, further analysis by hypoxyprobe unraveled their preferential localization in deep hypoxic areas of the tumors. The hypoxic-associated distribution of TDECs and elevated expression of HIF-1α, a hypoxia-induced transcription factor, indicate the role of hypoxia as the key determinant in forcing putative glioma cells to differentiate into endothelial-like cells.

Nocturnal home hemodialysis and its impact on erythropoietin responsiveness

Anemia secondary to end-stage renal disease (ESRD) is an important but complex syndrome which directly contributes to significant morbidity and mortality in this patient population. The interactions between uremia, bone marrow biology and erythropoietin (EPO) responsiveness are of significant interest to improve our basic understanding of anemia management in ESRD. Nocturnal home hemodialysis is an intensive mode of renal replacement therapy, which has been associated with an improvement in EPO responsiveness. The aims of the present review are (1) to update the recent advances in uremia associated perturbations in bone marrow-derived hematopoietic stem cells and (2) to discuss the potential mechanistic explanations by which augmented uremia clearance may directly affect EPO responsiveness.

Bone Marrow-derived Human Hematopoietic Stem Cells Engraft NOD/SCID Mice and Traffic Appropriately to an Inflammatory Stimulus in the Joint

Studies of human inflammatory arthritis would be significantly aided by the development of better animal models. Our hypothesis is that it is possible to develop humanized arthritis models through novel techniques of hematopoietic stem and progenitor cell (HSPC) delivery. Bone marrow was obtained from patients with osteoarthritis who were undergoing total hip replacement. HSPC were enriched by negative selection and injected into the femur of irradiated anti-CD122 treated nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Human cell engraftment was analyzed by flow cytometry. Arthritis was induced by an intraarticular injection of Chlamydia trachomatis and injected knee joints were examined 5 days later by histology and immunohistochemistry. Human bone marrow HSPC successfully engrafted NOD/SCID mice, with some mice showing up to 90% engrafted human cells. Human B lymphoid and myeloid cells were detected in the bone marrow and spleen 6 weeks following transfer of HSPC, and engrafted recipient mice remained healthy up to 12 weeks postinjection. Chlamydia-injected mice that had been repopulated with HSPC had synovial inflammation, consisting of human neutrophils and macrophages. Bone marrow-derived human HSPC engraft NOD/SCID mice and traffic appropriately to an inflammatory stimulus in the joint, thus offering the potential for direct studies on the immunopathogenesis and treatment of human arthritis.

Are Circulating Monocytes as Microglia Orthologues Appropriate Biomarker Targets for Neuronal Diseases? (Supplementry Table)

Microglial cells, in contrast to other central nervous system cell types such as neurons and macroglia, are of myeloid origin. They constitute the immune cells of the brain and are involved in neuroinflammatory and neurodegenerative processes. Moreover, diseases of the central nervous system with an inflammatory component are characterized by the migration of bone marrow-derived monocytes into the brain where they differentiate into microglia, the "tissue macrophages" of the nervous system, bearing a therapeutic potential for certain diseases by transplantation of bone marrow-derived hematopoietic stem and progenitor cells. Due to their common origin, microglial cells and monocytes/macrophages share expression of many surface receptors and signalling proteins. Moreover, there is overlap in the expression of many genes related to Alzheimer s disease. Activation of resident and blood-derived microglia in diseases of the central nervous system can be both beneficial, e.g. by degradation of protein aggregates, and detrimental, e.g. by secretion of neurotoxic factors. This review summarizes the current knowledge about the role of microglia in neurodegenerative diseases with a focus on Alzheimer s disease. Moreover, we present data how neuroinflammation is reflected by cellular changes in peripheral blood enabling the use of blood monocytes/macrophages for diagnosis, therapeutic target finding and outcome monitoring of neurodegenerative disorders. In summary, blood monocytes as microglia orthologues are an important model system to study the role of microglia in the pathogenesis of neurodegenerative diseases. They are suitable biomarker targets for diagnosis and prognosis and maybe also therapy of central nervous system disease.

338. Efficient Transduction of Human Bone Marrow-Derived Hematopoietic Stem Cells with Clinical Grade Lentiviral Vectors

338. Efficient Transduction of Human Bone Marrow-Derived Hematopoietic Stem Cells with Clinical Grade Lentiviral Vectors

Tracing of hematopoietic lineage cells in the pancreas during ß-cell regeneration

Regeneration of pancreatic ß-cell mass following damage is possible in the young rodent and decreases with age. However, transplantation of bone marrow-derived hematopoietic stem cells following ß-cell loss with streptozotocin (STZ) treatment in adult mice induced regeneration of ß-cell mass. Bone marrow-derived cells preferentially colonized the damaged pancreas and almost 10% demonstrated markers of endothelial precursor cells, probably differentiating into vascular endothelial cells that promoted ß-cell regeneration.

Treatment of amyotrophic lateral sclerosis patients by autologous bone marrow-derived hematopoietic stem cell transplantation: a 1-year follow-up

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive loss of spinal cord and cortical motoneurons. Despite improved understanding of the mechanisms underlying ALS, in clinical practice the management of ALS remains essentially supportive and focused on symptom relief. However, over the past few years stem cell research has expanded greatly as a tool for developing potential new therapies for treating incurable neurodegenerative diseases. Thirteen patients with sporadic amyotrophic lateral sclerosis (SALS) were included in this study, and bone marrow (BM)-derived hematopoietic progenitor stem cells were used. We selected patients with bulbar involvement and severe loss of movement. Our aim was to put the stem cells into the end of the brain stem and at the beginning of the spinal cord because the blood-brain barrier is intact in ALS and this region was the most affected part in our patients. Under general anesthesia, a total laminectomy was performed at the C1-C2 level. Stem cells were injected to the anterior part of the spinal cord. During the follow-up of 1 year after stem cell implantation, nine patients became much better compared with their pre-operative status, confirmed by electro neuro myography (ENMG). One patient was stable without any decline or improvement in his status. Three patients died 1.5, 2 and 9 months, respectively, after stem cell therapy as a result of lung infection and myocardial infarction (MI). These results show that stem cell therapy is a safe, effective and promising treatment for ALS patients.

Neonatal Bone Marrow Transplantation Following Ex Vivo Gene Transfer and in Vivo Chemoselection for Hereditary Disorders

Transplantation of genetically engineered hematopoietic stem cells (HSC) holds promise for treatment of genetic and other disorders; however, several obstacles restrict the clinical application of this approach. These include leukemogenesis resulting from insertional mutagenesis, the lack of a competitive advantage for transplanted genetically engineered autologous HSCs, and the requirement for the construction and clinical approval of a gene transfer vehicle specific to each disorder. Allogenic transplantation approaches are further limited by a shortage of compatible donors, the toxicity of preparative regimens, immunosuppression, and graft versus host disease (GVHD).We have established a neonatal transplantation model to develop strategies to overcome these hurdles to HSC transplantation and gene therapy. We have uniquely combined allogenic transplantation during the neonatal period, when tolerance may be more readily achieved, with a positive selection strategy for in vivo amplification of drug-resistant donor HSC. This model system enables the evaluation of tolerance induction mechanisms to neo-antigens, and allogenic stem cell engraftment during immune ontogeny. In this model, bone marrow-derived HSC are transduced ex vivo by lentivirus-mediated gene transfer of P140K-O6-methylguanine-methyltransferase (MGMTP140K) and GFP (MAG vector). The MGMTP140K DNA repair enzyme confers resistance to benzylguanine, an inhibitor of endogenous MGMT, and to chloroethylating agents such as BCNU. This enables enrichment of donor cells at the stem cell level by in vivo chemoselection. Furthermore, in vivo administration of BG/BCNU may potentially deplete allo-reactive cells of donor and host origin, reducing the need for toxic ablative or immunosuppressive treatment.The in vivo selection strategy was first tested in neonates in the absence of MHC barriers. Syngenic whole bone marrow (WBM) was transduced with MAG and 5 × 105 cells were transplanted. Five weeks after transplantation and prior to chemoselection, 0.5% of cells expressed GFP in peripheral blood. Following two cycles of in vivo selection we observed 39.5% expression of GFP in peripheral blood. To assess the engraftment of fully MHC-mismatched HSC in neonates without in vivo selection, 107 B10.Br (H-2k) WBM was transplanted into C57BL/6 (H-2b) neonates using a non-myleoablative regimen. This resulted in 98% engraftment in adults without development of GVHD. To evaluate in vivo selection in an allogenic setting, 2 × 106 MAG transduced WBM from BALB/c (H-2d) adult mice were transplanted into C57BL/6 × BALB/c F1 (H-2b/d) neonatal mice. Despite having a graft versus host MHC disparity, we observed an increase from 4.7% (5 weeks after transplant) to 37.4% GFP expression following two cycles of in vivo chemoselection without evidence of GVHD.We have demonstrated successful engraftment and enrichment of both syngenic and allogenic HSC expressing MGMTP140K following neonatal transplantation and in vivo selection. Stable engraftment was achieved without myeloablation or post-transplant immunosuppression. No evidence of GVHD was observed after full MHC-mismatched transplantation. These results hold promise for the development of non-myeloablative allogenic transplant approaches using this in vivo selection strategy.

Bortezomib Induces Thrombocytopenia by Inhibiting Proplatelet Formation but Not Proliferation and Endomitosis in Human Primary Megakaryocytes

The proteasome inhibitor bortezomib has therapeutic activity in patients with multiple myeloma. The most common adverse event from its application is thrombocytopenia, which has kinetics that differ from those induced by other cytotoxic agents. After treatment with bortezomib, platelet counts usually decrease within a couple of days but rapidly recover toward baseline during the rest periods between each cycle. The lowest count of platelets in each cycle does not worsen during the 8 courses of bortezomib treatment. Furthermore, bortezomib does not induce any cytotoxic injury in megakaryocyte in the murine model. Therefore, we postulated that bortezomib-induced thrombocytopenia is caused by inhibition of the platelet releasing process without megakaryocyte toxicity. In vitro assays using human bone marrow-derived CD34-positive hematopoietic stem cells revealed that bortezomib did not inhibit colony formation and endomitosis of human primary megakaryocytes in the presence of recombinant human thrombopoietin (rhTPO). As proplatelet formation (PPF) is often used as the indicator of the platelet releasing process in vitro, we evaluated the inhibitory effects of bortezomib for PPF. Seven days after culture of human CD34-postive cells with 10 ng/ml rhTPO, mature megakaryocytes were enriched by discontinuous bovine serum albumin gradients (purity>90%). The enriched mature megakaryocytes were treated with various concentrations of bortezomib for a further 4 days and the percentage of megakaryocytes bearing PPF was calculated under a microscope. Bortezomib dose-dependently inhibited PPF from mature megakaryocytes. Other proteasome inhibitors such as lactacystin and MG132 also demonstrated inhibitory effects on PPF without inhibiting colony formation of megakaryocytes. Since the inhibition of transcriptional factor NF-kB activity is one of the major pathways of proteasome inhibitors, we evaluated the effects of NF-kB inhibitors such as (−)-DHMEQ and Bay11-7082. Both of these inhibitors also demonstrated inhibitory effects on PPF but did not inhibit the colony formation of megakaryocytes. To exclude the direct effects of bortezomib on human platelets, we analyzed the effects of bortezomib for the activation of caspase-3 and mitochondrial potential in human platelets. We found that bortezomib did not directly induce apoptosis in human platelets. Our results demonstrate that bortezomib induces thrombocytopenia by inhibiting PPF but does not affect proliferation of megakaryocytes, endomitosis and platelet apoptosis. We believe this is the first report using human primary megakaryocytes to clarify the pathogenesis of thrombocytopenia caused by bortezomib therapy.

Identification of White Adipocyte Progenitor Cells In Vivo

The increased white adipose tissue (WAT) mass associated with obesity is the result of both hyperplasia and hypertrophy of adipocytes. However, the mechanisms controlling adipocyte number are unknown in part because the identity of the physiological adipocyte progenitor cells has not been defined in vivo. In this report, we employ a variety of approaches, including a noninvasive assay for following fat mass reconstitution in vivo, to identify a subpopulation of early adipocyte progenitor cells (Lin(-):CD29(+):CD34(+):Sca-1(+):CD24(+)) resident in adult WAT. When injected into the residual fat pads of A-Zip lipodystrophic mice, these cells reconstitute a normal WAT depot and rescue the diabetic phenotype that develops in these animals. This report provides the identification of an undifferentiated adipocyte precursor subpopulation resident within the adipose tissue stroma that is capable of proliferating and differentiating into an adipose depot in vivo.

Hematopoietic Stem Cells Reduce Postischemic Inflammation and Ameliorate Ischemic Brain Injury

Systemic injection of hematopoietic stem cells after ischemic cardiac or neural lesions is one approach to promote tissue repair. However, mechanisms of possible protective or reparative effects are poorly understood. In this study we analyzed the effect of lineage-negative bone marrow-derived hematopoietic stem and precursor cells (Lin(-)-HSCs) on ischemic brain injury in mice. Lin(-)-HSCs were injected intravenously at 24 hours after onset of a 45-minute transient cerebral ischemia. Effects of Lin(-)-HSCs injection on infarct size, apoptotic cell death, postischemic inflammation and cytokine gene transcription were analyzed. Green fluorescent protein (GFP)-marked Lin(-)-HSCs were detected at 24 hours after injection in the spleen and later in ischemic brain parenchyma, expressing microglial but no neural marker proteins. Tissue injury assessment showed significantly smaller infarct volumes and less apoptotic neuronal cell death in peri-infarct areas of Lin(-)-HSC-treated animals. Analysis of immune cell infiltration in ischemic hemispheres revealed a reduction of invading T cells and macrophages in treated mice. Moreover, Lin(-)-HSC therapy counter-regulated proinflammatory cytokine and chemokine receptor gene transcription within the spleen. Our data demonstrate that systemically applied Lin(-)-HSCs reduce cerebral postischemic inflammation, attenuate peripheral immune activation and mediate neuroprotection after ischemic stroke.

Inhibition of protein kinase CK2 suppresses angiogenesis and hematopoietic stem cell recruitment to retinal neovascularization sites

Ubiquitous protein kinase CK2 participates in a variety of key cellular functions. We have explored CK2 involvement in angiogenesis. As shown previously, CK2 inhibition reduced endothelial cell proliferation, survival and migration, tube formation, and secondary sprouting on Matrigel. Intraperitoneally administered CK2 inhibitors significantly reduced preretinal neovascularization in a mouse model of proliferative retinopathy. In this model, CK2 inhibitors had an additive effect with somatostatin analog, octreotide, resulting in marked dose reduction for the drug to achieve the same effect. CK2 inhibitors may thus emerge as potent future drugs aimed at inhibiting pathological angiogenesis. Immunostaining of the retina revealed predominant CK2 expression in astrocytes. In human diabetic retinas, mRNA levels of all CK2 subunits decreased, consistent with increased apoptosis. Importantly, a specific CK2 inhibitor prevented recruitment of bone marrow-derived hematopoietic stem cells to areas of retinal neovascularization. This may provide a novel mechanism of action of CK2 inhibitors on newly forming vessels.

Electrospun nanofiber scaffolds for rapid and rich capture of bone marrow-derived hematopoietic stem cells

Interactions between bone marrow-derived hematopoietic stem cells (BM-HSCs) and their local microenvironment are an integral part of signaling control of BM-HSCs migration, proliferation and differentiation. We hypothesized that both substrate topographical and biochemical cues promote BM-HSCs adhesive behaviors, which are crucial for BM-HSCs' homing, self-renewal and lineage commitment within their microenvironment. We employed electrospinning technique to fabricate nanofiber scaffolds (NFS) with poly( dl-lactide- co-glycolide) blended with collagen I. NFS was further coated with E-selectin, a critical adhesive biomolecule. Capture efficiency study showed that blended NFS, after coated with E-selectin, significantly increased cell capture percentage from 23.40% to 67.41% within 30 min and from 29.44% to 70.19% within 60 min of incubation at room temperature. This study highlights the potential of using a biomimetic scaffold to design a site-specific niche-like unit for facilitating proliferation or differentiation functions of BM-HSCs.

Treatment of chronic spinal cord injured patients with autologous bone marrow-derived hematopoietic stem cell transplantation: 1-year follow-up

Transplanted bone marrow (BM) cells have been found to improve neurologic disease in central nervous system (CNS) injury models by generating neural cells or myelin-producing cells. The results in treated patients and animal models suggest that BM cells could potentially be used as a therapy for spinal cord injury (SCI) patients. Nine patients with chronic complete SCI with American Spinal Injury Association (ASIA) Impairment Scale (ASIA) grade A were included in this study. They were treated with autologous BM-derived hematopoietic progenitor stem cell transplantation without any serious complications. All patients completed the protocols successfully. Three weeks after the operation all patients' movements and sensations were improved. All patients had ASIA grade B or C after the operation. We used autologous hematopoietic progenitor stem cells in order to avoid the problems associated with immunologic rejection and graft-versus-host (GvH) reactions, which are frequently caused by allografts. The advantage of this type of cell therapy is that it is not associated with carcinogenesis, which sometimes occurs with embryogenic stem cell therapy. To evaluate the patients we used neurologic impairment scales (ASIA scores), pre- and post-operative Somato Sensorial Evoked Potential (SSEP) assessments and pre- and post-operative Magnetic Resonance Imaging (MRI). All the data showed that BM-derived autologous stem cell therapy is effective and safe for the treatment of chronic SCI.

Mesenchymal Stem Cells Over-expressing Hepatocyte Growth Factor Improve Small-for-size Liver Grafts Regeneration

Ischemia-reperfusion (I/R) associated with small-for-size liver transplantation (SFSLT) impairs liver graft regeneration. Mesenchymal stem cells (MSCs) have the capability, under specific conditions, of differentiating into hepatocytes. Hepatocyte growth factor (HGF) has potent anti-apoptotic and mitogenic effects on hepatocytes during liver injury, and has been utilized in many experimental and clinical applications. In this study, we implanted HGF-expressing MSCs into liver grafts via the portal vein, using a 30% small-for-size rat liver transplantation model. HGF, c-met expression, hepatic injury and liver regeneration were assessed after liver transplantation. Our study demonstrated that MSCs over-expressing HGF prevented liver failure and reduced mortality in rats after SFSLT. These animals also exhibited improved liver function and liver weight recovery during the early post-transplantation period. Using green fluorescent protein (GFP) gene as a marker, we demonstrated that the engrafted cells and their progeny incorporated into remnant livers and produced albumin. These findings suggest that MSCs genetically modified to over-express HGF and implanted in the liver graft, may offer a novel approach to promoting liver regeneration after small-for-size transplantations.

Selective Functional Exhaustion of Hematopoietic Progenitor Cells in the Bone Marrow of Patients With Postinfarction Heart Failure

This study investigated whether reduced levels of circulating endothelial progenitors cells (EPCs) in chronic heart failure (CHF) are secondary to an exhaustion of hematopoietic stem cells (HSCs) in the bone marrow or to reduced mobilization. Circulating EPCs presumably originate from bone marrow-derived HSC. Persistent mobilization of EPCs was shown to be associated with favorable left ventricular infarct remodeling processes. We assessed the number and functional capacity of EPCs in 17 healthy controls, 25 patients with ischemic cardiomyopathy (ICM), and 20 patients with dilated cardiomyopathy (DCM). To document an impairment of HSC function in the bone marrow, the colony-forming unit capacity of bone marrow-derived mononuclear cells and the number of CD34+ HSCs were examined in 6 healthy volunteers, 94 ICM patients, and 25 DCM patients. The number of EPCs was reduced in CHF, irrespective of its etiology. In contrast, the migratory capacity was selectively impaired in EPCs of ICM patients (4.8 +/- 4.0 migrated cells; DCM 9.7 +/- 5.8; p = 0.02). On multivariate analysis, ICM, advanced New York Heart Association functional class, and CHF were independent predictors of functional EPC impairment. The number of bone marrow-derived CD34+ cells did not differ between the CHF populations. However, colony-forming units (CFUs) were selectively reduced in ICM patients (54.4 +/- 24.6; DCM 68.1 +/- 26.9; p < 0.02). Ischemic cardiomyopathy was the only independent predictor of impaired CFU capacity. Impaired CFU capacity was associated with reduced matrix metalloproteinase-9 activity in the bone marrow plasma. Ischemic cardiomyopathy is associated with selective impairment of progenitor cell function in the bone marrow and in the peripheral blood, which may contribute to an unfavorable left ventricular (LV) remodeling process.

Staying Young with p16 INK4a

In long-lived organisms, cells in many tissues are replaced from a population of stem or progenitor cells that retain the capacity to proliferate. The ability of these cells to proliferate decreases with age, which may be linked to a reduced capacity to repair or regenerate tissue. Three studies, focused on three different tissues, investigated the role of the cyclin-dependent kinase inhibitor p16 INK4a , the abundance of which increases in some cell types with age, in this loss of proliferative and regenerative capacity. Janzen et al . found that p16 INK4a mRNA expression increased in the bone marrow-derived hematopoietic stem cells (HSCs) of older mice. Older mice that lacked p16 INK4a had more HSCs than did older wild-type mice, and the ability of HSCs from older mice lacking p16 INK4a to reconstitute the immune system through bone marrow transplants was superior to that of HSCs from older wild-type mice. Expression of the Notch effector Hes1, which has been implicated in regulating HSC cycling and preserving their function, was enhanced in HSCs from mice lacking p16 INK4a and decreased in HSCs from mice overexpressing p16 INK4a . Molofsky et al . investigated the role of p16 INK4a in neural progenitor cell proliferation in the subventricular zone (SVZ) and olfactory bulb neurogenesis in aging mice. They found an increase in SVZ p16 INK4a mRNA expression with aging and observed an age-related decrease in SVZ proliferation, in the number of SVZ cells that could form multipotent colonies in culture, and in olfactory bulb neurogenesis. In older mice lacking p16 INK4a , the decreases in SVZ proliferation and olfactory bulb neurogenesis were attenuated and the decline in colony-forming cells was abolished (suggesting an effect on stem cells rather than downstream progenitor cells). However, p16 INK4a did not appear to affect progenitor cell function or neurogenesis in the dentate gyrus or in the enteric nervous system. Krishnamurthy et al . showed that p16 INK4a mRNA expression increased with age in mouse pancreatic islet cells. Transgenic mice with an additional copy of the p16 INK4a gene (in which young mice expressed p16 INK4a to an extent comparable to that of old wild-type mice) showed a reduction in islet proliferation, whereas an age-related decrease in proliferation seen in wild-type mice was profoundly attenuated in mice lacking p16 INK4a . Islet regeneration and the ability of mice to survive treatment with streptozotocin, a β cell toxin, decreased with age; both islet proliferation after streptozotocin treatment and survival were enhanced in older mice lacking p16 INK4a . Thus, in at least some tissues, p16 INK4a appears to play a role in aging-related loss of progenitor cell proliferation and regenerative capacity. Beausejour and Campisi discuss the research in the context of the role of stem cell proliferation in both regeneration and susceptibility to cancer, noting that p16 INK4a is a tumor suppressor and that mice lacking it are prone to tumor formation. V. Janzen, R. Forkert, H. E. Fleming, Y. Saito, M. T. Waring, D. M. Dombkowski, T. Cheng, R. A. DePinho, N. E. Sharpless, D. T. Scadden, Stem-cell ageing modified by the cyclin-dependent kinase inhibitor p16 INK4a . Nature 443 , 421-426 (2006). [PubMed] J. Krishnamurthy, M. R. Ramsey, K. L. Ligon, C. Torrice, A. Koh, S. Bonner-Weir, N. E. Sharpless, p16 INK4a induces an age-dependent decline in islet regenerative potential. Nature 443 , 453-457 (2006). [PubMed] A. V. Molofsky, S. G. Slutsky , N. M. Joseph, S. He, R. Pardal, J. Krishnamurthy, N. E. Sharpless, S. J. Morrison, Increasing p16 INK4a expression decreases forebrain progenitors and neurogenesis during ageing. Nature 443 , 448-452 (2006). [PubMed] C. M. Beausejour, J. Campisi, Balancing regeneration and cancer. Nature 443 , 404-405 (2006). [PubMed]