Host-derived CD8+ dendritic cells are required for induction of optimal graft-versus-tumor responses after experimental allogeneic bone marrow transplantation.

The graft-versus-tumor (GVT) effect after allogeneic hematopoietic cell transplantation (allo-HCT) represents an effective form of immunotherapy against many malignancies. Meaningful separation of the potentially curative GVT responses from graft-versus-host disease (GVHD), the most serious toxicity following T-cell replete allo-HCT, has been an elusive goal. GVHD is initiated by alloantigens, although both alloantigens and tumor-specific antigens (TSAs) initiate GVT responses. Emerging data have illuminated a role for antigen-presenting cells (APCs) in inducing alloantigen-specific responses. By using multiple clinically relevant murine models, we show that a specific subset of host-derived APCs-CD8(+) dendritic cells (DCs)-enhances TSA responses and is required for optimal induction of GVT. Stimulation of TLR3, which among host hematopoietic APC subsets is predominantly expressed on CD8(+) DCs, enhanced GVT without exacerbating GVHD. Thus, strategies that modulate host APC subsets without direct manipulation of donor T cells could augment GVT responses and enhance the efficacy of allo-HCT.

Efeito do exercício associado ao transplante de células-tronco sobre a função ventricular de ratos pós-infarto agudo do miocárdio / Effect of exercise associated with stem cell transplantation on ventricular function in rats after acute myocardial infarction

OBJETIVO: Avaliar o efeito da associação terapêutica entre o transplante autólogo de células-tronco e o exercício físico aquático, sobre a fração de ejeção do ventrículo esquerdo (FEVE) de ratos com disfunção ventricular pós-infarto agudo do miocárdio (IAM). MÉTODOS: Foram induzidos ao IAM, por ligadura da artéria coronária esquerda, 21 ratos Wistar. Os animais foram submetidos à ecocardiografia para avaliação da FEVE (%) e dos volumes diastólico e sistólico finais do ventrículo esquerdo (VDF, VSF, ml), randomizados e ao transplante das células-tronco mononucleares. Os animais foram divididos em quatro grupos: grupo sedentário sem células (n=5), sedentário com células (n=5), treinado sem células (n=5) e treinado com células (n=6). O treinamento físico foi iniciado 30 dias após o IAM e realizado em piscina adaptada durante 30 dias. No início e no final do protocolo de treinamento físico, foram realizadas dosagens de lactato. Os animais foram submetidos a nova ecocardiografia após 60 dias do IAM. RESULTADOS: Comparação dos valores de FEVE 30 dias e 60 dias pós-IAM, respectivamente: sedentário sem (35,20 ± 7,64% vs. 22,39 ± 4,56% P=0,026), com células (25,18 ± 7,73% vs. 23,85 ± 9,51% P=0,860) e no treinado sem (21,49 ± 2,70% vs. 20,71 ± 7,14% P=0,792), treinado com células (28,86 ± 6,68 vs. 38,43 ±7,56% P=0,062). Identificou-se a diminuição de fibras colágenas, nas regiões de fibrose miocárdica no grupo treinado com e sem células. CONCLUSÃO: A associação terapêutica entre exercício físico e o transplante autólogo de células-tronco foi benéfica contra as ações do remodelamento ventricular.

OBJECTIVE: To analyze the functional and anatomical-pathological effect of transplantation of bone marrow mononuclear cells associated to aquatic physical activity after myocardial infarction in rats. METHODS: Twenty-one rats were induced by myocardial infarction, through left coronary artery ligation. After a week, the animals were subjected to echocardiography for evaluation of left ventricle ejection fraction (LVEF, %) and dyastolic and end systolic volume of the left ventricle (EDV, ESV, ml), randomized and the transplantation of mononuclear stem cells. The animals were divided into four groups: sedentary group without cells (n=5), sedentary with cells (n=5), trained without cells (n=5) and trained with cells (n=6). The physical training was started 30 days after infarction and held in swimming during 30 days. At the beginning and at the end of the physical training protocol were held assay of lactate. The animals have been subjected to new echocardiography after 60 days of myocardial infarction. RESULTS: Two months after the transplant, were observed decrease in FE in the control group (35.2 to 23.54 P=0.022) and addition of LVEF and stabilization of ventricular remodeling in the group trained with cells (29.85 to 33.43% P=0.062 and 0.71 to 0.73 ml, P=0.776, respectively). Identified the reduction of collagen fibers, myocardial fibrosis regions in the group trained with and without cells. CONCLUSION: The group trained with cells improves ventricular function compared to the control group, suggesting the benefit of associated cell therapy will physical activity.

Poor absorption of high-dose posaconazole in pediatric bone marrow transplant patients.

OBJECTIVE: To describe the use of high-dose posaconazole in 2 pediatric patients who received bone marrow transplant (BMT) and highlight concerns regarding posaconazole absorption. CASE SUMMARY: We present 2 pediatric BMT patients in whom prescribed high doses of posaconazole (120-300 mg/kg/day for >3 months) provided serum concentrations less than 1 µg/mL. Both patients received posaconazole with other antifungal therapy and surgical debridement for Rhizopus spp. infections after allogeneic BMTs. Various alternative dosing strategies to potentially enhance posaconazole absorption to increase serum concentrations were attempted, including higher daily doses, frequent or continuous oral administration via feeding tube, use of enteral nutrition, and limiting use of acid-blocking agents. During high-dose therapy, frequent posaconazole serum concentration measurement and other monitoring techniques, such as continuous telemetry, were used. While the fungal infections resolved in both patients and no serious adverse effects could be attributed to high-dose posaconazole administration, posaconazole therapy may have contributed to nausea and vomiting in 1 of the patients. DISCUSSION: These 2 cases describe complex circumstances, with several reasons that may have affected the patients' posaconazole serum concentrations. Both patients received significantly higher doses than those recommended in the posaconazole prescribing information, but potentially serious adverse events were not observed since serum concentration measurements were rarely more than 0.5 µg/mL. CONCLUSIONS: The safety of high-dose posaconazole therapy was not determined in these 2 patients. However, given that limited alternative therapy options are available for severely ill patients with suspected posaconazole malabsorption, research regarding dosing strategies should be considered.

The effect of bone marrow microenvironment on the functional properties of the therapeutic bone marrow-derived cells in patients with acute myocardial infarction.

BACKGROUND: Treatment of acute myocardial infarction with stem cell transplantation has achieved beneficial effects in many clinical trials. The bone marrow microenvironment of ST-elevation myocardial infarction (STEMI) patients has never been studied even though myocardial infarction is known to cause an imbalance in the acid-base status of these patients. The aim of this study was to assess if the blood gas levels in the bone marrow of STEMI patients affect the characteristics of the bone marrow cells (BMCs) and, furthermore, do they influence the change in cardiac function after autologous BMC transplantation. The arterial, venous and bone marrow blood gas concentrations were also compared. METHODS: Blood gas analysis of the bone marrow aspirate and peripheral blood was performed for 27 STEMI patients receiving autologous stem cell therapy after percutaneous coronary intervention. Cells from the bone marrow aspirate were further cultured and the bone marrow mesenchymal stem cell (MSC) proliferation rate was determined by MTT assay and the MSC osteogenic differentiation capacity by alkaline phosphatase (ALP) activity assay. All the patients underwent a 2D-echocardiography at baseline and 4 months after STEMI. RESULTS: As expected, the levels of pO(2), pCO(2), base excess and HCO(3) were similar in venous blood and bone marrow. Surprisingly, bone marrow showed significantly lower pH and Na(+) and elevated K(+) levels compared to arterial and venous blood. There was a positive correlation between the bone marrow pCO(2) and HCO(3) levels and MSC osteogenic differentiation capacity. In contrast, bone marrow pCO(2) and HCO(3) levels displayed a negative correlation with the proliferation rate of MSCs. Patients with the HCO(3) level below the median value exhibited a more marked change in LVEF after BMC treatment than patients with HCO(3) level above the median (11.13 ± 8.07% vs. 2.67 ± 11.89%, P = 0.014). CONCLUSIONS: Low bone marrow pCO(2) and HCO(3) levels may represent the optimal environment for BMCs in terms of their efficacy in autologous stem cell therapy in STEMI patients.

Human extramedullary bone marrow in mice: a novel in vivo model of genetically controlled hematopoietic microenvironment.

The interactions between hematopoietic cells and the bone marrow (BM) microenvironment play a critical role in normal and malignant hematopoiesis and drug resistance. These interactions within the BM niche are unique and could be important for developing new therapies. Here, we describe the development of extramedullary bone and bone marrow using human mesenchymal stromal cells and endothelial colony-forming cells implanted subcutaneously into immunodeficient mice. We demonstrate the engraftment of human normal and leukemic cells engraft into the human extramedullary bone marrow. When normal hematopoietic cells are engrafted into the model, only discrete areas of the BM are hypoxic, whereas leukemia engraftment results in widespread severe hypoxia, just as recently reported by us in human leukemias. Importantly, the hematopoietic cell engraftment could be altered by genetical manipulation of the bone marrow microenvironment: Extramedullary bone marrow in which hypoxia-inducible factor 1α was knocked down in mesenchymal stromal cells by lentiviral transfer of short hairpin RNA showed significant reduction (50% ± 6%; P = .0006) in human leukemic cell engraftment. These results highlight the potential of a novel in vivo model of human BM microenvironment that can be genetically modified. The model could be useful for the study of leukemia biology and for the development of novel therapeutic modalities aimed at modifying the hematopoietic microenvironment.

Transplanted bone marrow cells do not provide new oocytes but rescue fertility in female mice following treatment with chemotherapeutic agents.

It is generally accepted that mammalian females are born with a finite pool of oocytes and that this is the sole source of ovules throughout the reproductive life of the adult. This dogma was shaken in 2003 when researchers showed that the oocyte stock might be renewable in adult mammals. It has been proposed that hematopoietic stem cells might be a source of new oocytes. These discoveries have puzzled many researchers and remain controversial. In our study, we attempted to determine if transplanted bone marrow cells could provide new oocytes in PU.1 mice and in severe combined immunodeficiency (SCID) mice after treatment with chemotherapeutic agents. We also examined the possibility that grafted bovine embryonic ovarian cortex might provide an environment favoring such a response. We found no evidence that transplanted bone marrow cells provide new fertilizable oocytes in PU.1 mice, in SCID mice treated with chemotherapeutic agents, or with bovine embryonic ovarian tissue grafts. However, transplanted bone marrow cells have improved the fertility of SCID mice previously treated with chemotherapeutic agents. These data suggest that bone marrow cells cannot provide new oocytes but can positively influence ovarian physiology to improve the fertility of mice previously treated with chemotherapeutic agents.

Transplantation of hypoxia preconditioned bone marrow mesenchymal stem cells enhances angiogenesis and neurogenesis after cerebral ischemia in rats.

Hypoxic preconditioning of stem cells and neural progenitor cells has been tested for promoting cell survival after transplantation. The present investigation examined the hypothesis that hypoxic preconditioning of bone marrow mesenchymal stem cells (BMSCs) could not only enhance their survival but also reinforce regenerative properties of these cells. BMSCs from eGFP engineered rats or pre-labeled with BrdU were pre-treated with normoxia (20% O(2), N-BMSCs) or sub-lethal hypoxia (0.5% O(2). H-BMSCs). The hypoxia exposure up-regulated HIF-1α and trophic/growth factors in BMSCs, including brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor (GDNF), vascular endothelial growth factor (VEGF) and its receptor FIK-1, erythropoietin (EPO) and its receptor EPOR, stromal derived factor-1 (SDF-1) and its CXC chemokine receptor 4 (CXCR4). Meanwhile, many pro-inflammatory cytokines/chemokines were down-regulated in H-BMSCs. N-BMSCs or H-BMSCs were intravenously injected into adult rats 24h after 90-min middle cerebral artery occlusion. Comparing to N-BMSCs, transplantation of H-BMSCs showed greater effect of suppressing microglia activity in the brain. Significantly more NeuN-positive and Glut1-positive cells were seen in the ischemic core and peri-infarct regions of the animals received H-BMSC transplantation than that received N-BMSCs. Some NeuN-positive and Glut-1-positive cells showed eGFP or BrdU immunoflourescent reactivity, suggesting differentiation from exogenous BMSCs into neuronal and vascular endothelial cells. In Rotarod test performed 15days after stroke, animals received H-BMSCs showed better locomotion recovery compared with stroke control and N-BMSC groups. We suggest that hypoxic preconditioning of transplanted cells is an effective means of promoting their regenerative capability and therapeutic potential for the treatment of ischemic stroke.

Systemically administered human bone marrow-derived mesenchymal stem home into peripheral organs but do not induce neuroprotective effects in the MCAo-mouse model for cerebral ischemia.

Mesenchymal stem cells (MSC) from bone marrow induce neuroprotective effects and improve clinical symptoms in animal models for acute cerebral ischemia. So far only few data are available from the murine system. Moreover, no data exist regarding neuroprotective effects depending on the application route. Because most preclinical trials regarding restorative therapy in stroke are performed in mice, we aimed to investigate the neuroprotective capacities of human MSC (hMSC) in the middle cerebral artery occlusion (MCAo)-mouse model of cerebral ischemia. As systemic transplantation of MSC could provide a gentle therapeutic procedure for the (mostly elderly) stroke patients, we analyzed effects of this application at a clinically relevant time point. Bone marrow-derived hMSCs were administered intravenously 24 h after MCAo. Mortality and clinical outcome of the transplanted mice did not differ from PBS-treated controls. After 3 and 7 days hMSC were robustly detected in lung, spleen, kidney and intestine, but not in the brain. MRI measurements revealed no differences in infarct size in hMSC injected animals compared to controls. In the neurogenic subventricular zone and the dentate gyrus no significant increase of endogenous cell proliferation was detected following systemic hMSC transplantation. This data further prove the week neurogenic and neuroprotective effect and the limitations of systemically administered hMSCs in cerebral ischemia.

Chemically-induced cancers do not originate from bone marrow-derived cells.

BACKGROUND: The identification and characterization of cancer stem cells (CSCs) is imperative to understanding the mechanism of cancer pathogenesis. Growing evidence suggests that CSCs play critical roles in the development and progression of cancer. However, controversy exists as to whether CSCs arise from bone marrow-derived cells (BMDCs). METHODOLOGY AND PRINCIPAL FINDINGS: In the present study, n-nitrosodiethylamine (DEN) was used to induce tumor formation in female mice that received bone marrow from male mice. Tumor formation was induced in 20/26 mice, including 12 liver tumors, 6 lung tumors, 1 bladder tumor and 1 nasopharyngeal tumor. Through comparison of fluorescence in situ hybridization (FISH) results in corresponding areas from serial tumor sections stained with H&E, we determined that BMDCs were recruited to both tumor tissue and normal surrounding tissue at a very low frequency (0.2-1% in tumors and 0-0.3% in normal tissues). However, approximately 3-70% of cells in the tissues surrounding the tumor were BMDCs, and the percentage of BMDCs was highly associated with the inflammatory status of the tissue. In the present study, no evidence was found to support the existence of fusion cells formed form BMDCs and tissue-specific stem cells. CONCLUSIONS: In summary, our data suggest that although BMDCs may contribute to tumor progression, they are unlike to contribute to tumor initiation.

Sciatic nerve repair by acellular nerve xenografts implanted with BMSCs in rats xenograft combined with BMSCs.

Acellular nerves possess the structural and biochemical features similar to those of naive endoneurial tubes, and have been proved bioactive for allogeneil graft in nerve tissue engineering. However, the source of allogenic donators is restricted in clinical treatment. To explore sufficient substitutes for acellular nerve allografts (ANA), we investigated the effectiveness of acellular nerve xenografts (ANX) combined with bone marrow stromal cells (BMSCs) on repairing peripheral nerve injuries. The acellular nerves derived from Sprague-Dawley rats and New Zealand rabbits were prepared, respectively, and BMSCs were implanted into the nerve scaffolds and cultured in vitro. All the grafts were employed to bridge 1 cm rat sciatic nerve gaps. Fifty Wistar rats were randomly divided into five groups (n = 10 per group): ANA group, ANX group, BMSCs-laden ANA group, BMSCs-laden ANX group, and autologous nerve graft group. At 8 weeks post-transplantation, electrophysiological study was performed and the regenerated nerves were assayed morphologically. Besides, growth-promoting factors in the regenerated tissues following the BMSCs integration were detected. The results indicated that compared with the acellular nerve control groups, nerve regeneration and functional rehabilitation for the xenogenic nerve transplantation integrated with BMSCs were advanced significantly, and the rehabilitation efficacy was comparable with that of the autografting. The expression of neurotrophic factors in the regenerated nerves, together with that of brain-derived neurotrophic factor (BDNF) in the spinal cord and muscles were elevated largely. In conclusion, ANX implanted with BMSCs could replace allografts to promote nerve regeneration effectively, which offers a reliable approach for repairing peripheral nerve defects.

Effect of exercise associated with stem cell transplantation on ventricular function in rats after acute myocardial infarction.

OBJECTIVE: To analyze the functional and anatomical-pathological effect of transplantation of bone marrow mononuclear cells associated to aquatic physical activity after myocardial infarction in rats. METHODS: Twenty-one rats were induced by myocardial infarction, through left coronary artery ligation. After a week, the animals were subjected to echocardiography for evaluation of left ventricle ejection fraction (LVEF, %) and dyastolic and end systolic volume of the left ventricle (EDV, ESV, ml), randomized and the transplantation of mononuclear stem cells. The animals were divided into four groups: sedentary group without cells (n=5), sedentary with cells (n=5), trained without cells (n=5) and trained with cells (n=6). The physical training was started 30 days after infarction and held in swimming during 30 days. At the beginning and at the end of the physical training protocol were held assay of lactate. The animals have been subjected to new echocardiography after 60 days of myocardial infarction. RESULTS: Two months after the transplant, were observed decrease in FE in the control group (35.2 to 23.54 P=0.022) and addition of LVEF and stabilization of ventricular remodeling in the group trained with cells (29.85 to 33.43% P=0.062 and 0.71 to 0.73 ml, P=0.776, respectively). Identified the reduction of collagen fibers, myocardial fibrosis regions in the group trained with and without cells. CONCLUSION: The group trained with cells improves ventricular function compared to the control group, suggesting the benefit of associated cell therapy will physical activity.

[Monitoring of chimerism in myeloid cells sorting of transplanted patients with acute myeloid leukaemia: a study from Lyon (France)]. / Suivi de chimérisme des populations cellulaires myéloïdes chez des patients allogreffés atteints de leucémie aiguë myéloïde : étude lyonnaise.

Chimerism analysis after allogeneic haematopoietic stem cell transplantation has been used to document engraftment and to adapt therapy promptly. The aim of this study was to document engraftment and to detect as soon as possible relapse in patients with acute myeloid leukaemia who underwent stem cell transplantation. Real-time quantitative polymerase chain reaction is a highly sensitive and reproducible technology. It is useful in some disease to target selected sub-populations in order to have an earlier detection of relapse on cell fractions. In the acute myeloid leukaemia (n=65), analysis of the chimerism on whole peripheral blood cells and bone marrow cells, CD3+ cells, specific myeloid CD33+ cells (from blood) and CD34+ cells (from bone marrow) is of importance. After transplant, 25 patients relapsed (38%), three massively, with chimerism detection in whole blood and bone marrow and 22 insidiously following two different schemes (GRI and GRII). In GRI, (n=13): chimerism of CD33+ and CD34+ cellular fractions allowed an early detection of relapse in 100% of cases undetected in whole cells whereas in GRII (n=9): myeloid cells could identified relapse in 89% of cases when whole blood cells and CD3+ cells expressed a mixed chimerism. This study highlighted the importance of sub-cellular population chimerism documentation enable to ascertain a stable engraftment and to detect early relapse. The selection of sub-cellular population studied with high sensitive technology allows a rapid and efficient intervention before the onset of clinical signs in patient with acute myeloid leukaemia and could improve the patient's follow-up.

Specific loss of toll-like receptor 2 on bone marrow derived cells decreases atherosclerosis in LDL receptor null mice.

Innate immunity and, notably, Toll-like receptors (TLR), have an important role in atherogenesis. We have tested the hypothesis that the selective loss of TLR-2 by cells of bone marrow (BM) origin will protect low-density receptor-deficient (Ldlr (-/-)) mice from both early- and late-stage atherosclerosis. BM cells from Tlr2(+/+) and Tlr2(-/-) littermates were used to reconstitute lethally irradiated Ldlr(-/-) mice. Following a recovery period, mice were placed either on a diet containing 21% saturated fat - 0.15% cholesterol for 8 weeks to study early-stage atherosclerosis, or on a diet richer in cholesterol (1.5%) for 16 weeks to study late-stage atherosclerosis. Donor cell Tlr2 genotype did not alter serum cholesterol levels or lipoprotein profiles in recipient animals. After 8 weeks on the 0.15% cholesterol diet, deficiency of TLR-2 expression on cells of BM origin reduced atherosclerosis in the aortic root and the aortic arch in both genders of mice. In contrast, the BM recipients who received the 1.5% cholesterol diet for 16 weeks showed much larger lesions in the aortic root, and TLR-2 deficiency in BM cells failed to provide protection. Thus, TLR-2 expression in BM-derived cells contributes primarily to early stage atherosclerosis.

An experimental study of bone healing around the titanium screw implants in ovariectomized rats: enhancement of bone healing by bone marrow stromal cells transplantation.

PURPOSE: : This study is to evaluate the bone quality of surrounding areas of implants with bone marrow stromal cells (BMSCs) transplantation to rat femur, which have become osteoporosis-induced models. MATERIALS AND METHODS: : The Sprague-Dawley rats were divided into 3 groups: the first group where their ovaries were removed (OVX group), the second group where a sham surgery was given (SHAM group), and the third group where BMSCs were transplanted to an OVX group (OVX-BMSCs group). In the OVX-BMSCs group, 1 × 10 BMSCs were transplanted into femur with implant. Each value of the bone to implant contact and the bone area of each cortical bone and cancellous bone was obtained. Bone density of the width of 500 µm from the implants was measured. RESULTS: : Each ratio of bone to implant contact, bone area, and bone density in the OVX-BMSCs group was significantly higher than those of OVX group as to the cancellous bone. CONCLUSION: : The BMSCs transplantation therapy improved local bone healing in the cancellous bone surrounding implants and also significantly improved bone binding with implants.

Endogenous oncogenic Nras mutation initiates hematopoietic malignancies in a dose- and cell type-dependent manner.

Both monoallelic and biallelic oncogenic NRAS mutations are identified in human leukemias, suggesting a dose-dependent role of oncogenic NRAS in leukemogenesis. Here, we use a hypomorphic oncogenic Nras allele and a normal oncogenic Nras allele (Nras G12D(hypo) and Nras G12D, respectively) to create a gene dose gradient ranging from 25% to 200% of endogenous Nras G12D/+. Mice expressing Nras G12D(hypo)/G12D(hypo) develop normally and are tumor-free, whereas early embryonic expression of Nras G12D/+ is lethal. Somatic expression of Nras G12D/G12D but not Nras G12D/+ leads to hyperactivation of ERK, excessive proliferation of myeloid progenitors, and consequently an acute myeloproliferative disease. Using a bone marrow transplant model, we previously showed that ∼ 95% of animals receiving Nras G12D/+ bone marrow cells develop chronic myelomonocytic leukemia (CMML), while ∼ 8% of recipients develop acute T-cell lymphoblastic leukemia/lymphoma [TALL] (TALL-het). Here we demonstrate that 100% of recipients transplanted with Nras G12D/G12D bone marrow cells develop TALL (TALL-homo). Although both TALL-het and -homo tumors acquire Notch1 mutations and are sensitive to a γ-secretase inhibitor, endogenous Nras G12D/+ signaling promotes TALL through distinct genetic mechanism(s) from Nras G12D/G12D. Our data indicate that the tumor transformation potential of endogenous oncogenic Nras is both dose- and cell type-dependent.

TIMP-1 deficiency subverts cell-cycle dynamics in murine long-term HSCs.

In addition to the well-recognized role in extracellular matrix remodeling, the tissue inhibitor of metalloproteinases-1 (TIMP-1) has been suggested to be involved in the regulation of numerous biologic functions, including cell proliferation and survival. We therefore hypothesized that TIMP-1 might be involved in the homeostatic regulation of HSCs, whose biologic behavior is the synthesis of both microenvironmental and intrinsic cues. We found that TIMP-1(-/-) mice have decreased BM cellularity and, consistent with this finding, TIMP-1(-/-) HSCs display reduced capability of long-term repopulation. Interestingly, the cell cycle distribution of TIMP-1(-/-) stem cells appears distorted, with a dysregulation at the level of the G(1) phase. TIMP-1(-/-) HSCs also display increased levels of p57, p21, and p53, suggesting that TIMP-1 could be intrinsically involved in the regulation of HSC cycling dynamics. Of note, TIMP-1(-/-) HSCs present decreased levels of CD44 glycoprotein, whose expression has been proven to be controlled by p53, the master regulator of the G(1)/S transition. Our findings establish a role for TIMP-1 in regulating HSC function, suggesting a novel mechanism presiding over stem cell quiescence in the framework of the BM milieu.

Differentiation of mesenchymal stem cells to support peripheral nerve regeneration in a rat model.

Mesenchymal stem cells (MSCs) support axon regeneration across artificial nerve bridges but their differentiative capacity and ability to promote nerve regeneration remains unclear. In this study, MSCs isolated from bone marrow of Sprague-Dawley rats were characterized by plastic adherence and pluripotency towards mesodermal lineages. Isolated undifferentiated MSCs (uMSCs) were stimulated towards a Schwann cell (SC) phenotype using specific growth factors, and cell marker analysis was performed to verify SC phenotype in vitro. Differentiation resulted in temporally dependent positive immunocytochemical staining for the SC markers, glial fibrillary acidic protein (GFAP), S100, and nerve growth factor receptor (NGFR), with maximal marker expression achieved after 6days of treatment with differentiation media. Quantitative analysis demonstrated that ~50% of differentiated MSCs (dMSCs) have a SC phenotype. Using an indirect co-culture system, we compared the ability of dorsal root ganglion (DRG) cells to extend neurites in indirect contact with uMSCs and dMSCs as compared to SCs. The mean values of the longest length of the DRG neurites were the same for the dMSCs and SCs and significantly higher than the uMSC and DRG mono-culture systems (p < 0.05). In vivo, compared to an empty conduit, dMSC seeded collagen nerve conduits resulted in a greater number of sciatic motoneurons regenerating axons through the conduit into the distal nerve stump. We conclude that bone marrow-derived MSCs differentiate into a SC-phenotype that expresses SC markers transiently and sufficiently to support limited neurite outgrowth in vitro and axonal regeneration equivalent to that of SCs in vitro and in vivo. The nerve autograft remains the most effective conduit for supporting regeneration across nerve gaps.

Accumulation of CD4+ T cells in the colon of CsA-treated mice following myeloablative conditioning and bone marrow transplantation.

Syngeneic graft vs. host disease (SGVHD) was first described as a graft vs. host disease-like syndrome that developed in rats following syngeneic bone marrow transplantation (BMT) and cyclosporin A (CsA) treatment. SGVHD can be induced by reconstitution of lethally irradiated mice with syngeneic bone marrow cells followed by 21 days of treatment with the immunosuppressive agent CsA. Clinical symptoms of the disease appear 2-3 wk following cessation of CsA therapy, and disease-associated inflammation occurs primarily in the colon and liver. CD4(+) T cells have been shown to play an important role in the inflammatory response observed in the gut of SGVHD mice. Time-course studies revealed a significant increase in migration of CD4(+) T cells into the colon during CsA therapy, as well as significantly elevated mRNA levels of TNF-α, proinflammatory chemokines, and cell adhesion molecules in colonic tissue of CsA-treated animals compared with BMT controls, as early as day 14 post-BMT. Homing studies revealed a greater migration of labeled CD4(+) T cells into the gut of CsA-treated mice at day 21 post-BMT than control animals via CsA-induced upregulation of mucosal addressin cell adhesion molecule. This study demonstrates that, during the 21 days of immunosuppressive therapy, functional mechanisms are in place that result in increased homing of CD4(+) T effector cells to colons of CsA-treated mice.

Bone marrow-derived cells rescue salivary gland function in mice with head and neck irradiation.

Treatment for most patients with head and neck cancers includes ionizing radiation. A consequence of this treatment is irreversible damage to salivary glands (SGs), which is accompanied by a loss of fluid-secreting acinar-cells and a considerable decrease of saliva output. While there are currently no adequate conventional treatments for this condition, cell-based therapies are receiving increasing attention to regenerate SGs. In this study, we investigated whether bone marrow-derived cells (BMDCs) can differentiate into salivary epithelial cells and restore SG function in head and neck irradiated mice. BMDCs from male mice were transplanted into the tail-vein of 18Gy-irradiated female mice. Salivary output was increased in mice that received BMDCs transplantation at week 8 and 24 post-irradiation. At 24 weeks after irradiation (IR), harvested SGs (submandibular and parotid glands) of BMDC-treated mice had greater weights than those of non-treated mice. Histological analysis shows that SGs of treated mice demonstrated an increased level of tissue regenerative activity such as blood vessel formation and cell proliferation, while apoptotic activity was increased in non-transplanted mice. The expression of stem cell markers (Sca-1 or c-kit) was detected in BMDC-treated SGs. Finally, we detected an increased ratio of acinar-cell area and approximately 9% of Y-chromosome-positive (donor-derived) salivary epithelial cells in BMDC-treated mice. We propose here that cell therapy using BMDCs can rescue the functional damage of irradiated SGs by direct differentiation of donor BMDCs into salivary epithelial cells.

Murine erythroid short-term radioprotection requires a BMP4-dependent, self-renewing population of stress erythroid progenitors.

Acute anemic stress induces a systemic response designed to increase oxygen delivery to hypoxic tissues. Increased erythropoiesis is a key component of this response. Recovery from acute anemia relies on stress erythropoiesis, which is distinct from steady-state erythropoiesis. In this study we found that the bone morphogenetic protein 4-dependent (BMP4-dependent) stress erythropoiesis pathway was required and specific for erythroid short-term radioprotection following bone marrow transplantation. BMP4 signaling promoted the development of three populations of stress erythroid progenitors, which expanded in the spleen subsequent to bone marrow transplantation in mice. These progenitors did not correspond to previously identified bone marrow steady-state progenitors. The most immature population of stress progenitors was capable of self renewal while maintaining erythropoiesis without contribution to other lineages when serially transplanted into irradiated secondary and tertiary recipients. These data suggest that during the immediate post-transplant period, the microenvironment of the spleen is altered, which allows donor bone marrow cells to adopt a stress erythropoietic fate and promotes the rapid expansion and differentiation of stress erythroid progenitors. Our results also suggest that stress erythropoiesis may be manipulated through targeting the BMP4 signaling pathway to improve survival after injury.