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Author(s): Neziha Celebi [sup.1] , Jesus G. Vallejo [sup.2] , Olive S. Eckstein [sup.3] , Jessica Geer [sup.1] , Jyotinder N. Punia [sup.4] , Ewa Elenberg [sup.1] Author Affiliations: (Aff1) [...]

Age-related changes in the hematopoietic compartment are primarily attributed to cell-intrinsic alterations in hematopoietic stem cells (HSCs); however, the contribution of the aged microenvironment has not been adequately evaluated. Understanding the role of the bone marrow (BM) microenvironment in supporting HSC function may prove to be beneficial in treating age-related functional hematopoietic decline. Here, we determined that aging of endothelial cells (ECs), a critical component of the BM microenvironment, was sufficient to drive hematopoietic aging phenotypes in young HSCs. We used an ex vivo hematopoietic stem and progenitor cell/EC (HSPC/EC) coculture system as well as in vivo EC infusions following myelosuppressive injury in mice to demonstrate that aged ECs impair the repopulating activity of young HSCs and impart a myeloid bias. Conversely, young ECs restored the repopulating capacity of aged HSCs but were unable to reverse the intrinsic myeloid bias. Infusion of young, HSC-supportive BM ECs enhanced hematopoietic recovery following myelosuppressive injury and restored endogenous HSC function in aged mice. Coinfusion of young ECs augmented aged HSC engraftment and enhanced overall survival in lethally irradiated mice by mitigating damage to the BM vascular microenvironment. These data lay the groundwork for the exploration of EC therapies that can serve as adjuvant modalities to enhance HSC engraftment and accelerate hematopoietic recovery in the elderly population following myelosuppressive regimens., Introduction The number of elderly individuals is expected to double in the next 40 years, creating an increased burden of treatment for aging-related disorders, including cardiovascular disease and cancer (1-4). [...]

Biodegradable scaffolds seeded with bone marrow mononuclear cells (BMCs) are the earliest tissue-engineered vascular grafts (TEVGs) to be used clinically. These TEVGs transform into living blood vessels in vivo, with an endothelial cell (EC) lining invested by smooth muscle cells (SMCs); however, the process by which this occurs is unclear. To test if the seeded BMCs differentiate into the mature vascular cells of the neovessel, we implanted an immunodeficient mouse recipient with human BMC (hBMC)-seeded scaffolds. As in humans, TEVGs implanted in a mouse host as venous interposition grafts gradually transformed into living blood vessels over a 6-month time course. Seeded hBMCs, however, were no longer detectable within a few days of implantation. Instead, scaffolds were initially repopulated by mouse monocytes and subsequently repopulated by mouse SMCs and ECs. Seeded BMCs secreted significant amounts of monocyte chemoattractant protein-1 and increased early monocyte recruitment. These findings suggest TEVGs transform into functional neovessels via an inflammatory process of vascular remodeling. bone marrow | monocyte chemoattractant protein-1 | tissue engineering | neovascularization www.pnas.org/cgi/doi/10.1073/pnas.0911465107

Granulocyte colony-stimulating factor (G-CSF) is often used to hasten neutrophil recovery after allogeneic bone marrow transplantation (BMT), but the clinical and immunological consequences evoked remain unclear (1). We examined the effect of G-CSF administration after transplantation in mouse models and found that exposure to either standard G-CSF or pegylated-G-CSF soon after BMT substantially increased graft-versus-host disease (GVHD). This effect was dependent on total body irradiation (TBI) rendering host dendritic cells (DCs) responsive to G-CSF by upregulating their expression of the G-CSF receptor. Stimulation of host DCs by G-CSF subsequently unleashed a cascade of events characterized by donor natural killer T cell (NKT cell) activation, interferon-[gamma] secretion and CD40-dependent amplification of donor cytotoxic T lymphocyte function during the effector phase of GVHD. Crucially, the detrimental effects of G-CSF were only present when it was administered after TBI conditioning and at a time when residual host antigen presenting cells were still present, perhaps explaining the conflicting and somewhat controversial clinical studies from the large European and North American BMT registries (2,3). These data have major implications for the use of G-CSF in disease states where NKT cell activation may have effects on outcome., Although G-CSF is commonly administered to accelerate neutrophil engraftment after autologous BMT (4-6), the immunological consequences of G-CSF treatment after allogeneic BMT are controversial. Although most studies have examined the [...]

Tissue injury may create a specific microenvironment for inducing the systemic participation of stromal-like cells in the repair process. Here we show that substance P is an injury-inducible factor that acts early in the wound healing process to induce [CD29.sup.+] stromal-like cell mobilization. Likewise, mobilization of such cells also occurs in uninjured mice, rats and rabbits if substance P is intravenously injected. Upon further characterization these substance P-mobilized [CD29.sup.+] cells were found to be similar to stromal cells from a number of connective tissues, including bone marrow (that is, bone marrow stromal cells, or BMSCs). Both substance P injection and transfusion of autologously derived substance P-mobilized [CD29.sup.+] cells from uninjured rabbits accelerated wound healing in an alkali burn model. Also, epithelial engraftment of the transfused cells into the injured tissue occurred during the wound healing. Finally, using human BMSCs as a test population, we show that substance P stimulates transmigration, cell proliferation, activation of the extracellular signal-related kinases (Erk) 1 and 2 and nuclear translocation of [beta]-catenin in vitro. This finding highlights a previously undescribed function of substance P as a systemically acting messenger of injury and a mobilizer of [CD29.sup.+] stromal-like cells to participate in wound healing., Tissue injury may create a specific microenvironment composed of cytokines, chemokines, growth factors and neurohormones initially released from the adjacent epithelium, stroma, sensory neuron and peripheral blood upon the event [...]

Impaired host defense post-bone marrow transplant (BMT) is related to overproduction of prostaglandin [E.sub.2] (PG[E.sub.2]) by alveolar macrophages (AMs). We show AMs post-BMT overproduce granulocyte-macrophage colony-stimulating factor (GM-CSF), whereas GM-CSF in lung homogenates is impaired both at baseline and in response to infection post-BMT. Homeostatic regulation of GM-CSF may occur by hematopoietic/ structural cell cross talk. To determine whether AM overproduction of GM-CSF influenced immunosuppression post-BMT, we compared mice that received BMT from wild-type donors (control BMT) or mice that received BMT from GM-CSF-/- donors (GM-CSF-/BMT) with untransplanted mice. GM-CSF-/- BMT mice were less susceptible to pneumonia with Pseudomonas aeruginosa compared with control BMT mice and showed antibacterial responses equal to or better than untransplanted mice. GM-CSF-/- BMT AMs displayed normal phagocytosis and a trend toward enhanced bacterial killing. Surprisingly, AMs from GM-CSF-/- BMT mice overproduced PG[E.sub.2], but expression of the inhibitory E[P.sub.2] receptor was diminished. As a consequence of decreased E[P.sub.2] receptor expression, we found diminished accumulation of cAMP in response to PG[E.sub.2] stimulation in GM-CSF-/- BMT AMs compared with control BMT AMs. In addition, GM-CSF-/- BMT AMs retained cysteinyl leukotriene production and normal TNF-[alpha] response compared with AMs from control BMT mice. GM-CSF-/- BMT neutrophils also showed improved bacterial killing. Although genetic ablation of GM-CSF in hematopoietic cells post-BMT improved host defense, transplantation of wild-type bone marrow into GM-CSF-/- recipients demonstrated that parenchymal cell-derived GM-CSF is necessary for effective innate immune responses post-BMT. These results highlight the complex regulation of GM-CSF and innate immunity post-BMT. lung; Pseudomonas aeruginosa; eicosanoid; neutrophil

In conditions of severe T cell depletion, such as HIV-1 infection, limited T cell production by the thymus can thwart the immune response, putting individuals at increased risk of infection with opportunistic pathogens. In this issue of the JCI, Napolitano et al. report, in a prospective, randomized study, that treatment of HIV-1-infected adults with growth hormone may reverse thymic atrophy, as reflected by increased de novo thymic T cell production accompanied by increased peripheral T cell production (see the related article beginning on page 1085). While the long-term immunological and clinical benefits of growth hormone treatment remain unclear, the data suggest a way in which to enhance thymopoiesis and peripheral T cell production in immunodeficient individuals., T cell depletion due to (a) chemo- or radiotherapy for the treatment of cancer; (b) myeloablative chemotherapy prior to bone marrow transplantation; (c) immunosuppressive treatment to avoid transplant rejection; or [...]

Allogeneic bone-marrow transplantation (BMT) can induce a powerful graft-vs.-tumor (GVT) effect not only on hematological malignancies but also on solid tumors. However, graft-vs.-host disease (GVHD) is a major complication of allogeneic BMT. We assessed GVT effect on hepatocellular carcinoma (HCC) and the effects of hepatocyte growth factor (HGF) gene transduction on GVHD in HCC transplanted mice. (C57BL/6 x C3H/HeJ)[F.sub.1](B6C3F1, H-[2.sup.bxk]) mice were used as recipients and C3H/HeJ(H-[2.sup.k]) mice were used as donors. Hepal-a (a C57L mouse-derived hepatoma cell, H-[2.sup.b]) was subcutaneously injected into the recipient mice. Tumor beating mice were treated in the following ways: group 1, no treatment; group 2, total body irradiation (TBI); group 3, TBI and BMT; group 4, TBI and BMT with empty vector; group 5, TBI and BMT with HGF gene transduction; group 6, TBI and BMT with administration of FK506, a representative immunosuppressive agent. Acute GVHD was assessed by histological examination of the liver, small intestines, and large intestines. Tumor growth was markedly suppressed in mice that received an allogeneic BMT. Dignor-derived [CD8.sup.+] T cells had infiltrated into the tumor, and cytotoxic [CD8.sup.+] T cells against HCC were present. However, among the four groups that received a BMT, this suppressive effect was weaker in group 6 compared with the other three groups (groups 3, 4, and 5). HGF gene transduction improved GVHD while preserving the GVT effects. Allogeneic BMT markedly suppresses the growth of HCC. Simultaneous HGF gene transfer can suppress GVHD while preserving the GVT effect. hepatocellular carcinoma; bone marrow transplantation; graft versus tumor; graft-versus-host disease; hepatocyte growth factor

MicroRNAs (miRNAs) are a family of [approximately equal to] 22-nt noncoding RNAs that can posttranscriptionally regulate gene expression. Several miRNAs are specifically expressed in hematopoietic cells. Here we show that one such miRNA, miR-150, is mainly expressed in the lymph nodes and spleen and is highly up-regulated during the development of mature T and B cells; expression of miR-150 is sharply up-regulated at the immature B cell stage. Overexpression of miR-150 in hematopoietic stem cells, followed by bone marrow transplantation, had little effect on the formation of either mature CD8- and CD4-positive T cells or granulocytes or macrophages, but the formation of mature B cells was greatly impaired. Furthermore, premature expression of miR-150 blocked the transition from the pro-B to the pre-B stage. Our results indicate that miR-150 most likely down-regulates mRNAs that are important for pre- and pro-B cell formation or function, and its ectopic expression in these cells blocks further development of B cells. bone marrow transplantation | hematopoiesis | hematopoietic stem/progenitor cell | lymphopoiesis

Hematopoietic stem cells (HSCs) execute self-renewal divisions throughout fetal and adult life, although some of their properties do alter. Here we analyzed the magnitude and timing of changes in the self-renewal properties and differentiated cell outputs of transplanted HSCs obtained from different sources during development. We also assessed the expression of several 'stem cell' genes in corresponding populations of highly purified HSCs. Fetal and adult HSCs displayed marked differences in their self-renewal, differentiated cell output, and gene expression properties, with persistence of a fetal phenotype until 3 weeks after birth. Then, 1 week later, the HSCs became functionally indistinguishable from adult HSCs. The same schedule of changes in HSC properties occurred when HSCs from fetal or 3-week-old donors were transplanted into adult recipients. These findings point to the existence of a previously unrecognized, intrinsically regulated master switch that effects a developmental change in key HSC properties. bone marrow transplantation | development | gene expression | self-renewal

Acute inflammatory stimuli rapidly mobilize neutrophils from the bone marrow by shortening postmitotic maturation time and releasing younger neutrophils; however, the kinetics of this change in maturation time remains unknown. We propose a kinetic model that examines the rate of change in neutrophil average age at exit from the bone marrow during active mobilization to quantify this response and use this model to examine the temporal profile of late neutrophil phenotypic maturation. Total and CD[10.sup.-]/CD[16.sup.low] circulating neutrophils were quantified in cardiac surgery patients during extracorporeal circulation (ECC). Net growth in the circulating neutrophil pool occurred during the procedural (0.04 [+ or -] 0.02 x [10.sup.9]*[1.sup.-1]*[min.sup.-1]), warming (0.14 [+ or -] 0.02 x [10.sup.9]*[1.sup.1]*[min.sup.-1]), and weaning (0.12 [+ or -] 0.06 X [10.sup.9]*[1.sup.1]*[min.sup.-1]) phases of ECC. When applied to our differential equation mathematical model, these results predict that neutrophil average age at exit from the bone marrow decreased continually during ECC, resulting in average neutrophil release 8.44 [+ or -] 2.20 h earlier during the weaning phase than at the beginning of ECC sampling. Modeling of concurrent changes in CD[10.sup.-]/CD[16.sup.low] neutrophil numbers indicates that CD10 expression is directly related to neutrophil mean age and predicts that the proportion of mobilizable postmitotic neutrophils that are CD[10.sup.+] increases from 64 to 81% during these sampled 8.4 h of maturation. bone marrow; postmitotic maturation; granulopoiesis; neutrophil recruitment; mathematical modeling

The interaction of stem cells with their bone marrow microenvironment is a critical process in maintaining normal hematopoiesis. We applied an approach to resolve the spatial organization that underlies these interactions by evaluating the distribution of hematopoietic cell subsets along an in vivo Hoechst 33342 (Ho) dye perfusion gradient. Cells isolated from different bone marrow regions according to Ho fluorescence intensity contained the highest concentration of hematopoietic stem cell (HSC) activity in the lowest end of the Ho gradient (i.e., in the regions reflecting diminished perfusion). Consistent with the ability of Ho perfusion to simulate the level of oxygenation, bone marrow fractions separately enriched for HSCs were found to be the most positive for the binding of the hypoxic marker pimonidazole. Moreover, the in vivo administration of the hypoxic cytotoxic agent tirapazamine exhibited selective toxicity to the primitive stem cell subset. These data collectively indicate that HSCs and the supporting cells of the stem cell niche are predominantly located at the lowest end of an oxygen gradient in the bone marrow with the implication that regionally defined hypoxia plays a fundamental role in regulating stem cell function. Hoechst perfusion | stem cell niche | oxygen gradient | pimonidazole | tirapazamine

Thrombopoietic cells may differentially promote or inhibit tissue vascularization by releasing both pro- and antiangiogenic factors. However, the molecular determinants controlling the angiogenic phenotype of thrombopoietic cells remain unknown. Here, [...]

An increase in adipocyte number is a major contributor to the increase in adipose tissue mass that is characteristic of obesity. The identity and regulation of the adipocyte precursor cell [...]

The most common inherited form of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease affecting adult motoneurons, is caused by dominant mutations in the ubiquitously expressed [Cu.sup.2+]/[Zn.sup.2+] superoxide dismutase (SOD1). Recent studies suggest that glia may contribute to motoneuron injury in animal models of familial ALS. To determine whether the expression of mutant SOD1 ([mSOD1.sup.G93A]) in CNS microglia contributes to motoneuron injury, [PU.1.sup.-/-] mice that are unable to develop myeloid and lymphoid cells received bone marrow transplants resulting in donor-derived microglia. Donor-derived microglia from mice overexpressing [mSOD1.sup.G93A], an animal model of familial ALS, transplanted into [PU.1.sup.-/-] mice could not induce weakness, motoneuron injury, or an ALS-like disease. To determine whether expression of [mSOD1.sup.G93A] in motoneurons and astroglia, as well as microglia, was required to produce motoneuron disease, [PU.1.sup.-/-] mice were bred with [mSOD1.sup.G93A] mice. In [mSOD1.sup.G93A]/[PU.1.sup.-/-] mice, wild-type donor-derived microglia slowed motoneuron loss and prolonged disease duration and survival when compared with mice receiving [mSOD1.sup.G93A] expressing cells or [mSOD1.sup.G93A] mice. In vitro studies confirmed that wild-type microglia were less neurotoxic than similarly cultured [mSOD1.sup.G93A] microglia. Compared with wild-type microglia, [mSOD1.sup.G93A] microglia produced and released more superoxide and nitrite+nitrate, and induced more neuronal death. These data demonstrate that the expression of [mSOD1.sup.G93A] results in activated and neurotoxic microglia, and suggests that the lack of [mSOD1.sup.G93A] expression in microglia may contribute to motoneuron protection. This study confirms the importance of microglia as a double-edged sword, and focuses on the importance of targeting microglia to minimize cytotoxicity and maximize neuroprotection in neurodegenerative diseases. bone marrow transplant | neuroprotection | superoxide dismutase | nitric oxide | motoneurons

Dendritic cells (DCs) are actively used as cellular adjuvant in cancer immunotherapy. However, although DC immunotherapies primarily target the elderly population, little is known about the effect of aging on DC functions. Here, we compared the T-cell stimulation, cytokine production, and tumor surveillance functions of bone marrow-derived [CD11.sup.c+][CD4.sup.-][CD8[alpha].sup.-] DCs of old and young C57BL/6 mice. Old immature bone marrow-derived [CD4.sup.-] [CD8.sup.c+] DCs (imDCs) were 4 times less effective than were young DCs in stimulating syngeneic [CD4.sup.+] T-cell proliferation. Old imDCs also have decreased DC-specific/intracellular adhesion molecule type 3-grabbing, nonintegrin (DC-SIGN) expression compared to young DCs. Interestingly, mice treated with the ovalbumin peptide-pulsed young DCs exhibited significantly greater tumor regression than with ovalbumin peptide-pulsed old DCs. Old terminally differentiated bone marrow-derived DCs (tDC) also have increased interleukin-10, but decreased interleukin-6 and tumor necrosis factor-[alpha] production. Taken together, these results have important implications in the clinical application of DC-based tumor immunotherapy in elderly persons.

Stem cells have been identified as essential for maintaining multiple organ systems, including the hematopoietic system. The distinct cell fates of self-renewal and differentiation of hematopoietic stem cells (HSCs) depend on cell division. Recently, several negative regulators of the cell cycle, such as the cyclin-dependent kinase inhibitors [p21.sup.Cip1], [p27.sup.Kip1], and [p16.sup.INK4a]/[p19.sup.ARF], have been demonstrated to have a role in regulating HSC fate decisions, suggesting that regulation of the [G.sup.1]-S phase transition can contribute to HSC self-renewal. Because the retinoblastoma protein, Rb, plays a central role in the regulation of the [G.sub.1]-S phase cell cycle, we sought to determine whether it has an intrinsic role in the regulation of HSC fate. Surprisingly, we found that HSC function was essentially normal in the absence of Rb. [Rb.sup.[DELTA]/[DELTA]] HSCs contributed normally to both myeloid and lymphoid lineages in both primary and secondary recipients, and no evidence of transformation was observed. Additionally, we observed a mild myeloid expansion and decrease in mature B cells within the [Rb.sup.[DELTA][DELTA]] bone marrow but a similar contribution to phenotypic HSC populations compared with non-deleted bone marrow. The Rb family members p107 and p130 were not deregulated in cells in which Rb had been deleted, as determined by quantitative RT-PCR on the highly enriched stem and primitive progenitor cell [lin.sup.-c]-[Kit.sup.+][Sca-1.sup.+] population. These studies demonstrate that Rb is not intrinsically required for self-renewal and multilineage differentiation of adult HSCs. retinoblastoma | conditional mutation | bone marrow transplantation

A murine model of bone marrow transplant (BMT)-related lung injury was developed to study how infection sensitizes lung to the damaging effects of total body irradiation (TBI) at infectious and TBI doses that individually do not cause injury. Mice infected with Pneumocystis carinii exhibited an asymptomatic, rapid, and transient influx of eosinophils and T cells in bronchoalveolar lavage fluid (BALF). In contrast, mice infected with P. carinii 7 days before receiving TBI and syngeneic BMT (P. carinii/TBI mice) exhibited severe pulmonary dysfunction, surfactant aggregate depletion, and surfactant activity reductions at 17 days post-BMT. BALF from P. carinii/TBI mice contained a disproportionate initial influx of CD[4.sup.+] T cells (CD[4.sup.+]: CD[8.sup.+] ratio of 2.7) that correlated with progressive lung injury (from 8 to 17 days post-BMT). Levels of TNF-[alpha] in BALF were significantly increased in P. carinii/TBI mice compared with mice given either insult alone, with peak values found at 11 days post-BMT. In vivo depletion of CD[4.sup.+] T cells in P. carinii/TBI mice abrogated pulmonary dysfunction and reduced TNF-[alpha] levels in BALF, whereas depletion of CD[8.sup.+] T cells did not affect lung compliance or TNF-[alpha]. Lung injury was not attributable to direct P. carinii damage, since CD4-depleted P. carinii/TBI mice that exhibited no injury had higher average lung P. carinii burdens than either mice given P. carinii alone or undepleted P. carinii/TBI mice. Together, these results indicate that P. carinii infection can sensitize the lung to subsequent TBI-mediated lung injury via a process dependent on non-alloreactive CD[4.sup.+] T cells. idiopathic pneumonia syndrome; pneumonitis: tumor necrosis factor-[alpha]; inflammation; opportunistic infection; bone marrow transplantation; total body irradiation

Type IV collagen is a predominant component of basement membranes, and glomeruli of a kidney filter [approximately equal to] 70-90 liters of plasma every day through a specialized glomerular basement membrane (GBM). In Alport syndrome, a progressive disease primarily affecting kidneys, mutations in GBM-associated type IV collagen genes (COL4A3, COL4A4, or COL4A5) lead to basement membrane structural defects, proteinuria, renal failure, and an absence of all three GBM collagen triple helical chains because of obligatory posttranslational assembly requirements. Here, we demonstrate that transplantation of wild-type bone marrow (BM) into irradiated COL4A[3.sup.-/-] mice results in a possible recruitment of BM-derived progenitor cells as epithelial cells (podocytes) and mesangial cells within the damaged glomerulus, leading to a partial restoration of expression of the type IV collagen [alpha]3 chain with concomitant emergence of [alpha]4 and [alpha]5 chain expression, improved glomerular architecture associated with a significant reduction in proteinuria, and improvement in overall kidney histology compared with untreated COL4A[3.sup.-/-] mice or irradiated COL4A[3.sup.-/-] mice with BM from adult COL4A[3.sup.-/-] mice. The [alpha]3(IV) collagen produced by BM-derived podocytes integrates into the GBM and associates with other [alpha]-chains to form type IV collagen triple helical networks. This study demonstrates that BM-derived stem cells can offer a viable strategy for repairing basement membrane defects and conferring therapeutic benefit for patients with Alport syndrome. Alport syndrome | bone marrow transplantation | glomerular basement membrane | type IV collogen [alpha]3 chain | glomeruli

Naturally occurring [CD4.sup.+][CD25.sup.+] T regulatory (Treg) cells have been shown to inhibit adaptive responses by T cells. Natural killer (NK) cells represent an important component of innate immunity in both cancer and infectious disease states. We investigated whether [CD4.sup.+][CD25.sup.+] Treg cells could affect NK cell function in vivo by using allogeneic (full H2-disparate) bone marrow (BM) transplantation and the model of hybrid resistance, in which parental marrow grafts are rejected solely by the NK cells of irradiated (BALB/c x C57BL/6) [F.sub.1] recipients. We demonstrate that the prior removal of host Treg cells, but not [CD8.sup.+] T cells, significantly enhanced NK cell-mediated BM rejection in both models. The inhibitory role of Treg cells on NK cells was confirmed in vivo with adoptive transfer studies in which transferred [CD4.sup.+][CD25.sup.+] cells could abrogate NK cell-mediated hybrid resistance. Anti-TGF-[beta] mAb treatment also increased NK cell-mediated BM graft rejection, suggesting that the NK cell suppression is exerted through TGF-[beta]. Thus, [CD4.sup.+][CD25.sup.+] Treg cells can potently inhibit NK cell function in vivo, and their depletion may have therapeutic ramifications for NK cell function in BM transplantation and cancer therapy. anti-CD25 | bone marrow transplantation | hybrid resistance | Foxp3

Although the wild-type prion protein (PrP) is abundant and widely expressed in various types of tissues and cells, its physiological function(s) remain unknown, and PrP knockout mice do not exhibit overt and undisputed phenotypes. Here we showed that PrP is expressed on the surface of several bone marrow cell populations successively enriched in long-term (LT) hematopoietic stem cells (HSCs) using flow cytometry analysis. Affinity purification of the PrP-positive and -negative fractions from these populations, followed by competitive bone marrow reconstitution assays, shows that all LT HSCs express PrP. HSCs from PrP-null bone marrow exhibited impaired self-renewal in serial transplantation of lethally irradiated mouse recipients both in the presence and absence of competitors. When treated with a cell cycle-specific myelotoxic agent, the animals reconstituted with PrP-null HSCs exhibit increased sensitivity to hematopoietic cell depletion. Ectopic expression of PrP in PrP-null bone marrow cells by retroviral infection rescued the defective hematopoietic engraftment during serial transplantation. Therefore, PrP is a marker for HSCs and supports their self-renewal. bone marrow | serial transplantation | hematopoiesis | reconstitution

The study is conducted to compare outcomes and immune reconstitution in a large cohort of patients with severe combined immune deficiency (SCID) who received HLA-identical donor (RID), HLA-matched unrelated donor (MUD) or HLA-mismatched related donor bone marrow transplantation (MMRD BMT). It suggests that in the absence of a relative with identical HLA, MUD BMT may provide better engraftment, immune reconstitution and survival for patients with SCID than MMRD BMT.

Treatment of refractory schizophrenia with the atypical antipsychotic drug clozapine is associated with life-threatening agranulocytosis, characterised by a drop in neutrophil count. Theoretically, toxicity may be accounted for by direct action of parent drug or one of its stable metabolites on bone marrow stroma given importance of these cells to neutrophil maturation. Effects of clozapine, N-desmethylclozapine and clozapine N-oxide on stromal cell viability were therefore assessed using human primary long-term bone marrow culture and stromal cell lines, HAS303 and LP101, to define cell-specificity of response. Clozapine, N-desmethylclozapine and clozapine N-oxide had no significant effect on bone marrow stromal, HAS303 and LP101 viability over a wide drug concentration range (10-20000 ng [mL.sup.-1]) compared with cells in absence of drug. Hence it is unlikely that parent drug or its stable metabolites are directly toxic to stroma under clinical conditions. Reduced capability of stroma to support myelopoiesis, however, cannot be excluded. Key words: Clozapine, metabolites, stroma, agranulocytosis, schizophrenia, INTRODUCTION Clinical studies have defined the effectiveness of the antipsychotic drug clozapine in the treatment of refactory schizophrenia [1]. Its demonstrated efficacy and expanding indications for use, however, are mitigated [...]

Breast cancer remains the cancer with the highest mortality among women in the United States. Peptides derived from the oncogenic Tac1 gene (full transcript: [beta]PPT-A) stimulate the proliferation of breast cancer cells (BCCs) via seven-transmembrane G proteincoupled neurokinin 1 (NK1) and NK2 receptors. The NK1 gene could generate full-length (NK1-FL) and truncated (NK1-Tr) transcripts. NK1-Tr lacks 100 residues in their cytoplasmic end, could couple to G proteins, and shows reduced efficiency with respect to internalization and desensitization. This study reports on a role of NK1-Tr in the transformation of nontumorigenic breast cells, and investigates whether Tac1 expression is linked to the generation of NK1-Tr. Western blots and Northern analyses showed coexpressions of NK1-Tr and NK1-FL in BCCs (cell lines and primary cells from patients with different stages of breast cancer). Stable transfections of [beta]PPT-A or NK1-Tr expression vectors in nontumorigenic cells showed each induces the expression of the other, consequently resulting in a transformed phenotype. Analyses with microarrays indicate similar patterns of cytokine production by NK1-Tr transfectants and BCCs, but not NK1-FL transfectants. These observations indicate tumor-promoting properties by NK1-Tr, but not NK1-FL. Overall, the oncogenic property of Tac1 in breast cells involves concomitant expression of NK1-Tr and vice versa, consequently leading to the production of cytokines with growth promoting functions. breast cancer | cytokines | bone marrow metastasis | substance P | tachykinin