Bone marrow-derived stromal cells can express neuronal markers by DHA/GPR40 signaling

The exact origin of neural stem cells in the adult neurogenesis niche remains unknown. Our previous studies, however, indicated an implication of both bone marrow cells as potential progenitors of hippocampal newborn neurons and polyunsaturated fatty acids as ligands of G protein-coupled receptor 40 (GPR40) signaling. Here, we aimed at studying whether bone marrow-derived stromal cells (BMSC) treated by docosahexaenoic acid (DHA) can express neuronal markers in vitro. We focused on implication of DHA/GPR40 signaling for the expression of neural markers in clonally-expanded BMSC from young macaque monkeys. Cell cycle analysis revealed that the DHA plus bFGF treatment induced a decrease of BMSC proliferation and increased the cells in the G0 resting phase. The transitions from nestin-positive progenitors via immature neuronal (beta III-tubulin-positive) to mature neuronal (NF-M and Map2-positive) phenotypes were examined using RT-PCR, Western blot and immunocytochemistry. We detected a significant increase of GPR40 mRNA and protein expression after bFGF induction, being compared with the untreated BMSC. Addition of DHA, a representative GPR40 ligand, led to a significant down-regulation of GPR40, i.e., G protein-coupled receptor-specific internalization, with a subsequent upregulation of neuronal markers such as beta III-tubulin, NF-M and Map2. These data altogether suggest that adult primate BMSC can express neuronal markers with the aid of DHA/GPR40 signaling.

Treatment of streptozotocin-induced diabetes mellitus in mice by intra-bone marrow bone marrow transplantation plus portal vein injection of beta cells induced from bone marrow cells

Curative therapy for diabetes mellitus mainly involves pancreas or islet transplantation to recruit insulin-producing cells. This approach is limited, however, because of both the shortage of donor organs and allograft rejection. Intra-bone marrow bone marrow transplantation (IBM-BMT) has recently been shown to be effective in inducing donor-specific tolerance in mice and rats without the use of immunosuppressants. After induction of diabetes in 15 C3H mice with streptozotocin, the mice received both allotransplants of bone marrow cells from C57BL/6 mice by IBM-BMT and injections via the portal vein of insulin-producing cells that were induced in vitro from stem cells derived from adult C57BL/6 bone marrow. We evaluated the expression of these cells by examining the expression of not only insulin but also the crucial transcription factors insulin I and insulin II. The diabetic mice were treated with IBM-BMT and precultured insulin-producing cells. Hyperglycemia was normalized by 5 days after the treatment and remained normal for more than 45 days. This strategy might be applicable to patients with type I diabetes mellitus.

Optimal protocol for total body irradiation for allogeneic bone marrow transplantation in mice

We have previously demonstrated, using chimeric resistant MRL/lpr mice, that a fractionated total body irradiation (FTBI) (5 Gy x 2 with a 4 h interval on the day before allogeneic bone marrow transplantation (BMT)) is the best conditioning regimen for the treatment of autoimmune diseases in radiosensitive MRL/lpr mice. In the present study, using various standard strains of mice (not radiosensitive mice), we explore the best protocol for irradiation (doses and intervals) as the conditioning regimen for allogeneic BMT. Recipient mice were exposed to various irradiation regimens: a single total body irradiation (TBI) of 9.5 or 12 Gy and FTBI of (5+5) Gy to (7+7) Gy with a 1 to 24 h interval. The method generally utilized for humans ((2+2) Gy with a 4 h interval for 3 days (total 12 Gy)) was also used. One day after the last irradiation, donor BMCs from BALB/c, C3H, or C57BL/6 (B6) mice were transplanted into C3H or B6 mice. The irradiation protocol of (2+2) Gy for 3 days was found to be insufficient to enable the complete removal of recipient immunocompetent cells, since donor-reactive T cells were observed in the recipient spleens and many recipient-type NK and CD4(+) cells were also detected in the recipient hematolymphoid tissues. In all the combinations, the highest survival rate was achieved in the recipients irradiated with (6+6) or (6.5+6.5) Gy with a 4 h interval. In the surviving mice, the hematolymphoid tissues had been fully reconstituted with donor cells.

Crucial role of donor-derived stromal cells in successful treatment for intractable autoimmune diseases in mrl/lpr mice by bmt via portal vein

We have recently established a new bone marrow transplantation (BMT) method for the treatment of intractable autoimmune diseases in MRL/lpr mice; the method consists of fractionated irradiation (5.5 Gy x 2), followed by BMT of whole bone marrow cells (BMCs) from allogeneic C57BL/6 mice via the portal vein (abbreviated as 5.5 Gy x 2 + PV). In the present study, we investigate the mechanisms underlying the early engraftment of donor-derived cells in MRL/lpr mice by this method. In the mice treated with this method, the number of donor-derived cells possessing the mature lineage (Lin) markers rapidly increased in the BM, spleen, and liver; almost 100% were donor-derived cells by 14 days after the treatment. The number of donor-derived hemopoietic progenitor cells (defined as c-kit(+)/Lin(-) cells) increased in the BMCs, hepatic mononuclear cells, and especially spleen cells by 14 days after the treatment. Simultaneously, hemopoietic foci adjoining donor-derived stromal cells were observed in the liver when injected via the PV, but not via the peripheral vein (i.v.). When adherent cell-depleted BMCs were injected via the PV, recipients showed a marked reduction in the survival rate. However, when mice were transplanted with adherent cell-depleted BMCs with cultured stromal cells, all the recipients survived. These findings suggest that not only donor hematopoietic stem cells (HSCs) but also donor stromal cells administered via the PV were trapped in the liver, resulting in the early engraftment of donor HSCs in cooperation with donor-derived stromal cells. This new strategy to facilitate the early recovery of hemopoiesis would therefore be of great advantage in human application.

Successful allogeneic bone marrow transplantation (BMT) by injection of bone marrow cells via portal vein: stromal cells as BMT-facilitating cells

We examined the importance of the coadministration of bone marrow (BM) stromal cells with BM cells via the portal vein. A significant increase in the number of day-14 colony-forming unit-spleen (CFU-S) was observed in the recipient mice injected with hemopoietic stem cells (HSCs) along with donor BM stromal cells obtained after three to four weeks of culture. Histological examination revealed that hematopoietic colonies composed of both donor hemopoietic cells and stromal cells coexist in the liver of these mice. However, when donor HSCs plus BM stromal cells were administered i.v., neither the stimulatory effects on CFU-S formation nor the hemopoietic colonies in the recipient liver were observed. These findings suggest that the interaction of HSCs with stromal cells in the liver is the first crucial step for successful engraftment of allogeneic HSCs. It is likely that donor stromal cells and HSCs trapped in the liver migrate into the recipient BM and spleen, where they form CFU-BM and CFU-S, respectively.

Major histocompatibility complex restriction between hematopoietic stem cells and stromal cells in vitro

We have previously found that a significant number of hematopoietic progenitors accumulate in engrafted bones with the same major histocompatibility complex (MHC) as the transplanted bone marrow cells. In the present study, to further clarify the MHC restriction between hematopoietic stem cells (HSC) and microenvironment, we carried out cobblestone colony formation assays by culturing HSCs with MHC-matched or -mismatched stromal cell monolayers. The formation of cobblestone colonies under MHC-mismatched stromal cells significantly decreased in comparison with MHC-matched stromal cells. However, the decrease in cobblestone colony formation under MHC-mismatched stromal cells was not significant when using MHC class I-deficient HSC or stromal cells. Taken together with the results using B10 congenic strains, it is suggested that the MHC preference is restricted by MHC class Ia molecules. Treatment with monoclonal antibodies (mAbs) against MHC class Ia molecules of stromal cell phenotypes significantly enhanced the cobblestone colony formation, whereas treatment with mAbs against HSC phenotypes significantly inhibited it. The expression of cytokines to promote hematopoiesis was enhanced by the mAbs against stromal cell phenotypes. The enhancement of cytokine expression was also observed when stromal cells and HSCs were MHC-matched. These results suggest that signaling via the MHC molecules augments stromal cell activity and elicits the MHC restriction.

Intra-bone marrow injection of allogeneic bone marrow cells: a powerful new strategy for treatment of intractable autoimmune diseases in MRL/lpr mice

Intractable autoimmune diseases in chimeric resistant MRL/lpr mice were treated by a new bone marrow transplantation (BMT) method consisting of fractionated irradiation, 5.5 Gy x 2, followed by intra-bone marrow (IBM) injection of whole bone marrow cells (BMCs) from allogeneic normal C57BL/6 (B6) mice (5.5 Gy x 2 + IBM). In MRL/lpr mice treated with this method, the number of donor-derived cells in the bone marrow, spleen, and liver rapidly increased (almost 100% donor-derived cells by 14 days after the treatment), and the number of donor-derived hemopoietic progenitor cells concomitantly increased. Furthermore, donor-derived stromal cells were clearly detected in the cultured bone pieces from MRL/lpr mice treated with 5.5 Gy x 2 + IBM. All the recipients thus treated survived more than 1 year (> 60 weeks after birth) and remained free from autoimmune diseases. Autoantibodies decreased to almost normal levels, and abnormal T cells (Thy1.2(+)/B220(+)/CD4(-)/CD8(-)) disappeared. Hematolymphoid cells were reconstituted with donor-derived cells, and newly developed T cells were tolerant to both donor (B6)-type and host (MRL/lpr)-type major histocompatibility complex determinants. Successful cooperation was achieved among T cells, B cells, and antigen-presenting cells when evaluated by in vitro antisheep red blood cell responses. These findings clearly indicate that this new strategy (IBM-BMT) creates the appropriate hemopoietic environment for the early recovery of hemopoiesis and donor cell engraftment, resulting in the complete amelioration of intractable autoimmune diseases in chimeric resistant MRL/lpr mice without recourse to immunosuppressants. This strategy would therefore be suitable for human therapy.

A new method for bone marrow cell harvesting

To minimize contamination of bone marrow cells (BMCs) with T cells from the peripheral blood, a new "perfusion method" for collecting BMCs is proposed using cynomolgus monkeys. Two BM puncture needles are inserted into a long bone such as the humerus, femur, or tibia. One needle is connected to an extension tube and the end of the tube is inserted into a culture flask to collect the BM fluid. The other needle is connected to a syringe containing 30 ml of phosphate-buffered saline. The solution is pushed gently from the syringe into the medullary cavity, and the medium containing the BM fluid is collected into the culture flask. There is significantly less contamination with peripheral blood, determined from the frequencies of CD4(+) and CD8(+) T cells, when using this method (<6%) than when using the conventional method (>20%) consisting of multiple BM aspirations from the iliac crest. Furthermore, the number and progenitor activities of the cells harvested using this "perfusion method" are greater than those harvested using the conventional aspiration method. This perfusion method was carried out 42 times using 15 cynomolgus monkeys, and no complications such as pulmonary infarction or paralysis were observed. These findings suggest that the "perfusion method" is safe and simple and would be of great advantage in obtaining pure BMCs, resulting in a less frequent occurrence of acute graft-versus-host-disease in allogeneic BM transplantation.

Evidence for migration of donor bone marrow stromal cells into recipient thymus after bone marrow transplantation plus bone grafts: A role of stromal cells in positive selection

Intrathymic T-cell differentiation is characterized by two selection events: positive and negative selection. It has been shown that thymic epithelial cells in the cortex are involved in the positive selection, while macrophages and dendritic cells, derived from hemopoietic stem cells, are involved in the negative selection. Here we investigate whether donor-derived bone marrow stromal cells can migrate into the thymus and participate there in positive selection after bone marrow transplantation plus bone grafts (to recruit bone marrow stromal cells). Allogeneic bone marrow transplantation with or without bone grafts was carried out in the [C57BL/6-->C3H] combination. Fluorescence-activated cell sorter analyses of recipient thymic adherent cells showed that donor-type bone marrow stromal cells exist in the thymus of mice that received bone marrow plus bone grafts but not in the mice that received bone marrow cells alone. Histological examination using confocal microscopy also confirmed the existence of donor-type stromal cells in the thymus of mice that received bone marrow cells plus bones. Both T-cell proliferation and plaque-forming cell assays indicated that the T cells of such mice show donor-type major histocompatibility complex-restriction. These findings strongly suggest that stromal cells can migrate from the bone marrow to the thymus, where they participate in the positive selection of thymocytes.

Experimental autoimmune thyroiditis induced by thyroglobulin-pulsed dendritic cells

Dendritic cells (DCs), which are the most effective professional antigen-presenting cells (APCs), initiate and regulate immune responses. In this report, we examine the role of DCs in the induction of autoimmune thyroiditis. Experimental autoimmune thyroiditis (EAT) induced by immunization with thyroglobulin (Tg) plus adjuvant is considered to be an animal model of autoimmune thyroiditis, and is categorized as a T cell-mediated autoimmune disease. To examine the contribution of DCs to EAT, naive DCs were purified from high responder B10BR mice and pulsed with various concentrations of porcine Tg (pTg). These pTg-pulsed DCs were transferred without adjuvant to syngenic BIOBR mice to induce EAT. Mice that had received pTg-pulsed DCs showed thyroiditis, and the degree of thyroiditis induced was positively correlated to the amounts of pTg used for the incubation (pulsing) of DCs. The severity of thyroiditis was also correlated to the amounts of anti-pTg IgG2a antibodies and IFN-gamma in the recipient sera, but not to IL-4 or IL-10, indicating that Th1 cells are mainly activated by pTg-pulsed DCs and attributable to the pathogenesis of EAT.

Differentiation from thymic B cell progenitors to mature B cells in vitro

The role of the thymic microenvironment in the development of murine thymic B cells has yet to be fully clarified. We therefore investigate the microenvironment that supports the development of mature thymic B cells (sIg+/B220+/CD43-B cells) from thymic B cell progenitors with immunophenotypes of sIg-/B220med/CD43+ cells. As we have previously reported, thymic B cells generated from these progenitors in the thymus are CD5+ B cells. We next study the in vitro condition that supports the differentiation of thymic B cell progenitors. Stromal cells (from the bone marrow or thymus), thymus-derived cell lines with the character of thymic nurse cells (TNCs) or thymic epithelial cells (TECs), or the bone marrow-derived cell line (MS-5) are tested for their ability to support B-lymphopoiesis from thymic B cell progenitors. Interestingly, thymic stromal cells (but neither stromal cells from the bone marrow nor stromal cell lines) support the differentiation of thymic B cell progenitors into thymic B cells in the presence of IL-7. Cortical epithelia (but not medullary epithelia, thymic macrophages or dendritic cells) are found to contribute to thymic B cell differentiation. Surface phenotype and Ig rearrangement analyses reveal that mature B cells generated in this condition are primarily CD5+ B cells, indicating that the thymic microenvironment (particularly cortical epithelia) determines the differentiation of thymic B cells.

Age-dependent abnormalities of hematopoietic stem cells in (NZW x BXSB)F1 mice

The (NZW x BXSB)F1 (W/BF1) mouse is known as an autoimmune-prone strain which develops lupus nephritis, thrombocytopenia due to platelet-specific autoantibodies, leukocytosis, and myocardial infarction. In this experiment, we investigated the age-dependent abnormalities of the hematopoietic stem cells (HSCs) and hematopoiesis in this mouse. White blood cell counts (especially Mac-1- or Gr-1-positive cells) in the peripheral blood of 12-week-old W/BF1 mice increased in comparison with those of four-week-old W/BF1 or normal mice. To investigate whether the abnormal hematopoiesis can be attributed to the HSCs of W/BF1 mice, colony-forming unit in spleen (CFU-S) and colony-forming unit in culture (CFU-C) assays were performed. Day 12 CFU-S counts of 12-week-old W/BF1 mice significantly increased in comparison with those of four-week-old W/BF1 mice or normal mice. In the CFU-C assay, CFU-GEMM and CFU-GM counts in 12-week-old W/BF1 mice increased in comparison with those of four-week-old W/BF1 or control mice. The bone marrow cells (BMCs) from 12-week-old W/BF1 mice showed a high level of G-CSF and a low level of GM-CSF in mRNA expression. To examine the effect of HSCs from 12-week-old W/BF1 mice on the onset of autoimmune diseases and the abnormal hematopoiesis, T- and B-cell-depleted BMCs of four-week-old or 12-week-old W/BF1 mice were transplanted to C3H mice. Recipient C3H mice that had received the BMCs from 12-week-old W/BF1 mice showed an earlier onset of autoimmune diseases and a shorter survival rate than those that had received the BMCs from four-week-old W/BF1 mice. These data suggest that the HSCs from 12-week-old W/BF1 mice showing the symptoms of autoimmune diseases have the capacity to induce autoimmune diseases earlier than the HSCs from four-week-old W/BF1 mice.

c-kit<low Pluripotent hemopoietic stem cells form CFU-S on day 16

Using Ly5 congenic mice, we characterized the early differentiation step of pluripotent hemopoietic stem cells. Lineage- (Lin-)/CD71- cells in the bone marrow cells were separated into major histocompatibility complex (MHC) class I(high)/c-kit(low) and MHC class I(high)/c-kit<low populations from C57BL/6 Ly5.1 male mice. These two populations (1,000 cells) were transplanted into lethally irradiated (5.5 Gy x 2) C57BL/6 Ly5.2 female mice. Colony-forming unit in spleen (CFU-S) assays were carried out on days 10, 12, 14, 16, and 20. In the mice that received c-kit(low) cells, CFU-S were first detected on day 12, and the CFU-S counts gradually increased. In contrast, no visible colony was detected until day 14 in the mice that received c-kit<low cells; CFU-S were first observed on day 16. Donor-derived (Ly5.1+) cells, such as B cells, T cells, and myeloid cells, were detected by fluorescence-activated cell sorter analyses, and donor-derived erythroid cells were detected by polymerase chain reaction analyses using Y-chromosome-specific primers. Donor-derived cells in the recipients of c-kit(low) cells were detected in the spleen, bone marrow, and peripheral blood on day 12 after transplantation, while they were detected on day 16 in the mice that received c-kit<low cells. Therefore, c-kit<low cells have the capacity not only to form CFU-S on day 16 but also to reconstitute the recipients with donor-derived hematolymphoid cells 16 days after transplantation.

HGF activates signal transduction from EPO receptor on human cord blood CD34+/CD45+ cells

Hepatocyte growth factor (HGF) is a multifunctional cytokine with early hematopoiesis-stimulatory activity. Here, we focus on its erythropoiesis-stimulatory effect on highly purified human hematopoietic progenitor cells (CD34+/CD45+ cells) derived from the cord blood. In immunoblot analyses, c-met protein (a receptor of HGF) was detected in the CD34+/CD45+ cells, although the expression levels were different among samples. The c-met expression was facilitated by incubation of the cells with stem cell factor (SCF) or interleukin 3 (IL-3), even if the expression level had been low. IL-6, G-CSF, or erythropoietin (EPO) did not show such a stimulatory effect on the c-met expression of the cells. When HGF was added to the CD34+/CD45+ cells in the presence of SCF, the numbers of CD36+/CD11b- cells (very early erythroid lineage cells) and BFU-E increased. EPO-dependent tyrosine phosphorylation of Stat 5 also increased, but the EPO receptor (EPO-R) expression remained unchanged in the CD34+/CD45+ cells treated with SCF + HGF. Our present study suggests that stimulation of the HGF/c-met signal is concomitant with induction of c-met protein by SCF. The subsequent enhancement of signal transduction via the activation of Stat 5 from the EPO-R plays a crucial role in the commitment of hematopoietic stem cells into erythroid lineage cells.

Stimulatory effects of hepatocyte growth factor on hemopoiesis of SCF/c-kit system-deficient mice

In this study, we report that W/W mutant mice, which have severe macrocytic anemia caused by a deficit of extracellular domain in c-kit molecules and therefore die perinatally, have hemopoietic stem cells (HSCs) and mature hematolymphoid cells in the bone marrow (BM), thymus, and spleen, although there are significant decreases in cell counts. Moreover, the mitogen-induced proliferative response, mixed lymphocyte reaction, and anti-SRBC plaque formation of spleen cells in W/W mice are similar to those in age-matched +/? littermates and normal mice, suggesting that the SCF/c-kit system is necessary for cell proliferation but not essential for HSCs to differentiate. We next examine the stimulatory effects of hepatocyte growth factor (HGF) on hemopoiesis in W/W mice. HGF has a stimulatory effect on the colony formation (CFU-C) of W/W BM cells when cultured using either a methylcellulose assay (containing cytokines) or a long-term culture (LTC) assay. A similar stimulatory effect of HGF is observed in the other W or SI locus-mutant mice (W/Wv and SI/SId mice), which show less severe anemia than W/W. The numbers of nonadherent cells and cobblestone colonies significantly increase in the LTCs using their BM cells. In addition, in vivo administration of HGF shows a transient increase in the CFU-C counts in BM cells and peripheral blood cells. RBC, WBC, and platelet counts also increased. These results suggest that the SCF/c-kit system is not essential to hemopoiesis but that a compensatory system such as the HGF/c-met system functions in the SCF/c-kit system-deficient mice.

Induction of c-kit molecules on human CD34+/c-kit < low cells: evidence for CD34+/c-kit < low cells as primitive hematopoietic stem cells

c-kit, a receptor for stem cell factor, has been widely accepted as a distinctive marker for hematopoietic stem cells. However, the level of c-kit expression on pluripotent hematopoietic stem cells is still controversial in mice and humans. We purified CD34+/c-kit < low cells (phenotypically c-kit-negative but only detectable at the message level) from human cord blood and examined their maturational steps in relation to the expression of c-kit molecules. When the CD34+/c-kit < low cells were cultured with cytokines (flt 3 ligand, interleukin 6 and interleukin 7) plus immobilized anti-CD34 monoclonal antibody (to crosslink CD34 molecules), c-kit molecules were clearly induced within 24 h. The c-kit expression gradually increased until day 8. When CD34+/c-kit(low) or CD34+/c-kit+ cells that had been induced from CD34+/c-kit < low cells were resorted and recultured using a methylcellulose culture system, they showed the same colony-forming ability as the freshly isolated CD34+/c-kit(low) or CD34+/c-kit+ cells, respectively. Furthermore, CD34+/c-kit < low cells have a similar hematopoietic potential to CD34+/c-kit(low) cells in assays for long-term culture initiating cell and colony-forming unit culture generated from long-term cultures. These findings suggest that CD34+/c-kit < low cells mature into CD34+/c-kit(low) and CD34+/c-kit+ cells, and acquire the reactivity to various humoral hematopoietic stimuli. Moreover, CD34+/c-kit < low cells showed a low level of rhodamine 123 retention, suggesting that CD34+/c-kit < low cells have multidrug resistance. Therefore, the CD34+/c-kit < low cells without colony-forming unit-granulocyte-erythroid-macrophage-megakaryocyte activity are also a pluripotent hematopoietic stem cell population, and the expression of c-kit on c-kit < low cells is the first maturational step of hematopoiesis.

Intrathymically injected hemopoietic stem cells can differentiate into all lineage cells in the thymus: differences between c-kit+ cells and c-kit < low cells

To investigate whether hemopoietic stem cells (HSCs) can differentiate into all lineage cells even in the thymus, we injected two types of HSCs (c-kit+ and c-kit < low cells) obtained from C57BL/6 Ly5.1 mice directly into the thymus of 7.5 Gy-irradiated C57BL/6 Ly5.2 mice. When c-kit < low cells (low density/lineage-/CD71-/major histocompatibility complex class I high/Sca-1+/Thy-1low/ c-kit < low) were injected, donor-derived (Ly5.1) cells were detected on day 8 after intrathymic (i.t.) injection, and the number reached a maximum on day 24 after injection. Granulocytes and macrophages were also detected on day 8 after injection. However, B220+ B cells were observed on day 13. Eighteen days after i.t. injection, the injected lobes showed red color due to the synchronous development of erythroid cells. Histological studies revealed the development not only of erythroid lineage cells but also of megakaryocytes in the thymus. In contrast, when c-kit+ cells were injected, a significant number of donor-derived cells were detected on day 5 after i.t. injection (three days earlier than in the case of c-kit < low cell injection). The differentiation into erythroid lineage cells was also observed six days earlier than when c-kit < low HSCs were injected. These findings suggest that c-kit < low HSCs are more primitive than c-kit+ HSCs, although both can differentiate into all lineage cells after i.t. injection.

Requirement of major histocompatibility complex-compatible microenvironment for spleen colony formation (CFU-S on day 12 but not on day 8)

To clarify major histocompatibility complex (MHC) restriction between hematopoietic stem cells (HSCs) and microenvironments, T cell-depleted bone marrow cells (BMCs) were transplanted into MHC-compatible and MHC-incompatible recipients. A significantly larger number of spleen colony-forming units (CFU-S) on day 12 were noted in MHC-compatible recipients, while only a small number were observed in MHC-incompatible recipients. There was, however, no significant difference in CFU-S counts on day 8 between the two groups. A large number of CFU-S counts on day 12 were also observed in F1 hybrid recipients, as seen in syngeneic recipients. The decrease in CFU-S counts on day 12 in MHC-incompatible recipients was also observed even after in vivo abrogation of T and NK cells. The difference in CFU-S counts on day 12 became more prominent when HSC-enriched cells were transferred. These results suggest that an MHC restriction exists between pluripotent HSCs (P-HSCs) and spleen microenvironments. Furthermore, experiments using B10. A recombinant strains revealed that H-2D and S loci play a crucial role in the MHC restriction. The experiments of serial transplantation suggest that the differentiation and proliferation of P-HSCs are inhibited in MHC-incompatible microenvironments. It is therefore likely that the MHC-compatible microenvironment is essential to the differentiation and proliferation of P-HSCs.

Isolation and identification of hematopoietic stem cell-stimulating substances from Kampo (Japanese herbal) medicine, Juzen-taiho-to

We have previously found that TJ-48 has the capacity to accelerate recovery from hematopoietic injury induced by radiation and the anti-cancer drug mitomycin C (MMC). The effects are found to be due to its stimulation of spleen colony-forming unit (CFU-S) counts on day 14. In the present study, we attempt to isolate and purify the active components in TJ-48 extracts using a new in vitro hematopoietic stem cell (HSC) assay method. n-Hexane extract from TJ-48 shows a significant stimulatory activity. The extract is further fractionated by silica gel chromatography and HPLC in order to identify its active components. 1H-NMR and GC-EI-MS indicate that the active fraction is composed of free fatty acids (oleic acid and linolenic acid). When 27 kinds of free fatty acids (commercially available) are tested using the HSC proliferating assay, oleic acid, elaidic acid, and linolenic acid are found to have potent activity. The administration of oleic acid to MMC-treated mice enhances CFU-S counts on days 8 and 14 to twice the control group. These findings strongly suggest that fatty acids contained in TJ-48 actively promote the proliferation of HSCs. Although many mechanisms seem to be involved in the stimulation of HSC proliferation, we speculate that at least one of the signals is mediated by stromal cells, rather than any direct interaction with the HSCs.

Pluripotent hemopoietic stem cells are c-kit<low

Pluripotent hemopoietic stem cells (P-HSCs) were thought to be c-kit+, but recent reports indicate that they are c-kit(low). In the present report, we provide evidence using Ly5 congenic mice that P-HSCs are c-kit(<low). Lineage-negative (Lin-)/CD71- cells among bone marrow cells (BMCs) from C57BL/6 Ly5.1 mice were separated into major histocompatibility complex class I(high) (class I(high))/c-kit(low) and class I(high)/ c-kit(<low) populations. Each population (500 cells) was transplanted into lethally (9.0 Gy) irradiated C57BL/6 Ly5.2 congenic mice along with Ly5.2 (2 x 10(5)) compromised cells. Donor-derived Ly5.1+ cells were detected 6 months after transplantation in primary recipients reconstituted with either class I(high)/c-kit(low) or class I(high)/c-kit(<low) cells. BMCs (1 x 10(6)) from the primary recipients were further transplanted into secondary recipients (Ly5.2 mice) to assess their long term repopulating activity. Six months after bone marrow transplantation, Ly5.1+ cells in all lineages were detected only in secondary recipients that had been given BMCs from the primary recipients reconstituted with class I(high)/c-kit(<low) cells but not in cells that were class I(high)/c-kit(low). When the BMCs (1 x 10(6)) of these secondary recipients were further transplanted into tertiary recipients, all tertiary recipients that had been given BMCs from the secondary recipients originally reconstituted with Lin-/CD71-/class I(high)/c-kit(low) cells died within 10 days whereas all six tertiary recipients originally reconstituted with Lin-/CD71-/class I(high)/c-kit(<low) cells showed donor (Ly5.1+)-derived cells in their peripheral blood. In the single tertiary recipient that was killed, donor-derived T cells, B cells, macrophages, and granulocytes also were detected in several major hematolymphoid organs. The remaining five mice continue to survive more than 6 months after the tertiary bone marrow transplantation.

Distinct qualitative differences between normal and abnormal hemopoietic stem cells in vivo and in vitro

The transplantation of partially purified hemopoietic stem cells (HSCs) plus the engraftment of bone from autoimmune-prone mice ((NZW x BXSB)F1 (W/BF1) mice) induces autoimmune diseases in major histocompatibility complex (MHC)-incompatible normal C3H/HeN mice. In contrast, W/BF1 mice die of infection or anemia within three weeks due to a failure in hemopoietic reconstitution when the mice receive partially purified HSCs plus bones from normal C3H/HeN mice, although they survive more than a year without showing any symptoms of autoimmune diseases when they receive T cell-depleted bone marrow cells (without bone grafts) from normal mice. This finding suggests that abnormal HSCs can proliferate even in MHC-incompatible microenvironments, while normal HSCs cannot. This is confirmed by spleen colony-forming assays (CFU-S) on day 12, using pluripotent HSCs (P-HSCs). The P-HSCs of old (> 4 mo) W/BF1 mice (after the development of autoimmune diseases) form high CFU-S counts on day 12 even in the allogeneic C3H environment, although the P-HSCs of normal mice form high CFU-S counts only in the MHC-compatible environments. In addition, abnormal P-HSCs of autoimmune-prone mice can proliferate in vitro in collaboration with MHC-incompatible stromal cells, although normal HSCs do so in collaboration with MHC-compatible stromal cells, but not MHC-incompatible stromal cells. These findings indicate that abnormal P-HSCs are more "resilient" than normal P-HSCs.

Changes in markers, receptors and adhesion molecules expressed on murine hemopoietic stem cells after a single injection of 5-fluorouracil

Cytokines play a crucial role in the differentiation and proliferation of hemopoietic cells, and it has recently been found that adhesion molecules play crucial roles not only in differentiation and proliferation, but also in the homing and other functions of hemopoietic cells. We have very recently established a new method for purifying pluripotent hemopoietic stem cells (P-HSC) in mice by injecting 5-fluorouracil (5-FU). The P-HSC were found to be low-density, lineage marker-negative (Lin-), CD71- and major histocompatibility complex class I(high). In the present study, we analyze changes in the expression of various HSC markers (Sca-1 and CD34), receptors (c-kit and interleukin-6 receptor [IL-6R]) and adhesion molecules (very late activation antigen-4 [VLA-4], lymphocyte function-associated antigen-1 [LFA-1], and CD44) after 5-FU injection. The percentage of Sca-1+ cells increases after 5-FU treatment, reaching a maximum on day 3, whereas the percentage of IL-6R+ cells decreases, reaching a minimum on day 3. The percentage of CD34+ cells does not change after 5-FU treatment. The percentages of both c-kit(low) and c-kit(high) cells decrease, reaching a minimum on day 3 after 5-FU treatment, whereas the percentage of c-kit- cells reciprocally increases, reaching a maximum on day 3. However, there is no change in the expression of adhesion molecules (VLA-4, LFA-1 and CD44) on the P-HSC.

Hepatocyte growth factor as a hematopoietic regulator

Hepatocyte growth factor (HGF) was originally isolated as a mitogen for adult hepatocytes, but this cytokine is now regarded as a multi-functional factor. In the present study, we show that the mouse liver in the middle and/or late stage of the fetal life expresses both HGF and c-met (its receptor) messages. HGF and c-met mRNA are coexpressed not only in the adherent layers of fetal liver long-term cultures (FL-LTCs) and adult bone marrow long-term cultures (BM-LTCs), but also in the stromal cell lines MS-5 and PA-6. Addition of human HGF (2 and 20 ng/mL) to the LTCs enhances (1) nonadherent cell counts (ninefold in FL-LTCs and sixfold in BM-LTCs), (2) nonadherent colony-forming unit-in culture (CFU-C) counts (eightfold in FL-LTCs and fivefold in BM-LTC), and (3) cobblestone colony counts. However, HGF slightly inhibits the proliferation of stromal cells. No direct effect of HGF on freshly isolated BM and/or FL cells is found in the CFU-C assay. However, an approximately 1.5-fold synergistic increase in CFU-C counts is noted when the BM or FL cells are cocultured with HGF in the presence of interleukin-3. These findings strongly suggest that HGF plays a crucial role as a hematopoietic regulator in the proliferation and differentiation of hematopoietic progenitors.

Activation of thymic B cells by signals of CD40 molecules plus interleukin-10

We have previously found that thymic B cells, particularly thymic CD5+ B cells, show low responsiveness to the usual B cell stimulants such as lipopolysaccharide or anti-IgM plus interleukin (IL)-4, although they proliferate and produce antibodies after direct interaction with major histocompatibility complex class II-restricted T blasts. These findings raise the possibility that a CD40-CD40 ligand (L) interaction is involved in the activation of thymic B cells. In the present study, we therefore examine this possibility using CD40L-transfected Chinese hamster ovary (CHO) cells or anti-CD40 monoclonal antibody (mAb). When B cells in the spleen and peritoneal cavity were stimulated, they proliferated and produced immunoglobulin (Ig) in the presence of CD40L-CHO cells or anti-CD40 mAb alone. However, another signal delivered by IL-10 in addition to CD40L-CHO cells or anti-CD40 mAb was found to be necessary for thymic B cells to proliferate and secrete Ig. Other interleukins acting on B cells, such as IL-4, IL-5, and IL-6, had no effect on the activation of thymic B cells, which thus have unique characteristics not found in peripheral B cells. This report discusses the physiological significance of IL-10- and CD40-driven signals in the activation of thymic B cells.

Successful bone marrow transplantation by bone grafts in chimeric-resistant combination

It has been shown that the bone marrow cells (BMCs) of DBA/2 mice do not readily take in bone marrow from C57BL/6 mice, even if more than 5 x 10(6) cells are injected. In this paper, we show that such chimerism resistance can be overcome by cografting DBA/2 bones from which the hematopoietic cells have been removed but in which the stromal cells remain. C57BL/6 mice reconstituted with BMCs plus bones of DBA/2 mice survive significantly longer than C57BL/6 mice reconstituted with DBA/2 BMC alone. In the former, not only the hematolymphoid cells but also the stromal cells are replaced by donor-type cells, whereas in the latter, the donor hematolymphoid cells are rejected. These findings indicate that the stromal cells in the engrafted bones play a crucial role in the prevention of graft rejection in bone marrow transplantation.

Autoimmune diseases as stem cell disorders

Using an animal model for insulin-dependent diabetes mellitus (IDDM), the NOD mouse, we have demonstrated that allogeneic bone marrow transplantation (BMT) has a preventative effect on IDDM, and that a combined transplantation of pancreas and bone marrow can be used to treat IDDM. We have also shown that BMT has a curative effect on systemic autoimmune disease in (NZB x NZW) F1, BXSB, and (NZW x BXSB) F1 mice but not in MRL/lpr mice. Since MRL/lpr mice possess abnormal radioresistant hemopoietic stem cells (HSCs), they suffer a relapse 5 months after BMT. Recently, we have found that major histocompatibility complex (MHC)-matched stromal cells in the bone marrow are essential to the support of HSCs in the Go phase. We therefore attempted to treat autoimmune diseases in MRL/lpr mice by the transplantation of stromal cells with HSCs. Transplantation of HSCs with bone to recruit stromal cells was indeed found to have a curative effect on autoimmune diseases in the mice. These results indicate that BMT with bone graft will become a valuable strategy for the treatment of patients with both systemic and organ-specific autoimmune diseases. To prove that autoimmune diseases originate from defects in HSCs, we transferred the HSCs of autoimmune-prone mice to normal mice. BMT or transplantation of stem-cell concentrates induced organ-specific and/or systemic autoimmune diseases in [NOD-->C3H/HeN] and [(NZW x BXSB)F1-->C3H/HeN or C57BL/6J] chimeric mice. These results provide direct evidence that the etiopathogenesis of autoimmune diseases, including both organ-specific and systemic autoimmune diseases, is attributable to defects in the HSCs themselves. We further provide that various intractable diseases such as non-insulin-dependent diabetes mellitus and chronic nephritis (focal glomerulosclerosis) are also organ-specific autoimmune diseases, and that BMT can be used to treat them.

Requirement of donor-derived stromal cells in the bone marrow for successful allogeneic bone marrow transplantation. Complete prevention of recurrence of autoimmune diseases in MRL/MP-Ipr/Ipr mice by transplantation of bone marrow plus bones (stromal cells) from the same donor

MRL/MP-Ipr/Ipr (MRL/Ipr) mice possess radioresistant (9.5 Gy) abnormal stem cells and show a recurrence of autoimmune diseases within 5 mo of conventional allogeneic bone marrow transplantation. We recently have found that the MHC preference exists between hemopoietic stem cells and stromal cells; when bones are engrafted, donor-derived stromal cells present in the engrafted bones can migrate into the recipient bone marrows, which are replaced with both donor-derived stromal cells and hematopoietic cells. Based on these findings, we attempted to prevent the recurrence of autoimmune diseases in MRL/Ipr mice by the transplantation of both bone marrow cells and bone (as a source of stromal cells). MRL/Ipr mice were irradiated (8.5 Gy) and then reconstituted with C57BL/6 bone marrow cells plus bone grafts. The mice survived more than 48 wk after this treatment. Immunohistologic studies revealed that the mice were completely free from both lymphadenopathy and autoimmune diseases such as lupus nephritis and rheumatoid arthritis. Sera from these mice showed normal levels of circulating immune complexes and rheumatoid factors. Normal functions of both T cells and B cells were noted. Abnormal T cells such as Thy-1+B220+ cells present in nontreated MRL/Ipr mice could not be seen in the thus-treated mice. In addition, to our surprise, spleen cells from treated mice showed completely normal in vitro primary anti-SRBC responses. These results indicate that stromal cells in allogeneic bone marrow transplantation play a crucial role not only in the prevention of graft failure but also in the successful cooperation among APCs, T cells, and B cells. Although MRL/Ipr mice are radiosensitive and usually die of interstitial pneumonia or fatty liver due to the side effects of radiation, it should be noted that this strategy allows a reduction in the radiation dose (9.5 Gy-->8.5 Gy), and that these mice can survive more than 48 wk without showing any symptoms of autoimmune diseases.

Requirement of donor-derived stromal cells in the bone marrow for successful allogeneic bone marrow transplantation. Complete prevention of recurrence of autoimmune diseases in MRL/MP-Ipr/Ipr mice by transplantation of bone marrow plus bones (stromal cells) from the same donor

MRL/MP-Ipr/Ipr (MRL/Ipr) mice possess radioresistant (9.5 Gy) abnormal stem cells and show a recurrence of autoimmune diseases within 5 mo of conventional allogeneic bone marrow transplantation. We recently have found that the MHC preference exists between hemopoietic stem cells and stromal cells; when bones are engrafted, donor-derived stromal cells present in the engrafted bones can migrate into the recipient bone marrows, which are replaced with both donor-derived stromal cells and hematopoietic cells. Based on these findings, we attempted to prevent the recurrence of autoimmune diseases in MRL/Ipr mice by the transplantation of both bone marrow cells and bone (as a source of stromal cells). MRL/Ipr mice were irradiated (8.5 Gy) and then reconstituted with C57BL/6 bone marrow cells plus bone grafts. The mice survived more than 48 wk after this treatment. Immunohistologic studies revealed that the mice were completely free from both lymphadenopathy and autoimmune diseases such as lupus nephritis and rheumatoid arthritis. Sera from these mice showed normal levels of circulating immune complexes and rheumatoid factors. Normal functions of both T cells and B cells were noted. Abnormal T cells such as Thy-1+B220+ cells present in nontreated MRL/Ipr mice could not be seen in the thus-treated mice. In addition, to our surprise, spleen cells from treated mice showed completely normal in vitro primary anti-SRBC responses. These results indicate that stromal cells in allogeneic bone marrow transplantation play a crucial role not only in the prevention of graft failure but also in the successful cooperation among APCs, T cells, and B cells. Although MRL/Ipr mice are radiosensitive and usually die of interstitial pneumonia or fatty liver due to the side effects of radiation, it should be noted that this strategy allows a reduction in the radiation dose (9.5 Gy--&gt;8.5 Gy), and that these mice can survive more than 48 wk without showing any symptoms of autoimmune diseases.

Increased cell surface expression of a newly identified heterodimer on activated blastic T cells

A hybridoma (F6C7) was established by fusing NS1 cells with spleen cells of MRL/Mp-+/+ (MRL/+) mice suffering from lpr-GVHD. This F6C7 mAb (IgG2b, kappa) stains a broad spectrum of blood cells at varying intensities in mice and rats. In normal (BALB/c) mice, granulocytes and B cells are highly positive for F6C7-reactive Ag (F6C7-Ag). Thymocytes and peripheral (CD4+ and CD8+) T cells show negative to low intensities. These staining profiles are similar in C57BL/6, AKR/J, C3H/HeJ, and MRL/+ mice. When spleen cells were activated in vitro, a blastic cell population of autoactivated CD4+ and CD8+ T cells showed increased F6C7-Ag expression. Alloactivated CD4+ blastic T cells also showed increased expression of F6C7-Ag, whereas alloactivated CD8+ blastic T cells as well as Con A-activated CD4+ and CD8+ blastic T cells remained at the level of small (nonblastic) cells. These findings suggest that the surface expression of F6C7-Ag is up-regulated in some activation processes of T cells, particularly in autoactivation. Young (2-month-old) MRL/Mp-lpr/lpr (MRL/lpr) mice show staining profiles of F6C7-Ag similar to those of normal mice, except that many more blastic (CD4+ and CD8+) T cells show high F6C7-Ag expression than those of normal mice. A small but significant number of CD4+F6C7-Ag(high) and a much higher number of CD8+F6C7-Ag(high) blastic T cells were observed in the spleen cells of MRL/+ mice suffering from lpr-GVHD. These blastic T cells may exert autoreactivity and participate in the initiation of autoimmune diseases, lymphadenopathy, and lpr-GVHD. Immunoprecipitation and SDS-PAGE revealed that F6C7-Ag is a heterodimer comprised of approximately 78- and 70-kDa molecules without disulfide bonds.

Effects of medicinal plants on hemopoietic cells

It has been found that Juzentaihoto (TJ-48), one of the traditional Japanese kampo (herbal) medicines, improves the general condition of cancer patients receiving chemotherapy and radiation therapy. We analyze how TJ-48 elicits such effect, and show that oral administration of TJ-48 accelerates recovery from hemopoietic injury induced by radiation and the anti-cancer drug mitomycin C. The effects are found to be due to its stimulation of spleen colony-forming units. Based on the present findings, we propose that the administration of TJ-48 should be of benefit to patients receiving chemotherapy, radiation therapy or bone marrow transplantation.

Organ-specific and systemic autoimmune diseases originate from defects in hematopoietic stem cells

Transplantation of bone marrow cells from nonobese diabetic (NOD) mice, a model for type 1 diabetes mellitus, to C3H/HeN mice, which express I-E alpha molecules and have aspartic acid at residue 57 of the I-A beta chain, induced insulitis followed by overt diabetes in the recipient C3H/HeN mice more than 40 weeks after bone marrow transplantation. When cyclosporin A, which perturbs T-cell functions, was injected intraperitoneally into [NOD----C3H/HeN] chimeric mice daily for 1 month, the chimeric mice developed insulitis and overt diabetes within 20 weeks following bone marrow transplantation. Transplantation of bone marrow cells from (NZW x BXSB)F1 mice, which develop lupus nephritis, myocardial infarction, and idiopathic thrombocytopenic purpura, into C3H/HeN or C57BL/6J mice induced in the recipient strains both lupus nephritis and idiopathic thrombocytopenic purpura more than 3 months after transplantation. Transplantation of a stem-cell-enriched population from (NZW x BXSB)F1 mice into normal mice also induced autoimmune disease in the recipients. These results indicate that both systemic autoimmune disease and organ-specific autoimmune disease originate from defects that reside within the stem cells; the thymus and environmental factors such as sex hormones appear to act only as accelerating factors.