A case of CD10-negative angioimmunoblastic T cell lymphoma with leukemic change and increased plasma cells mimicking plasma cell leukemia: A case report.

Angioimmunoblastic T cell lymphoma (AITL) is a peripheral T cell lymphoma, known to express CD3 and CD4, and, frequently, also CD10 and c-Maf-1. Hypergammaglobulinemia is not particularly rare in patients with AITL. However, AITL in conjunction with plasmacytosis in the peripheral blood is rare. The current report presents a case of CD10-negative AITL demonstrating leukemic change and plasmacytosis in the peripheral blood mimicking plasma cell leukemia. A 78-year-old male was admitted to hospital due to systemic lymph node enlargement, high serum IgG and IgA, and increased counts of plasmacytoid cells and lymphoid cells with atypical nuclei in the peripheral blood. Initially, plasma cell leukemia was suspected, due to the extreme increase in the number of plasma cells in the peripheral blood. However, the plasma cells did not show clonal expansion on examination by flow cytometry. Based on histological analyses, following a biopsy of an enlarged lymph node, the patient was diagnosed with AITL. This case suggests that when hypergammaglobulinemia and increases in B-lineage cells are observed, AITL should be considered in addition to disorders of B-lineage cells.

Gr-1 Ab administered after bone marrow transplantation plus thymus transplantation suppresses tumor growth by depleting granulocytic myeloid-derived suppressor cells.

It has been shown that allogeneic intra-bone marrow-bone marrow transplantation (IBM-BMT) plus thymus transplantation (TT) is effective in treating recipients with malignant tumors. Although TT increases the percentage of T cells in the early term after BMT, the myeloid-derived suppressor cells (MDSCs) are still the dominant population. We used the Gr-1 Ab to deplete the granulocytic MDSCs (G-MDSCs) in tumor-bearing mice that had received BMT+TT. Two weeks after the BMT, the mice injected with Gr-1 Ab showed smaller tumors than those in the control group. In addition, Gr-1 Ab significantly increased the percentages and numbers of CD4+ and CD8+ T cells, and decreased the percentages and numbers of MDSCs and G-MDSCs. No side effects of the Gr-1 Ab on recipient or donor thymus were observed. These findings indicate that Gr-1 Ab administered after BMT+TT may enhance the effectiveness of tumor suppression.

CD4+ T cell-depleted lymphocyte infusion impairs neither the recovery of recipient thymus nor the development of transplanted thymus.

Thymus transplantation, in conjunction with bone marrow transplantation (BMT), has been attracting attention for the treatment of various diseases. Recently, donor lymphocyte infusion (DLI) has been used as a helpful tool for establishing donor chimerism and preventing a relapse of leukemia/lymphoma. However, the effects of DLI on transplanted and recipient thymuses have not been explored. We therefore performed DLI in the intrabone marrow-BMT + thymus transplantation setting. We have found that DLI leads to derangements in both recipient thymuses and transplanted thymuses; by 2 wk after BMT, we saw a decrease in total cell number, a lower percentage of CD4(+)CD8(+) cells, and the obliteration of the thymic corticomedullary junction. Four weeks later, the thymic impairment became more serious. However, when we depleted the CD4(+) T cells (CD4(-)-DLI), the recipient thymic recovery and transplanted thymic development were significantly restored by the treatment. In addition, there were much greater levels of TNF-α and Fas ligand, and a lower percentage of regulatory T cells in the DLI group than in the CD4(-)-DLI group. These findings indicate that inflammation induced by DLI, especially by CD4(+) T cells, plays a crucial role in the thymic impairment.

Effects of intrabone marrow-bone marrow transplantation plus adult thymus transplantation on survival of mice bearing leukemia.

We recently found that allogeneic intrabone marrow-bone marrow transplantation (IBM-BMT) plus adult thymus transplantation (ATT) from the same donor is effective in mice bearing solid tumors. In the current study, we examined the effects of this strategy on the survival of mice with leukemia. One week after intravenous injection of 1×10(6) leukemic cells (EL-4, H-2(b)) into 8-week-old B6 (H-2(b)) mice, the mice were 8 Gy irradiated and transplanted with 1×10(7) bone marrow cells (BMCs) from 8-week-old BALB/c mice (H-2(d)) by IBM-BMT with or without donor lymphocyte infusion (DLI) or ATT. All the mice without treatment died within 70 days after injection of EL-4. About 40% of those treated with IBM-BMT alone died within 100 days due to tumor relapse. In contrast, those treated with IBM-BMT+DLI or ATT showed the longest survival rate without relapse of leukemia. In addition, the former showed less graft versus host disease (GVHD) than the latter. The mice treated with IBM-BMT+ATT also showed an intermediate percentage of effector memory (EM) and central memory (CM) cells between those treated with BMT alone and those treated with IBM-BMT+DLI. The numbers and functions of T cells increased in those treated with IBM-BMT+ATT with interleukin-2 and interferon-γ production. These results suggest that IBM-BMT+ATT is effective in the treatment of leukemia with strong graft versus leukemia without increased risk of GVHD.

Combination of intra-bone marrow-bone marrow transplantation and subcutaneous donor splenocyte injection diminishes risk of graft-versus-host disease and enhances survival rate.

The combination of allogeneic bone marrow transplantation (allo-BMT) and donor lymphocyte infusion (DLI) is a useful method for establishing donor chimerism and preventing a relapse of leukemia/lymphoma. However, there is a risk of inducing uncontrollable fatal graft-versus-host disease (GVHD). In fact, allo-BMT plus intravenous (IV)-DLI using donor splenocytes induces fatal GVHD in recipient mice. In this study, we examined the effects of the combination of intra-bone marrow (IBM)-BMT and the subcutaneous injection of donor splenocytes (SC-DLI) on the allo-BMT system. Recipient BALB/c mice were conditioned by sublethal irradiation (5 Gy), followed by IBM-BMT plus IV-DLI or SC-DLI in C57BL/6 mice. The IV-DLI group showed better engraftment of donor hemopoietic cells than the control group (without DLI) but showed fatal GVHD. The SC-DLI group, however, showed good reconstitution and mild GVHD. These results suggest that the combination of SC-DLI and IBM-BMT promotes the reconstitution of hemopoiesis and helps reduce the risk of GVHD.

Effects of allogeneic hematopoietic stem cell transplantation plus thymus transplantation on malignant tumors: comparison between fetal, newborn, and adult mice.

We have recently shown that allogeneic intrabone marrow-bone marrow transplantation + adult thymus transplantation (TT) is effective for hosts with malignant tumors. However, since thymic and hematopoietic cell functions differ with age, the most effective age for such intervention needed to be determined. We performed hematopoietic stem cell transplantation (HSCT) using the intrabone marrow method with or without TT from fetal, newborn, and adult B6 mice (H-2(b)) into BALB/c mice (H-2(d)) bearing Meth-A sarcoma (H-2(d)). The mice treated with all types of HSCT + TT showed more pronounced regression and longer survival than those treated with HSCT alone in all age groups. Those treated with HSCT + TT showed increased numbers of CD4(+) and CD8(+) T cells but decreased numbers of Gr-1/Mac-1 myeloid suppressor cells and decreased percentages of FoxP3 cells in CD4(+) T cells, compared with those treated with HSCT alone. In all mice, those treated with fetal liver cell (as fetal HSCs) transplantation + fetal TT or with newborn liver cell (as newborn HSCs) transplantation (NLT) + newborn TT (NTT) showed the most regression, and the latter showed the longest survival. The number of Gr-1/Mac-1 cells was the lowest, whereas the percentage of CD62L(-)CD44(+) effector memory T cells and the production of interferon γ (IFN-γ) were highest in the mice treated with NLT + NTT. These findings indicate that, at any age, HSCT + TT is more effective against cancer than HSCT alone and that NLT + NTT is most effective.

A successful haploidentical bone marrow transplantation method in rabbits: perfusion method plus intra-bone marrow-bone marrow transplantation.

Graft versus host disease (GVHD), rejection, delayed immune reconstitution and infections have been significant hurdles to haploidentical BMT. In order to improve the outcome of the current haploidentical-related BMT, we performed a novel BMT method consisting of the perfusion method (PM) plus intra-bone marrow-bone marrow transplantation (IBM-BMT) in a rabbit model. The percentages of T cells in BMCs harvested by the PM and the conventional aspiration method (AM) were 6% and 14%, respectively (p<0.01). Conversely, the CFU-C counts of BMCs in the PM group were significantly higher than those in the AM group. When the BMCs were transplanted into lethally irradiated offspring rabbits by IBM-BMT, hemopoietic recovery in the PM group was faster than in the AM group. The cumulative incidence of acute GVHD was 25% in the PM group versus 75% in the AM group (p<0.05). In addition, the survival rate was 75% in the PM group versus 33% in the AM group (p<0.05). Thus, the new method is able to provide rapid hemopoiesis, reduce the cumulative incidence of acute GVHD, and achieve a higher survival rate. This novel strategy paves the way for new dimensions in haploidentical BMT.

Prevention of premature ovarian failure and osteoporosis induced by irradiation using allogeneic ovarian/bone marrow transplantation.

BACKGROUND: Two side effects of irradiation are premature ovarian failure (POF) and osteoporosis, both of which are concerns not only clinically, for patients, but also experimentally, for animals. We examine whether bone marrow transplantation (BMT) can correct the POF induced by radiation and also address whether allogeneic ovarian transplantation (OT) can modulate the adverse effects of radiotherapy. METHODS: Eight-week-old female C57BL/6 mice were lethally irradiated with 6 Gy x2, and then injected with allogeneic bone marrow cells into their bone marrow cavity using our previously described intrabone marrow (IBM)-BMT technique. Allogeneic ovaries were simultaneously transplanted under the renal capsules of the mice. RESULTS: Three months after the transplantation, we noted that hematopoietic and lymphoid cells had been successfully reconstituted. The ovaries transplanted under the renal capsules demonstrated signs of development with a large number of differentiating follicles at different stages of development. Importantly, the total bone mineral density of the tibia in the "IBM-BMT+OT" (BMT/OT) group remained normal. However, the reproductive function of the recipient mice was not restored, despite the presence of many immature oocytes in the host ovaries in the BMT/OT group. In the BMT group, no oocytes were found in the host ovaries. CONCLUSIONS: These findings suggest that IBM-BMT with ovarian allografts can be advantageous for young women with POF and osteopenia or osteoporosis that is due to chemotherapy and radiotherapy for malignant diseases.

Mouse mesenchymal stem cells can support human hematopoiesis both in vitro and in vivo: the crucial role of neural cell adhesion molecule.

BACKGROUND: We previously established a mesenchymal stem cell line (FMS/PA6-P) from the bone marrow adherent cells of fetal mice. The cell line expresses a higher level of neural cell adhesion molecule and shows greater hematopoiesis-supporting capacity in mice than other murine stromal cell lines. DESIGN AND METHODS: Since there is 94% homology between human and murine neural cell adhesion molecule, we examined whether FMS/PA6-P cells support human hematopoiesis and whether neural cell adhesion molecules expressed on FMS/PA6-P cells contribute greatly to the human hematopoiesis-supporting ability of the cell line. RESULTS: When lineage-negative cord blood mononuclear cells were co-cultured on the FMS/PA6-P cells, a significantly greater hematopoietic stem cell-enriched population (CD34(+)CD38(-) cells) was obtained than in the culture without the FMS/PA6-P cells. Moreover, when lineage-negative cord blood mononuclear cells were cultured on FMS/PA6-P cells and transplanted into SCID mice, a significantly larger proportion of human CD45(+) cells and CD34(+)CD38(-) cells were detected in the bone marrow of SCID mice than in the bone marrow of SCID mice that had received lineage-negative cord blood mononuclear cells cultured without FMS/PA6-P cells. Furthermore, we found that direct cell-to-cell contact between the lineage-negative cord blood mononuclear cells and the FMS/PA6-P cells was essential for the maximum expansion of the mononuclear cells. The addition of anti-mouse neural cell adhesion molecule antibody to the culture significantly inhibited their contact and the proliferation of lineage-negative cord blood mononuclear cells. CONCLUSIONS: These findings suggest that neural cell adhesion molecules expressed on FMS/PA6-P cells play a crucial role in the human hematopoiesis-supporting ability of the cell line.

Facilitation of hematopoietic recovery by bone grafts with intra-bone marrow-bone marrow transplantation.

We have previously shown that T cells can acquire donor-type major histocompatibility complex (MHC) restriction and can interact with both donor-type antigen-presenting cells (APCs) and B cells, when adult donor bones are co-grafted with intravenous (IV) injection of bone marrow cells (BMCs) in order to supply donor bone marrow (BM) stromal cells. We have also found that the direct injection of donor BMCs into recipient BM (intra-bone marrow-bone marrow transplantation: IBM-BMT) produces more rapid reconstitution (including T-cell functions) and higher survival rates than IV injection (IV-BMT) even in chimerism-resistant combinations. In the present study, we show that the co-administration of bones from suckling (2-3 days old) donor mice is also effective in the IBM-BMT system. Even when a relatively low number of BMCs were injected into adult (more than 15 weeks old) mice, complete reconstitution was achieved in the mice that had received IBM-BMT+bone grafts, but not in the mice that had received IBM-BMT alone. Most BM and splenic adherent cells obtained from the recipients that had received IBM-BMT+bone grafts were reconstituted by donor-type cells. Both T-cell proliferation and plaque-forming cell assays indicated that the T cells of such mice showed donor-type MHC restriction. Moreover, the analyses of thymic sections using confocal microscopy revealed that donor BM stromal cells had migrated into the thymus. Thus, the co-administration of donor bones has great advantages for allogeneic BMT in adult mice.

Analysis of tolerance induction using triple chimeric mice: major histocompatibility complex-disparate thymus, hemopoietic cells, and microenvironment.

BACKGROUND: Although bone marrow transplantation (BMT) has become a valuable strategy for the treatment of various intractable diseases in recent years, success rates remain low in elderly patients because of low thymic function. We have previously shown that fetal thymus transplantation (TT) with BMT is effective for elderly recipients in mice. METHODS: We performed fully major histocompatibility complex (MHC)-mismatched fetal TT from B6 (H-2) mice plus allogeneic BMT from C3H/HeN (H-2) mice by intra-bone marrow-BMT (IBM-BMT) using congenitally athymic nude (nu/nu) BALB/c (H-2), or BALB/c adult-thymectomized recipients to obtain triple chimeras. We next carried out the IBM-BMT+TT using senescence-accelerated mouse P1 strain (SAMP1) to examine whether this method would be applicable to aging mice. RESULTS: Triple chimeric mice survived for a long period with sufficient T-cell functions comparable to the mice treated with BMT plus MHC-matched TT, whereas those without TT survived for a short period with insufficient T-cell reconstitution. Almost all the hematolymphoid cells were derived from donor bone marrow cells. Interestingly, they showed tolerance to all three types of MHC determinants with donor-derived thymic dendritic cells in TT. Triple chimeric SAMP1 also survived for long periods with T-cell functions restored in contrast to non-TT SAMP1 recipients. CONCLUSION: These findings suggest that third party combined TT with allogeneic IBM-BMT may be more advantageous for elderly recipients with low thymic function, than IBM-BMT alone (without TT).

Long-term donor-specific tolerance in rat cardiac allografts by intrabone marrow injection of donor bone marrow cells.

BACKGROUND: Donor-specific central tolerance in cardiac allograft can be induced by hematopoietic chimerism via conventional intravenous bone marrow transplantation (IV-BMT). However, there are problems with IV-BMT, such as the risk of graft failure and of the toxicity from conditioning regimens. METHODS: A new method for heart transplantation is presented. This method consists of administration of fludarabine phosphate (50 mg/kg) and fractionated low-dose irradiation (3.5 Gyx2 or 4.0 Gyx2), followed by intrabone marrow injection of whole bone marrow cells (IBM-BMT) plus heterotopic heart transplantation. RESULTS: Cardiac allografts with IBM-BMT were accepted and survived long-term (>10 months) showing neither acute rejection nor chronic rejection including cardiac allograft vasculopathy by such conditioning regimens. In contrast, cardiac allografts with conventional IV-BMT were rejected within 1 month after the treatment with irradiation of 3.5 Gyx2 or within 3 months after the treatment with irradiation of 4.0 Gyx2. Macrochimerism (>70%) was favorably established and stably maintained by IBM-BMT but not IV-BMT. Low levels of transient mixed chimerism (<7%) were induced by IV-BMT with fludarabine plus 4.0 Gyx2, but the chimerism was lost within 1 month after the treatment. CONCLUSIONS: These findings indicate that IBM-BMT is a feasible strategy for the induction of persistent donor-specific tolerance, enables the use of reduced radiation doses as conditioning regimens, and obviates the need for immunosuppressants.

Prevention of osteoporosis and hypogonadism by allogeneic ovarian transplantation in conjunction with intra-bone marrow-bone marrow transplantation.

BACKGROUND: We investigated the effects of ovarian allograft in conjunction with intra-bone marrow-bone marrow transplantation (IBM-BMT) on estrogen deficiency in mice. METHODS: Female C57BL/6 mice underwent ovariectomy (OvX). After 3 months, the mice were irradiated at 9.5 Gy, and the bone marrow cells (BMCs) of female BALB/c mice (8 weeks old) were then injected into the bone cavity of the B6 mice. Simultaneously, allogeneic ovaries from BALB/c mice were transplanted under the renal capsules of the B6 mice. RESULTS: Three months after the transplantation, the hematolymphoid cells were found to be completely reconstituted with donor-derived cells. The transplanted ovary tissues under the renal capsules were accepted without using immunosuppressants; there were a large number of growing follicles at different stages of development. Atrophic endometrium and its glands were also recovered by ovarian transplantation (OT). The transplanted allogeneic ovaries secreted estrogen at normal levels. Furthermore, bone loss was prevented to a certain extent. CONCLUSIONS: These findings suggest that IBM-BMT+OT will become a valuable strategy for young women with malignant tumors to prevent premature senescence, including hypogonadism and osteoporosis, after radiochemotherapy.

Extensive studies on perfusion method plus intra-bone marrow-bone marrow transplantation using cynomolgus monkeys.

The collection of bone marrow cells (BMCs) using a perfusion method has been advantageous not only because of the low contamination of BMCs with T cells from the peripheral blood but also the enrichment of stromal cells, which support hemopoiesis. Before the application of this new method to humans, its safety needed to be confirmed using cynomolgus monkeys. We therefore performed the perfusion method on more than 100 cynomolgus monkeys using the long bones (such as the humerus and femur) and also the iliac bones (for human application); in the more than 150 trials to date, there have been no accidental deaths. Furthermore, the technical safety of a new method for the intra-bone marrow (IBM) injection of BMCs (termed IBM-bone marrow transplantation) has also been confirmed using 30 monkeys. Disclosure of potential conflicts of interest is found at the end of this article.

Analyses of very early hemopoietic regeneration after bone marrow transplantation: comparison of intravenous and intrabone marrow routes.

In bone marrow transplantation (BMT), bone marrow cells (BMCs) have traditionally been injected intravenously. However, remarkable advantages of BMT via the intra-bone-marrow (IBM) route (IBM-BMT) over the intravenous route (IV-BMT) have been recently documented by several laboratories. To clarify the mechanisms underlying these advantages, we analyzed the kinetics of hemopoietic regeneration after IBM-BMT or IV-BMT in normal strains of mice. At the site of the direct injection of BMCs, significantly higher numbers of donor-derived cells in total and of c-kit(+) cells were observed at 2 through 6 days after IBM-BMT. In parallel, significantly higher numbers of colony-forming units in spleen were obtained from the site of BMC injection. During this early period, higher accumulations of both hemopoietic cells and stromal cells were observed at the site of BMC injection by the IBM-BMT route. The production of chemotactic factors, which can promote the migration of a BM stromal cell line, was observed in BMCs obtained from irradiated mice as early as 4 hours after irradiation, and the production lasted for at least 4 days. In contrast, sera collected from the irradiated mice showed no chemotactic activity, indicating that donor BM stromal cells that entered systemic circulation cannot home effectively into recipient bone cavity. These results strongly suggest that the concomitant regeneration of microenvironmental and hemopoietic compartments in the marrow (direct interaction between them at the site of injection) contributes to the advantages of IBM-BMT over IV-BMT. Disclosure of potential conflicts of interest is found at the end of this article.

An innovative approach to bone marrow collection and transplantation in a patient with beta-thalassemia major: marrow collection using a perfusion method followed by intra-bone marrow injection of collected bone marrow cells.

Using small animals (mice and rats) and monkeys, we have found that the combination of bone marrow collection using the perfusion method (PM) and intra-bone marrow-bone marrow transplantation (IBM-BMT) of the collected cells is safe and effective in treating various intractable diseases. Based on these findings, we attempted to apply this method to humans. We report here the first case of a patient (6 years old) with beta-thalassemia major who underwent allogeneic BMT using this new PM + IBM-BMT method. The white blood cell counts of the patient gradually increased to more than 1500/microL by day 47 and continued to increase, reaching the highest level (8600/microL) on day +55. Fluorescence in situ hybridization data on day +33 showed that 98% of the peripheral blood cells were from the donor. Notably, there were no symptoms of graft-versus-host disease (GvHD). However, on day +56, the patient regrettably died of asphyxia resulting from sticky sputum. There was no evidence of infection (in the lung or liver) or GvHD (in the skin) by necropsy. We hope that this case report will help make our new strategies more readily available for the treatment of patients with various intractable diseases.

Lin(-)CD34(-) bone marrow cells from adult mice can differentiate into neural-like cells.

Numerous studies have shown that some populations of bone marrow cells (BMCs) have the capacity to differentiate into neural cells, which is useful for repairing brain lesions. In this paper, we analyze neural differentiation features of lineage-negative/CD34-negative (Lin(-)CD34(-)) cells in the bone marrow of adult mice. The population of Lin(-)CD34(-) in BMCs was isolated by magnetic bead sorting and fluorescence-activated cell sorter (FACS) using specific lineage (CD4, CD8a, CD11b, CD45R, Gr-1 and TER-119) antibodies and CD34 antibody. First, we cultured Lin(-)CD34(-) BMCs in the presence of RNIF: vitamin A derivative retinoic acid (RA) and neural-inducing factors (platelet-derived growth factor BB (PDGF-BB), epidermal growth factor (EGF) and fibroblast growth factor-basic (FGF-b)). Analyses of RT-PCR and immunocytochemistry indicated that RNIF-treated Lin(-)CD34(-) BMCs expressed neural phenotypes as well as neurogenic transcription factors. When we implanted the Lin(-)CD34(-) BMCs isolated from enhanced green fluorescent protein (eGFP) transgenic mice into the subventricular zone (SVZ) of postnatal mice, eGFP-positive cells survived 3 weeks after the injection in the various brain regions, some of which expressed the neural phenotypes. Our data suggest that certain subsets in the CD34(-) populations of adult bone marrow could have the capacity to differentiate into neural cells in a suitable environment.

Characterization of mesenchymal stem cells isolated from mouse fetal bone marrow.

Mesenchymal stem cells (MSCs) are defined as cells that can differentiate into multiple mesenchymal lineage cells. MSCs have some features (surface molecules and cytokine production, etc.) common to so-called traditional bone marrow (BM) stromal cells, which have the capacity to support hemopoiesis. In the present study, we isolated murine MSCs (mMSCs) from the fetal BM using an anti-PA6 monoclonal antibody (mAb) that is specific for bone marrow stromal cells. The mMSCs, called FMS/PA6-P cells, are adherent, fibroblastic, and extensively expanded and have the ability to differentiate not only into osteoblasts and adipocytes but also into vascular endothelial cells. The FMS/PA6-P cells produce a broad spectrum of cytokines and growth factors closely related to hemopoiesis and show good hemopoiesis-supporting capacity both in vivo and in vitro, suggesting that they are a component of the hemopoietic stem cell niche in vivo. Interestingly, although the FMS/PA6-P cells express a high level of the PA6 molecule, which is reactive with anti-PA6 mAb, they gradually lose their ability to express this molecule during the course of differentiation into osteoblasts and adipocytes, indicating that the PA6 molecule might serve as a novel marker of mMSCs.

Neural cell adhesion molecule contributes to hemopoiesis-supporting capacity of stromal cell lines.

To clarify mechanisms underlying cell-to-cell interactions between hemopoietic stem cells (HSCs) and stromal cells, we established a stromal cell line (FMS/PA6-P) from day-16 fetal bone marrow (BM) adherent cells using an anti-PA6 monoclonal antibody (mAb) specific for BM stromal cells. Importantly, this FMS/PA6-P cell line, showing homogenous fibroblastic morphology, is absent from hematolymphoid and endothelial lineage markers and maintains a high level of expression of PA6 molecule, recognized by the anti-PA6 mAb, for approximately 20 passages. Further, the cell line expressing a high level of PA6 molecule has a better hemopoiesis-supporting capacity in vitro than other stromal cell lines such as PA6 and MS-5. In fact, the PA6 molecule is closely related to the hemopoiesis-supporting capacity of the stromal cells because the proliferation of HSCs was suppressed to a great extent by the anti-PA6 mAb. Affinity chromatography and mass peptide fingerprinting revealed that the protein reacting with the anti-PA6 mAb is neural cell adhesion molecule (NCAM). The frequencies of long-term cobblestone area-forming cells and long-term culture-initiating cells were significantly suppressed by repression of NCAM in the FMS/PA6-P cells using NCAM small interfering RNA. Our findings clearly indicate that NCAM functions on the maintenance of HSCs.

Simultaneous injection of bone marrow cells and stromal cells into bone marrow accelerates hematopoiesis in vivo.

We have previously demonstrated that stromal cells can support the proliferation and differentiation of hematopoietic cells in vitro and in vivo and that a major histocompatibility complex restriction exists between hematopoietic stem cells and stromal cells. We have also found that intra-bone marrow (IBM) injection of allogeneic bone marrow cells (BMCs) leads to more rapid reconstitution of hematopoietic cells than intravenous injection. In the present study, we examine the effect of simultaneous injection of stromal cells and BMCs into the same bone marrow on the recovery of donor hematopoietic cells and demonstrate that simultaneous IBM injection of BMCs plus stromal cells is more effective in reconstituting recipients with donor hematopoietic cells than intravenous injection of BMCs plus stromal cells or IBM injection of BMCs alone.