Wenhao Cui

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.

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.

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 Gy×2 or 4.0 Gy×2), 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 Gy×2 or within 3 months after the treatment with irradiation of 4.0 Gy×2. 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 Gy×2, 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.

Presence of donor-derived thymic epithelial cells in [B6-->MRL/lpr] mice after allogeneic intra-bone marrow-bone marrow transplantation (IBM-BMT).

We have previously shown that allogeneic intra-bone marrow-bone marrow transplantation (IBM-BMT) can be used to treat autoimmune diseases in MRL/lpr (H-2(K)) mice with replacing not only hematolymphoid cells but also stromal cells by normal C57BL/6 (B6: H-2(b)) mouse cells. In the present study, we examined for existence of donor-derived thymic epithelial cells (TECs) in the host thymus using green fluorescent protein (GFP)-B6 (H-2(b)) mice. In [GFP-B6-->MRL/lpr] chimeric mice, splenocytes and thymocytes were completely replaced by donor-type cells, and levels of serum autoantibodies and proteinuria were significantly - reduced to those levels of normal donors. Interestingly, GFP-expressing TECs - not only medullary TECs, which express mouse thymus stromal (MTS)-10, but also cortical TECs, which express cytokeratin 18 - were found. Also, the number of autoimmune regulator (AIRE) expressing TECs, which regulates tissue-specific antigens to delete autoreactive cells, was reduced in the chimeric mice to that of the donor, whereas the number of forkhead box N1 (FOXN1) expressing TECs, which are crucial in the terminal differentiation of TECs, remained unchanged. These findings suggest that BMCs contain the precursors of functional TECs, and that they can differentiate into TECs, thereby correcting thymic function.

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.

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.

Adult thymus transplantation with allogeneic intra-bone marrow-bone marrow transplantation from same donor induces high thymopoiesis, mild graft-versus-host reaction and strong graft-versus-tumour effects.

Although allogeneic bone marrow transplantation (BMT) plus donor lymphocyte infusion (DLI) is performed for solid tumours to enhance graft‐versus‐tumour (GVT) effects, a graft‐versus‐host reaction (GVHR) is also elicited. We carried out intra‐bone marrow–bone marrow transplantation (IBM‐BMT) plus adult thymus transplantation (ATT) from the same donor to supply alloreactive T cells continually. Normal mice treated with IBM‐BMT + ATT survived for a long time with high donor‐derived thymopoiesis and mild GVHR. The percentage of CD4+ FoxP3+ regulatory T cells in the spleen of the mice treated with IBM‐BMT + ATT was lower than in normal B6 mice or mice treated with IBM‐BMT alone, but higher than in mice treated with IBM‐BMT + DLI; the mice treated with IBM‐BMT + DLI showed severe GVHR. In tumour‐bearing mice, tumour growth was more strongly inhibited by IBM‐BMT + ATT than by IBM‐BMT alone. Mice treated with IBM‐BMT + a high dose of DLI also showed tumour regression comparable to that of mice treated with IBM‐BMT + ATT but died early of GVHD. By contrast, mice treated with IBM‐BMT + a low dose of DLI showed longer survival but less tumour regression than the mice treated with IBM‐BMT + ATT. Histologically, significant numbers of CD8+ T cells were found to have infiltrated the tumour in the mice treated with IBM‐BMT + ATT. The number of terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end‐labelling (TUNEL)‐positive apoptotic tumour cells also significantly increased in the mice treated with IBM‐BMT + ATT. Allogeneic IBM‐BMT + ATT thus can induce high thymopoiesis, preserving strong GVT effects without severe GVHR.

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.

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-2b) mice plus allogeneic BMT from C3H/HeN (H-2k) mice by intra-bone marrow-BMT (IBM-BMT) using congenitally athymic nude (nu/nu) BALB/c (H-2d), 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).

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 ×2, 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.