Nonmyeloablative allogeneic hematopoietic stem cell transplant using mismatched/haploidentical donors: a review

Tolerance induction between two different strains of parental mice prevents graft-versus-host disease in haploidentical hematopoietic stem cell transplantation to F1 mice

Haploidentical hematopoietic stem cell transplantation (Haplo-HSCT) has been employed worldwide in recent years and led to favorable outcome in a group of patients who do not have human leukocyte antigen (HLA)-matched donors. However, the high incidence of severe graft-versus-host disease (GVHD) is a major problem for Haplo-HSCT. In the current study, we performed a proof of concept mouse study to test whether induction of allogeneic tolerance between two different parental strains was able to attenuate GVHD in Haplo-HSCT to the F1 mice. We induced alloantigen tolerance in C3H mice (H-2k) using ultraviolet B (UVB) irradiated immature dendritic cells (iDCs) derived from the cultures of Balb/c bone marrow cells. Then, we performed Haplo-HSCT using tolerant C3H mice as donors to F1 mice (C3H×Balb/c). The results demonstrated that this approach markedly reduced GVHD-associated death and significantly prolonged the survival of recipient mice in contrast to the groups with donors (C3H mice) that received infusion of non-UVB-irradiated DCs. Further studies showed that there were enhanced Tregs in the tolerant mice and alloantigen-specific T cell response was skewed to more IL-10-producing T cells, suggesting that these regulatory T cells might have contributed to the attenuation of GVHD. This study suggests that it is a feasible approach to preventing GVHD in Haplo-HSCT in children by pre-induction of alloantigen tolerance between the two parents. This concept may also lead to more opportunities in cell-based immunotherapy for GVHD post Haplo-HSCT.

Assessing hematopoietic (stem-) cell behavior during regenerative pressure

Hematopoiesis is a complex and strongly regulated process. In case of regenerative pressure, efficient recovery of blood cell counts is crucial for survival of an individual. We propose a quantitative mathematical model of white blood cell formation based on the following cell parameters: (1) proliferation rate, (2) self-renewal, and (3) cell death. Simulating this model we assess the change of these parameters under regenerative pressure. The proposed model allows to quantitatively describe the impact of these cell parameters on engraftment time after stem cell transplantation. Results indicate that enhanced self-renewal during the posttransplant period is crucial for efficient regeneration of blood cell counts while constant or reduced self-renewal leads to delayed recovery or graft failure. Increased cell death in the posttransplant period has a similar impact. In contrast, reduced proliferation or pre-homing cell death causes only mild delays in blood cell recovery which can be compensated sufficiently by increasing the dose of transplanted cells.

Human umbilical cord blood-derived stromal cells: A new source of stromal cells in hematopoietic stem cell transplantation

The hematopoietic inductive microenvironment (HIM), which is composed of stromal cells, extracellular matrix and cytokines, plays a vital role in hematopoietic stem cell transplantation (HSCT). Bone marrow stromal cells (BMSCs), as the main component of HIM, have been well studied. However, the highly invasive procedure of bone marrow (BM) collection limits the clinical application of BMSCs. Human umbilical cord blood-derived stromal cells (hUCBDSCs) isolated and cultured in our laboratory have attracted much attention for their ease collection and low probability of pathophoresis. Previous research demonstrated that hUCBDSCs have numerous functions that are identical to those of BMSCs, for example, hUCBDSCs can support the growth of hematopoietic stem and progenitor cells, especially during the expansion of megakaryocyte colony-forming units (CFU-Mk), promote engraftment after hematopoietic stem cell transplantation (HSCT), exert immunosuppressive effects on xenogenic T cells in vitro and suppress acute graft-versus-host disease (aGVHD) in vivo. Although hUCBDSCs, as new stromal cells, have not been used in clinical practice, they have great practical significance because of their superiority in hematopoiesis and the regulation of immunity.

Treatment of hematological malignancies with nonmyeloablative, HLA-haploidentical bone marrow transplantation and high dose, post-transplantation cyclophosphamide

Hematopoietic stem cell transplantation provides the only potential curative option in many patients with hematological malignancies. Finding a suitably matched donor in a timely manner is often difficult. However, most patients have a partially HLA-mismatched (HLA-haploidentical) first-degree relative readily available. Historically, HLA-haploidentical bone marrow transplantation (BMT) has been considered extremely high risk due to high rates of life-threatening graft-versus-host disease (GVHD) and non-relapse mortality (NRM). Modifications of the stem cell graft, such as T-cell depletion, have resulted in poor rates of engraftment. We have recently completed a phase II clinical trial of nonmyeloablative HLA-haploidentical hematopoietic BMT followed by post-transplantation high-cyclophosphamide. High-dose cyclophosphamide has been shown to create immunogenic tolerance by specifically killing activated mature T-cells. As a result, alloreactive T-cells in the donor graft are selectively destroyed thereby decreasing the incidence of severe GVHD. As well, host-versus-graft reactive T-cells are also selectively eliminated thereby increasing rates of engraftment. Among 210 patients with hematological malignancies receiving nonmyeloablative, HLA-haploidentical BMT with post-transplantation cyclophosphamide, the rate of sustained donor cell engraftment has been 87%. The cumulative incidence of grade 2-4 acute GVHD is 27%, grade 3-4 acute GVHD is 5% and chronic GVHD is 15%. Interestingly, increasing HLA disparity between donor and recipient was not associated with increasing incidence of GVHD or decreased event-free survival. Nonmyeloablative haploidentical stem cell transplantation with post-transplantation cyclophosphamide seems to be a promising, potentially curative, option for patients with hematological malignancies who either lack an HLA-matched related or unrelated donor, or in whom a myeloablative preparative regimen is contraindicated due to significant co-morbidities or history of extensive pre-treatment.

Human umbilical cord blood-derived stromal cells: a new resource in hematopoietic reconstitution in mouse haploidentical transplantation

OBJECTIVE

Our previous study showed that human umbilical cord blood-derived stromal cells (hUcBdSCs) expanded CD34(+) cells in vitro. This study further explored the role of hUcBdSCs in vivo.

METHODS

The cultured hUcBdSCs were infused into transplanted haploidentical mice to observe hematopoietic recovery and complications.

RESULTS

The engraftment was faster in transplantation with hUcBdSCs than without hUcBdSCs. The numbers of fibroblast (CFU-F), granulocyte/monocyte (CFU-GM), erythrocytic (CFU-E), and megakaryocyte (CFU-Mg) colony-forming units were greater among mice transplanted with hUcBdSCs than without hUcBdSCs. The scoring of graft-versus-host disease was significantly lower in mice that had been subjected to transplantation with hUcBdSCs than without hUcBdSCs. The infused hUcBdSCs migrated to the bone marrow of the recipients.

CONCLUSIONS

These data indicated that hUcBdSCs improved hematopoietic reconstitution in haploidentical transplantation in mice.

Human umbilical cord blood-derived stromal cells, a new resource in the suppression of acute graft-versus-host disease in haploidentical stem cell transplantation in sublethally irradiated mice

Human umbilical cord blood-derived stromal cells (hUCBDSCs), a novel population isolated from CD34(+) cells by our laboratory, exerted an immunosuppressive effect on xenogenic T cells. This study aimed to investigate whether hUCBDSCs play a critical role in the suppression of acute graft-versus-host disease (aGVHD). The hUCBDSCs were co-cultured with splenocytes (SPCs) of donor C57BL/6 mice. The aGVHD in the recipient (B6×BALB/c) F1 mice was induced by the infusion of bone marrow cells and SPCs from donor mice following sublethal irradiation. The shift in vivo for hUCBDSCs was detected. The proliferation and cell cycle of SPCs were tested by cell counting kit-8 and flow cytometry, respectively. The expression of CD49b natural killer (NK) cells and CD3 T cells was detected by flow cytometry in co-culture and post-transplantation. IL-4, and IFN-γ were detected by ELISA in the serum of co-culture and post-transplantation. The survival time, body weight, clinical score, and histopathological score were recorded for mice post-transplantation. The hUCBDSCs promoted the proliferation of SPCs and significantly increased the ratio of the S and G(2)/M phase (p < 0.05). The hUCBDSCs significantly increased the expression of CD49b NK cells and IL-4 protein and decreased the expression of CD3 T cells and IFN-γ protein both in vitro and in vivo. The survival time of mice with co-transplantation of hUCBDSCs was significantly prolonged, and decreased clinical and histopathological scores were also observed. The hUCBDSCs were continually detected in the target organs of GVHD. These results suggest that hUCBDSCs possess the capability of suppressing aGVHD, possibly via their influence on CD3 T cells, NK cells, and cytokines.

The outcomes of family haploidentical hematopoietic stem cell transplantation in hematologic malignancies are not associated with patient age

Haploidentical hematopoietic cell transplantation (HCT) has been used to treat hematologic malignancies, but it is unknown whether the procedure is more effective in adults or children. To address this question, we analyzed patients aged 1 to 65 years old receiving myeloablative conditioning regimens followed by family 2 to 3 antigen HLA-mismatched HCT and reported to the Center for International Blood and Marrow Transplant Research (CIBMTR; n = 137) or performed in Dao-Pei Hospital in China, China (n = 181). The Dao-Pei cohort had more acute and chronic graft-versus-host disease (GVHD), less relapse, lower transplant-related mortality (TRM), and better leukemia-free survival (LFS) than the CIBMTR cohort. Overall survival (OS) and outcomes were similar between adults and children. In the CIBMTR cohort receiving ex vivo T cell depletion (TCD), adults had higher TRM (relative risk [RR] 2.71, 95% confidence interval [CI] 1.29-5.69, P = .008) and lower OS (RR 1.75, 95% CI 1.08-2.84, P = .023) than children. In the CIBMTR subset that did not receive ex vivo TCD, relapse was lower in adults compared to children (RR 0.24, 95% CI 0.07-0.80, P = .020), but TRM, LFS, and OS were similar. We conclude that outcomes in adults and children are similar overall, although children have better survival than adults if ex vivo TCD is used.

Granulocyte-colony stimulating factor-mobilized mesenchymal stem cells: A new resource for rapid engraftment in hematopoietic stem cell transplantation

The bone marrow (BM) microenvironment plays an important role in regulating hematopoietic stem cell self-renewal and differentiation. Mesenchymal stem cells (MSCs), which constitute approximately 0.01-0.0001% of the nucleated cells in the adult human BM, are an important component of the BM stroma that supports hematopoiesis. The BM stroma system is often damaged in patients who have undergone high-dose chemotherapy and/or radiation treatment. Thus, the BM stroma should be reconstructed during hematopoietic stem cell transplantation (HSCT). Granulocyte-colony stimulating factor (G-CSF) is a potent hematopoietic cytokine that regulates neutrophil generation within the BM by modulating the mobility, proliferation and maturation of neutrophil progenitor cells. The results from our study here show that G-CSF markedly increased the number of donor-derived MSCs in the BM and the peripheral blood. Engraftment was faster in HSCTs with bone marrow that was treated with G-CSF (G-BM) or with G-BM- and G-CSF-treated peripheral blood stem cells compared to stead-state bone marrow (SS-BM). Based on these findings, we hypothesize that G-CSF-mobilized treatment of MSCs may accelerate engraftment in HSCT.

Cost and outcome in stem cell collections in HLA-haplo identical/mismatched related transplantation with combined granulocyte-colony stimulating factor-mobilized blood and bone marrow for patients with hematologic malignancies

Unmanipulated HLA-haplo identical/mismatched related transplantation with combined granulocyte-colony stimulating factor-mobilized peripheral blood stem cells (G-PBSCs) and granulocyte-colony stimulating factor-mobilized bone marrow (G-BM) has been developed as an alternative transplantation strategy for patients without an HLA-matched related or unrelated donor. In this transplantation setting, the cost and outcome of stem cell collections have not been defined completely. The aim of this study was to compare the cost and outcome of stem cell collection in HLA-haplo identical/mismatched related transplantation with combined G-PBSCs and G-BM to the HLA-identical/matched transplantation with G-PBSCs alone for patients with hematologic malignancies. Hundred and fifty-two healthy donors received twice-daily granulocyte-colony stimulating factor (G-CSF) subcutaneously for 5 days. The PBSCs were collected on day 4 and 5 of G-CSF treatment for HLA-identical/matched transplantation from unrelated/related donors. The PBSC collections and BM harvests was performed on day 4 and 5 of G-CSF treatment for HLA-haplo identical/mismatched related transplantation from related donors, respectively. There was no difference in the major characteristics between groups. More stem cells were harvested in HLA-haplo identical/mismatched related donors than that of HLA-identical/matched donors and a lower cost was seen in the former. The HLA-haplo identical/mismatched related transplantation with combined G-PBSCs and G-BM was a feasible approach with high cell harvest and low cost of stem cell collection for patients with hematologic malignancies.

Stem cell collection in unmanipulated HLA-haploidentical/mismatched related transplantation with combined granulocyte-colony stimulating factor-mobilised blood and bone marrow for patients with haematologic malignancies: the impact of donor characteristics and procedural settings

Unmanipulated haploidentical/mismatched related transplantation with combined granulocyte-colony stimulating factor-mobilised peripheral blood stem cells (G-PBSCs) and granulocyte-colony stimulating factor-mobilised bone marrow (G-BM) has been developed as an alternative transplantation strategy for patients with haematologic malignancies. However, little information is available about the factors predicting the outcome of peripheral blood stem cell (PBSC) collection and bone marrow (BM) harvest in this transplantation. The effects of donor characteristics and procedure factors on CD34⁺ cell yield were investigated. A total of 104 related healthy donors received granulocyte-colony stimulating factor (G-CSF) followed by PBSC collection and BM harvest. Male donors had significantly higher yields compared with female donors. In multiple regression analysis for peripheral blood collection, age and flow rate were negatively correlated with cell yield, whereas body mass index, pre-aphaeresis white blood cell (WBC) and circulating immature cell (CIC) counts were positively correlated with cell yields. For BM harvest, age was negatively correlated with cell yields, whereas pre-BM collection CIC counts were positively correlated with cell yield. All donors achieved the final product of ≥6 ×10⁶ kg⁻¹ recipient body weight. This transplantation strategy has been shown to be a feasible approach with acceptable outcomes in stem cell collection for patients who received HLA-haploidentical/mismatched transplantation with combined G-PBSCs and G-BM. In donors with multiple high-risk characteristics for poor aphaeresis CD34⁺ cell yield, BM was an alternative source.

Screening of antimicrobial agents for in vitro radiation protection and mitigation capacity, including those used in supportive care regimens for bone marrow transplant recipients

Antibiotic and antifungal agents used in supportive care regimens for bone marrow transplantation recipients contribute to a significant dose-modifying effect of otherwise lethal total body irradiation. To determine whether drugs used in supportive care and other commonly used antibiotics such as tetracycline function as radiation protectors or damage mitigators in vitro, 13 drugs were tested for radiation protection and radiation damage mitigation of 32D cl 3 hematopoietic progenitor cells in clonagenic survival curves in vitro. Antibiotic/Antifungal agents including cilastatin, amikacin, ceftazidine, vancomycin, tetracycline, doxycycline, ciprofloxacin, metronidazole, methacycline, minocycline, meclocycline, oxytetracycline and rolitetracycline were added in 1, 10, or 100 micromolar concentrations to murine interleukin-3-dependent hematopoietic progenitor cell line 32D cl 3 cells either before or after irradiation of 0 to 8 Gy. Control irradiated 32D cl 3 cells showed radiosensitivity comparable to freshly explanted mouse marrow hematopoietic progenitor cells (D(0) 1.1+/-0.1 Gy, N 1.5+/-0.4). Positive control GS-nitroxide JP4-039 (known radiation mitigator) treated 32D cl 3 cells were radioresistant (D(0) 1.2+/-0.1, N 5.8+/-2.4 (p=0.009)). Of the 13 drugs tested, tetracycline was found to be a significant radiation mitigator (D(0) 0.9+/-0.1, N 13.9+/-0.4 (p=0.0027)). Thus, the radiation dose-modifying effect of some antibiotics, but not those currently used in the supportive care (antibiotic/antifungal regimens) for marrow transplant patients, may act as radiation damage mitigators for hematopoietic cells as well as decreasing the growth and inflammatory response to microbial pathogens.

The immunopathology of thymic GVHD

The clinical success of allogeneic hematopoietic stem cell transplantation (HSCT) depends on the appropriate reconstitution of the host's immune system. While recovery of T-cell immunity may occur in transplant recipients via both thymus-dependent and thymus-independent pathways, the regeneration of a population of phenotypically naive T cells with a broad receptor repertoire relies entirely on the de novo generation of T-cells in the thymus. Preclinical models and clinical studies of allogeneic HSCT have identified the thymus as a target of graft-versus-host disease (GVHD), thus limiting T-cell regeneration. The present review focuses on recent insight into how GVHD affects thymic structure and function and how this knowledge may aid in the design of new strategies to improve T-cell reconstitution following allogeneic HSCT.