Cotransplantation of allogeneic mesenchymal and hematopoietic stem cells in children with aplastic anemia

Mesenchymal Stem Cells in Acquired Aplastic Anemia: The Spectrum from Basic to Clinical Utility

Aplastic anemia (AA), a rare but potentially life-threatening disease, is a paradigm of bone marrow failure syndromes characterized by pancytopenia in the peripheral blood and hypocellularity in the bone marrow. The pathophysiology of acquired idiopathic AA is quite complex. Mesenchymal stem cells (MSCs), an important component of the bone marrow, are crucial in providing the specialized microenvironment for hematopoiesis. MSC dysfunction may result in an insufficient bone marrow and may be associated with the development of AA. In this comprehensive review, we summarized the current understanding about the involvement of MSCs in the pathogenesis of acquired idiopathic AA, along with the clinical application of MSCs for patients with the disease. The pathophysiology of AA, the major properties of MSCs, and results of MSC therapy in preclinical animal models of AA are also described. Several important issues regarding the clinical use of MSCs are discussed finally. With evolving knowledge from basic studies and clinical applications, we anticipate that more patients with the disease can benefit from the therapeutic effects of MSCs in the near future.

Alterations of mesenchymal stem cells on regulating Th17 and Treg differentiation in severe aplastic anemia

Immune-mediated hematopoietic destruction is a key factor in idiopathic severe aplastic anemia (SAA). With great immunomodulatory functions, mesenchymal stem cells (MSCs) are important for bone marrow niche. While the underlying etiology of immunologic changes in SAA bone marrow remains unknown, dysfunctional MSCs are implicated as a major cause. To provide evidence for their defects in immunomodulation, alterations of SAA MSCs in regulating T cell differentiation were determined. During differentiation from CD4+ T cells into T helper 17 (Th17) cells under polarization conditions, impaired inhibition on IL-17 and IL-1β production was noted when cocultured with SAA MSCs compared to control MSCs (P < 0.05). After stimulation of Th17 activation, the percentage of IL-17-secreting cells was significantly increased in the SAA group (9.1 ± 1.5% vs 6.6 ± 0.4%, P < 0.01). Under regulatory T (Treg) polarization, a higher percentage of CD4+CD25+FoxP3+ Treg cells was detected when cocultured with SAA MSCs compared to control MSCs (8.1 ± 0.5% vs 5.8 ± 0.8%, P < 0.01). Inconsistently, transforming growth factor-β (TGF-β) concentrations in the culture supernatant were decreased and IL-1β concentrations were elevated in the SAA group. Our data indicated impaired inhibition of SAA MSCs on Th17 activation and aberrant regulation of SAA MSCs on Treg differentiation. Increased IL-17 and IL-1β levels with decreased TGF-β levels in the supernatant suggested the potential of SAA MSCs for triggering a hyperinflammatory environment. Dysfunctional MSCs could contribute to the lack of immunoprotection in the bone marrow, which may be associated with SAA.

Mesenchymal Stromal Cells for Enhancing Hematopoietic Engraftment and Treatment of Graft-Versus-Host Disease, Hemorrhages and Acute Respiratory Distress Syndrome

Mesenchymal stromal cells (MSCs) possess profound immunomodulatory and regenerative properties that are of clinical use in numerous clinical indications with unmet medical need. Common sources of MSCs include among others, bone marrow (BM), fat, umbilical cord, and placenta-derived decidua stromal cells (DSCs). We here summarize our more than 20-years of scientific experience in the clinical use of MSCs and DSCs in different clinical settings. BM-MSCs were first explored to enhance the engraftment of autografts in hematopoietic cell transplantation (HCT) and osteogenesis imperfecta around 30 years ago. In 2004, our group reported the first anti-inflammatory use of BM-MSCs in a child with grade IV acute graft-versus-host disease (GvHD). Subsequent studies have shown that MSCs appear to be more effective in acute than chronic GvHD. Today BM-MSC-therapy is registered for acute GvHD in Japan and for GvHD in children in Canada and New Zeeland. MSCs first home to the lung following intravenous injection and exert strong local and systemic immunomodulatory effects on the host immune system. Thus, they were studied for ameliorating the cytokine storm in acute respiratory distress syndrome (ARDS). Both, MSCs and DSCs were used to treat SARS-CoV-2 coronavirus-induced disease 2019 (COVID-19)-induced ARDS. In addition, they were also used for other novel indications, such as pneumomediastinum, colon perforation, and radiculomyelopathy. MSC and DSCs trigger coagulation and were thus explored to stop hemorrhages. DSCs appear to be more effective for acute GvHD, ARDS, and hemorrhages, but randomized studies are needed to prove superiority. Stromal cell infusion is safe, well tolerated, and only gives rise to a slight fever in a limited number of patients, but no major side effects have been reported in multiple safety studies and metaanalysis. In this review we summarize current evidence from in vitro studies, animal models, and importantly our clinical experience, to support stromal cell therapy in multiple clinical indications. This encloses MSC’s effects on the immune system, coagulation, and their safety and efficacy, which are discussed in relation to prominent clinical trials within the field.

Mesenchymal stromal cells as prophylaxis for graft-versus-host disease in haplo-identical hematopoietic stem cell transplantation recipients with severe aplastic anemia?-a systematic review and meta-analysis

BACKGROUND

Mesenchymal stromal cells (MSCs) are an emerging prophylaxis option for graft-versus-host disease (GVHD) in haplo-identical hematopoietic stem cell transplantation (haplo-HSCT) recipients with severe aplastic anemia (SAA), but studies have reported inconsistent results. This systematic review and meta-analysis evaluates the efficacy of MSCs as prophylaxis for GVHD in SAA patients with haplo-HSCT.

METHODS

Studies were retrieved from PubMed, EMBASE, Cochrane, Web of Science, and http://clinicaltrials.gov from establishment to February 2020. Twenty-nine single-arm studies (n = 1456) were included, in which eight (n = 241) studies combined with MSCs and eleven (n = 1215) reports without MSCs in haplo-HSCT for SAA patients. The primary outcomes were the incidences of GVHD. Other outcomes included 2-year overall survival (OS) and the incidence of cytomegalovirus (CMV) infection. Odds ratios (ORs) were calculated to compare the results pooled through random or fixed effects models.

RESULTS

Between MSCs and no MSCs groups, no significant differences were found in the pooled incidences of acute GVHD (56.0%, 95% CI 48.6-63.5% vs. 47.2%, 95% CI 29.0-65.4%; OR 1.43, 95% CI 0.91-2.25; p = 0.123), grade II-IV acute GVHD (29.8%, 95% CI 24.1-35.5% vs. 30.6%, 95% CI 26.6-34.6%; OR 0.97, 95% CI 0.70-1.32; p = 0.889), and chronic GVHD (25.4%, 95% CI 19.8-31.0% vs. 30.0%, 95% CI 23.3-36.6%; OR 0.79, 95% CI 0.56-1.11; p = 0.187). Furtherly, there was no obvious difference in 2-year OS (OR 0.98, 95% CI 0.60-1.61; p = 1.000) and incidence of CMV infection (OR 0.61, 95% CI 0.40-1.92; p = 0.018).

CONCLUSIONS

Our meta-analysis indicates that the prophylactic use of MSC co-transplantation is not an effective option for SAA patients undergoing haplo-HSCT. Hence, the general co-transplantation of MSCs for SAA haplo-HSCT recipients may lack evidence-based practice.

A study of human leukocyte antigen-haploidentical hematopoietic stem cells transplantation combined with allogenic mesenchymal stem cell infusion for treatment of severe aplastic anemia in pediatric and adolescent patients

The clinical applications of human leukocyte antigen (HLA) haploidentical hematopoietic stem cells transplantation (haplo‐HSCT) have offered most of the young severe aplastic anemia (SAA) patients an opportunity to accept curative therapy at the early stage of bone marrow lesions. However, the outcome of juvenile SAA patients received haplo‐HSCT remain to be improved due to high incidence of graft failure and graft vs host disease (GVHD). Mesenchymal stem cells (MSCs) have been characterized by their hematopoiesis‐supporting and immunomodulatory properties. In the current study, we designed a combination of haplo‐HSCT with allogenic MSC for treatment of SAA in pediatric and adolescent patients and evaluated its effects. Juvenile patients (<18 years) with SAA (n = 103) were given HLA‐haploidentical HSC combined with allogenic MSC after a conditioning regimen consisting of busulfan, cyclophosphamide, fludarabine, and antithymocyte globulin and an intensive GVHD prophylaxis, including cyclosporine, short‐term methotrexate, mycophenolate mofetil, and basiliximab. Neutrophil engraftment was achieved in 102 of 103 patients in a median time of 14.3 days (range 9‐25 days). The median time of platelet engraftment was 25.42 days (range 8‐93 days). The cumulative incidence of II‐IV acute GVHD at day +100 was 26.32% ± 0.19% and III‐IV acute GVHD was 6.79% ± 0.06% at day +100, respectively. The cumulative incidence of chronic GVHD was 25.56% ± 0.26%. The overall survival was 87.15% ± 3.3% at a median follow‐up of 40 (1.3‐98) months. Our data suggest that cotransplantation of HLA‐haploidentical HSC and allogenic mesenchymal stem cell may provide an effective and safe treatment for children and adolescents with SAA who lack matched donors.

Mesenchymal Stem Cells in Aplastic Anemia and Myelodysplastic Syndromes: The "Seed and Soil" Crosstalk

There is growing interest in the contribution of the marrow niche to the pathogenesis of bone marrow failure syndromes, i.e., aplastic anemia (AA) and myelodysplastic syndromes (MDSs). In particular, mesenchymal stem cells (MSCs) are multipotent cells that contribute to the organization and function of the hematopoietic niche through their repopulating and supporting abilities, as well as immunomodulatory properties. The latter are of great interest in MDSs and, particularly, AA, where an immune attack against hematopoietic stem cells is the key pathogenic player. We, therefore, conducted Medline research, including all available evidence from the last 10 years concerning the role of MSCs in these two diseases. The data presented show that MSCs display morphologic, functional, and genetic alterations in AA and MDSs and contribute to immune imbalance, ineffective hematopoiesis, and leukemic evolution. Importantly, adoptive MSC infusion from healthy donors can be exploited to heal the "sick" niche, with even better outcomes if cotransplanted with allogeneic hematopoietic stem cells. Finally, future studies on MSCs and the whole microenvironment will further elucidate AA and MDS pathogenesis and possibly improve treatment.

Synthetic biology for improving cell fate decisions and tissue engineering outcomes

Synthetic biology is a relatively new field of science that combines aspects of biology and engineering to create novel tools for the construction of biological systems. Using tools within synthetic biology, stem cells can then be reprogrammed and differentiated into a specified cell type. Stem cells have already proven to be largely beneficial in many different therapies and have paved the way for tissue engineering and regenerative medicine. Although scientists have made great strides in tissue engineering, there still remain many questions to be answered in regard to regeneration. Presented here is an overview of synthetic biology, common tools built within synthetic biology, and the way these tools are being used in stem cells. Specifically, this review focuses on how synthetic biologists engineer genetic circuits to dynamically control gene expression while also introducing emerging topics such as genome engineering and synthetic transcription factors. The findings mentioned in this review show the diverse use of stem cells within synthetic biology and provide a foundation for future research in tissue engineering with the use of synthetic biology tools. Overall, the work done using synthetic biology in stem cells is in its early stages, however, this early work is leading to new approaches for repairing diseased and damaged tissues and organs, and further expanding the field of tissue engineering.

Ganoderma spore lipid protects mouse bone marrow mesenchymal stem cells and hematopoiesis from the cytotoxicity of the chemotherapeutic agent

Cancer chemotherapeutic agents are frequently toxic to bone marrow and impair bone marrow functions. It is unclear whether ganoderma spore lipid (GSL) can protect bone marrow cells from the cytotoxicity of chemotherapy. To investigate the protective effects of GSL on bone marrow mesenchymal stem cells (MSCs) and hematopoiesis, we examined the effects of GSL on MSCs in vitro and hematopoiesis in vivo after treatment with the chemotherapeutic agent cyclophosphamide. MSCs and peripheral blood cells were isolated and counted from the bone marrow of normal mice were pre-treated with GSL before CTX treatment or co-treated with GSL and CTX, followed by examining the changes in phenotype, morphology, proliferation, apoptosis, and differentiation potentials. The results showed that GSL could reduce the CTX-induced changes in the phenotype of MSCs and maintain the elongated fibroblast-like morphology. MTT and annexin V/propidium iodide (PI) analyses found that GSL pre-treatment and co-treatment increased the proliferation and decreased the apoptosis in CTX-treated MSCs. Furthermore, GSL improved the osteogenic and adipogenic differentiation potentials of CTX-treated MSCs. In vivo, GSL treatment increased the number of peripheral blood cells including white blood cells (WBC) and platelets (PLT) in the CTX-treated mice and enhanced the in vitro formation of hematopoietic lineage colonies (erythrocyte colony forming unit, CFU-E; erythroid burst-forming units, BFU-E; and granulocyte macrophage colony-forming units, CFU-GM) from bone marrow cells in these mice. These findings suggest GSL could protect MSCs and hematopoiesis from the cytotoxicity of CTX and might become an effective adjuvant to attenuate side effects of chemotherapy during cancer treatment.

Therapeutic Outcomes of Haploidentical Allogeneic Hematopoietic Stem Cell Transplantation in Patients With Severe Aplastic Anemia: A Multicenter Study

BACKGROUND

Haploidentical donor (HID) allogeneic hematopoietic stem cell transplantation (HSCT) is an alternative curative treatment for patients with severe aplastic anemia (SAA) who do not have suitable matched related donors (MRD). The aim of this study was to compare the therapeutic outcomes of HID-HSCT with those of MRD-HSCT for SAA.

METHODS

A total of 235 SAA patients who underwent HID-HSCT (116) or MRD-HSCT (119) at 11 transplantation centers from January 2007 to January 2016 were included. Complications and survival outcomes were evaluated and compared between the 2 groups.

RESULTS

The HID group had a lower incidence of secondary graft failure but higher incidences of acute graft-versus-host disease (aGVHD) and chronic GVHD (cGVHD). However, the incidence of severe aGVHD (grades III-IV), poor graft function, and infections was comparable between groups. Patients in the HID group had a significantly lower survival and overall survival rates than those in the MRD group. The estimated 3-year survival rates for the MRD and HID groups were 82.82% and 75.00%, respectively. Ferritin levels, graft failure, poor graft function, severe aGVHD, and infections were the significant risk factors for survival.

CONCLUSIONS

The overall survival rate is acceptable for patients who underwent HID-HSCT, making it a feasible treatment choice for SAA patients.

The regulatory roles of VEGF-Notch signaling pathway on aplastic anemia with kidney deficiency and blood stasis

OBJECTIVE

Vascular endothelial growth factor (VEGF)-Notch signaling pathway plays an important role in aplastic anemia (AA). This study aimed to evaluate the regulatory roles of VEGF-Notch signaling pathway on mesenchymal stem cells (MSCs) isolated from AA patients with kidney deficiency and blood stasis (KB) (AA MSCs).

METHODS

Expression of VEGF-Notch signaling related factors, including VEGF, VEGFR, Notch-1, Jagged1, Delta-like1, and hes1 was detected in bone marrow (BM) tissues and AA MSCs by Western blot analysis. VEGF (100 ng/mL) and γ-secretase inhibitor (DAPT) (10 μM) was used to active and inhibit VEGF-Notch signaling in AA MSCs, respectively. After treatment, the proliferation, apoptosis, and adipogenic differentiation of AA MSCs was detected by Cell Counting Kit-8, flow cytometry, and Oil red O staining, respectively. Lentivirus short hairpin RNA (shRNA) were constructed to downregulate Notch-1 and VEGF in normal bone marrow mesenchymal stem cells (BMSCs), and the effects of VEGF/Notch-1 shRNA transfected BMSCs on the proliferation, migration, and angiogenesis of human umbilical vein endothelial cells (HUVECs) were evaluated.

RESULTS

Significantly lower expression of VEGF, VEGFR, Notch-1, Jagged1, Delta-like1, and hes1 was revealed in AA BM tissues and AA MSCs when compared with the normal control (P < 0.05). The intervention of DAPT significantly inhibited the proliferation, and promoted the apoptosis and adipogenic differentiation of AA MSCs, while VEGF intervention exhibited opposite results (P < 0.05). Meanwhile, the proliferation, migration, and angiogenesis of HUVECs were significantly promoted by normal BMSCs, while inhibited by VEGF/Notch-1 shRNA transfected BMSCs (P < 0.05).

CONCLUSION

The activation of VEGF-Notch signaling pathway may be a potential therapeutic target for AA with KB.

Co-transplantation of Human Fetal Mesenchymal and Hematopoietic Stem Cells in Type 1 Diabetic Mice Model

Introduction: Cell therapy can overcome the limitation of conventional treatments (including different medications and β cell replacement) for type 1 diabetes. Based- on several studies human fetal mesenchymal and hematopoietic stem cells are ideal candidates for stem cell therapy. On the other hand, co-transplantation of them can improve their effects. Accordingly, the aim of this research is co-transplantation of human fetal mesenchymal and hematopoietic stem cells in type 1 diabetes. Materials and Methods: The liver of legally aborted fetus was harvested. Then, mononuclear cells were isolated and extracted mesenchymal stromal cells and CD34⁺ hematopoietic stem cells were cultured. Expression of pluripotency markers were evaluated. For molecular imaging, mesenchymal stromal cells were labeled using GFP- vector. BALB/c inbred male mice were modeled by injection a single dose of Streptozotocin. Diabetic animals were received stem cells. After stem cell transplantation, in vivo imaging was performed and blood glucose levels were measured weekly. Results: Fetal mesenchymal stromal cells were demonstrated differentiation potential. Expression of pluripotency markers were positive. The mean of blood glucose levels were reduced in mixed mesenchymal and hematopoietic stem cells transplantation. A lot of GFP-labeled mesenchymal stem cells were engrafted in the pancreas of animal models that received a mixed suspension of hematopoietic and mesenchymal stromal cells. Conclusions: Human fetal stem cells are valuable source for cell therapy and co-transplantation of mesenchymal stromal cells can improve therapeutic effects of hematopoietic stem cells.

Clinical evaluation of haploidentical hematopoietic combined with human umbilical cord-derived mesenchymal stem cells in severe aplastic anemia

BACKGROUND

This study not only evaluated the clinical effects of treatment using haploidentical hematopoietic stem cells (haplo-HSCs) combined with human umbilical cord mesenchymal stem cells (UC-MSCs) in patients with severe aplastic anemia (SAA), but also investigated the factors related to graft versus host disease (GVHD).

METHODS

Cotransplantation of haplo-HSCs and UC-MSCs was performed in 24 SAA patients. The conditioning regimens consisted of rabbit anti-human T-lymphocyte immunoglobulin (ATG), cyclophosphamide, and fludarabine with or without busulfan. GVHD was prevented using cyclosporine A, ATG, anti-CD25 monoclonal antibody, and mycophenolate material.

RESULTS

The incidence of acute GVHD was 50%. The incidence of severe acute GVHD was not related to gender, age, donor-recipient relations, and patient/donor pair, while patient/donor pair (r = 0.541, P = 0.022) was significantly correlated with incidence of chronic GVHD. Upon follow-up for a median of 13 months, 5 of the 24 patients (20.8%) were dead. The survival rates at 3 and 6 months in all patients were 87.5% (21/24) and 83.3% (20/24), respectively.

CONCLUSION

Cotransplantation of haplo-HSCs combined with UC-MSCs was an effective and safe approach for the treatment of patients with SAA. The appropriate conditioning regimen and early treatment for infection also played a critical role in the success of HSCT.

Yin and Yang of mesenchymal stem cells and aplastic anemia

Acquired aplastic anemia (AA) is a bone marrow failure syndrome characterized by peripheral cytopenias and bone marrow hypoplasia. It is ultimately fatal without treatment, most commonly from infection or hemorrhage. Current treatments focus on suppressing immune-mediated destruction of bone marrow stem cells or replacing hematopoietic stem cells (HSCs) by transplantation. Our incomplete understanding of the pathogenesis of AA has limited development of targeted treatment options. Mesenchymal stem cells (MSCs) play a vital role in HSC proliferation; they also modulate immune responses and maintain an environment supportive of hematopoiesis. Some of the observed clinical manifestations of AA can be explained by mesenchymal dysfunction. MSC infusions have been shown to be safe and may offer new approaches for the treatment of this disorder. Indeed, infusions of MSCs may help suppress auto-reactive, T-cell mediated HSC destruction and help restore an environment that supports hematopoiesis. Small pilot studies using MSCs as monotherapy or as adjuncts to HSC transplantation have been attempted as treatments for AA. Here we review the current understanding of the pathogenesis of AA and the function of MSCs, and suggest that MSCs should be a target for further research and clinical trials in this disorder.

Human Mesenchymal Stem/Stromal Cells from Umbilical Cord Blood and Placenta Exhibit Similar Capacities to Promote Expansion of Hematopoietic Progenitor Cells In Vitro

Mesenchymal stem/stromal cells (MSCs) from bone marrow (BM) have been used in coculture systems as a feeder layer for promoting the expansion of hematopoietic progenitor cells (HPCs) for hematopoietic cell transplantation. Because BM has some drawbacks, umbilical cord blood (UCB) and placenta (PL) have been proposed as possible alternative sources of MSCs. However, MSCs from UCB and PL sources have not been compared to determine which of these cell populations has the best capacity of promoting hematopoietic expansion. In this study, MSCs from UCB and PL were cultured under the same conditions to compare their capacities to support the expansion of HPCs in vitro. MSCs were cocultured with CD34⁺CD38^-Lin^- HPCs in the presence or absence of early acting cytokines. HPC expansion was analyzed through quantification of colony-forming cells (CFCs), long-term culture-initiating cells (LTC-ICs), and CD34⁺CD38^-Lin^- cells. MSCs from UCB and PL have similar capacities to increase HPC expansion, and this capacity is similar to that presented by BM-MSCs. Here, we are the first to determine that MSCs from UCB and PL have similar capacities to promote HPC expansion; however, PL is a better alternative source because MSCs can be obtained from a higher proportion of samples.

Cotransplantation of bone marrow-derived mesenchymal stem cells in haploidentical hematopoietic stem cell transplantation in patients with severe aplastic anemia: an interim summary for a multicenter phase II trial results

This corrects the article DOI: 10.1038/bmt.2016.347.

Comparable Allogeneic Hematopoietic Cell Transplantation Outcome of a Haplo-Identical Family Donor with an Alternative Donor in Adult Aplastic Anemia

We performed a study on allogeneic hematopoietic cell transplantation (alloHCT) from an HLA-haplo-identical familial donor (haploFD) using a busulfan-fludarabine-antithymocyte globulin conditioning regimen for severe aplastic anemia (sAA) and hypoplastic myelodysplastic syndrome. For the comparison between a haploFD and an alternative donor (AD; matched unrelated or partially matched donor) for sAA in adults, we collected haploFD data retrospectively and prospectively. Forty-eight AD cases were selected for the comparison with 16 haploFD cases. All transplantation outcomes except for extensive chronic graft versus host disease (GvHD) were similar. The frequencies of hepatic sinusoidal obstruction syndrome (p = 1.000), acute GvHD (p = 0.769), grade 3/4 acute GvHD (p = 0.258), chronic GvHD (p = 0.173), extensive chronic GvHD (p = 0.099), primary neutrophil engraftment failure (p = 1.000), secondary graft failure (p = 1.000) and platelet engraftment failure (p = 0.505) were similar. Time to neutrophil engraftment was faster in haploFD (p = 0.003), while the cumulative incidence of platelet engraftment was similar (p = 0.505). Overall survival was also similar between AD and haploFD (p = 0.730). In conclusion, alloHCT from haploFD in sAA was comparable with alloHCT from AD, but extensive chronic GvHD seemed frequent in haploFD. Therefore alloHCT from haploFD could be an alternative approach for alloHCT from AD in adult sAA.

Heterogeneity in Studies of Mesenchymal Stromal Cells to Treat or Prevent Graft-versus-Host Disease: A Scoping Review of the Evidence

Effective treatments are lacking for the treatment of steroid-refractory graft-versus-host disease (GVHD), a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation. Mesenchymal stromal cells (MSCs) have demonstrated promise but there is uncertainty regarding their clinical effectiveness. A systematic scoping review of the literature was performed to characterize the heterogeneity of published studies and identify opportunities for standardization. Thirty studies were identified, including 19 studies (507 patients) addressing the treatment of acute or chronic GVHD and 11 prevention studies (277 patients). Significant heterogeneity was observed in the age and diagnoses of study subjects, intensity and specifics of the conditioning regimens, degree of HLA matching, and source of hematopoietic cells. MSCs were derived from bone marrow (83% of studies), cord blood (13%), or adipose tissue (3%) and were cryopreserved from third-party allogeneic donors in the majority of studies (91% of prevention studies and 63% of treatment studies). Culture conditions and media supplements were highly variable and characterization of MSCs did not conform to all International Society for Cellular Therapy criteria in any study. MSCs were harvested from cell culture at passage 1 to 7 and the dosage of MSCs ranged from 0.3 to 10 × 10(6)/kg, using varying schedules of administration. Treatment response criteria were not standardized and effectiveness in controlled treatment studies (5 studies) was unconvincing. Details of actively recruiting trials suggest heterogeneity still persists with only 53% of registered trials describing the use of standard GVHD response criteria and few detailing methods of MSC manufacturing. Future studies will need to make substantial coordinated efforts to reduce study heterogeneity and clarify the role of MSCs in GVHD.

Hematopoietic Support Capacity of Mesenchymal Stem Cells: Biology and Clinical Potential

Mesenchymal stem cells (MSCs) play an important role in the physiology and homeostasis of the hematopoietic system. Because MSCs generate most of the stromal cells present in the bone marrow (BM), form part of the hematopoietic stem cell (HSC) niche, and produce various molecules regulating hematopoiesis, their hematopoiesis-supporting capacity has been demonstrated. In the last decade, BM-MSCs have been proposed to be useful in some ex vivo protocols for HSC expansion, with the aim of expanding their numbers for transplant purposes (HSC transplant, HSCT). Furthermore, application of MSCs has been proposed as an adjuvant cellular therapy for promoting rapid hematopoietic recovery in HSCT patients. Although the MSCs used in preliminary clinical trials have come from the BM, isolation of MSCs from far more accessible sources such as neonatal tissues has now been achieved, and these cells have been found to possess similar biological characteristics to those isolated from the BM. Therefore, such tissues are now considered as a potential alternative source of MSCs for clinical applications. In this review, we discuss current knowledge regarding the biological characteristics of MSCs as related to their capacity to support the formation of hematopoietic stem and progenitor cells. We also describe MSC manipulation for ex vivo HSC expansion protocols used for transplants and their clinical relevance for hematopoietic recovery in HSCT patients.

Haploidentical parental hematopoietic stem cell transplantation in pediatric refractory Langerhans cell histiocytosis

Children with MS-LCH that fail to respond to conventional chemotherapy have poor outcomes. HSCT represents a potential salvage approach. It has been applied in over 50 cases in recent years. HSCT can achieve greater disease control than chemotherapy, but it carries a high risk of transplant-related mortality; thus, the haploidentical parental HSCT is used infrequently in pediatric refractory LCH. We report the first successful haploidentical parental HSCT, with no T-cell depletion, in two girls, aged 26 months and five months, with refractory MS-LCH. The mothers were donors with 5/6 and 4/6 HLA matches, respectively. The conditioning regimen included busulfan + cyclophosphamide + etoposide + antithymocyte-globulin ± fludarabine; the GVHD prophylaxis was based on cyclosporine + methotrexate ± mycophenolate-mofetil ± zenapax. In both cases, the stem cells were sourced from peripheral blood and BM, which included CD34+ cells (13.17 × 10(6)/kg and 40.23 × 10(6)/kg, respectively). These patients survived and showed no signs of disease activity in 54- and 44-month post-HSCT follow-ups. Our results indicated that, for patients that fail chemotherapy delivered early in the disease, but do not show organ dysfunction progression, it may be possible to achieve successful haploidentical parental HSCT with a strong myeloablative regimen.

Bone marrow mesenchymal stem cells from patients with aplastic anemia maintain functional and immune properties and do not contribute to the pathogenesis of the disease

Aplastic anemia is a life-threatening bone marrow failure disorder characterized by peripheral pancytopenia and marrow hypoplasia. The majority of cases of aplastic anemia remain idiopathic, although hematopoietic stem cell deficiency and impaired immune responses are hallmarks underlying the bone marrow failure in this condition. Mesenchymal stem/stromal cells constitute an essential component of the bone marrow hematopoietic microenvironment because of their immunomodulatory properties and their ability to support hematopoiesis, and they have been involved in the pathogenesis of several hematologic malignancies. We investigated whether bone marrow mesenchymal stem cells contribute, directly or indirectly, to the pathogenesis of aplastic anemia. We found that mesenchymal stem cell cultures can be established from the bone marrow of aplastic anemia patients and display the same phenotype and differentiation potential as their counterparts from normal bone marrow. Mesenchymal stem cells from aplastic anemia patients support the in vitro homeostasis and the in vivo repopulating function of CD34(+) cells, and maintain their immunosuppressive and anti-inflammatory properties. These data demonstrate that bone marrow mesenchymal stem cells from patients with aplastic anemia do not have impaired functional and immunological properties, suggesting that they do not contribute to the pathogenesis of the disease.

Mouse Flk-1+Sca-1- mesenchymal stem cells: functional plasticity in vitro and immunoregulation in vivo

OBJECTIVES

Mesenchymal stem cells (MSCs) represent a powerful tool in regenerative medicine because of their differentiation and migration capacities. Moreover, the immunomodulatory ability of MSCs may be used to develop therapies for the treatment of autoimmune diseases.

METHODS

In this study, we isolated Flk-1Sca-1 MSCs from bone marrow (bMSCs). Next, we studied their biological characteristics and immunologic functions. We also investigated their effects on graft-versus-host disease (GVHD) associated with allogeneic bone marrow transplantation in mice.

RESULTS

Flk-1Sca-1 bMSCs were able to differentiate into fat and cartilage cells, indicating that the isolated cells had stem cell properties. They could also suppress alloantigen-induced T cell proliferation in vitro in a dose-dependent manner. Infusion of bMSCs into allogeneic bone marrow-transplanted mice alleviated the lethal GVHD that occurred in control recipient mice. There was significantly lower mortality among the recipients of the Flk-1Sca-1 bMSCs that also ameliorated the clinical symptoms and GVHD histopathology. Beneficial effects on GVHD by Flk-1Sca-1 bMSCs were also observed when MSCs were engineered to express anti-inflammatory cytokines IL-4 and IL-10 and decrease expression of proinflammatory cytokines IFN-γ, TNF-α, and IL-2.

CONCLUSION

Flk-1Sca-1 bMSCs have stem cell properties and can efficiently ameliorate the GVHD associated with allogeneic bone marrow transplantation in mice.

Mesenchymal stem cells from pediatric patients with aplastic anemia: isolation, characterization, adipogenic, and osteogenic differentiation

Aplastic anemia is a syndrome of bone marrow (BM) failure characterized by peripheral pancytopenia and marrow hypoplasia. Its exact pathophysiology is still not clear. Mesenchymal stem cells (MSCs) play an important role in providing the specialized BM microenvironment for hematopoietic stem cells survival and differentiation. MSCs were isolated from BM of five patients with aplastic anemia and five controls. MSCs were characterized by morphology and immunophenotyping. Their viability, proliferative capacity, and adipogenic as well as osteogenic differentiation potentials were assessed. MSCs from aplastic anemia patients and controls shared similar spindle-shaped morphology and surface marker expression. MSCs derived from patients with aplastic anemia showed lower viability (74.2 ± 4.44% vs. 97.0 ± 1.58, p < 0.0001) and slower expansion rate as indicated by smaller population doubling and smaller cumulative population doubling from passages 1 to 4 (0.70 ± 0.22 vs. 2.34 ± 0.84; p = 0.009). Besides, aplastic anemia MSCs had poor capacity to differentiate into adipocytic and osteocytic lineages.

Acquired aplastic anemia in children

This article provides a practice-based and concise review of the etiology, diagnosis, and management of acquired aplastic anemia in children. Bone marrow transplantation, immunosuppressive therapy, and supportive care are discussed in detail. The aim is to provide the clinician with a better understanding of the disease and to offer guidelines for the management of children with this uncommon yet serious disorder.

Mesenchymal stem cells as cellular immunotherapeutics in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment option in hematopoietic disorders, immunodeficiencies and leukemia. To date graft-versus-host disease (GvHD) represents a life-threatening complication even if associated with beneficial antileukemic reactivity. GvHD is the clinical manifestation of donor cells reacting against host tissue. Because of their ability to facilitate endogenous repair and to attenuate inflammation, MSC have evolved as a highly attractive cellular therapeutic in allo-HSCT. Here we report on the clinical experience in the use of MSC to enhance engraftment and prevent and treat acute and chronic GvHD. In early clinical trials, MSC have shown considerable benefit in the setting of manifest GvHD. These encouraging results warrant further exploration.