Effect of prior lenalidomide or daratumumab exposure on hematopoietic stem cell collection and reconstitution in multiple myeloma.

BACKGROUND: The roles of Lenalidomide (Len) and Daratumumab (Dara) in multiple myeloma treatment are well-established, yet their influences on hematopoietic stem cell harvesting and reconstitution remain disputed. METHODS: We conducted a systematic database review to identify cohort studies or RCTs evaluating the effect of the use of Len or Dara on hematopoietic stem cell collection and peripheral blood count recovery in multiple myeloma patients. Effects on hematopoietic collection or reconstitution were estimated by comparing standardized mean differences (SMD) and mean differences (MD), or median differences. RESULTS: Eighteen relevant studies were identified, summarizing mobilization results. For Len, data from 13 studies were summarized, including total CD34+ cell yield, collection failure rate, and time to neutrophil and platelet engraftment. Results indicated that Len exposure led to decreased stem cell collection [SMD=-0.23, 95% CI (-0.34, -0.12)]. However, collection failure (<2×106) could be mitigated by plerixafor [OR=2.14, 95% CI (0.96, 4.77)]. For Dara, two RCTs and three cohort studies were included, showing that Dara exposure resulted in a reduction in total stem cells even with optimized plerixafor mobilization [SMD=-0.75, 95% CI (-1.26, -0.23)], and delayed platelet engraftment recovery [MD=1.20, 95% CI (0.73, 1.66)]. CONCLUSIONS: Our meta-analysis offers a comprehensive view of Len and Dara's impacts on hematopoietic stem cell collection and reconstitution in multiple myeloma. Len usage could lead to reduced stem cell collection, counteracted by plerixafor mobilization. Dara usage could result in diminished stem cell collection and delayed platelet engraftment.

The "Mystery Cell Population" Residing in Murine Bone Marrow - A Missing Link Between Very Small Embryonic Like Stem Cells and Hematopoietic Stem Cells?

Bone marrow (BM) contains not only hematopoietic stem cells (HSCs) but also some very rare, early development, small quiescent stem cells that, upon activation, may differentiate across germlines. These small cells, named very small embryonic like stem cells (VSELs), can undergo specification into several types of cells including HSCs. Interestingly, murine BM is also home to a "mystery" population of small CD45+ stem cells with many of the phenotypic characteristics attributed to resting HSCs. Since the size of the "mystery" population cells are between that of VSELs and HSCs, and because CD45- VSELs can be specified into CD45+ HSCs, we hypothesized that the quiescent CD45+ "mystery" population could be a missing developmental link between VSELs and HSCs. To support this hypothesis, we showed that VSELs first became enriched for HSCs after acquiring expression of the CD45 antigen already expressed on "mystery" stem cells. Moreover, VSELs freshly isolated from BM similar to the "mystery" population cells, are quiescent and do not reveal hematopoietic potential in in vitro and in vivo assays. However, we noticed that CD45+ "mystery" population cells, similar to CD45- VSELs, became specified into HSCs after co-culture over OP9 stroma. We also found that mRNA for Oct-4, a pluripotency marker that is highly expressed in VSELs, is also detectable in the "mystery" population cells, albeit at a much lower level. Finally, we determined that the "mystery" population cells specified over OP9 stroma support were able to engraft and establish hematopoietic chimerism in lethally irradiated recipients. Based on these results, we propose that the murine BM "mystery" population could be an intermediate population between BM-residing VSELs and HSCs already specified for lympho-hematopoietic lineages.

[The Relationship between Occurrence of aGVHD in Patients with Acute Myeloid Leukemia after Allogeneic Hematopoietic Stem Cell Transplantation and Immune Cell Components in Graft].

OBJECTIVE: To explore the relationship between occurrence of acute graft-versus-host disease (aGVHD) and various immune cell composition in patients with acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). METHODS: The clinical data of 104 patients with AML undergoing allo-HSCT in our hospital were retrospectively analyzed, and the hematopoietic reconstitution and occurrence of GVHD were analyzed. Flow cytometry was used to detect the proportion of various types of immune cells in the grafts, the number of graft composition in patients with different degrees of aGVHD was calculated and compared, and to analyze the correlation between the severity of aGVHD in AML patients after allo-HSCT and the immune cell components in the graft. RESULTS: There was no significant difference in the time of hematopoietic reconstitution between the high number group of total number of nucleated cells (TNC) and the low number group, while the time of neutrophil and platelet reconstruction in the high number of CD34 group was significantly faster than that in the low number of CD34 group (P＜0.05), and the total hospital stay also tends to be shorten. Compared with patients in 0-Ι aGVHD group, both HLA-matched and HLA-haploidentical transplantation, the infusion amounts of CD3+ cells, CD3+CD4+ cells, CD3+CD8+ cells, NK cells and CD14+ monocytes were higher in patients of Ⅱ-Ⅳ aGVHD group， but the difference was not statistically significant (P>0.05); In addition, in patients with HLA-haploidentical transplantation, the number of CD4+CD25+ cells in Ⅱ-Ⅳ aGVHD group was significantly lower than that in 0-Ι aGVHD group (P<0.05), and the same trend was also observed in HLA-matched transplanted patients, but the difference was not significant (P=0.078). CONCLUSION: High number of CD34+ cells in the graft is beneficial to hematopoietic reconstitution in AML patients. To a certain degree, high number of CD3+ cells, CD3+CD4+ cells, CD3+CD8+ cells, NK cells and CD14+ cells tend to increase the occurrence of aGVHD, but high number of CD4+CD25+ regulatory T cells is beneficial to reduce the incidence of aGVHD in AML patients.

[Effect of Recombinant Human Thrombopoietin (rhTPO) on Hematopoietic Reconstitution in Allogeneic Hematopoietic Stem Cell Transplantation Model].

OBJECTIVE: To explore the effect of recombinant human thrombopoietin (rhTPO) on hematopoietic reconstruction in allogeneic hematopoietic stem cell transplantation (allo-HSCT) model. METHODS: The C57BL/6 mice were employed as the donors, and BALB/c mice as recipients. The bone marrow mononuclear cells of the donor mice were extracted and pretreated, which then were injected with 5×106 per mouse through the tail vein of the recipient to establish an allo-HSCT model. The implantation of hematopoietic stem cells in the recipient mice was detected by flow cytometry on the 28th day after transplantation. Next, the successfully modeled recipient mice were randomly divided into experimental group and control group. The rhTPO was injected into mice in the experimental group on the first day after transplantation, while the saline was injected into mice in the control group. Both groups were injected for 14 consecutive days. The peripheral blood and bone marrow hematopoiesis of the two groups were observed on day 1, 3, 7, 14, and 21 after transplantation. RESULTS: The expression rate of H-2Kb in the bone marrow of recipient mice was 43.85% (>20%) on the 28th day after transplantation, which indicated that the recipient mice were successfully chimerized. Meanwhile, counts of PLTs on the day 3, 7, 14, and 21 after transplantation in the experimental group were higher than those in the control group with statistical significances (P<0.05). In addition, hematopoietic function of bone marrow was suppressed in both groups on day 1, 3 and 7 after transplantation, but hematopoietic bone marrow hyperplasia was better in the experimental group than in the control group. On day 14 and 21 after transplantation, the hematopoietic function of bone marrow in the two groups was recovered, and the experimental group showed more obvious than the control group. CONCLUSION: rhTPO can effectively stimulate the production of PLTs and facilitate the recovery of white blood cells and hemoglobin after allo-HSCT, and promote hematopoietic recovery and reconstitution of bone marrow.

Magnetically empowered bone marrow cells as a micro-living motor can improve early hematopoietic reconstitution.

BACKGROUND AIMS: Bone marrow-derived hematopoietic stem cell transplantation/hematopoietic progenitor cell transplantation (HSCT/HPCT) is widely used and one of the most useful treatments in clinical practice. However, the homing rate of hematopoietic stem cells/hematopoietic progenitor cells (HSCs/HPCs) by routine cell transfusion is quite low, influencing hematopoietic reconstitution after HSCT/HPCT. METHODS: The authors developed a micro-living motor (MLM) strategy to increase the number of magnetically empowered bone marrow cells (ME-BMCs) homing to the bone marrow of recipient mice. RESULTS: In the in vitro study, migration and retention of ME-BMCs were greatly improved in comparison with non-magnetized bone marrow cells, and the biological characteristics of ME-BMCs were well maintained. Differentially expressed gene analysis indicated that ME-BMCs might function through gene regulation. In the in vivo study, faster hematopoietic reconstitution was observed in ME-BMC mice, which demonstrated a better survival rate and milder symptoms of acute graft-versus-host disease after transplantation of allogeneic ME-BMCs. CONCLUSIONS: This study demonstrated that ME-BMCs serving as MLMs facilitated the homing of HSCs/HPCs and eventually contributed to earlier hematopoietic reconstitution in recipients. These data might provide useful information for other kinds of cell therapies.

The Relationship between Occurrence of aGVHD in Patients with Acute Myeloid Leukemia after Allogeneic Hematopoietic Stem Cell Transplantation and Immune Cell Components in Graft / 中国实验血液学杂志

OBJECTIVE@#To explore the relationship between occurrence of acute graft-versus-host disease (aGVHD) and various immune cell composition in patients with acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT).@*METHODS@#The clinical data of 104 patients with AML undergoing allo-HSCT in our hospital were retrospectively analyzed, and the hematopoietic reconstitution and occurrence of GVHD were analyzed. Flow cytometry was used to detect the proportion of various types of immune cells in the grafts, the number of graft composition in patients with different degrees of aGVHD was calculated and compared, and to analyze the correlation between the severity of aGVHD in AML patients after allo-HSCT and the immune cell components in the graft.@*RESULTS@#There was no significant difference in the time of hematopoietic reconstitution between the high number group of total number of nucleated cells (TNC) and the low number group, while the time of neutrophil and platelet reconstruction in the high number of CD34 group was significantly faster than that in the low number of CD34 group (P＜0.05), and the total hospital stay also tends to be shorten. Compared with patients in 0-Ι aGVHD group, both HLA-matched and HLA-haploidentical transplantation, the infusion amounts of CD3+ cells, CD3+CD4+ cells, CD3+CD8+ cells, NK cells and CD14+ monocytes were higher in patients of Ⅱ-Ⅳ aGVHD group， but the difference was not statistically significant (P>0.05); In addition, in patients with HLA-haploidentical transplantation, the number of CD4+CD25+ cells in Ⅱ-Ⅳ aGVHD group was significantly lower than that in 0-Ι aGVHD group (P<0.05), and the same trend was also observed in HLA-matched transplanted patients, but the difference was not significant (P=0.078).@*CONCLUSION@#High number of CD34+ cells in the graft is beneficial to hematopoietic reconstitution in AML patients. To a certain degree, high number of CD3+ cells, CD3+CD4+ cells, CD3+CD8+ cells, NK cells and CD14+ cells tend to increase the occurrence of aGVHD, but high number of CD4+CD25+ regulatory T cells is beneficial to reduce the incidence of aGVHD in AML patients.

Effect of Recombinant Human Thrombopoietin (rhTPO) on Hematopoietic Reconstitution in Allogeneic Hematopoietic Stem Cell Transplantation Model / 中国实验血液学杂志

OBJECTIVE@#To explore the effect of recombinant human thrombopoietin (rhTPO) on hematopoietic reconstruction in allogeneic hematopoietic stem cell transplantation (allo-HSCT) model.@*METHODS@#The C57BL/6 mice were employed as the donors, and BALB/c mice as recipients. The bone marrow mononuclear cells of the donor mice were extracted and pretreated, which then were injected with 5×106 per mouse through the tail vein of the recipient to establish an allo-HSCT model. The implantation of hematopoietic stem cells in the recipient mice was detected by flow cytometry on the 28th day after transplantation. Next, the successfully modeled recipient mice were randomly divided into experimental group and control group. The rhTPO was injected into mice in the experimental group on the first day after transplantation, while the saline was injected into mice in the control group. Both groups were injected for 14 consecutive days. The peripheral blood and bone marrow hematopoiesis of the two groups were observed on day 1, 3, 7, 14, and 21 after transplantation.@*RESULTS@#The expression rate of H-2Kb in the bone marrow of recipient mice was 43.85% (>20%) on the 28th day after transplantation, which indicated that the recipient mice were successfully chimerized. Meanwhile, counts of PLTs on the day 3, 7, 14, and 21 after transplantation in the experimental group were higher than those in the control group with statistical significances (P<0.05). In addition, hematopoietic function of bone marrow was suppressed in both groups on day 1, 3 and 7 after transplantation, but hematopoietic bone marrow hyperplasia was better in the experimental group than in the control group. On day 14 and 21 after transplantation, the hematopoietic function of bone marrow in the two groups was recovered, and the experimental group showed more obvious than the control group.@*CONCLUSION@#rhTPO can effectively stimulate the production of PLTs and facilitate the recovery of white blood cells and hemoglobin after allo-HSCT, and promote hematopoietic recovery and reconstitution of bone marrow.

How mesenchymal stem cell cotransplantation with hematopoietic stem cells can improve engraftment in animal models.

BACKGROUND: Bone marrow transplantation (BMT) can be applied to both hematopoietic and nonhematopoietic diseases; nonetheless, it still comes with a number of challenges and limitations that contribute to treatment failure. Bearing this in mind, a possible way to increase the success rate of BMT would be cotransplantation of mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) to improve the bone marrow niche and secrete molecules that enhance the hematopoietic engraftment. AIM: To analyze HSC and MSC characteristics and their interactions through cotransplantation in murine models. METHODS: We searched for original articles indexed in PubMed and Scopus during the last decade that used HSC and MSC cotransplantation and in vivo BMT in animal models while evaluating cell engraftment. We excluded in vitro studies or studies that involved graft versus host disease or other hematological diseases and publications in languages other than English. In PubMed, we initially identified 555 articles and after selection, only 12 were chosen. In Scopus, 2010 were identified, and six were left after the screening and eligibility process. RESULTS: Of the 2565 articles found in the databases, only 18 original studies met the eligibility criteria. HSC distribution by source showed similar ratios, with human umbilical cord blood or animal bone marrow being administered mainly with a dose of 1 × 107 cells by intravenous or intrabone routes. However, MSCs had a high prevalence of human donors with a variety of sources (umbilical cord blood, bone marrow, tonsil, adipose tissue or fetal lung), using a lower dose, mainly 106 cells and ranging 104 to 1.5 × 107 cells, utilizing the same routes. MSCs were characterized prior to administration in almost every experiment. The recipient used was mostly immunodeficient mice submitted to low-dose irradiation or chemotherapy. The main technique of engraftment for HSC and MSC cotransplantation evaluation was chimerism, followed by hematopoietic reconstitution and survival analysis. Besides the engraftment, homing and cellularity were also evaluated in some studies. CONCLUSION: The preclinical findings validate the potential of MSCs to enable HSC engraftment in vivo in both xenogeneic and allogeneic hematopoietic cell transplantation animal models, in the absence of toxicity.

Prophylactic NAC promoted hematopoietic reconstitution by improving endothelial cells after haploidentical HSCT: a phase 3, open-label randomized trial.

BACKGROUND: Poor graft function (PGF) or prolonged isolated thrombocytopenia (PT), which are characterized by pancytopenia or thrombocytopenia, have become serious complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Our previous single-arm trial suggests that N-acetyl-L-cysteine (NAC) prophylaxis reduced PGF or PT after allo-HSCT. Therefore, an open-label, randomized, phase 3 trial was performed to investigate the efficacy and tolerability of NAC prophylaxis to reduce PGF or PT after allo-HSCT. METHODS: A phase 3, open-label randomized trial was performed. Based on the percentage of CD34+VEGFR2 (CD309)+ endothelial cells (ECs) in bone marrow (BM) detected by flow cytometry at 14 days before conditioning, patients aged 15 to 60 years with acute leukemia undergoing haploidentical HSCT were categorized as low-risk (EC ≥ 0.1%) or high-risk (EC < 0.1%); patients at high risk were randomly assigned (2:1) to receive NAC prophylaxis or nonprophylaxis. The primary endpoint was PGF and PT incidence at +60 days post-HSCT. RESULTS: Between April 18, 2019, and June 24, 2021, 120 patients with BM EC <0.1% were randomly assigned for NAC (group A, N = 80) or nonprophylaxis (group B, N = 40), and 105 patients with EC≥0.1% (group C) were also analyzed. The +60 days incidence of PGF and PT was 7.5% (95% CI, 1.7 to 13.3%) and 22.5% (95% CI, 9.1 to 35.9%) in group A and group B (hazard ratio, 0.317; 95% CI, 0.113 to 0.890; P = 0.021) and 11.4% (95% CI, 5.2 to 17.6%) in group C (hazard ratio, 0.643; 95% CI, 0.242 to 1.715; P = 0.373). Consistently, NAC prophylaxis gradually improved BM ECs and CD34+ cells in group A, whereas reduced their reactive oxygen species (ROS) levels post-HSCT. Within 60 days post-HSCT, the most common grade 3 to 5 adverse events for the NAC and control groups were infections (19/80 [24%] vs. 10/40 [25%]) and gastrointestinal adverse events (16/80 [20%] vs. 7/40 [18%]). There were no treatment-related deaths. CONCLUSIONS: N-Acetyl-L-cysteine prophylaxis can prevent the occurrence of poor hematopoietic function and is well tolerated in haploidentical HSCT. It may offer a potential pathogenesis-oriented therapeutic approach for patients with poor hematopoietic function. TRIAL REGISTRATION: This trial was registered at ClinicalTrials.gov as #NCT03967665.

Highly specific functional equivalence of XN-HPC for optimum CD34+ cell count in harvested allogeneic bone marrow stem cell products.

OBJECTIVES: To establish a reliable XN-HPC cutoff, for an effective CD34 + cell count of ≥2 × 106cells/kg of the recipient's body weight, in harvested bone marrow products in allogenic transplantation. METHODS: The study was carried out in two phases. In retrospective Phase 1, data from 47 donors were analyzed. Sysmex analyzer XN-20 and BD FACS Calibur were employed to process XN-HPC and CD34 + cell enumeration, respectively. To make the two variables comparable, both XN-HPC and CD34 + cell counts were reported as the number of cells/kg of the recipient's body weight. Spearman's rank correlation coefficient was calculated for CD34 + cells and XN-HPC, followed by the calculation of the receiver operating characteristic (ROC) curve to identify the XN-HPC value which could effectively predict the cutoff of ≥2 × 106 CD34 + cells/kg of the recipient's body weight. In Phase 2, the computed XN-HPC cutoff was validated in a prospective set of 53 donors by obtaining the positive and negative predictive values. RESULTS: Statistically significant correlation was obtained between XN-HPC and CD34 + cell count with Spearman's rho of 0.54 (p-value <0.001). The optimal XN-HPC cutoff, for the required CD34 + ve cell count of ≥2 × 106 cells/kg of the recipient's body weight, was calculated to be ≥2.80×106 cells/kg of the recipient's body weight with the specificity and sensitivity of 100% and 31%, respectively. The ROC curve demonstrated the area under the curve to be 0.74. Phase 2 validation revealed 100% PPV. CONCLUSIONS: For harvested bone marrow products with XN-HPC of ≥2.80×106 cell/kg of the recipient's body weight, CD34 + cell enumeration by flow cytometry can safely be disposed of.

Piezo1-mediated mechanosensation in bone marrow macrophages promotes vascular niche regeneration after irradiation injury.

Background: Irradiation disrupts the vascular niche where hematopoietic stem cells (HSCs) reside, causing delayed hematopoietic reconstruction. The subsequent recovery of sinusoidal vessels is key to vascular niche regeneration and a prerequisite for hematopoietic reconstruction. We hypothesize that resident bone marrow macrophages (BM-Mφs) are responsible for repairing the HSC niche upon irradiation injury. Methods: We examined the survival and activation of BM-Mφs in C57BL/6 mice upon total body irradiation. After BM-Mφ depletion via injected clodronate-containing liposomes and irradiation injury, hematopoietic reconstruction and sinusoidal vascular regeneration were assessed with immunofluorescence and flow cytometry. Then enzyme-linked immunosorbent assay (ELISA) and flow cytometry were performed to analyze the contribution of VEGF-A released by BM-Mφs to the vascular restructuring of the HSC niche. VEGF-A-mediated signal transduction was assessed with transcriptome sequencing, flow cytometry, and pharmacology (agonists and antagonists) to determine the molecular mechanisms of Piezo1-mediated responses to structural changes in the HSC niche. Results: The depletion of BM-Mφs aggravated the post-irradiation injury, delaying the recovery of sinusoidal endothelial cells and HSCs. A fraction of the BM-Mφ population persisted after irradiation, with residual BM-Mφ exhibiting an activated M2-like phenotype. The expression of VEGF-A, which is essential for sinusoidal regeneration, was upregulated in BM-Mφs post-irradiation, especially CD206+ BM-Mφs. The expression of mechanosensory ion channel Piezo1, a response to mechanical environmental changes induced by bone marrow ablation, was upregulated in BM-Mφs, especially CD206+ BM-Mφs. Piezo1 upregulation was mediated by the effects of irradiation, the activation of Piezo1 itself, and the M2-like polarization induced by the phagocytosis of apoptotic cells. Piezo1 activation was associated with increased expression of VEGF-A and increased accumulation of NFATC1, NFATC2, and HIF-1α. The Piezo1-mediated upregulation in VEGF-A was suppressed by inhibiting the calcineurin/NFAT/HIF-1α signaling pathway. Conclusion: These findings reveal that BM-Mφs play a critical role in promoting vascular niche regeneration by sensing and responding to structural changes after irradiation injury, offering a potential target for therapeutic efforts to enhance hematopoietic reconstruction.

Consequence of Histoincompatibility beyond GvH-Reaction in Cytomegalovirus Disease Associated with Allogeneic Hematopoietic Cell Transplantation: Change of Paradigm.

Hematopoietic cell (HC) transplantation (HCT) is the last resort to cure hematopoietic malignancies that are refractory to standard therapies. Hematoablative treatment aims at wiping out tumor cells as completely as possible to avoid leukemia/lymphoma relapse. This treatment inevitably co-depletes cells of hematopoietic cell lineages, including differentiated cells that constitute the immune system. HCT reconstitutes hematopoiesis and thus, eventually, also antiviral effector cells. In cases of an unrelated donor, that is, in allogeneic HCT, HLA-matching is performed to minimize the risk of graft-versus-host reaction and disease (GvHR/D), but a mismatch in minor histocompatibility antigens (minor HAg) is unavoidable. The transient immunodeficiency in the period between hematoablative treatment and reconstitution by HCT gives latent cytomegalovirus (CMV) the chance to reactivate from latently infected donor HC or from latently infected organs of the recipient, or from both. Clinical experience shows that HLA and/or minor-HAg mismatches increase the risk of complications from CMV. Recent results challenge the widespread, though never proven, view of a mechanistic link between GvHR/D and CMV. Instead, new evidence suggests that histoincompatibility promotes CMV disease by inducing non-cognate transplantation tolerance that inhibits an efficient reconstitution of high-avidity CD8+ T cells capable of recognizing and resolving cytopathogenic tissue infection.

NLRP1 in Bone Marrow Microenvironment Controls Hematopoietic Reconstitution After Transplantation.

Pretreatment before transplantation initiates an inflammatory response. Inflammasomes are key regulators of immune and inflammatory responses, but their role in regulating hematopoiesis is unclear. Our study intended to assess the role and mechanism of nucleotide-binding domain and leucine-rich repeat pyrin-domain containing protein 1 (NLRP1) in the bone marrow microenvironment on hematopoiesis regulation. To explore the effects of an absence of NLRP1 on hematopoietic reconstitution, we established a hematopoietic cell transplantation model by infusing bone marrow mononuclear cells of wild-type C57BL/6 mice into either NLRP1 knockout (NLRP1-KO) or wild-type C57BL/6 mice. Using the transplantation model, the role of NLRP1 in the bone marrow microenvironment was determined by flow cytometry, hemacytometry, and hematoxylin and eosin staining. As the major component of the bone marrow microenvironment, mesenchymal stem cells (MSCs) were isolated to analyze the effects of NLRP1 on them by osteogenic and adipogenic induction. Endothelial cells (ECs) were isolated and sorted by magnetic beads. The expression of adhesion molecules and their relationship with nuclear factor kappa B (NF-κB) were measured by immunofluorescence, enzyme-linked immunosorbent assay, and western blot. Finally, the effect of NLRP1-deleted MSCs or ECs on hematopoietic stem and progenitor cells (HSPCs) was examined by establishing co-culture models. Compared with C57BL/6 recipients, reduced inflammatory cell infiltration, decreased levels of proinflammatory cytokines interleukin (IL)-18, IL-1ß, IL-6, tumor necrosis factor alpha (TNF-α), and interferon gamma (IFN-γ), together with reduced pathological injury of bone marrow, were observed in NLRP1-KO recipients after transplantation. However, increased HSPC engraftment and hematopoietic reconstitution were detected in NLRP1-KO recipients after transplantation. Furthermore, MSCs isolated from NLRP1-KO mice had decreased osteogenic and adipogenic differentiation and increased proliferation and differentiation of HSPCs. The expression of adhesion molecules in ECs from NLRP1-KO mice was increased due to the promotion of nuclear translocation of NF-κB; these adhesion molecules are critical for hematopoietic stem cell homing. Knockout of NLRP1 in the bone marrow microenvironment could significantly relieve bone marrow inflammatory response and promote hematopoietic reconstitution, perhaps by regulating MSCs and ECs, indicating that NLRP1 might be a target for the treatment of delayed hematopoietic and immune recovery in patients after hematopoietic stem cell transplantation.

Evaluation of a clinical-grade, cryopreserved, ex vivo-expanded stem cell product from cryopreserved primary umbilical cord blood demonstrates multilineage hematopoietic engraftment in mouse xenografts.

BACKGROUND AIMS: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative therapy for a wide range of malignant and genetic disorders of the hematopoietic and immune systems. Umbilical cord blood (UCB) is a readily available source of stem cells for allo-HSCT, but the small fixed number of hematopoietic stem and progenitor cells (HSPCs) found in a single unit limits its widespread use in adult recipients. The authors have previously reported that culturing UCB-CD34+ cells in serum-free media supplemented with a combination of cytokines and the histone deacetylase inhibitor valproic acid (VPA) led to expansion of the numbers of functional HSPCs. Such fresh expanded product has been advanced to the clinic and is currently evaluated in an ongoing clinical trial in patients with hematological malignancies undergoing allo-HSCT. Here the authors report on the cryopreservation of this cellular product under current Good Manufacturing Practice (cGMP). METHODS: cGMP VPA-mediated expansion was initiated with CD34+ cells isolated from cryopreserved primary UCB collections, and the functionality after a second cryopreservation step of the expanded product evaluted in vitro and in mouse xenografts. RESULTS: The authors found that the cryopreserved VPA-expanded grafts were characterized by a high degree of viability, retention of HSPC phenotypic subtypes and maintenance of long-term multilineage repopulation capacity in immunocompromised mice. All cellular and functional parameters tested were comparable between the fresh and cryopreserved VPA-expanded cellular products. CONCLUSIONS: The authors' results demonstrate and support the practicality of cryopreservation of VPA-expanded stem cell grafts derived from UCB-CD34+ cells for clinical utilization.

Application study of EAC mobilization scheme in autologous hematopoietic stem cell transplantation of lymphoma / 国际肿瘤学杂志

Objective:To explore the safety and efficacy of EAC [etoposide+ cytarabine+ cyclophosphamide (CTX)] mobilization scheme for mobilizing stem cells in patients with lymphoma undergoing autologous hematopoietic stem cell transplantation (ASCT).Methods:A total of 36 patients with lymphoma who had collected peripheral blood stem cells through EAC or CTX+ granulocyte colony stimulating factor (G-CSF) mobilization scheme in Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College from June 2018 to March 2020 were retrospectively analyzed. Among them, 16 patients used EAC mobilization (EAC group), and 20 patients used CTX (CTX group). When white blood cells≤1.0×10 9/L, G-CSF (10 μg/kg per day) was given subcutaneously in two doses. The changes of hematology indexes, the number of collected cells, adverse reactions during mobilization collection and hematopoietic reconstitution after ASCT were observed. Results:The peripheral blood stem cells were collected on 5 d (3-8 d) after EAC+ G-CSF mobilization and 7 d (4-12 d) after CTX+ G-CSF mobilization. The success rates of collection in the EAC group and CTX group were 100% (16/16) and 75.0% (15/20) respectively, the high-quality collection rates were 87.5% (14/16) and 25.0% (5/20) respectively, and there were statistically significant differences ( P=0.041; P<0.001). The median of CD34 + cells of the two groups was 13.67×10 6/kg and 3.45×10 6/kg respectively, the median of mononuclear cells was 7.16×10 8/kg and 5.09×10 8/kg respectively, the median of CD34 + cells/mononuclear cells was 1.44% and 0.67% respectively, and there were statistically significant differences ( Z=-4.219, P<0.001; Z=-2.118, P=0.034; Z=-3.104, P=0.002). In the EAC group and CTX group, the incidences of grade 3 and above granulocytopenia were 100% (16/16) and 90.0% (18/20) respectively, the incidences of grade 3 and above hemoglobin reduction were 43.8% (7/16) and 25.0% (5/20) respectively, the incidences of grade 3 and above thrombocytopenia were 87.5% (14/16) and 65.0% (13/20) respectively, and there were no statistically significant differences ( P=0.492; P=0.298; P=0.245). There were no significant differences in the incidences of infection, adverse reactions of digestive system or other adverse reactions between the two groups (all P>0.05). All patients accepted improved Bucy scheme before ASCT. The median implantation time of neutrophils and platelets was 9.0 d and 10.5 d in the EAC group, which was 12.0 d and 13.5 d in the CTX group, and there were statistically significant differences ( Z=-4.698, P<0.001; Z=-3.757, P<0.001). Conclusion:EAC mobilization scheme can significantly increase the number of hematopoietic stem cell. This scheme has a high success rate of high-quality collection and the adverse reactions are within the controllable range. It provides a high-quality mobilization scheme for hematopoietic stem cell mobilization and collection, which is worthy of clinical promotion and application.

PEDF promotes the repair of bone marrow endothelial cell injury and accelerates hematopoietic reconstruction after bone marrow transplantation.

BACKGROUND: Preconditioning before bone marrow transplantation such as irradiation causes vascular endothelial cells damage and promoting the repair of damaged endothelial cells is beneficial for hematopoietic reconstitution. Pigment epithelium-derived factor (PEDF) regulates vascular permeability. However, PEDF's role in the repair of damaged endothelial cells during preconditioning remains unclear. The purpose of our study is to investigate PEDF's effect on preconditioning-induced damage of endothelial cells and hematopoietic reconstitution. METHODS: Damaged endothelial cells induced by irradiation was co-cultured with hematopoietic stem cells (HSC) in the absence or presence of PEDF followed by analysis of HSC number, cell cycle, colony formation and differentiation. In addition, PEDF was injected into mice model of bone marrow transplantation followed by analysis of bone marrow injury, HSC number and peripheral hematopoietic reconstitution as well as the secretion of cytokines (SCF, TGF-ß, IL-6 and TNF-α). Comparisons between two groups were performed by student t-test and multiple groups by one-way or two-way ANOVA. RESULTS: Damaged endothelial cells reduced HSC expansion and colony formation, induced HSC cell cycle arrest and apoptosis and promoted HSC differentiation as well as decreased PEDF expression. Addition of PEDF increased CD144 expression in damaged endothelial cells and inhibited the increase of endothelial permeability, which were abolished after addition of PEDF receptor inhibitor Atglistatin. Additionally, PEDF ameliorated the inhibitory effect of damaged endothelial cells on HSC expansion in vitro. Finally, PEDF accelerated hematopoietic reconstitution after bone marrow transplantation in mice and promoted the secretion of SCF, TGF-ß and IL-6. CONCLUSIONS: PEDF inhibits the increased endothelial permeability induced by irradiation and reverse the inhibitory effect of injured endothelial cells on hematopoietic stem cells and promote hematopoietic reconstruction.

Splenomegaly Negatively Impacts Neutrophil Engraftment in Cord Blood Transplantation.

Delayed neutrophil engraftment (NE) has been reported in cord blood transplantation (CBT) compared with other stem cell transplantation methods. The numbers of total nucleated cells (TNCs), CD34+ cells (generally ≥ 1 × 105/kg), and granulocyte/macrophage colony-forming units (CFU-GM) significantly impact NE. Splenomegaly exerts negative effects on NE, but the appropriate cell dose for the patients with splenomegaly has not yet been determined, especially in CBT. We retrospectively investigated the effect of splenomegaly and number of CD34+ cells infused on NE through the analysis of outcomes of 502 consecutive patients who underwent single CBT for the first time at Toranomon Hospital between 2011 and 2018. Spleen index, Lmax × Hvert (SI Lmax × Hvert), was defined as maximal length at any transverse section, (Lmax) × vertical height (Hvert), and splenomegaly was defined as SI Lmax × Hvert ≥ 115 cm2. Our results show that splenomegaly (hazard ratio [HR], .60; P < .01) and low dose of infused CD34+ cells (HR, .58; P < .01) had significant negative impact on NE, whereas neither CFU-GM dose nor TNC dose had any impact on NE in multivariate analysis. Other factors with a significant negative impact on NE in multivariate analysis were myeloid disease (HR, .62; P < .01), nonremission status at CBT (HR, .71; P < .01), low Eastern Cooperative Oncology Group Performance Status (HR, .68; P < .01), and graft-versus-host disease prophylaxis (other than tacrolimus alone) (HR, .76; P < .01). Without splenomegaly, even patients infused with < .8 × 105/kg CD34+ cells achieved up to 94.3% NE, with the median value observed at 21 days post-CBT. This study shows that splenomegaly has a significant negative impact on NE after CBT. Cord blood units with < .8 × 105/kg CD34+ cells may still be a suitable choice for patients without splenomegaly.

Enhancement of Antigen Presentation by Deletion of Viral Immune Evasion Genes Prevents Lethal Cytomegalovirus Disease in Minor Histocompatibility Antigen-Mismatched Hematopoietic Cell Transplantation.

Hematoablative treatment followed by hematopoietic cell transplantation (HCT) for reconstituting the co-ablated immune system is a therapeutic option to cure aggressive forms of hematopoietic malignancies. In cases of family donors or unrelated donors, immunogenetic mismatches in major histocompatibility complex (MHC) and/or minor histocompatibility (minor-H) loci are unavoidable and bear a risk of graft-vs.-host reaction and disease (GvHR/D). Transient immunodeficiency inherent to the HCT protocol favors a productive reactivation of latent cytomegalovirus (CMV) that can result in multiple-organ CMV disease. In addition, there exists evidence from a mouse model of MHC class-I-mismatched GvH-HCT to propose that mismatches interfere with an efficient reconstitution of antiviral immunity. Here we used a mouse model of MHC-matched HCT with C57BL/6 donors and MHC-congenic BALB.B recipients that only differ in polymorphic autosomal background genes, including minor-H loci coding for minor-H antigens (minor-HAg). Minor-HAg mismatch is found to promote lethal CMV disease in absence of a detectable GvH response to an immunodominant minor-HAg, the H60 locus-encoded antigenic peptide LYL8. Lethality of infection correlates with inefficient reconstitution of viral epitope-specific CD8+ T cells. Notably, lethality is prevented and control of cytopathogenic infection is restored when viral antigen presentation is enhanced by deletion of immune evasion genes from the infecting virus. We hypothesize that any kind of mismatch in GvH-HCT can induce "non-cognate transplantation tolerance" that dampens not only a mismatch-specific GvH response, which is beneficial, but adversely affects also responses to mismatch-unrelated antigens, such as CMV antigens in the specific case, with the consequence of lethal CMV disease.

Insufficient Antigen Presentation Due to Viral Immune Evasion Explains Lethal Cytomegalovirus Organ Disease After Allogeneic Hematopoietic Cell Transplantation.

Reactivation of latent cytomegalovirus (CMV) poses a clinical problem in transiently immunocompromised recipients of hematopoietic cell (HC) transplantation (HCT) by viral histopathology that results in multiple organ manifestations. Compared to autologous HCT and to syngeneic HCT performed with identical twins as HC donor and recipient, lethal outcome of CMV infection is more frequent in allogeneic HCT with MHC/HLA or minor histocompatibility loci mismatch between donor and recipient. It is an open question if a graft-vs.-host (GvH) reaction exacerbates CMV disease, or if CMV exacerbates GvH disease (GvHD), or if interference is mutual. Here we have used a mouse model of experimental HCT and murine CMV (mCMV) infection with an MHC class-I mismatch by gene deletion, so that either HCT donor or recipient lack a single MHC class-I molecule, specifically H-2 Ld. This particular immunogenetic disparity has the additional advantage that it allows to experimentally separate GvH reaction of donor-derived T cells against recipient's tissues from host-vs.-graft (HvG) reaction of residual recipient-derived T cells against the transplanted HC and their progeny. While in HvG-HCT with Ld-plus donors and Ld-minus recipients almost all infected recipients were found to control the infection and survived, almost all infected recipients died of uncontrolled virus replication and consequent multiple-organ viral histopathology in case of GvH-HCT with Ld-minus donors and Ld-plus recipients. Unexpectedly, although anti-Ld-reactive CD8+ T cells were detected, mortality was not found to be associated with GvHD histopathology. By comparing HvG-HCT and GvH-HCT, investigation into the mechanism revealed an inefficient reconstitution of antiviral high-avidity CD8+ T cells, associated with lack of formation of protective nodular inflammatory foci (NIF) in host tissue, selectively in GvH-HCT. Most notably, mice infected with an immune evasion gene deletion mutant of mCMV survived under otherwise identical GvH-HCT conditions. Survival was associated with enhanced antigen presentation and formation of protective NIF by antiviral CD8+ T cells that control the infection and prevent viral histopathology. This is an impressive example of lethal viral disease in HCT recipients based on a failure of the immune control of CMV infection due to viral immune evasion in concert with an MHC class-I mismatch.

Cytomegalovirus-Associated Inhibition of Hematopoiesis Is Preventable by Cytoimmunotherapy With Antiviral CD8 T Cells.

Reactivation of latent cytomegalovirus (CMV) in recipients of hematopoietic cell transplantation (HCT) not only results in severe organ manifestations, but can also cause "graft failure" resulting in bone marrow (BM) aplasia. This inhibition of hematopoietic stem and progenitor cell engraftment is a manifestation of CMV infection that is long known in clinical hematology as "myelosuppression." Previous studies in a murine model of sex-chromosome mismatched but otherwise syngeneic HCT and infection with murine CMV have shown that transplanted hematopoietic cells (HC) initially home to the BM stroma of recipients but then fail to further divide and differentiate. Data from this model were in line with the hypothesis that infection of stromal cells, which constitute "hematopoietic niches" where hematopoiesis takes place, causes a local deficiency in essential hematopoietins. Based on this understanding, one must postulate that preventing infection of stromal cells should restore the stroma's capacity to support hematopoiesis. Adoptively-transferred antiviral CD8+ T cells prevent lethal CMV disease by controlling viral spread and histopathology in vital organs, such as liver and lungs. It remained to be tested, however, if they can also prevent infection of the BM stroma and thus allow for successful HC engraftment. Here we demonstrate that antiviral CD8+ T cells control stromal infection. By tracking male donor-derived sry+ HC in the BM of infected female sry- recipients, we show the CD8+ T cells allow for successful donor HC engraftment and thereby prevent CMV-associated BM aplasia. These data provide a further argument for cytoimmunotherapy of CMV infection after HCT.