Fucosylation with fucosyltransferase VI or fucosyltransferase VII improves cord blood engraftment

Harnessing upregulated E-selectin while enhancing SDF-1α sensing redirects infused NK cells to the AML-perturbed bone marrow

Increased bone marrow (BM) homing of NK cells is associated with positive outcome in patients with acute myeloid leukemia (AML) treated within adoptive NK cell transfer trials. While most efforts to further improve the efficacy focus on augmenting NK cell persistence and cytotoxicity, few address their ability to home to the tumor. Here, we decipher how AML growth alters the BM niche to impair NK cell infiltration and how insights can be utilized to resolve this issue. We show that AML development gradually impairs the BM homing capacity of infused NK cells, which was tightly linked to loss of SDF-1α in this environment. AML development also triggered up-regulation of E-selectin on BM endothelial cells. Given the poor E-selectin-binding capacity of NK cells, introduction of fucosyltransferase-7 (FUT7) to the NK cells per mRNA transfection resulted in potent E-selectin binding and stronger adhesion to E-selectin+ endothelial cells. Co-introduction of FUT7 and gain-of-function CXCR4 (CXCR4R334X) redirected NK cell homing to the BM of AML-bearing mice nearly to the levels in AML-free mice. This work shows how impaired NK cell homing caused by AML-induced microenvironmental changes can be overcome by genetic engineering. We speculate our insights can help further advance future NK cell immunotherapies.

Glycosyltransferases as versatile tools to study the biology of glycans

All cells are decorated with complex carbohydrate structures called glycans that serve as ligands for glycan-binding proteins (GBPs) to mediate a wide range of biological processes. Understanding the specific functions of glycans is key to advancing an understanding of human health and disease. However, the lack of convenient and accessible tools to study glycan-based interactions has been a defining challenge in glycobiology. Thus, the development of chemical and biochemical strategies to address these limitations has been a rapidly growing area of research. In this review, we describe the use of glycosyltransferases (GTs) as versatile tools to facilitate a greater understanding of the biological roles of glycans. We highlight key examples of how GTs have streamlined the preparation of well-defined complex glycan structures through chemoenzymatic synthesis, with an emphasis on synthetic strategies allowing for site- and branch-specific display of glyco-epitopes. We also describe how GTs have facilitated expansion of glyco-engineering strategies, on both glycoproteins and cell surfaces. Coupled with advancements in bioorthogonal chemistry, GTs have enabled selective glyco-epitope editing of glycoproteins and cells, selective glycan subclass labeling, and the introduction of novel biomolecule functionalities onto cells, including defined oligosaccharides, antibodies, and other proteins. Collectively, these approaches have contributed great insight into the fundamental biological roles of glycans and are enabling their application in drug development and cellular therapies, leaving the field poised for rapid expansion.

Refining the migration and engraftment of short-term and long-term HSCs by enhancing homing-specific adhesion mechanisms

In contrast to the short-term(ST)-CD34pos stem cells, studies have suggested that long-term (LT) hematopoietic stem cells (HSC) found in the CD34neg stem cell pool have trouble migrating and engrafting when introduced intravenously. We set out to fully elucidate the adhesion mechanisms used by ST/LT-HSCs to migrate to the bone marrow in order to understand these deficiencies. Focusing on murine ST-HSCs(Flk2negCD34pos) and LT-HSCs(Flk2negCD34neg), we observed a distinctive expression pattern of bone marrow homing effectors necessary for the first step, namely sialyl Lewis-X(sLex;ligand for E-selectin), and the second step, namely CXCR4 (receptor for SDF-1). sLex expression was higher on Flk2negCD34pos ST-HSCs(>60%) compared to Flk2negCD34neg LT-HSCs(<10%), which correlated to binding to E-selectin. Higher levels of CXCR4 were observed on Flk2negCD34pos ST-HSCs compared to Flk2negCD34neg LT-HSCs. Interestingly, expression of CD26, a peptidase known to deactivate chemokines (i.e.SDF-1), was higher on Flk2negCD34neg LT-HSCs. Given that migration is compromised in Flk2negCD34neg LT-HSCs, we aimed to enhance their ability to migrate using recombinant fucosyltransferase 6 (rhFTVI) and DiprotinA (CD26-inhibitor). We observed that although LT-HSCs expressed low levels of sLex, in vivo engraftment was not compromised. Moreover, although both treaments enhanced migration in vitro, only pre-treatment of LT-HSCs with DiprotinA enhanced engraftment in vivo. Remarkably, fucosylation of Flk2negCD34pos ST-HSCs consistently led to their ability to transplant secondary recipients, the gold standard for testing functionality of LT-HSCs. These data suggest that treatments to overcome the molecular disparity in adhesion mechanisms among ST-HSCs and LT-HSCs, differentially influences their abilities to migrate and engraft in vivo and boosts ST-HSCs engraftment in vivo.

Fucosylation Promotes Cytolytic Function and Accumulation of NK Cells in B Cell Lymphoma

Natural killer (NK) cells have been demonstrated as a promising cellular therapy as they exert potent anti-tumor immune responses. However, applications of NK cells to tumor immunotherapy, especially in the treatment of advanced hematopoietic and solid malignancies, are still limited due to the compromised survival and short persistence of the transferred NK cells in vivo. Here, we observed that fucosyltransferase (FUT) 7 and 8 were highly expressed on NK cells, and the expression of CLA was positively correlated with the accumulation of NK cells in clinical B cell lymphoma development. Via enzyme-mediated ex vivo cell-surface fucosylation, the cytolytic effect of NK cells against B cell lymphoma was significantly augmented. Fucosylation also promoted NK cell accumulation in B cell lymphoma-targeted tissues by enhancing their binding to E-selectin. Moreover, fucosylation of NK cells also facilitated stronger T cell anti-tumor immune responses. These findings suggest that ex vivo fucosylation contributes to enhancing the effector functions of NK cells and may serve as a novel strategy for tumor immunotherapy.

Allogeneic stem cell transplantation with omidubicel in sickle cell disease

Many patients with sickle cell disease (SCD) do not have HLA-matched related donors for hematopoietic stem cell transplantation (HSCT). Unrelated cord blood (UCB) is an alternative graft option but is historically associated with high graft failure rates, with inadequate cell dose a major limitation. Omidubicel is a nicotinamide-based, ex vivo-expanded UCB product associated with rapid engraftment in adults with hematologic malignancies. We hypothesized that increasing the UCB cell dose with this strategy would lead to improved engraftment in pediatric patients undergoing myeloablative HSCT for SCD. We report the outcomes of a phase 1/2 study in 13 patients with severe SCD who received omidubicel in combination with an unmanipulated UCB graft and 3 who received a single omidubicel graft. Grafts were minimally matched with patients at 4 of 6 HLA alleles. Median age at transplant was 13 years. A median CD34+ expansion of ∼80-fold was observed in omidubicel and led to rapid neutrophil engraftment (median, 7 days). Long-term engraftment was derived from the unmanipulated graft in most of the double cord blood recipients. Two of the 3 single omidubicel recipients also had sustained engraftment. Incidence of acute graft-versus-host disease (GVHD) was high, but resolved in all surviving patients. Event-free survival in the double cord group was 85% (median follow-up 4 years). All 3 patients in the single cord group were alive at 1 year after transplantation. Ex vivo expansion of UCB with omidubicel supports engraftment in patients with SCD. This approach to decreasing the incidence of GVHD should be optimized for general use in patients with SCD. This study was registered at www.clinicaltrials.gov as #NCT01590628.

Enforced sialyl-Lewis-X (sLeX) display in E-selectin ligands by exofucosylation is dispensable for CD19-CAR T-cell activity and bone marrow homing

CD19-directed chimeric antigen receptors (CAR) T cells induce impressive rates of complete response in advanced B-cell malignancies, specially in B-cell acute lymphoblastic leukemia (B-ALL). However, CAR T-cell-treated patients eventually progress due to poor CAR T-cell persistence and/or disease relapse. The bone marrow (BM) is the primary location for acute leukemia. The rapid/efficient colonization of the BM by systemically infused CD19-CAR T cells might enhance CAR T-cell activity and persistence, thus, offering clinical benefits. Circulating cells traffic to BM upon binding of tetrasaccharide sialyl-Lewis X (sLeX)-decorated E-selectin ligands (sialofucosylated) to the E-selectin receptor expressed in the vascular endothelium. sLeX-installation in E-selectin ligands is achieved through an ex vivo fucosylation reaction. Here, we sought to characterize the basal and cell-autonomous display of sLeX in CAR T-cells activated using different cytokines, and to assess whether exofucosylation of E-selectin ligands improves CD19-CAR T-cell activity and BM homing. We report that cell-autonomous sialofucosylation (sLeX display) steadily increases in culture- and in vivo-expanded CAR T cells, and that, the cytokines used during T-cell activation influence both the degree of such endogenous sialofucosylation and the CD19-CAR T-cell efficacy and persistence in vivo. However, glycoengineered enforced sialofucosylation of E-selectin ligands was dispensable for CD19-CAR T-cell activity and BM homing in multiple xenograft models regardless the cytokines employed for T-cell expansion, thus, representing a dispensable strategy for CD19-CAR T-cell therapy.

Using Eukaryotic Expression Systems to Generate Human α1,3-Fucosyltransferases That Effectively Create Selectin-Binding Glycans on Stem Cells

Recruitment of circulating cells toward target sites is primarily dependent on selectin/ligand adhesive interactions. Glycosyltransferases are involved in the creation of selectin ligands on proteins and lipids. α1,3-Fucosylation is imperative for the creation of selectin ligands, and a number of fucosyltransferases (FTs) can modify terminal lactosamines on cells to create these ligands. One FT, fucosyltransferase VI (FTVI), adds a fucose in an α1,3 configuration to N-acetylglucosamine to generate sialyl Lewis X (sLe^x) epitopes on proteins of live cells and enhances their ability to bind E-selectin. Although a number of recombinant human FTVIs have been purified, apart from limited commercial enzymes, they were not characterized for their activity on live cells. Here we focused on establishing a robust method for producing FTVI that is active on living cells (hematopoietic cells and mesenchymal stromal cells). To this end, we used two expression systems, Bombyx mori (silkworm) and Pichia pastoris (yeast), to produce significant amounts of N-terminally tagged FTVI and demonstrated that these enzymes have superior activity when compared to currently available commercial enzymes that are produced from various expression systems. Overall, we outline a scheme for obtaining large amounts of highly active FTVI that can be used for the application of FTVI in enhancing the engraftment of cells lacking the sLe^x epitopes.

Current and future perspectives on allogeneic transplantation using ex vivo expansion or manipulation of umbilical cord blood cells

In patients with hematologic malignancies, the outcome of umbilical cord blood transplantation has improved and is now comparable to that of matched unrelated donor transplantation. However, the limitation of using umbilical cord blood has been a delay in both hematopoietic and immunologic recovery. Strategies have been proposed to overcome these limitations. One strategy involves ex vivo expansion of the umbilical cord blood unit prior to transplantation. A second strategy involves exposure of the umbilical cord blood graft to compounds aimed at improving homing and engraftment following transplantation. Many of these strategies are now being tested in late phase multi-center clinical trials. If proven cost effective and efficacious, they may alter the landscape of donor options for allogeneic stem cell transplantation.

Fucosylated umbilical cord blood hematopoietic stem cell expansion on selectin-coated scaffolds

Despite the advantages of transplantation of umbilical cord blood's (UCB's) hematopoietic stem cells (uHSCs) for hematologic malignancy treatment, there are two major challenges in using them: (a) Insufficient amount of uHSCs in a UCB unit; (b) a defect in uHSCs homing to bone marrow (BM) due to loose binding of their surface glycan ligands to BM's endothelium selectin receptors. To overcome these limitations, after poly l-lactic acid (PLLA) scaffold establishment and incubation of uHSCs with fucosyltransferase-VI and GDP-fucose, ex vivo expansion of these cells on selectin-coated scaffold was done. The characteristics of the cultured fucosylated and nonfucosylated cells on a two-dimensional culture system, PLLA, and a selectin-coated scaffold were evaluated by flow cytometry, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, colony-forming unit (CFU) assay, and CXCR4 expression at the messenger RNA and protein levels. According to the findings of this study, optimized attachment to the scaffold in scanning electron microscopy micrograph, maximum count of CFU, and the highest 570 nm absorption were observed in fucosylated cells expanded on selectin-coated scaffolds. Furthermore, real-time polymerase chain reaction showed the highest expression of the CXCR4 gene, and immunocytochemistry data confirmed that the CXCR4 protein was functional in this group compared with the other groups. Considered together, the results showed that selectin-coated scaffold could be a supportive structure for fucosylated uHSC expansion and homing by nanotopography. Fucosylated cells placed on the selectin-coated scaffold serve as a basal surface for cell-cell interaction and more homing potential of uHSCs. Accordingly, this procedure can also be considered as a promising technique for the hematological disorder treatment and tissue engineering applications.

Fucosylation Enhances the Efficacy of Adoptively Transferred Antigen-Specific Cytotoxic T Lymphocytes

PURPOSE

Inefficient homing of adoptively transferred cytotoxic T lymphocytes (CTLs) to tumors is a major limitation to the efficacy of adoptive cellular therapy (ACT) for cancer. However, through fucosylation, a process whereby fucosyltransferases (FT) add fucose groups to cell surface glycoproteins, this challenge may be overcome. Endogenously fucosylated CTLs and ex vivo fucosylated cord blood stem cells and regulatory T cells were shown to preferentially home to inflamed tissues and marrow. Here, we show a novel approach to enhance CTL homing to leukemic marrow and tumor tissue.

EXPERIMENTAL DESIGN

Using the enzyme FT-VII, we fucosylated CTLs that target the HLA-A2-restricted leukemia antigens CG1 and PR1, the HER2-derived breast cancer antigen E75, and the melanoma antigen gp-100. We performed in vitro homing assays to study the effects of fucosylation on CTL homing and target killing. We used in vivo mouse models to demonstrate the effects of ex vivo fucosylation on CTL antitumor activities against leukemia, breast cancer, and melanoma.

RESULTS

Our data show that fucosylation increases in vitro homing and cytotoxicity of antigen-specific CTLs. Furthermore, fucosylation enhances in vivo CTL homing to leukemic bone marrow, breast cancer, and melanoma tissue in NOD/SCID gamma (NSG) and immunocompetent mice, ultimately boosting the antitumor activity of the antigen-specific CTLs. Importantly, our work demonstrates that fucosylation does not interfere with CTL specificity.

CONCLUSIONS

Together, our data establish ex vivo CTL fucosylation as a novel approach to improving the efficacy of ACT, which may be of great value for the future of ACT for cancer.

ABO phenotype-protected reproduction based on human specific α1,2 L-fucosylation as explained by the Bombay type formation

The metabolic relationship between the formation of the ABO(H) blood group phenotype and human fertility is evident in the case of the (Oh) or Bombay blood type, which Charles Darwin would have interpreted as resulting from reduced male fertility in consanguinities, based on the history of his own family, the Darwin/Wedgwood Dynasty. The classic Bombay type occurs with the extremely rare, human-specific genotype (h/h; se/se), which (due to point mutations) does not encode fucosyltransferases 1(FUT1) and 2 (FUT2). These enzymes are the basis for ABO(H) phenotype formation on the cell surfaces and fucosylation of plasma proteins, involving neonatal immunoglobulin M (IgM). In the normal human blood group O(H), which is not protected by clonal selection with regard to environmental A/B immunization, the plasma contains a mixture of non-immune and adaptive anti-A/B reactive isoagglutinins, which in the O(h) Bombay type show extremely elevated levels, associated with decreased levels of fucosylation-dependent functional plasma proteins, suchs as the van Willebrand factor (vWF) and clotting factor VIII. In fact, while the involvement of adaptive immunoglobulins remains unknown, poor fucosylation may explain the polyreactivity in the Bombay type plasma, which exhibits pronounced complement-binding cross-reactive anti-A/Tn and anti-B IgM levels, with additional anti-H reactivity, acting over a wide range of temperatures, with an amplitude at 37 °C. This aggressive anti-glycan-reactive IgM molecule suggests the induction of ADCC (antibody-dependent) and/or complement-mediated cytotoxicity via overexpressed glycosidic bond sites against the embryogenic stem cell-to-germ cell transformation, which is characterized by fleeting appearances of A-like, developmental trans-species GalNAcα1-O-Ser/Thr-R glycan, also referred to as the Tn (T "nouvelle") antigen.

mRNA-mediated glycoengineering ameliorates deficient homing of human stem cell-derived hematopoietic progenitors

Generation of functional hematopoietic stem and progenitor cells (HSPCs) from human pluripotent stem cells (PSCs) has been a long-sought-after goal for use in hematopoietic cell production, disease modeling, and eventually transplantation medicine. Homing of HSPCs from bloodstream to bone marrow (BM) is an important aspect of HSPC biology that has remained unaddressed in efforts to derive functional HSPCs from human PSCs. We have therefore examined the BM homing properties of human induced pluripotent stem cell-derived HSPCs (hiPS-HSPCs). We found that they express molecular effectors of BM extravasation, such as the chemokine receptor CXCR4 and the integrin dimer VLA-4, but lack expression of E-selectin ligands that program HSPC trafficking to BM. To overcome this deficiency, we expressed human fucosyltransferase 6 using modified mRNA. Expression of fucosyltransferase 6 resulted in marked increases in levels of cell surface E-selectin ligands. The glycoengineered cells exhibited enhanced tethering and rolling interactions on E-selectin-bearing endothelium under flow conditions in vitro as well as increased BM trafficking and extravasation when transplanted into mice. However, glycoengineered hiPS-HSPCs did not engraft long-term, indicating that additional functional deficiencies exist in these cells. Our results suggest that strategies toward increasing E-selectin ligand expression could be applicable as part of a multifaceted approach to optimize the production of HSPCs from human PSCs.

Quality and exploitation of umbilical cord blood for cell therapy: Are we beyond our capabilities?

There is increasing interest in identifying novel stem cell sources for application in emerging cell therapies. In this context, umbilical cord blood (UCB) shows great promise in multiple clinical settings. The number of UCB banks has therefore increased worldwide, with the objective of preserving potentially life-saving cells that are usually discarded after birth. After a rather long and costly processing procedure, the resultant UCB-derived cell products are cryopreserved until transplantation to patients. However, in many cases, only a small proportion of administered cells engraft successfully. Thus, can we do any better regarding current UCB-based therapeutic approaches? Here we discuss concerns about the use of UCB that are not critically pondered by researchers, clinicians, and banking services, including wasting samples with small volumes and the need for more reliable quality and functional controls to ensure the biological activity of stem cells and subsequent engraftment and treatment efficacy. Finally, we appeal for collaborative agreements between research institutions and UCB banks in order to redirect currently discarded small-volume UCB units for basic and clinical research purposes. Developmental Dynamics 245:710-717, 2016. © 2016 Wiley Periodicals, Inc.

Ex Vivo Expansion of Hematopoietic Stem and Progenitor Cells from Umbilical Cord Blood

Transplantation of umbilical cord blood cells is currently widely used in modern cell therapy. However, the limited number of hematopoietic stem and progenitor cells (HSPCs) and prolonged time of recovery after the transplantation are significant limitations in the use of cord blood. Ex vivo expansion with various cytokine combinations is one of the most common approaches for increasing the number of HSPCs from one cord blood unit. In addition, there are protocols that enable ex vivo amplification of cord blood cells based on native hematopoietic microenvironmental cues, including stromal components and the tissue-relevant oxygen level. The newest techniques for ex vivo expansion of HSPCs are based on data from the elucidation of the molecular mechanisms governing the hematopoietic niche function. Application of these methods has provided an improvement of several important clinical outcomes. Alternative methods of cord blood transplantation enhancement based on optimization of HPSC homing and engraftment in patient tissues have also been successful. The goal of the present review is to analyze recent methodological approaches to cord blood HSPC ex vivo amplification.

Optimizing autologous cell grafts to improve stem cell gene therapy

Over the past decade, stem cell gene therapy has achieved unprecedented curative outcomes for several genetic disorders. Despite the unequivocal success, clinical gene therapy still faces challenges. Genetically engineered hematopoietic stem cells are particularly vulnerable to attenuation of their repopulating capacity once exposed to culture conditions, ultimately leading to low engraftment levels posttransplant. This becomes of particular importance when transduction rates are low or/and competitive transplant conditions are generated by reduced-intensity conditioning in the absence of a selective advantage of the transduced over the unmodified cells. These limitations could partially be overcome by introducing megadoses of genetically modified CD34(+) cells into conditioned patients or by transplanting hematopoietic stem cells hematopoietic stem cells with high engrafting and repopulating potential. On the basis of the lessons gained from cord blood transplantation, we summarize the most promising approaches to date of increasing either the numbers of hematopoietic stem cells for transplantation or/and their engraftability, as a platform toward the optimization of engineered stem cell grafts.

Potential of glycosylation research in graft versus host disease after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Glycans, complex oligosaccharides, are directly involved in almost every biological process, have a fundamental role in the immune system, and are probably involved in nearly every human disease. However, glycosylation has been greatly ignored in the area of allogeneic hematopoietic stem cell transplantation (alloHSCT) and graft versus host disease (GVHD). Both acute and chronic GVHD are multisystemic debilitating immunological disturbances arising after alloHSCT.

SCOPE OF REVIEW

In this paper, we review the glycosylation research already done in the field of alloHSCT and GVHD and evaluate further potential of glycan analysis in GVHD by looking into resembling inflammatory and autoimmune conditions.

MAJOR CONCLUSIONS

Glycan research could bring significant improvement in alloHSCT procedure with reduction in following complications, such as GVHD. Identifying glycan patterns that induce self-tolerance and the ones that cause the auto- and allo-immune response could lead to innovative and tissue-specific immunomodulative therapy instead of the current immunosuppressive treatment, enabling preservation of the graft-versus-tumor effect. Moreover, improved glycan pattern analyses could offer a more complete assessment and greatly needed dynamic biomarkers for GVHD.

GENERAL SIGNIFICANCE

This review is written with a goal to encourage glycan research in the field of alloHSCT and GVHD as a perspective tool leading to improved engraftment, discovery of much needed biomarkers for GVHD, enabling an appropriate therapy and improved monitoring of therapeutic response. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.

Do human leukocyte antigen-typed cellular therapeutics based on induced pluripotent stem cells make commercial sense?

The promise of off-the-shelf cellular therapeutics (CTPs) based on allogeneic induced pluripotent stem cells (iPSCs) may be hindered by alloimmunity, leading many to suggest that such products could be based on a series of human leukocyte antigen (HLA)-typed iPSC lines allowing at least some degree of tissue matching. While based on sound scientific principles, this suggestion presupposes that other immune responses will not be limiting. Technically this approach would present a number of major challenges, the first being the development of a suitably reliable reprogramming method amenable to validation that results in highly consistent iPSC lines. Further, the resulting array of HLA-typed iPSCs would need to be shown to be capable of being manufactured into the same CTP and exhibit comparable quality, safety, and efficacy. When the enormities of these challenges are laid out, it becomes apparent that the manufacturing and product development challenges would be unprecedented. Given the uncertainties and lack of clinical experience with iPSC-based CTPs at this time, the financial costs and commercial risks do not appear to be acceptable.

Umbilical cord blood donation: public or private?

Umbilical cord blood (UCB) is a graft source for patients with malignant or genetic diseases who can be cured by allogeneic hematopoietic cell transplantation (HCT), but who do not have an appropriately HLA-matched family or volunteer unrelated adult donor. Starting in the 1990s, unrelated UCB banks were established, accepting donations from term deliveries and storing UCB units for public use. An estimated 730 000 UCB units have been donated and stored to date and ~35 000 UCB transplants have been performed worldwide. Over the past 20 years, private and family banks have grown rapidly, storing ~4 million UCB units for a particular patient or family, usually charging an up-front and yearly storage fee; therefore, these banks are able to be financially sustainable without releasing UCB units. Private banks are not obligated to fulfill the same regulatory requirements of the public banks. The public banks have released ~30 times more UCB units for therapy. Some countries have transitioned to an integrated banking model, a hybrid of public and family banking. Today, pregnant women, their families, obstetrical providers and pediatricians are faced with multiple choices about the disposition of their newborn's cord blood. In this commentary, we review the progress of UCB banking technology; we also analyze the current data on pediatric and adult unrelated UCB, including the recent expansion of interest in transplantation for hemoglobinopathies, and discuss emerging studies on the use of autologous UCB for neurologic diseases and regenerative medicine. We will review worldwide approaches to UCB banking, ethical considerations, criteria for public and family banking, integrated banking ideas and future strategies for UCB banking.

The potential of cytotherapeutics in hematologic reconstitution and in the treatment and prophylaxis of graft-versus-host disease. Chapter II: emerging transformational cytotherapies

Hematopoietic stem cell transplantation (HSCT) is a life-saving treatment for inherited anemias, immunodeficiencies or hematologic malignancies. A major complication of allo-HSCT associated with high transplant-related mortality rates is graft-versus-host disease (GvHD). Current and future clinical benefits in HSCT enabled by advances in hematopoietic stem cells, mesenchymal stem cells, Tregs and natural killer cells technologies are reviewed here and discussed. Among these evolutions, based on the need for mesenchymal stem cells to be recruited by an inflammatory environment, the development and use of novel GvHD biomarkers could be explored further to deliver the right pharmaceutical to the right patient at the right time. The successful commercialization of cytotherapeutics to efficiently manage GvHD will create a virtuous ‘halo’ effect for regenerative medicine.

Improving the outcome of umbilical cord blood transplantation through ex vivo expansion or graft manipulation

The outcome of umbilical cord blood transplantation for adult patients with hematologic malignancies now rivals that of matched unrelated donor transplantation. However, relatively low lymphocyte and hematopoietic stem and progenitor cell dose is a source of significant morbidity and mortality. Multiple strategies are now being studied to overcome these limitations. One strategy involves ex vivo expansion of the umbilical cord blood unit before transplantation. Ex vivo expansion has the potential to increase the number of lymphocytes, committed progenitors and long-term repopulating hematopoietic stem cells. Increasing the numbers of lymphocytes and committed progenitor cells will address the issue of delayed hematopoietic recovery after umbilical cord blood transplantation. Increasing the hematopoietic stem cell content will improve the availability of adequately sized and matched cord blood units for transplantation. It may also eliminate the need for dual umbilical cord blood transplantation for those without an adequately sized single umbilical cord blood graft. The second strategy involves exposure of the umbilical cord blood graft to compounds aimed at improving homing and engraftment following transplantation. Such a strategy may also address the problem of slow hematopoietic recovery as well as the increased risk of graft failure. Many of these strategies are now being tested in late-phase multi-center clinical trials. If proven cost-effective and efficacious, they may alter the landscape of donor options for allogeneic stem cell transplantation.

Optimization of intrabone delivery of hematopoietic progenitor cells in a swine model using cell radiolabeling with [89]zirconium

Intrabone (IB) hematopoietic cell transplantation (HCT) of umbilical cord blood in humans remains experimental and the technique has not been optimized. It is unknown whether hematopoietic progenitor cells (HPCs) injected IB are initially retained in the marrow or rapidly enter into the venous circulation before homing to the marrow. To develop an IB-injection technique that maximizes HPC marrow-retention, we tracked radiolabeled human HPCs following IB-injection into swine. We developed a method to radionuclide-label HPCs using a long-lived positron emitter (89) Zr and protamine sulfate that resulted in cellular-retention of low-dose radioactivity. This approach achieved radioactivity levels sufficient for detection by positron emission tomography with both high sensitivity and spatial resolution when fused with computed tomography. We found that conditions utilized in pilot IB-HCT clinical trials conducted by others led to both rapid drainage into the central venous circulation and cellular extravasation into surrounding muscle and soft tissues. By optimizing the needle design, using continuous real-time intra-marrow pressure monitoring, and by reducing the infusion-volume and infusion-rate, we overcame this limitation and achieved high retention of HPCs in the marrow. This method of IB cellular delivery is readily applicable in the clinic and could be utilized in future investigational IB-HCT trials aimed at maximizing marrow retention of HPCs.

Ex vivo fucosylation of third-party human regulatory T cells enhances anti-graft-versus-host disease potency in vivo

Adoptive therapy with regulatory T cells (Tregs) to prevent graft-versus-host disease (GVHD) would benefit from a strategy to improve homing to the sites of inflammation. We hypothesized that adding fucose to human Tregs, forming the Sialyl Lewis X moiety on P-selectin glycoprotein ligand-1, would improve their trafficking pattern. The selectin pathway recruiter, α-1,3-fucosyltransferase-VI enzyme, significantly increased Treg surface fucosylation (66% vs 8%). In a xenogenic GVHD mouse model, fucosylated Tregs showed prolonged periods of in vivo persistence. When given at a lower dose compared with the untreated Tregs, the murine recipients of fucosylated Tregs maintained weight, had ameliorated clinical GVHD, and improved survival (70% vs 30%; P < .0001). These preclinical data indicate that fucosylated human Tregs is an effective strategy for prevention of GVHD and, as such, warrants consideration for future clinical trials.

Expansion and homing of umbilical cord blood hematopoietic stem and progenitor cells for clinical transplantation

The successful expansion of hematopoietic stem and progenitor cells (HSPCs) from umbilical cord blood (UCB) for transplantation could revolutionize clinical practice by improving transplantation-related outcomes and making available UCB units that have suboptimal cell doses for transplantation. New cytokine combinations appear able to promote HSPC growth with minimal differentiation into mature precursors and new agents, such as insulin-like growth factor-binding protein 2, are being used in clinical trials. Molecules that simulate the HSPC niche, such as Notch ligand, have also shown promise. Further improvements have been made with the use of mesenchymal stromal cells, which have made possible UCB expansion without a potentially deleterious prior CD34/CD133 cell selection step. Chemical molecules, such as copper chelators, nicotinamide, and aryl hydrocarbon antagonists, have shown excellent outcomes in clinical studies. The use of bioreactors could further add to HSPC studies in future. Drugs that could improve HSPC homing also appear to have potential in improving engraftment times in UCB transplantation. Technologies to expand HSPC from UCB and to enhance the homing of these cells appear to have attained the goal of accelerating hematopoietic recovery. Further discoveries and clinical studies are likely to make the goal of true HSPC expansion a reality for many applications in future.

Concise review: umbilical cord blood transplantation: past, present, and future

Allogeneic hematopoietic stem cell transplantation is an important treatment option for fit patients with poor-risk hematological malignancies; nevertheless, the lack of available fully matched donors limits the extent of its use. Umbilical cord blood has emerged as an effective alternate source of hematopoietic stem cell support. Transplantation with cord blood allows for faster availability of frozen sample and avoids invasive procedures for donors. In addition, this procedure has demonstrated reduced relapse rates and similar overall survival when compared with unrelated allogeneic hematopoietic stem cell transplantation. The limited dose of CD34-positive stem cells available with single-unit cord transplantation has been addressed by the development of double-unit cord transplantation. In combination with improved conditioning regimens, double-unit cord transplantation has allowed for the treatment of larger children, as well as adult patients with hematological malignancies. Current excitement in the field revolves around the development of safer techniques to improve homing, engraftment, and immune reconstitution after cord blood transplantation. Here the authors review the past, present, and future of cord transplantation.

Advances in umbilical cord blood transplant: an overview of the 12th International Cord Blood Symposium, San Francisco, 5-7 June 2014

From 5 to 7 June the 12th Annual International Cord Blood Symposium was held in San Francisco. The meeting was devoted to advances in umbilical cord blood research with a major focus on translational and clinical results in cord blood transplant and in regenerative medicine. Over 3 days, a comprehensive summary of the state of the art was provided. We have summarized the most important data, organized around the following themes: use of umbilical cord blood for tissue repair, new indications for umbilical cord blood unit stem cell transplant (CBU SCT), enhancing count recovery after CBU SCT, improving outcomes, product quality and financial and cost considerations.