Neutralizing negative epigenetic regulation by HDAC5 enhances human haematopoietic stem cell homing and engraftment

Umbilical Cord Blood Hematopoietic Cells: From Biology to Hematopoietic Transplants and Cellular Therapies

Umbilical cord blood (UCB) is a rich source of hematopoietic stem and progenitor cells that are biologically superior to their adult counterparts. UCB cells can be stored for several years without compromising their numbers or function. Today, public and private UCB banks have been established in several countries around the world. After 35 years since the first UCB transplant (UCBT), more than 50,000 UCBTs have been performed worldwide. In pediatric patients, UCBT is comparable to or superior to bone marrow transplantation. In adult patients, UCB can be an alternative source of hematopoietic cells when an HLA-matched unrelated adult donor is not available and when a transplant is urgently needed. Delayed engraftment (due to reduced absolute numbers of hematopoietic cells) and higher costs have led many medical institutions not to consider UCB as a first-line cell source for hematopoietic transplants. As a result, the use of UCB as a source of hematopoietic stem and progenitor cells for transplantation has declined over the past decade. Several approaches are being investigated to make UCBTs more efficient, including improving the homing capabilities of primitive UCB cells and increasing the number of hematopoietic cells to be infused. Several of these approaches have already been applied in the clinic with promising results. UCB also contains immune effector cells, including monocytes and various lymphocyte subsets, which, together with stem and progenitor cells, are excellent candidates for the development of cellular therapies for hematological and non-hematological diseases.

Class I HDAC inhibitors enhance antitumor efficacy and persistence of CAR-T cells by activation of the Wnt pathway

Epigenetic modification shapes differentiation trajectory and regulates the exhaustion state of chimeric antigen receptor T (CAR-T) cells. Limited efficacy induced by terminal exhaustion closely ties with intrinsic transcriptional regulation. However, the comprehensive regulatory mechanisms remain largely elusive. Here, we identify class I histone deacetylase inhibitors (HDACi) as boosters of CAR-T cell function by high-throughput screening of chromatin-modifying drugs, in which M344 and chidamide enhance memory maintenance and resistance to exhaustion of CAR-T cells that induce sustained antitumor efficacy both in vitro and in vivo. Mechanistically, HDACi decrease HDAC1 expression and enhance H3K27ac activity. Multi-omics analyses from RNA-seq, ATAC-seq, and H3K27ac CUT&Tag-seq show that HDACi upregulate expression of TCF4, LEF1, and CTNNB1, which subsequently activate the canonical Wnt/β-catenin pathway. Collectively, our findings elucidate the functional roles of class I HDACi in enhancing CAR-T cell function, which provides the basis and therapeutic targets for synergic combination of CAR-T cell therapy and HDACi treatment.

Noncoding rules of survival: epigenetic regulation of normal and malignant hematopoiesis

Hematopoiesis is an essential process for organismal development and homeostasis. Epigenetic regulation of gene expression is critical for stem cell self-renewal and differentiation in normal hematopoiesis. Increasing evidence shows that disrupting the balance between self-renewal and cell fate decisions can give rise to hematological diseases such as bone marrow failure and leukemia. Consequently, next-generation sequencing studies have identified various aberrations in histone modifications, DNA methylation, RNA splicing, and RNA modifications in hematologic diseases. Favorable outcomes after targeting epigenetic regulators during disease states have further emphasized their importance in hematological malignancy. However, these targeted therapies are only effective in some patients, suggesting that further research is needed to decipher the complexity of epigenetic regulation during hematopoiesis. In this review, an update on the impact of the epigenome on normal hematopoiesis, disease initiation and progression, and current therapeutic advancements will be discussed.

Update on histone deacetylase inhibitors in peripheral T-cell lymphoma (PTCL)

Peripheral T-cell lymphomas (PTCLs) are a group of highly aggressive malignancies with generally poor prognoses, and the first-line chemotherapy of PTCL has limited efficacy. Currently, several novel targeted agents, including histone deacetylase inhibitors (HDACis), have been investigated to improve the therapeutic outcome of PTCLs. Several HDACis, such as romidepsin, belinostat, and chidamide, have demonstrated favorable clinical efficacy and safety in PTCLs. More novel HDACis and new combination therapies are undergoing preclinical or clinical trials. Mutation analysis based on next-generation sequencing may advance our understanding of the correlation between epigenetic mutation profiles and relevant targeted therapies. Multitargeted HDACis and HDACi-based prodrugs hold promising futures and offer further directions for drug design.

Nuclear Tubulin Enhances CXCR4 Transcription and Promotes Chemotaxis Through TCF12 Transcription Factor in human Hematopoietic Stem Cells

Tubulins are cytoskeleton components in all eukaryotic cells and play crucial roles in various cellular activities by polymerizing into dynamic microtubules. A subpopulation of tubulin has been shown to localize in the nucleus, however, the function of nuclear tubulin remains largely unexplored. Here we report that microtubule depolymerization specifically upregulates surface CXCR4 expression in human hematopoietic stem cells (HSCs). Mechanistically, microtubule depolymerization results in accumulation of tubulin subunits in the nucleus, leading to elevated CXCR4 transcription and increased chemotaxis of human HSCs. Treatment with microtubule stabilizer Epothilone B strongly suppresses the phenotypes induced by microtubule depolymerizing agents in human HSCs. Furthermore, chromatin immunoprecipitation assay reveals an increased binding of nuclear tubulin and TCF12 transcription factor at the CXCR4 promoter region. Depletion of TCF12 significantly suppresses microtubule depolymerization mediated upregulation of CXCR4 surface expression. These results demonstrate a previously unknown function of nuclear tubulin in regulating gene transcription through TCF12. New strategy targeting nuclear tubulin-TCF12-CXCR4 axis may be applicable to enhance HSC transplantation.

An improved medium formulation for efficient ex vivo gene editing, expansion and engraftment of hematopoietic stem and progenitor cells

Gene editing has emerged as a powerful tool for the therapeutic correction of monogenic diseases. CRISPR-Cas9 applied to hematopoietic stem and progenitor cells (HSPCs) has shown great promise in proof-of-principle preclinical studies to treat hematological disorders, and clinical trials using these tools are now under way. Nonetheless, there remain important challenges that need to be addressed, such as the efficiency of targeting primitive, long-term repopulating HSPCs and their in vitro expansion for clinical application. In this study, we assessed the effect of different culture medium compositions on the ability of HSPCs to proliferate and undergo homology-directed repair-mediated knock-in of a reporter gene, while preserving their stemness features during ex vivo culture. We demonstrated that by supplementing the culture medium with stem cell agonists and by fine-tuning its cytokine composition it is possible to achieve high levels of gene targeting in long-term repopulating HSPCs both in vitro and in vivo, with a beneficial balance between preservation of stemness and cell expansion. Overall, the implementation of this optimized ex vivo HSPC culture protocol can improve the efficacy, feasibility, and applicability of gene editing as a key step to unlocking the full therapeutic potential of this powerful technology.

Epigenetic Modification of Mesenchymal Stromal Cells Derived from Bone Marrow and Embryonal Tumors to Facilitate Immunotherapeutic Approaches in Pediatric Malignancies

Mesenchymal stromal cells (MSC) are part of the bone marrow architecture and contribute to the homeostasis of hematopoietic stem cells. Moreover, they are known to regulate immune effector cells. These properties of MSC are pivotal under physiologic conditions, and they may aberrantly also protect malignant cells. MSCs are also found in the leukemic stem cell niche of the bone marrow and as part of the tumor microenvironment. Here, they protect malignant cells from chemotherapeutic drugs and from immune effector cells in immunotherapeutic approaches. Modulation of these mechanisms may improve the efficacy of therapeutic regimens. We investigated the effect of the histone deacetylase inhibitor (HDACi) suberoylanilide hydroxamic acid (SAHA, Vorinostat™) on the immunomodulatory effect and cytokine profile of MSC derived from bone marrow and pediatric tumors. The immune phenotype of MSC was not markedly affected. SAHA-treated MSC showed reduced immunomodulatory effects on T cell proliferation and NK cell cytotoxicity. This effect was accompanied by an altered cytokine profile of MSC. While untreated MSC inhibited the production of certain pro-inflammatory cytokines, SAHA treatment led to a partial increase in IFNγ and TNFα secretion. These alterations of the immunosuppressive milieu might be beneficial for immunotherapeutic approaches.

Therapeutic targeting and HSC proliferation by small molecules and biologicals

Hematopoietic stem cells (HSCs) have considerably therapeutic value on autologous and allogeneic transplantation for many malignant/non-malignant hematological diseases, especially with improvement of gene therapy. However, acquirement of limited cell dose from HSC sources is the main handicap for successful transplantation. Therefore, many strategies based on the utilization of various cytokines, interaction of stromal cells, modulation of several extrinsic and intrinsic factors have been developed to promote ex vivo functional HSC expansion with high reconstitution ability until today. Besides all these strategies, small molecules become prominent with their ease of use and various advantages when they are translated to the clinic. In the last two decades, several small molecule compounds have been investigated in pre-clinical studies and, some of them were evaluated in different stages of clinical trials for their safety and efficiencies. In this chapter, we will present an overview of HSC biology, function, regulation and also, pharmacological HSC modulation with small molecules from pre-clinical and clinical perspectives.

Ex Vivo Expansion and Homing of Human Cord Blood Hematopoietic Stem Cells

Cord blood (CB) has been proven to be an alternative source of haematopoietic stem cells (HSCs) for clinical transplantation and has multiple advantages, including but not limited to greater HLA compatibility, lower incidence of graft-versus-host disease (GvHD), higher survival rates and lower relapse rates among patients with minimal residual disease. However, the limited number of HSCs in a single CB unit limits the wider use of CB in clinical treatment. Many efforts have been made to enhance the efficacy of CB HSC transplantation, particularly by ex vivo expansion or enhancing the homing efficiency of HSCs. In this chapter, we will document the major advances regarding human HSC ex vivo expansion and homing and will also discuss the possibility of clinical translation of such laboratory work.

Cell-free immunomodulatory biomaterials mediated in situ periodontal multi-tissue regeneration and their immunopathophysiological processes

Cell-free biomaterials-inducing endogenous in situ multi-tissue regeneration is very challenging and applying advanced immunomodulatory biomaterials can be an effective strategy to overcome it. In-depth knowledge of the immunopathophysiological mechanisms should be acquired before applying such an immunomodulation strategy. In this study, we implanted different immunoregulatory cell-free biomaterials into periodontal multi-tissue defects and showed that the outcome of multi-tissue regeneration is closely regulated by the immune reaction. The underlying immunopathophysiological processes, including the blood clotting response and fibrinoid necrosis, innate and adaptive immune response, local and systemic immune reaction, growth factors release, and stem cells recruitment, were revealed. The implantation of biomaterials with anti-inflammatory properties could direct the immunopathophysiological process and make it more favorable for in situ multi-tissue regeneration, ultimately enabling the regeneration of the periodontal ligament, the acellular cementum matrix, and the alveolar bone in the periodontium. These findings further confirm the effectiveness of immunomodulatory based strategy and the unveiling of their immunopathophysiological processes could provide some favorable theoretical bases for the development of advanced cell-free immunomodulatory multi-tissue regenerative biomaterials.

Tyrosine kinase receptor RON activates MAPK/RSK/CREB signal pathway to enhance CXCR4 expression and promote cell migration and invasion in bladder cancer

Bladder cancer (BC) is one of the most lethal malignancies worldwide. The poor survival may be due to a high proportion of tumor metastasis. RON and CXCR4 are the key regulators of cell motility in BC, while the relationship between RON and CXCR4 remains elusive. In the present study, immunohistochemistry analysis of BC and adjacent normal tissues found that higher RON expression was positively correlated with CXCR4 expression. Inhibiting and replenishing RON level were used to regulate CXCR4 expression, observing the effects on migration and invasion of BC cells. Overexpression of RON reversed the inhibited cell migration and invasion following siCXCR4 treatment. Conversely, overexpression of CXCR4 restored the inhibition of cell migration and invasion caused by shRON. The activation of RON-MAPK/RSK/CREB pathway was demonstrated in BC cells under MSP treatment. Dual luciferase and CHIP assay showed that p-CREB targeted CXCR4 by binding to its CRE sequence. RON knockdown suppressed BC tumor growth in xenograft mouse tumors, accompanied by reduced expression of CXCR4. In conclusion, our data adds evidence that RON, a membrane tyrosine kinase receptor, promotes BC migration and invasion not only by itself, but also by activating MAPK/RSK/CREB signaling pathway to enhance CXCR4 expression.

Histone Deacetylases Function in the Control of Early Hematopoiesis and Erythropoiesis

Numerous studies have highlighted the role of post-translational modifications in the regulation of cell proliferation, differentiation and death. Among these modifications, acetylation modifies the physicochemical properties of proteins and modulates their activity, stability, localization and affinity for partner proteins. Through the deacetylation of a wide variety of functional and structural, nuclear and cytoplasmic proteins, histone deacetylases (HDACs) modulate important cellular processes, including hematopoiesis, during which different HDACs, by controlling gene expression or by regulating non-histone protein functions, act sequentially to provide a fine regulation of the differentiation process both in early hematopoietic stem cells and in more mature progenitors. Considering that HDAC inhibitors represent promising targets in cancer treatment, it is necessary to decipher the role of HDACs during hematopoiesis which could be impacted by these therapies. This review will highlight the main mechanisms by which HDACs control the hematopoietic stem cell fate, particularly in the erythroid lineage.

Clinical Progress and Preclinical Insights Into Umbilical Cord Blood Transplantation Improvement

The application of umbilical cord blood (UCB) as an important source of hematopoietic stem and progenitor cells (HSPCs) for hematopoietic reconstitution in the clinical context has steadily grown worldwide in the past 30 years. UCB has advantages that include rapid availability of donors, less strict HLA-matching demands, and low rates of graft-versus-host disease (GVHD) versus bone marrow (BM) and mobilized peripheral blood (PB). However, the limited number of HSPCs within a single UCB unit often leads to delayed hematopoietic engraftment, increased risk of transplant-related infection and mortality, and proneness to graft failure, thus hindering wide clinical application. Many strategies have been developed to improve UCB engraftment, most of which are based on 2 approaches: increasing the HSPC number ex vivo before transplantation and enhancing HSPC homing to the recipient BM niche after transplantation. Recently, several methods have shown promising progress in UCB engraftment improvement. Here, we review the current situations of UCB manipulation in preclinical and clinical settings and discuss challenges and future directions.

C/EBPα regulates the fate of bone marrow mesenchymal stem cells and steroid-induced avascular necrosis of the femoral head by targeting the PPARγ signalling pathway

BACKGROUND

The imbalance of osteogenic/adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is closely related to steroid-induced avascular necrosis of the femoral head (SANFH). We aimed to investigate the epigenetic mechanism of intramedullary fat accumulation and continuous osteonecrosis after glucocorticoid (GC) withdrawal in SANFH.

METHODS

An SANFH model was established in SD rats, which received an intermittent high GC dose for the first 4 weeks followed by an additional 4 weeks without GC. We explored the synergistic effects and mechanisms of C/EBPα and PPARγ on the differentiation of BMSCs by lentivirus-mediated gene knockdown and overexpression assays. A chromatin immunoprecipitation assay was performed to identify epigenetic modification sites on PPARγ in vivo and in vitro.

RESULTS

In the SANFH model, intramedullary fat was significantly increased, and the transcription factors C/EBPα and PPARγ were upregulated simultaneously in the femoral head. In vitro, C/EBPα promoted adipogenic differentiation of BMSCs by targeting the PPARγ signalling pathway, while overexpression of C/EBPα significantly impaired osteogenic differentiation. Further studies demonstrated that histone H3K27 acetylation of PPARγ played an important role in the epigenetic mechanism underlying SANFH. C/EBPα upregulates the histone H3K27 acetylation level in the PPARγ promoter region by inhibiting HDAC1. Additionally, inhibiting the histone acetylation level of PPARγ effectively prevented adipogenic differentiation, thus slowing the progression of SANFH.

CONCLUSIONS

Our results demonstrate the molecular mechanism by which C/EBPα regulates PPARγ expression by acetylating histones and revealed the epigenetic phenomenon in SANFH for the first time.

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.

SAHA Enhances Differentiation of CD34+CD45+ Hematopoietic Stem and Progenitor Cells from Pluripotent Stem Cells Concomitant with an Increase in Hemogenic Endothelium

Epigenetic modification is an important process during hematopoietic cell differentiation. Histone deacetylase (HDAC) inhibitors have previously been shown to enhance expansion of umbilical cord blood-derived hematopoietic stem cells (HSCs). However, the effect of HDAC inhibitors on pluripotent stem cells (PSCs) in this context is less understood. For years, investigators have considered PSC-derived natural killer (NK) and T-cell therapies. These "off-the-shelf" cellular therapies are now entering the clinic. However, the in vitro commitment of PSCs to the hematopoietic lineage is inefficient and represents a major bottleneck. We investigated whether HDAC inhibitors (HDACi) influence human PSC differentiation into CD34+CD45+ hematopoietic stem and progenitor cells (HSPCs), focusing on hemogenic endothelium (HE). Pluripotent stem cells cultured in the presence of HDACi showed a 2-5 times increase in HSPCs. Concurrent with this, HDACi-treated PSCs increased expression of 7 transcription factors (HOXA5, HOXA9, HOXA10, RUNX1, ERG, SPI1, and LCOR) recently shown to convert HE to HSPCs. ChIP-qPCR showed that SAHA upregulated acetylated-H3 at the promoter region of the above key genes. SAHA-treated human PSC-derived CD34+CD45+ cells showed primary engraftment in immunodeficient mice, but not serial transplantation. We further demonstrate that SAHA-derived HSPCs could differentiate into functional NK cells in vitro. The addition of SAHA is an easy and effective approach to overcoming the bottleneck in the transition from PSC to HSPCs for "off-the-shelf" cellular immunotherapy.

Differential CXCR4 expression on hematopoietic progenitor cells versus stem cells directs homing and engraftment

Gene therapy involves a substantial loss of hematopoietic stem and progenitor cells (HSPC) during processing and homing. Intra-BM (i.b.m.) transplantation can reduce homing losses, but prior studies have not yielded promising results. We studied the mechanisms involved in homing and engraftment of i.b.m. transplanted and i.v. transplanted genetically modified (GM) human HSPC. We found that i.b.m. HSPC transplantation improved engraftment of hematopoietic progenitor cells (HPC) but not of long-term repopulating hematopoietic stem cells (HSC). Mechanistically, HPC expressed higher functional levels of CXCR4 than HSC, conferring them a retention and homing advantage when transplanted i.b.m. Removing HPC and transplanting an HSC-enriched population i.b.m. significantly increased long-term engraftment over i.v. transplantation. Transient upregulation of CXCR4 on GM HSC-enriched cells, using a noncytotoxic portion of viral protein R (VPR) fused to CXCR4 delivered as a protein in lentiviral particles, resulted in higher homing and long-term engraftment of GM HSC transplanted either i.v. or i.b.m. compared with standard i.v. transplants. Overall, we show a mechanism for why i.b.m. transplants do not significantly improve long-term engraftment over i.v. transplants. I.b.m. transplantation becomes relevant when an HSC-enriched population is delivered. Alternatively, CXCR4 expression on HSC, when transiently increased using a protein delivery method, improves homing and engraftment specifically of GM HSC.

Chemically-defined generation of human hemogenic endothelium and definitive hematopoietic progenitor cells

Human hematopoietic stem cells (HSCs), which arise from aorta-gonad-mesonephros (AGM), are widely used to treat blood diseases and cancers. However, a technique for their robust generation in vitro is still missing. Here we show temporal manipulation of Wnt signaling is sufficient and essential to induce AGM-like hematopoiesis from human pluripotent stem cells. TGFβ inhibition at the stage of aorta-like SOX17⁺CD235a^- hemogenic endothelium yielded AGM-like hematopoietic progenitors, which closely resembled primary cord blood HSCs at the transcriptional level and contained diverse lineage-primed progenitor populations via single cell RNA-sequencing analysis. Notably, the resulting definitive cells presented lymphoid and myeloid potential in vitro; and could home to a definitive hematopoietic site in zebrafish and rescue bloodless zebrafish after transplantation. Engraftment and multilineage repopulating activities were also observed in mouse recipients. Together, our work provided a chemically-defined and feeder-free culture platform for scalable generation of AGM-like hematopoietic progenitor cells, leading to enhanced production of functional blood and immune cells for various therapeutic applications.

Transient Inhibition of the JNK Pathway Promotes Human Hematopoietic Stem Cell Quiescence and Engraftment

The widespread clinical application of cord blood (CB) for hematopoietic stem cell (HSC) transplantation is limited mainly by the inadequate number of hematopoietic stem and progenitor cells (HSPCs) in single CB units, which results in unsuccessful or delayed engraftment in recipients. The identification of agents to promote CB HSPC engraftment has significant therapeutic value. Here, we found that transient inhibition of the JNK pathway increased the HSC frequency in CB CD34+ cells to 13.46-fold. Mechanistic studies showed that inhibition of the JNK pathway upregulated the expression of quiescence-associated and stemness genes in HSCs, preventing HSCs from entering the cell cycle, increasing glucose uptake and accumulating reactive oxygen species (ROS). Importantly, transient inhibition of the JNK pathway during CB CD34+ cell collection also enhanced long-term HSC (LT-HSC) recovery and engraftment efficiency. Collectively, these findings suggest that transient inhibition of the JNK pathway could promote a quiescent state in HSCs by preventing cell cycle entry and metabolic activation, thus enhancing the HSC number and engraftment potential. Together, these findings improve the understanding of the regulatory mechanisms governing HSC quiescence and stemness and have the potential to improve HSC collection and transplantation.

Important role of the SDF-1/CXCR4 axis in the homing of systemically transplanted human amnion-derived mesenchymal stem cells (hAD-MSCs) to ovaries in rats with chemotherapy-induced premature ovarian insufficiency (POI)

Background

Chemotherapy can induce premature ovarian insufficiency (POI). POI causes multiple sequelae and is currently incurable. As shown in our previous studies, systemically transplanted human amnion-derived mesenchymal stem cells (hAD-MSCs) home to ovaries with chemotherapy-induced POI and subsequently reduce ovarian injury and improve ovarian function in rats with POI. However, the cellular mechanisms that direct the migration and homing of hAD-MSCs to ovaries with chemotherapy-induced POI are incompletely understood. This study investigated the role of the SDF-1/CXCR4 axis in the migration and homing of systemically transplanted hAD-MSCs to ovaries with chemotherapy-induced POI and its relevant downstream signalling pathways.

Methods

CXCR4 expression in hAD-MSCs was assessed using Western blotting and immunofluorescence staining. hAD-MSC migration was tested using Transwell migration assays. SDF-1 levels were detected using ELISA. Seventy-two female SD rats were randomly divided into the control, POI, hAD-MSCs and hAD-MSCs + AMD3100 groups. Cyclophosphamide was used to establish rat POI models. For inhibitor treatment, hAD-MSCs were pretreated with AMD3100 before transplantation. PKH26-labeled hAD-MSCs were injected into the tail vein of POI rats 24 h after chemotherapy. After hAD-MSC transplantation, the homing of hAD-MSCs to ovaries and ovarian function and pathological changes were examined. We further investigated the molecular mechanisms by detecting the PI3K/Akt and ERK1/2 signalling pathways.

Results

hAD-MSCs expressed CXCR4. SDF-1 induced hAD-MSC migration in vitro. SDF-1 levels in ovaries and serum were significantly increased in rats with chemotherapy-induced POI, and ovaries with POI induced the homing of hAD-MSCs expressing CXCR4. Blocking the SDF-1/CXCR4 axis with AMD3100 significantly reduced the number of hAD-MSCs homing to ovaries with POI and further reduced their efficacy in POI treatment. The binding of SDF-1 to CXCR4 activated the PI3K/Akt signalling pathway, and LY294002 significantly inhibited hAD-MSC migration induced by SDF-1 in vitro. Moreover, inhibition of the PI3K/Akt signalling pathway significantly reduced the number of systemically transplanted hAD-MSCs homing to chemotherapy-induced ovaries in rats with POI.

Conclusions

SDF-1/CXCR4 axis partially mediates the migration and homing of systemically transplanted hAD-MSCs to the ovaries of rats with chemotherapy-induced POI, and the PI3K/Akt signalling pathway might be involved in the migration and homing of hAD-MSCs mediated by the SDF-1/CXCR4 axis.

Homotypic Cancer Cell Membranes Camouflaged Nanoparticles for Targeting Drug Delivery and Enhanced Chemo-Photothermal Therapy of Glioma

Glioma is among the deadliest types of brain cancer, for which there currently is no effective treatment. Chemotherapy is mainstay in the treatment of glioma. However, drug tolerance, non-targeting, and poor blood–brain barrier penetrance severely inhibits the efficacy of chemotherapeutics. An improved treatment method is thus urgently needed. Herein, a multifunctional biomimetic nanoplatform was developed by encapsulating graphene quantum dots (GQDs) and doxorubicin (DOX) inside a homotypic cancer cell membrane (CCM) for targeted chemo-photothermal therapy of glioma. The GQDs with stable fluorescence and a superior light-to-heat conversion property were synthesized as photothermal therapeutic agents and co-encapsulated with DOX in CCM. The as-prepared nanoplatform exhibited a high DOX loading efficiency. The cell membrane coating protected drugs from leakage. Upon an external laser stimuli, the membrane could be destroyed, resulting in rapid DOX release. By taking advantage of the homologous targeting of the cancer cell membrane, the GQDs/DOX@CCM were found to actively target tumor cells, resulting in significantly enhanced cellular uptake. Moreover, a superior suppression efficiency of GQDs/DOX@CCM to cancer cells through chemo-photothermal treatment was also observed. The results suggest that this biomimetic nanoplatform holds potential for efficient targeting of drug delivery and synergistic chemo-photothermal therapy of glioma.

Development and clinical advancement of small molecules for ex vivo expansion of hematopoietic stem cell

Hematopoietic stem cell (HSC) transplantation is the only curative therapy for many diseases. HSCs from umbilical cord blood (UCB) source have many advantages over from bone marrow. However, limited HSC dose in a single CB unit restrict its widespread use. Over the past two decades, ex vivo HSC expansion with small molecules has been an effective approach for obtaining adequate HSCs. Till now, several small-molecule compounds have entered the phase I/II trials, showing safe and favorable pharmacological profiles. As HSC expansion has become a hot topic over recent years, many newly identified small molecules along with novel biological mechanisms for HSC expansion would help solve this challenging issue. Here, we will give an overview of HSC biology, discovery and medicinal chemistry development of small molecules, natural products targeting for HSC expansion, and their recent clinical progresses, as well as potential protein targets for HSC expansion.

Enhanced self-renewal of human long-term hematopoietic stem cells by a sulfamoyl benzoate derivative targeting p18INK4C

The use of umbilical cord blood transplant has been substantially limited by the finite number of hematopoietic stem and progenitor cells in a single umbilical cord blood unit. Small molecules that not only quantitatively but also qualitatively stimulate enhancement of hematopoietic stem cell (HSC) self-renewal ex vivo should facilitate the clinical use of HSC transplantation and gene therapy. Recent evidence has suggested that the cyclin-dependent kinase inhibitor, p18INK4C (p18), is a critical regulator of mice HSC self-renewal. The role of p18 in human HSCs and the effect of p18 inhibitor on human HSC expansion ex vivo need further studies. Here we report that knockdown of p18 allowed for an increase in long-term colony-forming cells in vitro. We then identified an optimized small molecule inhibitor of p18, 005A, to induce ex vivo expansion of HSCs that was capable of reconstituting human hematopoiesis for at least 4 months in immunocompromised mice, and hence, similarly reconstituted secondary recipients for at least 4 more months, indicating that cells exposed to 005A were still competent in secondary recipients. Mechanistic studies showed that 005A might delay cell division and activate both the Notch signaling pathway and expression of transcription factor HoxB4, leading to enhancement of the self-renewal of long-term engrafting HSCs and the pool of progenitor cells. Taken together, these observations support a role for p18 in human HSC maintenance and that the p18 inhibitor 005A can enhance the self-renewal of long-term HSCs.

The contributory roles of histone deacetylases (HDACs) in hematopoiesis regulation and possibilities for pharmacologic interventions in hematologic malignancies

Although the definitive role of epigenetic modulations in a wide range of hematologic malignancies, spanning from leukemia to lymphoma and multiple myeloma, has been evidenced, few articles reviewed the task. Given the high accessibility of histone deacetylase (HDACs) to necessary transcription factors involved in hematopoiesis, this review aims to outline physiologic impacts of these enzymes in normal hematopoiesis, and also to outline the original data obtained from international research laboratories on their regulatory role in the differentiation and maturation of different hematopoietic lineages. Questions on how aberrant expression of HDACs contributes to the formation of hematologic malignancies are also responded, because these classes of enzymes have a respectable share in the development, progression, and recurrence of leukemia, lymphoma, and multiple myeloma. The last section provides a special focus on the therapeutic perspectiveof HDACs inhibitors, either as single agents or in a combined-modal strategy, in these neoplasms. In conclusion, optimizing the dose and the design of more patient-tailored inhibitors, while maintaining low toxicity against normal cells, will help improve clinical outcomes of HDAC inhibitors in hematologic malignancies.

All in for nuclear PFKP-induced CXCR4 metastasis: a T cell acute lymphoblastic leukemia prognostic marker

Phosphofructokinase 1 (PFK1) is expressed in T cell acute lymphoblastic leukemia (T-ALL), where its upregulation is linked with cancer progression. While PFK1 functions in the glycolysis pathway within the cytoplasm, it is also present in the nucleus where it regulates gene transcription. In this issue of the JCI, Xueliang Gao, Shenghui Qin, et al. focus their mechanism-based investigation on the nucleocytoplasmic shuttling aspect of the PFK1 platelet isoform, PFKP. Functional nuclear export and localization sequences stimulated CXC chemokine receptor type 4 (CXCR4) expression to promote T-ALL invasion that involved cyclin D3/CDK6, c-Myc, and importin-9. Since the presence of nuclear PFKP is associated with poor survival in T-ALL, nuclear PFKP-induced CXCR4 expression might serve as a prognostic marker for T-ALL. More promising, though, are the mechanistic insights suggesting that approaches to dampening metastatic migration may have application to benefit patients with T-ALL.

Uncoupling key determinants of hematopoietic stem cell engraftment through cell-specific and temporally controlled recipient conditioning

Hematopoietic stem cells (HSCs) are typically characterized by transplantation into irradiated hosts in a highly perturbed microenvironment. Here, we show that selective and temporally controlled depletion of resident HSCs through genetic deletion of Gata2 constitutes efficient recipient conditioning for transplantation without irradiation. Strikingly, we achieved robust engraftment of donor HSCs even when delaying Gata2 deletion until 4 weeks after transplantation, allowing homing and early localization to occur in a completely non-perturbed environment. When HSCs from the congenic strains Ly5.1 and Ly5.2 were competitively transplanted, we found that the more proliferative state of Ly5.2 HSCs was associated with superior long-term engraftment when using conditioning by standard irradiation, while higher CXCR4 expression and a better homing ability of Ly5.1 HSCs strongly favored the outcome in our inducible HSC depletion model. Thus, the mode and timing of recipient conditioning challenges distinct functional features of transplanted HSCs.

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Inducible gene deletion of Gata2 rapidly and selectively depletes the HSC pool

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Gata2 deletion constitutes efficient recipient conditioning for HSC transplantation

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The model enables detection of HSC engraftment in a non-perturbed microenvironment

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Transplantation without irradiation uniquely challenges homing properties of HSCs

Impairment of human terminal erythroid differentiation by histone deacetylase 5 deficiency

Histone deacetylases (HDACs) are a group of enzymes catalyzing the removal of acetyl groups from histone and non-histone proteins. HDACs have been shown to play diverse functions in a wide range of biological processes. However, their roles in mammalian erythropoiesis remain to be fully defined. We show here that of the eleven classic HDAC family members, six of them (HDAC 1,2,3 and HDAC 5,6,7) are expressed in human erythroid cells with HDAC5 most significantly up regulated during terminal erythroid differentiation. Knockdown of HDAC5 by either shRNA or siRNA in human CD34+ cells followed by erythroid cell culture led to increased apoptosis, decreased chromatin condensation, and impaired enucleation of erythroblasts. Biochemical analyses revealed that HDAC5 deficiency resulted in activation of p53 in association with increased acetylation of p53. Furthermore, while acetylation of histone 4 (H4) is decreased during normal terminal erythroid differentiation, HDAC5 deficiency led to increased acetylation of H4 (K12) in late stage erythroblasts. This increased acetylation was accompanied by decreased chromatin condensation, implying a role for H4 (K12) deacetylation in chromatin condensation. ATAC-seq and RNA-seq analyses revealed that HDAC5 knockdown leads to increased chromatin accessibility genome wide and global changes in gene expression. Moreover, pharmacological inhibition of HDAC5 by the inhibitor LMK235 also led to increased H4 acetylation, impaired chromatin condensation and enucleation. Taken together, our findings have uncovered previously unrecognized roles and molecular mechanisms of action for HDAC5 in human erythropoiesis. These results may provide insights into understanding the anemia associated with HDAC inhibitor treatment.

Exosome-guided bone targeted delivery of Antagomir-188 as an anabolic therapy for bone loss

The differentiation shift from osteogenesis to adipogenesis of bone marrow mesenchymal stem cells (BMSCs) characterizes many pathological bone loss conditions. Stromal cell-derived factor-1 (SDF1) is highly enriched in the bone marrow for C-X-C motif chemokine receptor 4 (CXCR4)-positive hematopoietic stem cell (HSC) homing and tumor bone metastasis. In this study, we displayed CXCR4 on the surface of exosomes derived from genetically engineered NIH-3T3 cells. CXCR4⁺ exosomes selectively accumulated in the bone marrow. Then, we fused CXCR4⁺ exosomes with liposomes carrying antagomir-188 to produce hybrid nanoparticles (NPs). The hybrid NPs specifically gathered in the bone marrow and released antagomir-188, which promoted osteogenesis and inhibited adipogenesis of BMSCs and thereby reversed age-related trabecular bone loss and decreased cortical bone porosity in mice. Taken together, this study presents a novel way to obtain bone-targeted exosomes via surface display of CXCR4 and a promising anabolic therapeutic approach for age-related bone loss.

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Surface display of CXCR4 grants exosomes bone targeting properties.

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Exosome-liposome hybrid nanoparticles carrying nucleic acid target bone.

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Antagomir-188 loaded hybrid nanoparticles regulate MSC differentiation in aged mice.

RXR Negatively Regulates Ex Vivo Expansion of Human Cord Blood Hematopoietic Stem and Progenitor Cells

Ex vivo expansion of human cord blood (CB) hematopoietic stem cells (HSCs) is one approach to overcome limited numbers of HSCs in single CB units. However, there is still no worldwide acceptable HSC ex vivo expansion system. A main reason is that we still have very limited knowldege regarding mechanisms underlying maintenance and expansion of CB HSCs. Here we report that retinoid X receptor (RXR) activity is of significance for CB HSC ex vivo expansion. RXR antagonist HX531 significantly promoted ex vivo expansion of CB HSCs and progenitor cells (HPCs). RXR agonist Bexarotene notably suppressed ex vivo expansion of CB HSCs. Activation of RXR by Bexarotene significantly blocked expansion of phenotypic HSCs and HPCs and expressed increased functional HPCs as assessed by colony formation induced by UM171 and SR1. In vivo transplantation experiments in immune-deficient mice demonstrated that HX531 expanded CB HSCs possess long-term reconstituting capacities, and Bexarotene treatment inhibited expansion of functional CB HSCs. RNA-seq analysis revealed that RXR regulates expression of FBP1 (a negative regulator of glucose metabolism) and many genes involved in differentation. ECAR analysis showed that HX531 significantly promoted glycolytic activity of CB CD34⁺ HSCs and HPCs. Our studies suggest that RXR is a negative regulator of ex vivo expansion of CB HSCs and HPCs.

Human Hematopoietic Stem, Progenitor, and Immune Cells Respond Ex Vivo to SARS-CoV-2 Spike Protein

Despite evidence that SARS-CoV-2 infection is systemic in nature, there is little known about the effects that SARS-CoV-2 infection or exposure has on many host cell types, including primitive and mature hematopoietic cells. The hematopoietic system is responsible for giving rise to the very immune cells that defend against viral infection and is a source of hematopoietic stem cells (HSCs) and progenitor cells (HPCs) which are used for hematopoietic cell transplantation (HCT) to treat hematologic disorders, thus there is a strong need to understand how exposure to the virus may affect hematopoietic cell functions. We examined the expression of ACE2, to which SARS-CoV-2 Spike (S) protein binds to facilitate viral entry, in cord blood derived HSCs/HPCs and in peripheral blood derived immune cell subtypes. ACE2 is expressed in low numbers of immune cells, higher numbers of HPCs, and up to 65% of rigorously defined HSCs. We also examined effects of exposing HSCs/HPCs and immune cells to SARS-CoV-2 S protein ex vivo. HSCs and HPCs expand less effectively and have less functional colony forming capacity when grown with S protein, while peripheral blood monocytes upregulate CD14 expression and show distinct changes in size and granularity. That these effects are induced by recombinant S protein alone and not the infectious viral particle suggests that simple exposure to SARS-CoV-2 may impact HSCs/HPCs and immune cells via S protein interactions with the cells, regardless of whether they can be infected. These data have implications for immune response to SARS-CoV-2 and for HCT. Graphical Abstract • Human HSCs, HPCs, and immune cells express ACE2 on the cell surface, making them potentially susceptible to SARS-CoV-2 infection. • SARS-CoV-2 S protein, which binds to ACE2, induces defects in the colony forming capacity of human HPC and inhibits the expansion of HSC/HPC subpopulations ex vivo. These effects can be at least partially neutralized by treatment with SARS-CoV-2 targeting antibody, recombinant human ACE2, or Angiotensin1-7. • S protein also induces aberrant morphological changes in peripheral blood derived monocytes ex vivo. • Thus, there are many different manners in which SARS-CoV-2 virus may impact the functional hematopoietic system, which has important implications for hematological manifestations of COVID-19 (i.e. thrombocytopenia and lymphopenia), immune response, and hematopoietic stem cell transplant in the era of COVID-19.

Fate of Hematopoiesis During Aging. What Do We Really Know, and What are its Implications?

There is an ongoing shift in demographics such that older persons will outnumber young persons in the coming years, and with it age-associated tissue attrition and increased diseases and disorders. There has been increased information on the association of the aging process with dysregulation of hematopoietic stem (HSC) and progenitor (HPC) cells, and hematopoiesis. This review provides an extensive up-to date summary on the literature of aged hematopoiesis and HSCs placed in context of potential artifacts of the collection and processing procedure, that may not be totally representative of the status of HSCs in their in vivo bone marrow microenvironment, and what the implications of this are for understanding aged hematopoiesis. This review covers a number of interactive areas, many of which have not been adequately explored. There are still many unknowns and mechanistic insights to be elucidated to better understand effects of aging on the hematopoietic system, efforts that will take multidisciplinary approaches, and that could lead to means to ameliorate at least some of the dysregulation of HSCs and HPCs associated with the aging process. Graphical Abstract.

Contribution of the bone marrow stromal cells in mediating drug resistance in hematopoietic tumors

The bone marrow microenvironment (BMM) provides input via production of cytokines, chemokines, extracellular matrixes in the context of lower oxygen levels that influences self-renewal, survival, differentiation, progression, and therapeutic resistance of multiple myeloma and leukemic cells. Within the context of the BMM, tumor cells are supported by osteoblasts, bone marrow stromal cells (BMSCs), fibroblasts, myeloid cells, endothelial cells and blood vessels, as well as extracellular matrix (ECM) that contribute to tumor progression. Environmental mediated-drug resistance (EM-DR) contains cell adhesion-mediated drug resistance (CAM-DR) and soluble factor-mediated drug resistance (SM-DR) that contributes to de novo drug resistance. In this review, we focus on the crosstalk between the BMM and tumor cells as well as mechanisms underlying the BMM contributing to drug resistance in hematologic malignancies.

Progress towards improving homing and engraftment of hematopoietic stem cells for clinical transplantation

PURPOSE OF REVIEW

Hematopoietic cell transplantation (HCT) is a life-saving treatment for a variety of hematological and nonhematological disorders. Successful clinical outcomes after transplantation rely on adequate hematopoietic stem cell (HSC) numbers, and the homing and subsequent short-term and long-term engraftment of these cells in the bone marrow. Enhancing the homing capability of HSCs has the potential for high impact on improving HCT and patient survival.

RECENT FINDINGS

There are a number of ways to enhance HSC engraftment. Neutralizing negative epigenetic regulation by histone deacetylase 5 (HDAC5) increases surface CXCR4 expression and promotes human HSC homing and engraftment in immune-deficient NSG (NOD.Cg-Prkdc IL2rgt/Sz) mice. Short-term treatment of cells with glucocorticoids, pharmacological stabilization of hypoxia-inducible factor (HIF)-1α, increasing membrane lipid raft aggregation, and inhibition of dipeptidyl peptidase 4 (DPP4) facilitates HSC homing and engraftment. Added to these procedures, modulating the mitochondria permeability transition pore (MPTP) to mitigate ambient air-induced extra physiological oxygen stress/shock (EPHOSS) by hypoxic harvest and processing, or using cyclosporine A during air collection increases functional HSC numbers and improves HSC engraftment.

SUMMARY

A better understanding of the regulation of human HSC homing mediated by various signaling pathways will facilitate development of more efficient means to enhance HCT efficacy.

Effects of Eupalinilide E and UM171, alone and in combination on cytokine stimulated ex-vivo expansion of human cord blood hematopoietic stem cells

Eupalinilide E was assessed for ex-vivo expansion activity on hematopoietic stem cells (HSCs) from human cord blood (CB) CD34+ cells in serum-free, SCF, TPO and FL stimulated 7 day cultures. Eupalinilide E ex-vivo enhanced phenotyped (p) HSCs and glycolysis of CD34+ cells isolated 7 days after culture as measured by extracellular acidification rate, but did not alone show enhanced NSG engrafting capability of HSCs as determined by chimerism and numbers of SCID Repopulating cells, a quantitative measure of functional human HSCs. This is another example of pHSCs not necessarily recapitulating functional activity of these cells. Lack of effect on engrafting HSCs may be due to a number of possibilities, including down regulation of CXCR4 or of the homing capacity of these treated cells. However, Eupalinilide did act in an additive to synergistic fashion with UM171 to enhance ex vivo expansion of both pHSCs, and functionally engrafting HSCs. While reasons for the disconnect between pHSC and function of HSCs with Eupalinilide E alone cultured CB CD34+ cells is yet to be determined, the data suggest possible future use of Eupalinilide and UM171 together to enhance ex vivo production of CB HSCs for clinical hematopoietic cell transplantation.

Low-energy shock wave pretreatment recruit circulating endothelial progenitor cells to attenuate renal ischaemia reperfusion injury

Low‐energy shock wave (LESW) has been recognized as a promising non‐invasive intervention to prevent the organs or tissues against ischaemia reperfusion injury (IRI), whereas its effect on kidney injury is rarely explored. To investigate the protective role of pretreatment with LESW on renal IRI in rats, animals were randomly divided into Sham, LESW, IRI and LESW + IRI groups. At 4, 12, 24 hours and 3 and 7 days after reperfusion, serum samples and renal tissues were harvested for performing the analysis of renal function, histopathology, immunohistochemistry, flow cytometry and Western blot, as well as enzyme‐linked immunosorbent assay. Moreover, circulating endothelial progenitor cells (EPCs) were isolated, labelled with fluorescent dye and injected by tail vein. The fluorescent signals of EPCs were detected using fluorescence microscope and in vivo imaging system to track the distribution of injected circulating EPCs. Results showed that pretreatment with LESW could significantly reduce kidney injury biomarkers, tubular damage, and cell apoptosis, and promote cell proliferation and vascularization in IRI kidneys. The renoprotective role of LESW pretreatment would be attributed to the remarkably increased EPCs in the treated kidneys, part of which were recruited from circulation through SDF‐1/CXCR7 pathway. In conclusion, pretreatment with LESW could increase the recruitment of circulating EPCs to attenuate and repair renal IRI.

Biological Characteristics and Regulation of Early Megakaryocytopoiesis

For decades, megakaryocytopoiesis is believed to occur following a classical binary hierarchical developmental model. This model is based on an analysis of predefined flow-sorted cell populations by using cell surface markers. However, this classical model has been challenged by increasing evidences obtained with new techniques which integrating flow cytometric, transcriptomic and functional data at single-cell level and with lineage tracing technique. These recent advances in megakaryocytopoiesis proposed that commitment of haematopoietic stem cells (HSCs) towards megakaryocytic lineage occurs in much earlier stage than that postulated in the classical model. There may exist multipotent but megakaryocyte (MK)/platelet-biased HSCs within HSC compartment and even HSCs can directly differentiate into MKs in steady state or in response to stress. In this review, we focus on recent findings about differentiation from commitment of HSCs to MK and its regulation, and discuss future directions in this research field.

Understanding Normal and Malignant Human Hematopoiesis Using Next-Generation Humanized Mice

Rodent models for human diseases contribute significantly to understanding human physiology and pathophysiology. However, given the accelerating pace of drug development, there is a crucial need for in vivo preclinical models of human biology and pathology. The humanized mouse is one tool to bridge the gap between traditional animal models and the clinic. The development of immunodeficient mouse strains with high-level engraftment of normal and diseased human immune/hematopoietic cells has made in vivo functional characterization possible. As a patient-derived xenograft (PDX) model, humanized mice functionally correlate putative mechanisms with in vivo behavior and help to reveal pathogenic mechanisms. Combined with single-cell genomics, humanized mice can facilitate functional precision medicine such as risk stratification and individually optimized therapeutic approaches.

Role of HDACs in normal and malignant hematopoiesis

Normal hematopoiesis requires the accurate orchestration of lineage-specific patterns of gene expression at each stage of development, and epigenetic regulators play a vital role. Disordered epigenetic regulation has emerged as a key mechanism contributing to hematological malignancies. Histone deacetylases (HDACs) are a series of key transcriptional cofactors that regulate gene expression by deacetylation of lysine residues on histone and nonhistone proteins. In normal hematopoiesis, HDACs are widely involved in the development of various lineages. Their functions involve stemness maintenance, lineage commitment determination, cell differentiation and proliferation, etc. Deregulation of HDACs by abnormal expression or activity and oncogenic HDAC-containing transcriptional complexes are involved in hematological malignancies. Currently, HDAC family members are attractive targets for drug design, and a variety of HDAC-based combination strategies have been developed for the treatment of hematological malignancies. Drug resistance and limited therapeutic efficacy are key issues that hinder the clinical applications of HDAC inhibitors (HDACis). In this review, we summarize the current knowledge of how HDACs and HDAC-containing complexes function in normal hematopoiesis and highlight the etiology of HDACs in hematological malignancies. Moreover, the implication and drug resistance of HDACis are also discussed. This review presents an overview of the physiology and pathology of HDACs in the blood system.

Past, present, and future efforts to enhance the efficacy of cord blood hematopoietic cell transplantation

Cord blood (CB) has been used as a viable source of hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) in over 35,000 clinical hematopoietic cell transplantation (HCT) efforts to treat the same variety of malignant and non-malignant disorders treated by bone marrow (BM) and mobilized peripheral blood (mPB) using HLA-matched or partially HLA-disparate related or unrelated donor cells for adult and children recipients. This review documents the beginning of this clinical effort that started in the 1980’s, the pros and cons of CB HCT compared to BM and mPB HCT, and recent experimental and clinical efforts to enhance the efficacy of CB HCT. These efforts include means for increasing HSC numbers in single CB collections, expanding functional HSCs ex vivo, and improving CB HSC homing and engraftment, all with the goal of clinical translation. Concluding remarks highlight the need for phase I/II clinical trials to test the experimental procedures that are described, either alone or in combination.

Daily light and darkness onset and circadian rhythms metabolically synchronize hematopoietic stem cell differentiation and maintenance: The role of bone marrow norepinephrine, tumor necrosis factor, and melatonin cycles

Hematopoietic stem and progenitor cells (HSPCs) are essential for daily mature blood cell production, host immunity, and osteoclast-mediated bone turnover. The timing at which stem cells give rise to mature blood and immune cells while maintaining the bone marrow (BM) reservoir of undifferentiated HSPCs and how these opposite tasks are synchronized are poorly understood. Previous studies revealed that daily light onset activates norepinephrine (NE)-induced BM CXCL12 downregulation, followed by CXCR4⁺ HSPC release to the circulation. Recently, we reported that daily light onset induces transient elevations of BM NE and tumor necrosis factor (TNF), which metabolically program BM HSPC differentiation and recruitment to replenish the blood. In contrast, darkness onset induces lower elevations of BM NE and TNF, activating melatonin production, which metabolically reprograms HSPCs, increasing their short- and long-term repopulation potential, and BM maintenance. How the functions of BM-retained HSPCs are influenced by daily light and darkness cycles and their clinical potential are further discussed.

Epigenetic drug screen identifies the histone deacetylase inhibitor NSC3852 as a potential novel drug for the treatment of pediatric acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is a heterogeneous disease regarding morphology, immunophenotyping, genetic abnormalities, and clinical behavior. The overall survival rate of pediatric AML is 60% to 70%, and has not significantly improved over the past two decades. Children with Down syndrome (DS) are at risk of developing acute megakaryoblastic leukemia (AMKL), which can be preceded by a transient myeloproliferative disorder during the neonatal period. Intensification of current treatment protocols is not feasible due to already high treatment-related morbidity and mortality. Instead, more targeted therapies with less severe side effects are highly needed.

PROCEDURE

To identify potential novel therapeutic targets for myeloid disorders in children, including DS-AMKL and non-DS-AML, we performed an unbiased compound screen of 80 small molecules targeting epigenetic regulators in three pediatric AML cell lines that are representative for different subtypes of pediatric AML. Three candidate compounds were validated and further evaluated in normal myeloid precursor cells during neutrophil differentiation and in (pre-)leukemic pediatric patient cells.

RESULTS

Candidate drugs LMK235, NSC3852, and bromosporine were effective in all tested pediatric AML cell lines with antiproliferative, proapoptotic, and differentiation effects. Out of these three compounds, the pan-histone deacetylase inhibitor NSC3852 specifically induced growth arrest and apoptosis in pediatric AML cells, without disrupting normal neutrophil differentiation.

CONCLUSION

NSC3852 is a potential candidate drug for further preclinical testing in pediatric AML and DS-AMKL.

[Identification of differentially expressed genes between lung adenocarcinoma and squamous cell carcinoma using transcriber signature analysis]

OBJECTIVE

To analyze the differentially expressed genes (DEGs) between lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) with bioinformatics analysis and search for potential biomarkers for clinical diagnosis of nonsmall cell lung cancer (NSCLC).

METHODS

The gene expression profiling datasets of LUAD and LUSC were acquired. The transcriptome differences between LUAD and LUSC were identified using R language processing and t-test analysis. The differential expressions of the genes were shown by Venn diagram. The DEGs identified by GEO2R were analyzed with DAVID and Ingenuity Pathway Analysis (IPA) to identify the signaling pathways and biomarkers that could be used for differential diagnosis of LUAD and LUSC. The TCGA data and the biomarker expression data from clinical lung cancer samples were used to verify the differential expressions of the Osteoarthritis pathway and LXR/RXR between LUAD and LUSC. We further examined the differential expressions of miR-181 and its two target genes, WNT5A and MBD2, in 23 clinical specimens of lung squamous cell carcinoma and the paired adjacent tissues.

RESULTS

GEO data analysis identified 851 DEGs (including 276 up-regulated and 575 down-regulated genes) in LUAD and 885 DEGs (including 406 up-regulated and 479 down-regulated genes) in LUSC. DAVID and IPA analysis revealed that leukocyte migration and inflammatory responses were more abundant in LUAD than in LUSC. Osteoarthritis pathway was inhibited in LUAD and activated in LUSC. IPA analysis showed that transcription factors (GATA4, RELA, YBX1, TP63 and MBD2), cytokines (WNT5A and IL1A) and microRNAs (miR-34a, miR-181b and miR-15a) differed significantly between LUAD and LUSC. miR-34a with IL-1A, miR-15a with YBX1, and miR-181b with WNT5A and MBD2 could serve as the paired microRNA and mRNA targets for differential diagnosis of NSCLC subtypes. Analysis of the clinical samples showed an increased expression of miR-181b-5p and the down-regulation of WNT5A, which could be used as molecular markers for the diagnosis of LUSC.

CONCLUSIONS

Through transcriptome analysis, we identified candidate genes, paired microRNAs and pathways for differentiating LUAD and LUSC, and they can provide novel differential diagnosis and therapeutic strategies for LUAD and LUSC.

Secreted nuclear protein DEK regulates hematopoiesis through CXCR2 signaling

The nuclear protein DEK is an endogenous DNA-binding chromatin factor regulating hematopoiesis. DEK is one of only 2 known secreted nuclear chromatin factors, but whether and how extracellular DEK regulates hematopoiesis is not known. We demonstrated that extracellular DEK greatly enhanced ex vivo expansion of cytokine-stimulated human and mouse hematopoietic stem cells (HSCs) and regulated HSC and hematopoietic progenitor cell (HPC) numbers in vivo and in vitro as determined both phenotypically (by flow cytometry) and functionally (through transplantation and colony formation assays). Recombinant DEK increased long-term HSC numbers and decreased HPC numbers through a mechanism mediated by the CXC chemokine receptor CXCR2 and heparan sulfate proteoglycans (HSPGs) (as determined utilizing Cxcr2-/- mice, blocking CXCR2 antibodies, and 3 different HSPG inhibitors) that was associated with enhanced phosphorylation of ERK1/2, AKT, and p38 MAPK. To determine whether extracellular DEK required nuclear function to regulate hematopoiesis, we utilized 2 mutant forms of DEK: one that lacked its nuclear translocation signal and one that lacked DNA-binding ability. Both altered HSC and HPC numbers in vivo or in vitro, suggesting the nuclear function of DEK is not required. Thus, DEK acts as a hematopoietic cytokine, with the potential for clinical applicability.

Cord blood research, banking, and transplantation: achievements, challenges, and perspectives

The first hematopoietic transplant in which umbilical cord blood (UCB) was used as the source of hematopoietic cells was performed in October 1988. Since then, significant achievements have been reported in terms of our understanding of the biology of UCB-derived hematopoietic stem (HSCs) and progenitor (HPCs) cells. Over 40,000 UCB transplants (UCBTs) have been performed, in both children and adults, for the treatment of many different diseases, including hematologic, metabolic, immunologic, neoplastic, and neurologic disorders. In addition, cord blood banking has been developed to the point that around 800,000 units are being stored in public banks and more than 4 million units in private banks worldwide. During these 30 years, research in the UCB field has transformed the hematopoietic transplantation arena. Today, scientific and clinical teams are still working on different ways to improve and expand the use of UCB cells. A major effort has been focused on enhancing engraftment to potentially reduce risk of infection and cost. To that end, we have to understand in detail the molecular mechanisms controlling stem cell self-renewal that may lead to the development of ex vivo systems for HSCs expansion, characterize the mechanisms regulating the homing of HSCs and HPCs, and determine the relative place of UCBTs, as compared to other sources. These challenges will be met by encouraging innovative research on the basic biology of HSCs and HPCs, developing novel clinical trials, and improving UCB banking both in the public and private arenas.

Targeting JNK pathway promotes human hematopoietic stem cell expansion

The limited number of human hematopoietic stem cells (HSCs) has restrained their widespread clinical application. Despite great efforts in recent years, the in vitro expansion of HSCs remains a challenge due to incomplete understanding of the signaling networks underlying HSC self-renewal. Here, we show that culturing human cord blood (CB) CD34⁺ cells with JNK-IN-8, an inhibitor of the JNK signaling pathway, can enhance the self-renewal of HSCs with a 3.88-fold increase in cell number. These cultured CD34⁺ cells repopulated recipient mice for 21 weeks and can form secondary engraftment that lasted for more than 21 weeks. Knockdown of c-Jun, a major downstream target in the JNK pathway, promoted the expansion of hematopoietic stem and progenitor cells (HSPCs). Our findings demonstrate a critical role of the JNK pathway in regulating HSC expansion, provide new insights into HSC self-renewal mechanism, and may lead to improved clinical application of HSCs.