Advances in stem cell mobilization

Endogenus chondrocytes immobilized by G-CSF in nanoporous gels enable repair of critical-size osteochondral defects

Injured articular cartilage is a leading cause for osteoarthritis. We recently discovered that endogenous stem/progenitor cells not only reside in the superficial zone of mouse articular cartilage, but also regenerated heterotopic bone and cartilage in vivo. However, whether critical-size osteochondral defects can be repaired by pure induced chemotatic cell homing of these endogenous stem/progenitor cells remains elusive. Here, we first found that cells in the superficial zone of articular cartilage surrounding surgically created 3 × 1 mm defects in explant culture of adult goat and rabbit knee joints migrated into defect-filled fibrin/hylaro1nate gel, and this migration was significantly more robust upon delivery of exogenous granulocyte-colony stimulating factor (G-CSF). Remarkably, G-CSF-recruited chondrogenic progenitor cells (CPCs) showed significantly stronger migration ability than donor-matched chondrocytes and osteoblasts. G-CSF-recruited CPCs robustly differentiated into chondrocytes, modestly into osteoblasts, and barely into adipocytes. In vivo, critical-size osteochondral defects were repaired by G-CSF-recruited endogenous cells postoperatively at 6 and 12 weeks in comparison to poor healing by gel-only group or defect-only group. ICRS and O'Driscoll scores of articular cartilage were significantly higher for both 6- and 12-week G-CSF samples than corresponding gel-only and defect-only groups. Thus, endogenous stem/progenitor cells may be activated by G-CSF, a Food and Drug Administration (FDA)-cleared bone-marrow stimulating factor, to repair osteochondral defects.

Use of subgroup-specific hematopoietic stem cell collection efficiencies to improve truncation calculations for large-volume leukapheresis procedures

PURPOSE

A critical component of optimizing peripheral blood (PB) hematopoietic stem cell (HSC) collections is accurately determining the processed blood volume required to collect the targeted number of HSCs. Fundamental to most truncation equations employed to determine this volume is the procedure's estimated collection efficiency (CE), which is typically applied uniformly across all HSC collections. Few studies have explored the utility of using different CEs in subpopulations of donors that have substantially different CEs than the institutional average.

METHODS

Initial procedures from 343 autologous and 179 allogeneic HSC collections performed from 2018 to 2021 were retrospectively analyzed. Predictive equations were developed to determine theoretical truncation rates in various donor subgroups.

RESULTS

Quantitative variables (pre-procedure cell counts) and qualitative variables (relatedness to recipient, gender, method of venous access, and mobilization strategy) were found to significantly impact CE. However, much of the variability in CE between donors could not be explained by the variables assessed. Analyses of procedures with high pre-collection PB cell counts identified lower CE values for these donors' truncation equations which still allow truncation but minimize risk of collecting less CD34+ cells than requested.

CONCLUSIONS

Individualized CE does not substantially improve truncation volume calculations over use of a fixed CE and adds complexity to these calculations. The optimal fixed CE varies between autologous and allogeneic donors, and donors with high pre-collection PB cell counts in either of these groups. This model will be clinically validated and continuously refined through analysis of future HSC collections.

Addition of plerixafor in poorly mobilized allogeneic stem cell donors

Background

Peripheral blood stem cells (PBSCs) are the predominant graft source for adult allogeneic hematopoietic stem cell transplantation (HSCT). In poorly mobilized autologous donors, plerixafor improves collection outcomes. We examine plerixafor use in allogeneic donors who mobilize poorly with granulocyte colony‐stimulating factor (G‐CSF) in those who are healthy and those with pre‐existing medical conditions, and determine the optimal threshold to add plerixafor.

Study Design/Methods

We retrospectively examined all allogeneic PBSC collections from January 2013 to October 2020 at our center. Donors received G‐CSF 10 mcg/kg daily for 4 days before undergoing apheresis collection on day 5. Plerixafor was added based on poor CD34+ cell collection yield after the first or second collection day.

Results

Of the 1008 allogeneic donors, 41 (4.1%) received one dose of plerixafor in addition to G‐CSF due to poor collection yield. After starting plerixafor there was a 0.75‐ to 7.74‐fold (median 2.94) increase in CD34+ yield from the previous day. No donors with G‐CSF‐only mobilization who collected <2.0 × 10⁶ CD34+ cells/kg recipient weight on day one achieved the goal of ≥4.0 × 10⁶ CD34+ cells/kg recipient weight total over 2 days but 59.2% of donors who used rescue plerixafor did.

Conclusion

Donors both healthy and those with pre‐existing disease responded well to plerixafor with minimal side effects. If the first‐day collection yield is less than ~63% of the collection goal, addition of plerixafor may be necessary to reach the collection goal and limit the number of collection days in allogeneic donors.

Ziyuglycoside II alleviates cyclophosphamide-induced leukopenia in mice via regulation of HSPC proliferation and differentiation

Ziyuglycoside II (ZGS II) is a major bioactive ingredient of Sanguisorbae officinalis L., which has been widely used for managing myelosuppression or leukopenia induced by chemotherapy or radiotherapy. In the current study, we investigated the pro-hematopoietic effects and underlying mechanisms of ZGS II in cyclophosphamide-induced leukopenia in mice. The results showed that ZGS II significantly increased the number of total white blood cells and neutrophils in the peripheral blood. Flow cytometry analysis also showed a significant increase in the number of nucleated cells and hematopoietic stem and progenitor cells (HSPCs) including ST-HSCs, MPPs, and GMPs, and enhanced HSPC proliferation in ZGS II treated mice. The RNA-sequencing analysis demonstrated that ZGS II effectively regulated cell differentiation, immune system processes, and hematopoietic system-related pathways related to extracellular matrix (ECM)-receptor interaction, focal adhesion, hematopoietic cell lineage, cytokine-cytokine receptor interaction, the NOD-like receptor signaling pathway, and the osteoclast differentiation pathway. Moreover, ZGS II treatment altered the differentially expressed genes (DEGs) with known functions in HSPC differentiation and mobilization (Cxcl12, Col1a2, and Sparc) and the surface markers of neutrophilic precursors or neutrophils (Ngp and CD177). Collectively, these data suggest that ZGS II protected against chemotherapy-induced leukopenia by regulating HSPC proliferation and differentiation.

G-CSF Infusion for Stem Cell Mobilization Transiently Increases Serum Cell-Free DNA and Protease Concentrations

G-CSF for stem cell mobilization increases circulating levels of myeloid cells at different stages of maturation. Polymorphonuclear cells (PMNs) are also mobilized in high numbers. It was previously reported that G-CSF primes PMNs toward the release of neutrophils extracellular traps (NETs). Since NETs are often involved in thrombotic events, we hypothesized that high G-CSF blood concentrations could enhance PMN priming toward NET formation in healthy hematopoietic stem cell donors, predisposing them to thrombotic events. However, we found that G-CSF does not prime PMNs toward NETs formation, but increases the serum concentration of cell-free DNA, proteases like neutrophils elastase and myeloperoxidase, and reactive oxygen species. This could possibly create an environment disposed to induce thrombotic events in the presence of additional predisposing factors.

Oncogenic Deregulation of Cell Adhesion Molecules in Leukemia

Numerous cell⁻cell and cell⁻matrix interactions within the bone marrow microenvironment enable the controlled lifelong self-renewal and progeny of hematopoietic stem and progenitor cells (HSPCs). On the cellular level, this highly mutual interaction is granted by cell adhesion molecules (CAMs) integrating differentiation, proliferation, and pro-survival signals from the surrounding microenvironment to the inner cell. However, cell⁻cell and cell⁻matrix interactions are also critically involved during malignant transformation of hematopoietic stem/progenitor cells. It has become increasingly apparent that leukemia-associated gene products, such as activated tyrosine kinases and fusion proteins resulting from chromosomal translocations, directly regulate the activation status of adhesion molecules, thereby directing the leukemic phenotype. These observations imply that interference with adhesion molecule function represents a promising treatment strategy to target pre-leukemic and leukemic lesions within the bone marrow niche. Focusing on myeloid leukemia, we provide a current overview of the mechanisms by which leukemogenic gene products hijack control of cellular adhesion to subsequently disturb normal hematopoiesis and promote leukemia development.

Particulate and solubilized β-glucan and non-β-glucan fractions of Euglena gracilis induce pro-and anti-inflammatory innate immune cell responses and exhibit antioxidant properties

Purpose

The purpose of this work was to determine the pro-and anti-inflammatory properties of the single-cell organism Euglena gracilis (EG) and various fractions of its whole biomass.

Methods

Heterotrophically grown EG was tested, along with its aqueous fraction (E-AQ), the intact linear β-glucan paramylon granules (PAR), and alkaline-solubilized paramylon. Peripheral blood mononuclear cell cultures were treated with the test products and analyzed for a variety of cellular responses. Immune cell activation was evaluated by flow cytometry detection of CD69 levels on CD3^-CD56⁺ NK cells, CD3⁺CD56⁺ NKT cells, and monocytes, and cytokines were analyzed from the cell culture supernatants. Antioxidant capacity was measured by Folin-Ciocalteu assay and cellular antioxidant protection and MTT assays.

Results

EG and E-AQ were the most effective in driving immune cell responses as measured by CD69 upregulation on NK and NKT cells and proinflammatory (tumor necrosis factor, IL-6, IL-1β) cytokine production. None of the test products effectively stimulated monocyte. EG and PAR inhibited reactive oxygen species under conditions of oxidative stress. E-AQ contained antioxidants capable of providing cellular antioxidant protection from oxidative damage and protection of mitochondrial function under inflammatory conditions.

Conclusion

The effects of EG on immune function are only partially attributable to the content of the β-glucan, paramylon. The regulation of additional cellular responses, such a reactive oxygen species production and resistance to oxidative stress, is likely mediated by currently unknown molecules found in the EG cell.

Granulocyte-colony stimulating factor enhances load-induced muscle hypertrophy in mice

Granulocyte-colony stimulating factor (G-CSF) is a cytokine crucially involved in the regulation of granulopoiesis and the mobilization of hematopoietic stem cells from bone marrow. However, emerging data suggest that G-CSF exhibits more diverse functions than initially expected, such as conferring protection against apoptosis to neural cells and stimulating mitogenesis in cardiomyocytes and skeletal muscle stem cells after injury. In the present study, we sought to investigate the potential contribution of G-CSF to the regulation of muscle volume. We found that the administration of G-CSF significantly enhances muscle hypertrophy in two different muscle overload models. Interestingly, there was a significant increase in the transcripts of both G-CSF and G-CSF receptors in the muscles that were under overload stress. Using mutant mice lacking the G-CSF receptor, we confirmed that the anabolic effect is dependent on the G-CSF receptor signaling. Furthermore, we found that G-CSF increases the diameter of myotubes in vitro and induces the phosphorylation of AKT, mTOR, and ERK1/2 in the myoblast-like cell line C2C12 after differentiation induction. These findings indicate that G-CSF is involved in load-induced muscle hypertrophy and suggest that G-CSF is a potential agent for treating patients with muscle loss and sarcopenia.

GM-CSF Enhances Mobilization of Bone Marrow Mesenchymal Stem Cells via a CXCR4-Medicated Mechanism

Background

This study was conducted to investigate the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on the mobilization of mesenchymal stem cells (MSCs) from the bone marrow (BM) into the peripheral blood (PB) in rats.

Methods

GM-CSF was administered subcutaneously to rats at 50 μg/kg body weight for 5 consecutive days. The BM and PB of rats were collected at 1, 3, and 5 days during the administration for analysis.

Results

Upon GM-CSF administration, the number of mononuclear cells increased rapidly at day 1 both in the BM and PB. This number decreased gradually over time in the BM to below the initial amount by day 5, but was maintained at a high level in the PB until day 5. The colony-forming unit-fibroblasts were increased in the PB by 10.3-fold at day 5 of GM-CSF administration, but decreased in the BM. Compared to GM-CSF, granulocyte-colony stimulating factor (G-CSF) stimulated lower levels of MSC mobilization from the BM to the PB. Immunohistochemical analysis revealed that GM-CSF induced a hypoxic and proteolytic microenvironment and increased C-X-C chemokine receptor type 4 (CXCR4) expression in the BM. GM-CSF added to BM MSCs in vitro dose-dependently increased CXCR4 expression and cell migration. G-CSF and stromal cell derived factor-1 (SDF-1) showed similar results in these in vitro assays. Know-down of CXCR4 expression with siRNA significantly abolished GM-CSF- and G-CSF-induced MSC migration in vitro, indicating the involvement of the SDF-1-CXCR4 interaction in the mechanism.

Conclusion

These results suggest that GM-CSF is a useful tool for mobilizing BM MSCs into the PB.

Intraoperative Construct Preparation: A Practical Route for Cell-Based Bone Regeneration

Stem cell-based bone tissue engineering based on the combination of a scaffold and expanded autologous mesenchymal stem cells (MSCs) represents the current state-of-the-art treatment for bone defects and fractures. However, the procedure of such construct preparation requires extensive ex vivo manipulation of patient's cells to achieve enough stem cells. Therefore, it is impractical and not cost-effective compared to other therapeutic interventions. For these reasons, a more practical strategy circumventing any ex vivo manipulation and an additional surgery for the patient would be advantageous. Intraoperative concept-based bone tissue engineering, where constructs are prepared with easily accessible autologous cells within the same surgical procedure, allows for such a simplification. In this study, we discuss the concept of intraoperative construct preparation for bone tissue engineering and summarize the available cellular options for intraoperative preparation. Furthermore, we propose methods to prepare intraoperative constructs, and review data of currently available preclinical and clinical studies using intraoperatively prepared constructs for bone regenerative applications. We identify several obstacles hampering the application of this emerging approach and highlight perspectives of technological innovations to advance the future developments of intraoperative construct preparation.

Mesenchymal stromal cells contribute to quiescence of therapy-resistant leukemic cells in acute myeloid leukemia

OBJECTIVE

Persistence of leukemic cells after induction therapy has been shown to correlate with poor survival in acute myeloid leukemia (AML). In this study, we tested if human mesenchymal stromal cells (hMSCs) have protective effects on leukemic cells undergoing chemotherapy.

METHODS

Persistent disease was used as marker to identify cases with therapy-resistant leukemic cells in 95 patients with AML. Immunophenotyping, cell cycle, and apoptosis assays were assessed by flow cytometry. AML coculture studies were performed with hMSC of healthy donors.

RESULTS

Samples from patients with persistent disease had increased fractions of CD34⁺ CD38^- and quiescent leukemic cells. Comparison of sample series collected at time points of diagnosis and blast persistence showed a relative therapy resistance of quiescent leukemic cells. Consistent with these observations, relapsed disease always displayed higher proportions of quiescent cells compared to samples of first diagnosis suggesting that quiescence is an important therapy escape mechanism of resistant cells. Co-culture studies demonstrated that hMSC protect leukemic cells from the effect of AraC treatment by enriching for quiescent cells, mimicking the effects observed in patients. This effect was even detectable when no direct stromal contact was established.

CONCLUSIONS

Our data suggest that hMSC contribute to quiescence and therapy resistance of persistent AML cells.

GM-CSF and IL-4 Fusion Cytokine Induces B Cell-Dependent Hematopoietic Regeneration

Hematopoietic stem cells (HSCs) have the capacity to self-renew and differentiate into hematopoietic cells and have been utilized to replace diseased bone marrow for patients with cancers and blood disorders. Although remarkable progress has been made in developing new tools to manipulate HSCs for clinic use, there is still no effective method to expand HSCs in vivo for quick repopulation of hematopoietic cells following sublethal irradiation. We have recently described a novel synthetic cytokine that is derived from the fusion of granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin 4 (IL-4; named as GIFT4), and we have now discovered that GIFT4 fusokine promotes long-term hematopoietic regeneration in a B cell-dependent manner. We found that GIFT4 treatment triggered a robust expansion of endogenous bone marrow HSCs and multipotent progenitors in vivo. Delivery of GIFT4 protein together with B cells rescued lethally irradiated mice. Moreover, adoptive transfer of autologous or allogeneic GIFT4-treated B cells (GIFT4-B cells) enhanced long-term hematopoietic recovery in radiated mice and prevented the mice from irradiation-induced death. Our data suggest that GIFT4 as well as GIFT4-B cells could serve as means to augment HSC engraftment in the setting of bone marrow transplantation for patients with hematological malignancy.

Combination of low-energy shock-wave therapy and bone marrow mesenchymal stem cell transplantation to improve the erectile function of diabetic rats

Stem cell transplantation and low-energy shock-wave therapy (LESWT) have emerged as potential and effective treatment protocols for diabetic erectile dysfunction. During the tracking of transplanted stem cells in diabetic erectile dysfunction models, the number of visible stem cells was rather low and decreased quickly. LESWT could recruit endogenous stem cells to the cavernous body and improve the microenvironment in diabetic cavernous tissue. Thus, we deduced that LESWT might benefit transplanted stem cell survival and improve the effects of stem cell transplantation. In this research, 42 streptozotocin-induced diabetic rats were randomized into four groups: the diabetic group (n = 6), the LESWT group (n = 6), the bone marrow-derived mesenchymal stem cell (BMSC) transplantation group (n = 15), and the combination of LESWT and BMSC transplantation group (n = 15). One and three days after BMSC transplantation, three rats were randomly chosen to observe the survival numbers of BMSCs in the cavernous body. Four weeks after BMSC transplantation, the following parameters were assessed: the surviving number of transplanted BMSCs in the cavernous tissue, erectile function, real-time polymerase chain reaction, and penile immunohistochemical assessment. Our research found that LESWT favored the survival of transplanted BMSCs in the cavernous body, which might be related to increased stromal cell-derived factor-1 expression and the enhancement of angiogenesis in the diabetic cavernous tissue. The combination of LESWT and BMSC transplantation could improve the erectile function of diabetic erectile function rats more effectively than LESWT or BMSC transplantation performed alone.

TLR9-mediated inflammation drives a Ccr2-independent peripheral monocytosis through enhanced extramedullary monocytopoiesis

Monocytes are innate immune cells that interact with their environment through the expression of pattern recognition receptors, including Toll-like receptors (TLRs). Both monocytes and TLRs are implicated in driving persistent inflammation in autoimmune diseases. However, cell-intrinsic mechanisms to control inflammation, including TLR tolerance, are thought to limit inflammatory responses in the face of repeated TLR activation, leaving it unclear how chronic TLR-mediated inflammation is maintained in vivo. Herein, we used a well-characterized model of systemic inflammation to determine the mechanisms allowing sustained TLR9 responses to develop in vivo. Monocytes were identified as the main TLR9-responsive cell and accumulated in peripherally inflamed tissues during TLR9-driven inflammation. Intriguingly, canonical mechanisms controlling monocyte production and localization were altered during the systemic inflammatory response, as accumulation of monocytes in the liver and spleen developed in the absence of dramatic increases in bone marrow monocyte progenitors and was independent of chemokine (C-C motif) receptor 2 (Ccr2). Instead, TLR9-driven inflammation induced a Ccr2-independent expansion of functionally enhanced extramedullary myeloid progenitors that correlated with the peripheral accumulation of monocytes in both wild-type and Ccr2(-/-) mice. Our data implicate inflammation-induced extramedullary monocytopoiesis as a peripheral source of newly produced TLR9 responsive monocytes capable of sustaining chronic TLR9 responses in vivo. These findings help to explain how chronic TLR-mediated inflammation may be perpetuated in autoimmune diseases and increase our understanding of how monocytes are produced and positioned during systemic inflammatory responses.

Targeting stem cell niche can protect hematopoietic stem cells from chemotherapy and G-CSF treatment

INTRODUCTION

Hematopoietic stem/progenitor cells (HSPCs) reside in a tightly controlled local microenvironment called bone marrow niche. The specialized microenvironment or niche not only provides a favorable habitat for HSPC maintenance and development but also governs stem cell function.

METHOD

We investigated the effect of cytotoxic drugs on bone marrow niche. To mimic the multiple rounds of chemotherapy followed by autologous hematopoietic stem cells (HSCs) transplantation in a clinical setting, we further verified the hypothesis that targeting the niche might improve stem cell-based therapies in mouse models.

RESULTS

We found that multiple rounds of cytotoxic drug treatment significantly disrupted niche and serum osteocalcin level was significantly reduced after treatment in autologous HSPCs transplanted patients (P = 0.01). In mouse models, the number of CD45(-)Ter119(-)OPN(+) osteoblasts was significantly reduced after multiple rounds of chemotherapies and granulocyte colony stimulating factor (G-CSF) treatment (P < 0.01). Parathyroid hormone (PTH) or receptor activator of nuclear factor kappa-B ligand (RANKL) treatment significantly increased the number of HSCs mobilized into peripheral blood (PB) for stem cell harvesting and protected stem cells from repeated exposure to cytotoxic chemotherapy. Treatments with G-CSF and PTH significantly increased the preservation of the HSC pool (P < 0.05). Moreover, recipient mice transplanted with circulation HSPCs that were previously treated with PTH and RANKL showed robust myeloid and lymphatic cell engraftment compared to the mice transplanted with HSCs after chemotherapy or G-CSF treatment.

CONCLUSION

These data provide new evidence that the niche may be an important target for drug-based stem cell therapy.

Urokinase receptor and CXCR4 are regulated by common microRNAs in leukaemia cells

The urokinase-type plasminogen activator (uPA) receptor (uPAR) focuses uPA proteolytic activity on the cell membrane, promoting localized degradation of extracellular matrix (ECM), and binds vitronectin (VN), mediating cell adhesion to the ECM. uPAR-bound uPA and VN induce proteolysis-independent intracellular signalling, regulating cell adhesion, migration, survival and proliferation. uPAR cross-talks with CXCR4, the receptor for the stroma-derived factor 1 chemokine. CXCR4 is crucial in the trafficking of hematopoietic stem cells from/to the bone marrow, which involves also uPAR. Both uPAR and CXCR4 are expressed in acute myeloid leukaemia (AML), with a lower expression in undifferentiated and myeloid subsets, and higher expression in myelomonocytic and promyelocytic subsets. We hypothesized a microRNA (miR)-mediated co-regulation of uPAR and CXCR4 expression, which could allow their cross-talk at the cell surface. We identified three miRs, miR-146a, miR-335 and miR-622, regulating the expression of both uPAR and CXCR4 in AML cell lines. Indeed, these miRs directly target the 3'untranslated region of both uPAR- and CXCR4-mRNAs; accordingly, uPAR/CXCR4 expression is reduced by their overexpression in AML cells and increased by their specific inhibitors. Overexpression of all three miRs impairs migration, invasion and proliferation of myelomonocytic cells. Interestingly, we observed an inverse relationship between uPAR/CXCR4 expression and miR-146a and miR-335 levels in AML blasts, suggesting their possible role in the regulation of uPAR/CXCR4 expression also in vivo.

Optimizing mobilization strategies in difficult-to-mobilize patients: The role of plerixafor

Peripheral blood stem cell collection is currently the most widely used source for hematopoietic autologous transplantation. Several factors such as advanced age, previous chemotherapy, disease and marrow infiltration at the time of mobilization influence the efficacy of CD34(+) progenitor cell mobilization. Despite the safety and efficiency of the standard mobilization protocols (G-CSF ± chemotherapy), there is still a significant amount of mobilization failure rate (10-40%), which necessitate novel agents for effective mobilization. Plerixafor, is a novel agent, has been recently approved for mobilization of hematopoietic stem cells (HSCs). The combination of Plerixafor with G-CSF provides the collection of large numbers of stem cells in fewer apheresis sessions and can salvage those who fail with standard mobilization regimens. The development and optimization of practical algorithms for the use Plerixafor is crucial to make hematopoietic stem cell mobilization more efficient in a cost-effective way. This review is aimed at summarizing how to identify poor mobilizers, and define rational use of Plerixafor for planning mobilization in hard-to-mobilize patients.

Tbo-Filgrastim versus Filgrastim during Mobilization and Neutrophil Engraftment for Autologous Stem Cell Transplantation

There are limited data available supporting the use of the recombinant granulocyte colony-stimulating factor (G-CSF), tbo-filgrastim, rather than traditionally used filgrastim to mobilize peripheral blood stem cells (PBSC) or to accelerate engraftment after autologous stem cell transplantation (ASCT). We sought to compare the efficacy and cost of tbo-filgrastim to filgrastim in these settings. Patients diagnosed with lymphoma or plasma cell disorders undergoing G-CSF mobilization, with or without plerixafor, were included in this retrospective analysis. The primary outcome was total collected CD34(+) cells/kg. Secondary mobilization endpoints included peripheral CD34(+) cells/μL on days 4 and 5 of mobilization, adjunctive use of plerixafor, CD34(+) cells/kg collected on day 5, number of collection days and volumes processed, number of collections reaching 5 million CD34(+) cells/kg, and percent reaching target collection goal in 1 day. Secondary engraftment endpoints included time to neutrophil and platelet engraftment, number of blood product transfusions required before engraftment, events of febrile neutropenia, and length of stay. A total of 185 patients were included in the final analysis. Patients receiving filgrastim (n = 86) collected a median of 5.56 × 10(6) CD34(+) cells/kg, compared with a median of 5.85 × 10(6) CD34(+) cells/kg in the tbo-filgrastim group (n = 99; P = .58). There were no statistically significant differences in all secondary endpoints with the exception of apheresis volumes processed (tbo-filgrastim, 17.0 liters versus filgrastim, 19.7 liters; P < .01) and mean platelet transfusions (tbo-filgrastim, 1.7 units versus filgrastim, 1.4 units; P = .04). In conclusion, tbo-filgrastim demonstrated similar CD34(+) yield compared with filgrastim in mobilization and post-transplantation settings, with no clinically meaningful differences in secondary efficacy and safety endpoints. Furthermore, tbo-filgrastim utilization was associated with cost savings of approximately $1406 per patient utilizing average wholesale price.

Leukemia cell mobilization with G-CSF plus plerixafor during busulfan-fludarabine conditioning for allogeneic stem cell transplantation

We hypothesized that during conditioning chemotherapy for allogeneic stem cell transplant (allo-SCT), disruption of stromal-leukemia interactions using granulocyte-colony stimulating factor (G-CSF) in combination with the CXCR4-specific inhibitor plerixafor, may promote release of leukemic cells from the niche and increase tumor elimination. In a phase 1/2 investigation, we treated 45 AML/MDS/CML patients (34 AML, 7 MDS, and 4 CML) with G-CSF (10 μg/kg daily for 6 days starting on day −9) plus plerixafor (doses of 0, 80, 160 or 240 μg/kg daily for 4 days starting on day −7) along with the busulfan-fludarabine (Bu-Flu) conditioning regimen. In the phase 1 part, we determined that G-CSF plus plerixafor is safe in this setting. We compared clinical effects and outcomes of AML/MDS study patients (n = 40) to 164 patients from a historical data set who received Bu-Flu alone prior to allo-SCT by stratifying on cytogenetics and disease status to correct for bias. Study patients had increased myeloid chimerism and lower rates of GvHD. There was no significant difference in relapse free survival or overall survival. The G-CSF plus plerixafor combination increased circulating white blood cells, CD34+ cells, and CXCR4+ cells, and preferentially mobilized FISH+ leukemic cells. ClinicalTrials.gov identifier is NCT00822770.

Variant rs1801157 in the 3'UTR of SDF-1ß does not explain variability of healthy-donor G-CSF responsiveness

The genetics responsible for the inter-individually variable G-CSF responsiveness remain elusive. A single nucleotide polymorphism (SNP) in the 3’UTR of CXCL12, rs1801157, was implicated in X4-tropic HiV susceptibility and later, in two small studies, in G-CSR responsiveness in patients and donors. The position of the SNP in the 3’UTR together with in-silico predictions suggested differential binding of micro-RNA941 as an underlying mechanism. In a cohort of 515 healthy stem cell donors we attempted to reproduce the correlation of the CXCL12 3’UTR SNP and mobilization responses and tested the role of miR941 in this context. The SNP was distributed with the expected frequency. Mobilization efficiency for CD34+ cells in WT, heterozygous and homozygous SNP individuals was indistinguishable, even after controlling for gender. miR941 expression in non-hematopoietic bone marrow cells was undetectable and miR941 did not interact with the 3’ UTR of CXCL12. Proposed effects of the SNP rs1801157 on G-CSF responsiveness cannot be confirmed in a larger cohort.

Intensive chemotherapy as salvage treatment for solid tumors: focus on germ cell cancer

Germ cell tumors present contrasting biological and molecular features compared to many solid tumors, which may partially explain their unusual sensitivity to chemotherapy. Reduced DNA repair capacity and enhanced induction of apoptosis appear to be key factors in the sensitivity of germ cell tumors to cisplatin. Despite substantial cure rates, some patients relapse and subsequently die of their disease. Intensive doses of chemotherapy are used to counter mechanisms of drug resistance. So far, high-dose chemotherapy with hematopoietic stem cell support for solid tumors is used only in the setting of testicular germ cell tumors. In that indication, high-dose chemotherapy is given as the first or late salvage treatment for patients with either relapsed or progressive tumors after initial conventional salvage chemotherapy. High-dose chemotherapy is usually given as two or three sequential cycles using carboplatin and etoposide with or without ifosfamide. The administration of intensive therapy carries significant side effects and can only be efficiently and safely conducted in specialized referral centers to assure optimum patient care outcomes. In breast and ovarian cancer, most studies have demonstrated improvement in progression-free survival (PFS), but overall survival remained unchanged. Therefore, most of these approaches have been dropped. In germ cell tumors, clinical trials are currently investigating novel therapeutic combinations and active treatments. In particular, the integration of targeted therapies constitutes an important area of research for patients with a poor prognosis.

Cdc42 inhibitor ML141 enhances G-CSF-induced hematopoietic stem and progenitor cell mobilization

G-CSF is the most often used agent in clinical hematopoietic stem and progenitor cell (HSPC) mobilization. However, in about 10 % of patients, G-CSF does not efficiently mobilize HSPC in clinically sufficient amounts. Cdc42 activity is involved in HSPC mobilization. In the present study, we explore the impact of Cdc42 inhibitor ML141 on G-CSF-mediated HSPC mobilization in mice. We found that the use of ML141 alone only triggered modest HSPC mobilization effect in mice. However, combination of G-CSF and ML141 significantly promoted HPSC counts and colony forming units in peripheral blood, as compared to mice treated with G-CSF alone. ML141 did not significantly alter the levels of SDF-1 and MMP-9 in the bone marrow, when used alone or in combination with G-CSF. We also found that G-CSF administration significantly increases the level of GTP-bound Cdc42, but does not alter the expression of Cdc42 in the bone marrow. Our data indicate that the Cdc42 signal is a negative regulator in G-CSF-mediated HSPC mobilization, and that inhibition of the Cdc42 signal efficiently improves mobilization efficiency. These findings may provide a new strategy for efficient HSPC mobilization, especially in patients with poor G-CSF response.

Mobilization characteristics and strategies to improve hematopoietic progenitor cell mobilization and collection in patients with chronic granulomatous disease and severe combined immunodeficiency

BACKGROUND

Granulocyte-colony-stimulating factor (G-CSF)-mobilized autologous hematopoietic progenitor cells (HPCs) may be collected by apheresis of patients with chronic granulomatous disease (CGD) and severe combined immunodeficiency (SCID) for use in gene therapy trials. CD34+ cell mobilization has not been well characterized in such patients.

STUDY DESIGN AND METHODS

We retrospectively evaluated CD34+ cell mobilization and collection in 73 consecutive CGD and SCID patients and in 99 age-, weight-, and G-CSF dose-matched healthy allogeneic controls.

RESULTS

In subjects aged not more than 20 years, Day 5 preapheresis circulating CD34+ counts were significantly lower in CGD and SCID patients than in controls; mean peak CD34+ cell counts were 58 × 10(6) , 64 × 10(6) , and 87 × 10(6) /L, respectively (p = 0.01). The SCIDs had lower CD34+ collection efficiency than CGDs and controls; mean efficiencies were 40, 63, and 57%, respectively (p = 0.003). In subjects aged more than 20 years, the CGDs had significantly lower CD34+ cell mobilization than controls; mean peak CD34+ cell counts were 41 × 10(6) and 113 × 10(6) /L, respectively (p < 0.0001). In a multivariate analysis, lower erythrocyte sedimentation rate (ESR) at mobilization was significantly correlated with better CD34+ cell mobilization (p = 0.007). In SCIDs, CD34 collection efficiency was positively correlated with higher red blood cell (RBC) indices (mean RBC volume, R(2)  = 0.77; mean corpuscular hemoglobin [Hb], R(2)  = 0.94; mean corpuscular Hb concentration, R(2)  = 0.7; p < 0.007) but not Hb.

CONCLUSIONS

CGD and SCID populations are characterized by significantly less robust CD34+ HPC mobilization than healthy controls. The presence of active inflammation or infection as suggested by an elevated ESR may negatively impact mobilization. Among SCIDs, markedly reduced CD34 collection efficiencies were related to iron deficiency, wherein decreased RBC size and density may impair apheresis cell separation mechanics.

Predictive factors for a single successful cytapheresis session during the first mobilisation

To avoid repeated apheresis, the objective of this study was to analyse the predictive factors for a single successful cytapheresis during the first mobilisation. The pre-collection characteristics of 170 lymphoma and 95 myeloma patients were analysed. Among 60 lymphoma patients who had less than 30 CD34 cells/mm(3) the day before the first apheresis, an increase in the CD34 cell count between Day -1 and Day 1 was predictive of first stem cell mobilisation success, with a sensitivity of 100% if the Day 1 was higher than 30/mm(3) (10/60 patients). Success rate of obtaining an appropriate number of stem cells in one apheresis was 120 among 170 patients.

Hematopoietic stem cells and liver regeneration: differentially acting hematopoietic stem cell mobilization agents reverse induced chronic liver injury

Bone marrow (BM) could serve as a source of cells facilitating liver repopulation in case of hepatic damage. Currently available hematopoietic stem cell (HSC) mobilizing agents, were comparatively tested for healing potential in liver fibrosis. Carbon tetrachloride (CCl4)-injured mice previously reconstituted with Green Fluorescent Protein BM were mobilized with Granulocyte-Colony Stimulating Factor (G-CSF), Plerixafor or G-CSF+Plerixafor. Hepatic fibrosis, stellate cell activation and oval stem cell frequency were measured by Gomori and by immunohistochemistry for a-Smooth Muscle Actin and Cytokeratin-19, respectively. Angiogenesis was evaluated by ELISA and immunohistochemistry. Quantitative real-time PCR was used to determine the mRNA levels of liver Peroxisome Proliferator-Activated Receptor gamma (PPAR-γ), Interleukin-6 (IL-6) and Tumor Necrosis-alpha (TNFα). BM-derived cells were tracked by double immunofluorescence. The spontaneous migration of mobilized HSCs towards injured liver and its cytokine secretion profile was determined in transwell culture systems. Either single-agent mobilization or the combination of agents significantly ameliorated hepatic damage by decreasing fibrosis and restoring the abnormal vascular network in the liver of mobilized mice compared to CCl4-only mice. The degree of fibrosis reduction was similar among all mobilized mice despite that G-CSF+Plerixafor yielded significantly higher numbers of circulating HSCs over other agents. The liver homing potential of variously mobilized HSCs differed among the agents. An extended G-CSF treatment provided the highest anti-fibrotic effect over all tested modalities, induced by the proliferation of hepatic stem cells and decreased hepatic inflammation. Plerixafor-mobilized HSCs, despite their reduced liver homing potential, reversed fibrosis mainly by increasing hepatic PPAR-γ and VEGF expression. In all groups, BM-derived mature hepatocytes as well as liver-committed BM stem cells were detected only at low frequencies, further supporting the concept that alternative mechanisms rather than direct HSC effects regulate liver recovery. Overall, our data suggest that G-CSF, Plerixafor and G-CSF+Plerixafor act differentially during the wound healing process, ultimately providing a potent anti-fibrotic effect.

Transdifferentiation of autologous bone marrow cells on a collagen-poly(ε-caprolactone) scaffold for tissue engineering in complete lack of native urothelium

Urological reconstructive surgery is sometimes hampered by a lack of tissue. In some cases, autologous urothelial cells (UCs) are not available for cell expansion and ordinary tissue engineering. In these cases, we wanted to explore whether autologous mesenchymal stem cells (MSCs) from bone marrow could be used to create urological transplants. MSCs from human bone marrow were cultured in vitro with medium conditioned by normal human UCs or by indirect co-culturing in culture well inserts. Changes in gene expression, protein expression and cell morphology were studied after two weeks using western blot, RT-PCR and immune staining. Cells cultured in standard epithelial growth medium served as controls. Bone marrow MSCs changed their phenotype with respect to growth characteristics and cell morphology, as well as gene and protein expression, to a UC lineage in both culture methods, but not in controls. Urothelial differentiation was also accomplished in human bone marrow MSCs seeded on a three-dimensional poly(ε-caprolactone) (PCL)-collagen construct. Human MSCs could easily be harvested by bone marrow aspiration and expanded and differentiated into urothelium. Differentiation could take place on a three-dimensional hybrid PCL-reinforced collagen-based scaffold for creation of a tissue-engineered autologous transplant for urological reconstructive surgery.

Epigenetic reprogramming induces the expansion of cord blood stem cells

Cord blood (CB) cells that express CD34 have extensive hematopoietic capacity and rapidly divide ex vivo in the presence of cytokine combinations; however, many of these CB CD34+ cells lose their marrow-repopulating potential. To overcome this decline in function, we treated dividing CB CD34+ cells ex vivo with several histone deacetylase inhibitors (HDACIs). Treatment of CB CD34+ cells with the most active HDACI, valproic acid (VPA), following an initial 16-hour cytokine priming, increased the number of multipotent cells (CD34+CD90+) generated; however, the degree of expansion was substantially greater in the presence of both VPA and cytokines for a full 7 days. Treated CD34+ cells were characterized based on the upregulation of pluripotency genes, increased aldehyde dehydrogenase activity, and enhanced expression of CD90, c-Kit (CD117), integrin α6 (CD49f), and CXCR4 (CD184). Furthermore, siRNA-mediated inhibition of pluripotency gene expression reduced the generation of CD34+CD90+ cells by 89%. Compared with CB CD34+ cells, VPA-treated CD34+ cells produced a greater number of SCID-repopulating cells and established multilineage hematopoiesis in primary and secondary immune-deficient recipient mice. These data indicate that dividing CB CD34+ cells can be epigenetically reprogrammed by treatment with VPA so as to generate greater numbers of functional CB stem cells for use as transplantation grafts.

The CXCR4 and adhesion molecule expression of CD34+ hematopoietic cells mobilized by "on-demand" addition of plerixafor to granulocyte-colony-stimulating factor

Background

Granulocyte–colony-stimulating factor (G-CSF) is routinely used for mobilization of hematopoietic stem and progenitor cells preceding autologous transplantation after high-dose chemotherapy in hematologic malignancies. However, due to high mobilization failure rates, alternative mobilization strategies are required.

Study Design and Methods

Patients who poorly mobilized CD34+ hematopoietic cells (HCs) with G-CSF additionally received the CXCR4 antagonist plerixafor. The phenotype of CD34+ HCs collected after this plerixafor-induced “rescue” mobilization, in regard to adhesion molecule and CD133, CD34, and CD38 expression in comparison to CD34+ HCs collected after traditional G-CSF administration in good mobilizers, was analyzed flow cytometrically. To confirm previous studies in our patient cohort, the efficiency of mobilization and subsequent engraftment after this “on-demand” plerixafor mobilization were analyzed.

Results

Pronounced mobilization occurred after plerixafor administration in poor mobilizers, resulting in similar CD34+ cell yields as obtained by G-CSF in good mobilizers, whereby plerixafor increased the content of primitive CD133+/CD34+/CD38– cells. The surface expression profiles of the marrow homing and retention receptors CXCR4, VLA-4, LFA-1, and CD44 on mobilized CD34+ cells and hematopoietic recovery after transplantation were similar in patients receiving G-CSF plus plerixafor or G-CSF. Unexpectedly, the expression levels of respective adhesion receptors were not related to mobilization efficiency or engraftment.

Conclusion

The results show that CD34+ HCs collected by plerixafor-induced rescue mobilization are qualitatively equivalent to CD34+ HCs collected after traditional G-CSF mobilization in good mobilizers, in regard to their adhesive phenotype and engraftment potential. Thereby, plerixafor facilitates the treatment of poor mobilizers with autologous HC transplantation after high-dose chemotherapy.

Novel evidence that crosstalk between the complement, coagulation and fibrinolysis proteolytic cascades is involved in mobilization of hematopoietic stem/progenitor cells (HSPCs)

The role of blood proteinases in the mobilization of hematopoietic stem/progenitor cells (HSPCs) is still not well understood. As previously reported, activation of the complement cascade (ComC) and cleavage of C5 by C5 convertase are enabling events in the release of C5a that plays a crucial role in the egress of HSPCs from bone marrow (BM) into peripheral blood (PB) and explains why C5-deficient mice are poor mobilizers. Here we provide evidence that during granulocyte colony-stimulating factor- and AMD3100-induced mobilization, not only the ComC but also two other evolutionarily ancient proteolytic enzyme cascades, the coagulation cascade (CoaC) and the fibrynolytic cascade (FibC), become activated. Activation of all three cascades was measured by generation of C5a, decrease in prothrombin time and activated partial thromboplastin time as well as an increase in the concentrations of plasmin/antiplasmin and thrombin/antithrombin. More importantly, the CoaC and FibC, by generating thrombin and plasmin, respectively, provide C5 convertase activity, explaining why mobilization of HSPCs in C3-deficient mice, which do not generate ComC-generated C5a convertase, is not impaired. Our observations shed more light on how the CoaC and FibC modulate stem cell mobilization and may lead to the development of more efficient mobilization strategies in poor mobilizers. Furthermore, as it is known that all these cascades are activated in all the situations in which HSPCs are mobilized from BM into PB (for example, infections, tissue/organ damage or strenuous exercise) and show a circadian rhythm of activation, they must be involved in both stress-induced and circadian changes in HSPC trafficking in PB.

Neutropenia during HIV infection: adverse consequences and remedies

Neutropenia frequently occurs in patients with Human immunodeficiency virus (HIV) infection. Causes for neutropenia during HIV infection are multifactoral, including the viral toxicity to hematopoietic tissue, the use of myelotoxic agents for treatment, complication with secondary infections and malignancies, as well as the patient's association with confounding factors which impair myelopoiesis. An increased prevalence and severity of neutropenia is commonly seen in advanced stages of HIV disease. Decline of neutrophil phagocytic defense in combination with the failure of adaptive immunity renders the host highly susceptible to developing fatal secondary infections. Neutropenia and myelosuppression also restrict the use of many antimicrobial agents for treatment of infections caused by HIV and opportunistic pathogens. In recent years, HIV infection has increasingly become a chronic disease because of progress in antiretroviral therapy (ART). Prevention and treatment of severe neutropenia becomes critical for improving the survival of HIV-infected patients.

Roles of the chemokine system in development of obesity, insulin resistance, and cardiovascular disease

The escalating epidemic of obesity has increased the incidence of obesity-induced complications to historically high levels. Adipose tissue is a dynamic energy depot, which stores energy and mobilizes it during nutrient deficiency. Excess nutrient intake resulting in adipose tissue expansion triggers lipid release and aberrant adipokine, cytokine and chemokine production, and signaling that ultimately lead to adipose tissue inflammation, a hallmark of obesity. This low-grade chronic inflammation is thought to link obesity to insulin resistance and the associated comorbidities of metabolic syndrome such as dyslipidemia and hypertension, which increase risk of type 2 diabetes and cardiovascular disease. In this review, we focus on and discuss members of the chemokine system for which there is clear evidence of participation in the development of obesity and obesity-induced pathologies.

Targeting the molecular and cellular interactions of the bone marrow niche in immunologic disease

Recent investigations have expanded our knowledge of the regulatory bone marrow (BM) niche, which is critical in maintaining and directing hematopoietic stem cell (HSC) self-renewal and differentiation. Osteoblasts, mesenchymal stem cells (MSCs), and CXCL12-abundant reticular (CAR) cells are niche components in close association with HSCs and have been more clearly defined in immune cell function and homeostasis. Importantly, cellular inhabitants of the BM niche signal through G protein-coupled surface receptors (GPCRs) for various appropriate immune functions. In this article, recent literature on BM niche inhabitants (HSCs, osteoblasts, MSCs, CAR cells) and their GPCR mechanistic interactions are reviewed for better understanding of the BM cells involved in immune development, immunologic disease, and current immune reconstitution therapies.

Infection-induced changes in hematopoiesis

The bone marrow (BM) is an important site for the interrelated processes of hematopoiesis, granulopoiesis, erythropoiesis, and lymphopoiesis. A wide variety of microbial challenges are associated with profound changes in this compartment that impact on hematopoietic differentiation and mobilization of a variety of cell types. This article reviews some of the key pathways that control BM homeostasis, the infectious and inflammatory processes that affect the BM, and how addressing the knowledge gaps in this area has the potential to widen our comprehension of immune homeostasis.

Hematopoietic stem and progenitor cell mobilization in mice

Hematopoietic stem cell transplantation (HSCT) can be performed with hematopoietic stem and progenitor cells (HSPC) acquired directly from bone marrow, from umbilical cord blood or placental tissue, or from the peripheral blood after treatment of the donor with agents that enhance egress of HSPC into the circulation, a process known as "mobilization." Mobilized peripheral blood stem cells (PBSC) have become the predominate hematopoietic graft for HSCT, particularly for autologous transplants. Despite the success of PBSC transplant, many patients and donors do not achieve optimal levels of mobilization. Thus, accurate animal models and basic laboratory investigations are needed to further investigate the mechanisms that lead to PBSC mobilization and define improved or new mobilizing agents and/or strategies to enhance PBSC mobilization and transplant. This chapter outlines assays and techniques for exploration of hematopoietic mobilization using mice as a model organism.

Chemokine receptor modeling: an interdisciplinary approach to drug design

Chemokines and their receptors are integral components of the immune response, regulating lymphocyte development, homing and trafficking, and playing a key role in the pathophysiology of many diseases. Chemokine receptors have, therefore, become the target for both small-molecule, peptide and antibody therapeutics. Chemokine receptors belong to the family of seven transmembrane receptor class A G protein-coupled receptors. The publication of the crystal structure of the archetypal class A seven transmembrane receptor protein rhodopsin, and other G protein-coupled receptors, including C-X-C chemokine receptor 4 and C-C chemokine receptor 5, provided the opportunity to create homology models of chemokine receptors. In this review, we describe an interdisciplinary approach to chemokine receptor modeling and the utility of this approach for structure-based drug design of chemokine receptor inhibitors.

The effect of gradual increment in rhG-CSF dose on stem cell yields in patients with multiple myeloma mobilized with intermediate dose cyclophosphamide plus rhG-CSF

Cyclophosphamide along with recombinant human granulocyte-colony stimulating factor (rhG-CSF) is a commonly used strategy for mobilization. However, the optimal timing for rhG-CSF initiation after cyclophosphamide has not been determined as conclusively as has the G-CSF dose. In this paper, we aimed to present gradual dose increment of rhG-CSF between the third day of mobilization and time to apheresis that is started with 5 μg/kg (from day 3 to day 7) and continued with 10 μg/kg (from day 8 to time to apheresis) for peripheral blood stem cell (PBSC) mobilization in multiple myeloma (MM) patients and its effect on stem cell yield and mobilization success. Data from 30 consecutive patients with MM who underwent PBSC mobilization between October 2011 and June 2013, were retrospectively reviewed. While twenty-eight of 30 patients (93.3%) were successfully mobilized, 2 patients (6.7%) had mobilization failure. The final median CD34+ cell dose harvested from the patients was 9.5×10(6)/kg. The median number of apheresis was 2.5 (range, 0-3). Twenty-four patients (80%) yielded >2×10(6) CD34+ cells/kg in one apheresis procedure. In conclusion, our regimen might be used to decrease the mobilization failure regarding the low dose rhG-CSF use and provide a cost effective strategy.

Physiology and pharmacology of plerixafor

Autologous hematopoietic stem cell (HSC) transplantation is an important therapeutic option for patients with non-Hodgkin's lymphoma and multiple myeloma. The primary source of HSC is from the peripheral blood which requires mobilization from the bone marrow. Current mobilization regimens include cytokines such as G-CSF and/or chemotherapy. However not all patients mobilize enough HSC to proceed to transplant. The chemokine receptor CXCR4 and its ligand CXCL12 are an integral part of the mechanism of HSC retention in the bone marrow niche. The discovery of plerixafor, a selective inhibitor of CXCR4, has provided a new additional means of mobilizing HSC for autologous transplantation. Plerixafor consists of two cyclam rings with a phenylenebis(methylene) linker. It inhibits CXCL12 binding to CXCR4 and subsequent downstream events including chemotaxis. The molecular interactions of plerixafor have been defined indicating a unique binding mode to CXCR4. Plerixafor rapidly mobilizes HSC within hours compared with the multi-day treatment required by G-CSF in mouse, dog and non-human primate. The mobilized cells once transplanted are capable of timely and endurable engraftment. Additionally CXCR4 has been implicated in the pathology of HIV, inflammatory disease and cancer and the pharmacology of plerixafor in various disease models is described.

Regulatory systems in bone marrow for hematopoietic stem/progenitor cells mobilization and homing

Regulation of hematopoietic stem cell release, migration, and homing from the bone marrow (BM) and of the mobilization pathway involves a complex interaction among adhesion molecules, cytokines, proteolytic enzymes, stromal cells, and hematopoietic cells. The identification of new mechanisms that regulate the trafficking of hematopoietic stem/progenitor cells (HSPCs) cells has important implications, not only for hematopoietic transplantation but also for cell therapies in regenerative medicine for patients with acute myocardial infarction, spinal cord injury, and stroke, among others. This paper reviews the regulation mechanisms underlying the homing and mobilization of BM hematopoietic stem/progenitor cells, investigating the following issues: (a) the role of different factors, such as stromal cell derived factor-1 (SDF-1), granulocyte colony-stimulating factor (G-CSF), and vascular cell adhesion molecule-1 (VCAM-1), among other ligands; (b) the stem cell count in peripheral blood and BM and influential factors; (c) the therapeutic utilization of this phenomenon in lesions in different tissues, examining the agents involved in HSPCs mobilization, such as the different forms of G-CSF, plerixafor, and natalizumab; and (d) the effects of this mobilization on BM-derived stem/progenitor cells in clinical trials of patients with different diseases.

Mouse models in bone marrow transplantation and adoptive cellular therapy

Mouse models of transplantation have been indispensable to the development of bone marrow transplantation (BMT). Their role in the generation of basic science knowledge is invaluable and is subject to discussion below. However, this article focuses on the direct role and relevance of mouse models towards the clinical development and advances in BMT and adoptive T-cell therapy for human diseases. The authors aim to present a thoughtful perspective on the pros and cons of mouse models while noting that despite imperfections these models are obligatory for the development of science-based medicine.

The evolving role of plerixafor in hematopoietic progenitor cell mobilization

The introduction of plerixafor as a peripheral blood stem cell mobilization agent has allowed more patients with multiple myeloma, non-Hodgkin's lymphoma, and Hodgkin's disease to mobilize sufficient hematopoietic progenitor cells (HPCs) to proceed to autologous transplantation. Because of the high cost of plerixafor, it is not routinely used in all patients undergoing HPC mobilization. If cost were not an issue, an argument could be made that plerixafor could be added to every mobilization regimen, but cost is an issue so in an attempt to be more cost-effective, many centers have limited plerixafor use to patients who have failed or who are predicted to fail collection of adequate numbers of cells by other methods. Additionally, plerixafor is now under investigation both for HPC collection of healthy donors for allogeneic stem cell transplantation and as an adjunct therapy (i.e., chemosensitizing agent) for acute leukemias. This article briefly reviews the role of plerixafor in autologous and allogeneic transplantation as well as its emerging role in the treatment of acute leukemias. Emphasis is placed on the choice of appropriate patients for plerixafor use to assure an adequate stem cell yield while maximizing the cost effectiveness of using plerixafor. The role of prophylactic collections and future areas of research are also presented.