Early endothelial progenitor cells in bone marrow are a biomarker of cell therapy success in patients with critical limb ischemia

BACKGROUND AIMS

Endothelial progenitor cells (EPC) have been proposed for autologous angiogenic therapy. The objectives of this study were to quantify EPC in the peripheral blood and bone marrow mononuclear cells (BM-MNC) of patients with critical limb ischemia that had received BM-MNC as a cell therapy product, and to study the putative relationship between the presence of EPC and the process of neovascularization in toe or transmetatarsal amputation specimens.

METHODS

Early and late endothelial progenitor cells (CFU-EC and ECFC) were cultivated and quantified according to published methods in peripheral blood and BM-MNC from patients with critical limb ischemia (CLI; n = 11) enrolled in the OPTIPEC trial ( http://clinicaltrials.gov/ct2/show/NCT00377897 ) to receive BM-MNC as a cell therapy product.

RESULTS

Eight out of the 11 patients had undergone amputations. Three of the patients displayed a neoangiogenic process that was associated with a higher number of CFU-EC in BM-MNC, while CD3+ , CFU-GM and CD34+ in BM-MNC, and EPC in peripheral blood, did not correlate with the appearance of newly formed vessels. As expected, circulating CFU-EC and ECFC counts were significantly lower in CLI patients compared with age-matched controls.

CONCLUSIONS

In patients with critical limb ischemia, EPC in peripheral blood were decreased compared with healthy individuals. However, in BM-MNC we found that relative numbers of CFU-EC could be used as an indicator to discriminate patients with neoangiogenic processes. These results need to be confirmed in a randomized study.

First experience of autologous peripheral blood stem cell mobilization with biosimilar granulocyte colony-stimulating factor

INTRODUCTION

Mobilization techniques for autologous peripheral blood stem cell (PBSC) collection include chemotherapy followed by hematopoietic growth factors, such as granulocyte colony-stimulating factor (G-CSF). Biosimilar versions of G-CSF are now available in Europe.

METHODS

In this study, 40 patients with a hematological malignancy scheduled to receive biosimilar G-CSF (Zarzio(®) Sandoz Biopharmaceuticals, Paris, France) following first-cycle chemotherapy for treatment and autologous PBSC mobilization were prospectively included at a single center. These patients were compared with a historical control group who had been treated with G-CSF (Neupogen(®) Paris, France) at the same center according to the same clinical protocol. PBSC harvesting was considered successful if at least 3×10(6) CD34+ cells/kg were collected. If three consecutive CD34+ tests were below 10/μL then PBSC harvesting was not performed.

RESULTS

Patient characteristics were similar in both groups with no significant differences in age, diagnosis, previous chemotherapy, or chemotherapy mobilization regimen. No significant differences were observed between groups in median CD34+ cells mobilized and collected, or the number of G-CSF injections and leukaphereses required to obtain the minimal CD34+ cell count. Proportion of failures was also similar in both groups.

CONCLUSION

Zarziois(®) comparable to Neupogen(®) for PBSC mobilization and collection after chemotherapy and so may provide a more cost-effective strategy.

Advances in adoptive immunotherapy to accelerate T-cellular immune reconstitution after HLA-incompatible hematopoietic stem cell transplantation

Although partially HLA-mismatched hematopoietic stem cell transplantation (HSCT) has become an important therapeutic option for children with primary immunodeficiencies, delayed reconstitution of the T-cell compartment remains a major clinical concern. Adoptive immunotherapies to provide recipients with a protective and diverse T-cell repertoire in the months following HSCT are warranted. In order to improve T-cell reconstitution after T-cell-depleted HSCT, different strategies are currently being studied. Some are based on administration of modified mature T cells (e.g., allodepleted T cells or pathogen-specific T cells). Others aim at accelerating de novo thymopoiesis from donor-derived hematopoietic stem cells in vivo via the administration of thymopoietic agents or the transfer of large numbers of T-cell precursors generated ex vivo. The present article will provide a brief summary of recent advances in the field of allodepletion and adoptive transfer of pathogen-specific T cells and a detailed discussion of strategies for enhancing thymopoiesis in vivo.

Immune reconstitution after haematopoietic stem cell transplantation: obstacles and anticipated progress

Improvement of immune reconstitution after haematopoietic stem cell transplantation (HSCT) is a key issue determining the clinical outcome of this widely used therapeutic approach. To this end, new strategies have been prompted by recent discoveries in immunology. In the setting of human leukocyte antigen (HLA) geno(pheno)identical HSCT, better prevention and treatment of acute and chronic graft-versus-host disease (GvHD) could significantly attenuate the thymic epithelium damage responsible for delayed and incomplete T-cell reconstitution. In a haploidentical setting, methods that would significantly accelerate neothymopoiesis in the months following injection of highly purified CD34+ cells are warranted. If these objectives could be achieved, the haploidentical procedure would become more readily available to patients affected by acquired or inherited disorders of the haematopoietic system.

Shortening the immunodeficient period after hematopoietic stem cell transplantation

The delayed reconstitution of the T-lymphoid compartment represents a major clinical challenge after HLA-mismatched hematopoietic stem cell transplantation. The generation of new T lymphocytes deriving from transplanted hematopoietic stem cells requires several months, a period associated with an increased risk of opportunistic infections and relapses. Recently, the early steps of human lymphopoiesis and the nature of the thymus-seeding progenitors were described. Moreover several scientific groups succeeded to generate T-cell precursors from murine and human hematopoietic stem cells in vitro by transitory exposition to Notch-ligands. Here we summarize and discuss these results and their possible usage in the development of new cell therapies to shorten the immunodeficient period following hematopoietic stem cell transplantation.

Use of hematopoietic progenitor cell count on the Sysmex XE-2100 for peripheral blood stem cell harvest monitoring

Successful peripheral blood stem cell (PBSC) collection depends on the timing of apheresis based on CD34+ cell enumeration. Because this analysis is expensive and induces organization difficulties, we evaluated hematopoietic progenitor cell (HPC) quantification on the Sysmex XE-2100 as a surrogate analysis. We tested 157 blood samples for CD34+ cells and HPC counts. We found a good linear correlation between HPC and CD34+ and determined simple rules allowing to use HPC count in daily practice. We set a positive cut-off >30 HPC/mm(3) for allowing PBSC harvest and a negative cut-off at 0 HPC/mm(3) for which collection should be delayed. These two situations accounted for 62% of cases and CD34+ cell count by flow cytometry confirmed HPC result in 95% of cases. Between 0 and 30 HPC/mm3, CD34+ enumeration is required for decision-making. We conclude that HPC count may be a useful surrogate for CD34+ enumeration in PBSC harvest monitoring.

Insertional oncogenesis in 4 patients after retrovirus-mediated gene therapy of SCID-X1

Previously, several individuals with X-linked SCID (SCID-X1) were treated by gene therapy to restore the missing IL-2 receptor gamma (IL2RG) gene to CD34+ BM precursor cells using gammaretroviral vectors. While 9 of 10 patients were successfully treated, 4 of the 9 developed T cell leukemia 31-68 months after gene therapy. In 2 of these cases, blast cells contained activating vector insertions near the LIM domain-only 2 (LMO2) proto-oncogene. Here, we report data on the 2 most recent adverse events, which occurred in patients 7 and 10. In patient 10, blast cells contained an integrated vector near LMO2 and a second integrated vector near the proto-oncogene BMI1. In patient 7, blast cells contained an integrated vector near a third proto-oncogene,CCND2. Additional genetic abnormalities in the patients' blast cells included chromosomal translocations, gain-of-function mutations activating NOTCH1, and copy number changes, including deletion of tumor suppressor gene CDKN2A, 6q interstitial losses, and SIL-TAL1 rearrangement. These findings functionally specify a genetic network that controls growth in T cell progenitors. Chemotherapy led to sustained remission in 3 of the 4 cases of T cell leukemia, but failed in the fourth. Successful chemotherapy was associated with restoration of polyclonal transduced T cell populations. As a result, the treated patients continued to benefit from therapeutic gene transfer.

Insertional oncogenesis in 4 patients after retrovirus-mediated gene therapy of SCID-X1

Previously, several individuals with X-linked SCID (SCID-X1) were treated by gene therapy to restore the missing IL-2 receptor gamma (IL2RG) gene to CD34+ BM precursor cells using gammaretroviral vectors. While 9 of 10 patients were successfully treated, 4 of the 9 developed T cell leukemia 31-68 months after gene therapy. In 2 of these cases, blast cells contained activating vector insertions near the LIM domain-only 2 (LMO2) proto-oncogene. Here, we report data on the 2 most recent adverse events, which occurred in patients 7 and 10. In patient 10, blast cells contained an integrated vector near LMO2 and a second integrated vector near the proto-oncogene BMI1. In patient 7, blast cells contained an integrated vector near a third proto-oncogene,CCND2. Additional genetic abnormalities in the patients' blast cells included chromosomal translocations, gain-of-function mutations activating NOTCH1, and copy number changes, including deletion of tumor suppressor gene CDKN2A, 6q interstitial losses, and SIL-TAL1 rearrangement. These findings functionally specify a genetic network that controls growth in T cell progenitors. Chemotherapy led to sustained remission in 3 of the 4 cases of T cell leukemia, but failed in the fourth. Successful chemotherapy was associated with restoration of polyclonal transduced T cell populations. As a result, the treated patients continued to benefit from therapeutic gene transfer.

A human postnatal lymphoid progenitor capable of circulating and seeding the thymus

Identification of a thymus-seeding progenitor originating from human bone marrow (BM) constitutes a key milestone in understanding the mechanisms of T cell development and provides new potential for correcting T cell deficiencies. We report the characterization of a novel lymphoid-restricted subset, which is part of the lineage-negative CD34(+)CD10(+) progenitor population and which is distinct from B cell-committed precursors (in view of the absence of CD24 expression). We demonstrate that these Lin(-)CD34(+)CD10(+)CD24(-) progenitors have a very low myeloid potential but can generate B, T, and natural killer lymphocytes and coexpress recombination activating gene 1, terminal deoxynucleotide transferase, PAX5, interleukin 7 receptor alpha, and CD3epsilon. These progenitors are present in the cord blood and in the BM but can also be found in the blood throughout life. Moreover, they belong to the most immature thymocyte population. Collectively, these findings unravel the existence of a postnatal lymphoid-polarized population that is capable of migrating from the BM to the thymus.

Evaluation of an algorithm based on peripheral blood hematopoietic progenitor cell and CD34+ cell concentrations to optimize peripheral blood progenitor cell collection by apheresis

BACKGROUND

Quantification of peripheral blood (PB) CD34+ cells is commonly used to plan peripheral blood progenitor cell (PBPC) collection but is time-consuming. Sysmex has developed a hematology analyzer that can quickly identify a population of immature hematopoietic cells (HPCs) according to cell size, cell density, and differential lysis resistance, which may indicate the presence of PBPCs in PB. This prospective study has evaluated the potential of such method to predict the PBPC mobilization.

STUDY DESIGN AND METHODS

A total of 141 patients underwent PBPC mobilization. PB HPCs and PB CD34+ cells were simultaneously quantified with a hematology analyzer (SE2100, Sysmex) and flow cytometry, respectively. The number of blood volumes processed was then based on PB CD34+ cell concentration.

RESULTS

The optimal PB HPC level able to predict a minimal level of 10 x 10(6) PB CD34+ cells per L was 5 x 10(6) per L with positive and negative predictive values of 0.93 and 0.36 percent, respectively. For this cutoff point, sensitivity and specificity were 0.81 and 0.65, respectively. The median number of blood volumes processed according to the PB CD34+ cell count allowed us to perform only one apheresis procedure for a majority of patients.

CONCLUSION

PB HPC quantification is very useful to quickly determine the initiation of PBPC apheresis especially for patients with higher concentrations. For patients exhibiting a lower HPC count (<5 x 10(6)/L), other parameters such as a CD34 test may be needed. Such a policy associated with a length of apheresis adapted to the richness in the PB CD34+ cells allows for optimizing the organization of centers with an improvement in patient comfort and economical savings.

A double-blind low dose-finding phase II study of granulocyte colony-stimulating factor combined with chemotherapy for stem cell mobilization in patients with non-Hodgkin's lymphoma

The aim of the study was to define the minimal effective dose (MED) of granulocyte colony-stimulating factor (G-CSF) among five daily doses following chemotherapy for peripheral blood stem cell (PBSC) collection. Twenty-five patients were included in this double-blind dose-finding phase II study conducted according to a two-stage Bayesian design. The estimated probabilities of success for PBSC collection for the G-CSF doses of 50, 75, 100, 125 and 150 microg/m2/day were 84%, 87.7%, 91%, 93.9 and 96.4%, respectively. Low G-CSF doses may be used with a similar probability of success as conventional doses and could allow significant savings.

Gene transfer for activation of cmv specific t cells

Cytomegalovirus (CMV) is responsible for significant morbidity and mortality in immunocompromised patients undergoing allogeneic hematopoietic stem cell transplantation. The limitations of antiviral drugs and a better understanding of the cellular immune response to CMV has lead to the development of alternative therapies that restore host cellular immunity to CMV. Infusion of donor T lymphocytes results in variable protection against CMV but a high incidence of graft-versus-host disease in the allogeneic setting. To prevent this complication and further improve anti-CMV immune response, several groups have developed new approaches, such as the introduction of a suicide gene to control alloreactivity against the host or the selective activation of CMV-specific T cells by antigen-presenting cells expressing CMV antigens introduced by gene transfer. Depending on the target cells and the strategy chosen, adenovirus, retrovirus or poxviruses derived vectors are used for gene transfer. The protocols as well as the preclinical and clinical results obtained in the field of anti-CMV immunotherapy using gene transfer are reported and discussed.

Association of CD34 cell dose with hematopoietic recovery, infections, and other outcomes after HLA-identical sibling bone marrow transplantation

Although CD34 cell dose is known to influence outcome of peripheral stem cell- and/or T-cell-depleted transplantation, such data on unmanipulated marrow transplantation are scarce. To study the influence of CD34(+) cell dose on hematopoietic reconstitution and incidence of infections after bone marrow transplantation, we retrospectively analyzed 212 patients from January 1994 to August 1999 who received a transplant of an unmanipulated graft from an HLA-identical sibling donor. Median age was 31 years; 176 patients had hematologic malignancies. Acute graft-versus-host disease prophylaxis consisted mainly in cyclosporin associated with methotrexate (n = 174). Median number of bone marrow nucleated cells and CD34(+) cells infused were 2.4 x 10(8)/kg and 3.7 x 10(6)/kg, respectively. A CD34(+) cell dose of 3 x 10(6)/kg or more significantly influenced neutrophil (hazard ratio [HR] = 1.37, P =.04), monocyte (HR = 1.47, P =.02), lymphocyte (HR = 1.70, P =.003), erythrocyte (HR = 1.77, P =.0002), and platelet (HR = 1.98, P =.00008) recoveries. CD34(+) cell dose also influenced the incidence of secondary neutropenia (HR = 0.60, P =.05). Bacterial and viral infections were not influenced by CD34 cell dose, whereas it influenced the incidence of fungal infections (HR = 0.41, P =.008). Estimated 180-day transplantation-related mortality (TRM) and 5-year survival were 25% and 56%, respectively, and both were highly affected by CD34(+) cell dose (HR = 0.55, P =.006 and HR = 0.54, P =.03, respectively). Five-year survival and 180-day TRM were, respectively, 64% and 19% for patients receiving a CD34(+) cell dose of 3 x 10(6)/kg or more and 40% and 37% for the remainders. In conclusion a CD34(+) cell dose of 3 x 10(6)/kg or more improved all hematopoietic recoveries, decreased the incidence of fungal infections and TRM, and improved overall survival.