Factors predicting engraftment of autologous blood stem cells: CD34+ subsets inferior to the total CD34+ cell dose

Mobilization strategies with and without plerixafor for autologous stem cell transplant in patients with multiple myeloma

Autologous stem cell transplantation is a standard treatment strategy for patients with multiple myeloma that requires effective mobilization and apheresis of peripheral blood progenitor cells; however, in the current era of novel myeloma induction therapies, the optimal mobilization regimen to enhance stem cell yield while limiting toxicity and resource utilization remains unknown. In this multicenter retrospective study, we assessed apheresis and transplant outcomes in myeloma patients mobilized with granulocyte colony stimulating factor (G-CSF) alone (n = 62), G-CSF with chemotherapy (n = 43), or G-CSF with the CXCR4 antagonist plerixafor (n = 417). Compared to patients treated with G-CSF alone, the plerixafor group required significantly fewer median apheresis sessions (1 vs 2, p = 0.0023) with higher CD34+ stem cell yield (9.9 vs 5.8 × 106 cells/kg, p < 0.001) and had significantly faster engraftment of neutrophils (HR 1.54, 95% CI 1.17-2.03) and platelets (HR 2.24, 95% CI 1.69-2.96) after transplant. Additionally, the plerixafor group showed a significantly better toxicity profile and lower adverse event rate than patients treated with G-CSF alone (p = 0.0028) or chemomobilization (p < 0.0001), with a trend toward reduced survival in chemomobilization patients. Taken together, these data support the routine use of plerixafor-based mobilization to increase apheresis efficiency and reduce toxicity in myeloma patients undergoing transplant.

Mobilization-based engraftment of haematopoietic stem cells: a new perspective for chemotherapy-free gene therapy and transplantation

INTRODUCTION

In haematopoietic stem cell transplantation (HSCT), haematopoietic stem cells (HSCs) from a healthy donor replace the patient's ones. Ex vivo HSC gene therapy (HSC-GT) is a form of HSCT in which HSCs, usually from an autologous source, are genetically modified before infusion, to generate a progeny of gene-modified cells. In HSCT and HSC-GT, chemotherapy is administered before infusion to free space in the bone marrow (BM) niche, which is required for the engraftment of infused cells. Here, we review alternative chemotherapy-free approaches to niche voidance that could replace conventional regimens and alleviate the morbidity of the procedure.

SOURCES OF DATA

Literature was reviewed from PubMed-listed peer-reviewed articles. No new data are presented in this article.

AREAS OF AGREEMENT

Chemotherapy exerts short and long-term toxicity to haematopoietic and non-haematopoietic organs. Whenever chemotherapy is solely used to allow engraftment of donor HSCs, rather than eliminating malignant cells, as in the case of HSC-GT for inborn genetic diseases, non-genotoxic approaches sparing off-target tissues are highly desirable.

AREAS OF CONTROVERSY

In principle, HSCs can be temporarily moved from the BM niches using mobilizing drugs or selectively cleared with targeted antibodies or immunotoxins to make space for the infused cells. However, translation of these principles into clinically relevant settings is only at the beginning, and whether therapeutically meaningful levels of chimerism can be safely established with these approaches remains to be determined.

GROWING POINTS

In pre-clinical models, mobilization of HSCs from the niche can be tailored to accommodate the exchange and engraftment of infused cells. Infused cells can be further endowed with a transient engraftment advantage.

AREAS TIMELY FOR DEVELOPING RESEARCH

Inter-individual efficiency and kinetics of HSC mobilization need to be carefully assessed. Investigations in large animal models of emerging non-genotoxic approaches will further strengthen the rationale and encourage application to the treatment of selected diseases.

Genome-wide association study identifies variants at 16p13 associated with survival in multiple myeloma patients

Here we perform the first genome-wide association study (GWAS) of multiple myeloma (MM) survival. In a meta-analysis of 306 MM patients treated at UCSF and 239 patients treated at the Mayo clinic, we find a significant association between SNPs near the gene FOPNL on chromosome 16p13 and survival (rs72773978; P=6 × 10(-10)). Patients with the minor allele are at increased risk for mortality (HR: 2.65; 95% CI: 1.94-3.58) relative to patients homozygous for the major allele. We replicate the association in the IMMEnSE cohort including 772 patients, and a University of Utah cohort including 318 patients (rs72773978 P=0.044). Using publicly available data, we find that the minor allele was associated with increased expression of FOPNL and increased expression of FOPNL was associated with higher expression of centrosomal genes and with shorter survival. Polymorphisms at the FOPNL locus are associated with survival among MM patients.

Storage time affects umbilical cord blood viability

BACKGROUND

Cryopreserved umbilical cord blood (CB) is increasingly used as a cell source to reconstitute marrow in hematopoietic stem cell transplant patients. Delays in cryopreservation may adversely affect cell viability, thereby reducing their potential for engraftment after transplantation.

STUDY DESIGN AND METHODS

The impact of delayed cryopreservation for up to 3 days on the viability of both CD45+ and CD34+ cell populations in 28 CB donations with volumes of 58.40 ± 15.4 mL (range, 39.4-107.4 mL) was investigated to establish whether precryopreservation storage time could be extended from our current time of 24 to 48 hours in line with other CB banks. Viability was assessed on 3 consecutive days, both before and after cryopreservation, by flow cytometry using 7-aminoactinomycin D (7-AAD) and annexin V methods.

RESULTS

The results using 7-AAD and annexin V indicated the viability of CD34+ cells before cryopreservation remained high (>92.33 ± 4.11%) over 3 days, whereas the viability of CD45+ cells decreased from 86.36 ± 4.97% to 66.24 ± 7.78% (p < 0.0001) by Day 3. Storage time significantly affected the viability of CD34+ cells after cryopreservation. Using 7-AAD, the mean CD34+ cell viability decreased by approximately 5% per extra day in storage from 84.30 ± 6.27% on Day 1 to 79.01 ± 7.44% (p < 0.0057) on Day 2 and to 73.95 ± 7.54% (p < 0.0001) on Day 3. With annexin V staining CD34+ cell viability fell by approximately 7% per extra day in storage from 77.17 ± 8.47% on Day 1 to 69.56 ± 13.30% (p < 0.0194) on Day 2 and to 62.89 ± 15.22% (p < 0.0002) on Day 3.

CONCLUSION

This study demonstrates that extended precryopreservation storage adversely affects viability and should be avoided.

Analysis of pediatric autologous PBSC apheresis and transplant: age is a major factor affecting post-transplant toxicity

BACKGROUND

High-dose chemotherapy followed by autologous hematopoietic cell transplantation (HCT) is used in many therapeutic protocols for pediatric intra- and extra-cranial solid tumors. HCT can be curative, but is associated with significant toxicity.

PROCEDURE

Between January 2001 and June 2009, 92 solid tumor patients (age 6 months to 27 years) underwent 94 autologous apheresis procedures at Children's National Medical Center. Out of that group, 71 patients, who underwent 162 autologous HCT, were analyzed for transplant outcomes. Multiple variable modeling was used to identify independent variables related to transplant toxicity outcome measures, such as bacteremia, intensive care admission, and death. Other outcome measures (time to pre-apheresis peripheral blood CD34+ count, product yield, and time to engraftment) were also analyzed. Independent variables included patient-specific variables (age, weight, tumor type, chemotherapy administered, and primary vs. relapsed disease) and harvest or transplant-related variables (total white blood cell and CD34+ cell counts prior to transplant, and quantity of total nucleated cells and CD34+ cells infused during transplant).

RESULTS

Transplant toxicity was significantly greater in younger patients (P = 0.001) and in neuroblastoma patients (P = 0.003). The time to neutrophil engraftment, controlling for weight, age, and chemotherapy, was positively related to absolute CD34+ cells/kg infused (P = 0.01). The time to CD34+ recovery pre-apheresis was affected by patient diagnosis (P = 0.05).

CONCLUSIONS

Younger patients had increased transplant toxicity, with infants <1 year of age at highest risk for fever, bacteremia, admission to intensive care, and death. Infants would likely benefit from hospitalization after autologous HCT until neutrophil recovery.

Effect of the surface density of nanosegments immobilized on culture dishes on ex vivo expansion of hematopoietic stem and progenitor cells from umbilical cord blood

Umbilical cord blood (UCB) is an attractive source of hematopoietic stem and progenitor cells for hematopoietic stem cell (HSC) transplantation. However, the low number of HSCs obtainable from a single donor of UCB limits direct transplantation of UCB to the treatment of pediatric patients. In this study, we investigated the ex vivo expansion of HSCs cultured on biomaterials grafted with several nanosegments, i.e. polyamine, fibronectin, RGDS, and CS1 (EILDVPST), at several surface densities. No direct correlation was found between fold expansion of HSCs and physical parameters of the culture dishes, i.e. surface roughness and water contact angle of the culture dishes. However, a small amount of grafted amino groups, less than 0.8 residual μmol cm(-2), on the dishes was effective for the ex vivo expansion of HSCs. A high amount of grafted amino groups hindered the ex vivo expansion of HSCs on the dishes. HSCs cultured on dishes with a high concentration of CS1 (2.40 residual μmol cm(-2)) showed greater expansion of HSCs and more pluripotent colony-forming units (i.e. colony-forming unit-granulocyte, erythroid, macrophage, and megakaryocyte (CFU-GEMM)) than those on fibronectin-grafted and polyamine-grafted dishes. These data suggest that the specific interaction between HSCs and CS1 helps to maintain the pluripotency of HSCs during the ex vivo expansion of HSCs.

An osteoconductive, osteoinductive, and osteogenic tissue-engineered product for trauma and orthopaedic surgery: how far are we?

The management of large bone defects due to trauma, degenerative disease, congenital deformities, and tumor resection remains a complex issue for the orthopaedic reconstructive surgeons. The requirement is for an ideal bone replacement which is osteoconductive, osteoinductive, and osteogenic. Autologous bone grafts are still considered the gold standard for reconstruction of bone defects, but donor site morbidity and size limitations are major concern. The use of bioartificial bone tissues may help to overcome these problems. The reconstruction of large volume defects remains a challenge despite the success of reconstruction of small-to-moderate-sized bone defects using engineered bone tissues. The aim of this paper is to understand the principles of tissue engineering of bone and its clinical applications in reconstructive surgery.

A validation study of new cryopreservation bags for implementation in a blood and marrow transplant laboratory

BACKGROUND

A new cryopreservation bag for hematopoietic cell transplantation requires validation as a safe alternative to the bag currently being used in the laboratory.

STUDY DESIGN AND METHODS

The new bag was validated using both laboratory and clinical criteria. Laboratory validation proceeded using paired samples of mononuclear cells processed using standard procedures. Cells cryopreserved in the new and old bags were compared for viability, cell counts, CD34 enumeration, colony-forming unit assays, and bag integrity. After completion of laboratory investigations, engraftment with the new bags was followed and compared to historical engraftment using the old bags.

RESULTS

There were no significant differences between the old and new bags detected using laboratory studies. Bag integrity was equivalent. The validation data suggested impaired cell function after cryopreservation in the new bags, but there were no significant differences in engraftment potential using either material. Days to engraftment was longer using the new bags, but statistical analysis revealed an association with CD34 dose and not with cryopreservation bag type.

CONCLUSION

The new bags were noninferior to the old bags. A change in cryopreservation bag type may appear to affect cell function and potentially affect engraftment. Multiple analyses may be needed to understand the effect of cell processing changes.

Functional nanofiber scaffolds with different spacers modulate adhesion and expansion of cryopreserved umbilical cord blood hematopoietic stem/progenitor cells

OBJECTIVE

Nanofiber scaffolds with amino groups conjugated to fiber surface through different spacers (ethylene, butylenes, and hexylene groups, respectively) were prepared and the effect of spacer length on adhesion and expansion of umbilical cord blood hematopoietic stem/ progenitor cells (HSPCs) was investigated.

MATERIALS AND METHODS

Electrospun polymer nanofiber scaffolds were functionalized with poly(acrylic acid) grafting, followed by conjugation of amino groups with different spacers. HSPCs were expanded on aminated scaffolds for 10 days. Cell proliferation, surface marker expression, clonogenic potential, and nonobese diabetic (NOD)/severe combined immunodeficient (SCID) repopulation potential of the expanded cells were evaluated following expansion culture.

RESULTS

Aminated nanofiber scaffolds with ethylene and butylene spacers showed high-expansion efficiencies (773- and 805-fold expansion of total cells, 200- and 235-fold expansion of CD34+CD45' cells, respectively). HSPC proliferation on aminated scaffold with hexylene spacer was significantly lower (210-fold expansion of total cells and 86-fold expansion of CD34+CD45+ cells), but maintained the highest CD34+CD45+ cell fraction (41.1%). Colony-forming unit granulocyte-erythrocyte-monocyte-megakaryocyte and long-term culture-initiating cell maintenance was similar for HSPCs expanded on all three aminated nanofiber scaffolds; nevertheless, the NOD/SCID mice engraftment potential of HSPCs expanded on aminoethyl and aminobutyl conjugated nanofibers was significantly higher than that on aminohexyl conjugated nanofibers.

CONCLUSION

This study demonstrated that aminated nanofibers are superior substrates for ex vivo HSPC expansion, which was correlated with the enhanced HSPC adhesion to these aminated nanofibers. The spacer, through which amino groups were conjugated to nanofiber surface, affected the expansion outcome. Our results highlighted the importance of scaffold topography and cell-substrate interaction to regulating HSPC proliferation and self-renewal in cytokine-supplemented expansion.

Early and long-term engraftment after autologous peripheral stem cell transplantation in acute myeloid leukemia patients

This study aimed to identify which subset of CD34+ cells might be the most predictive of early and long-term hematopoietic recovery following autologous peripheral blood stem cell (PBSC) transplantation (PBSCT) in adult acute myeloid leukemia (AML) patients. The relationships between the number of 'mature' subsets of CD34+ cells (CD34+/CD33+, CD34+/CD38+, CD34+/DR+ and CD34+/CD90-) and 'immature' subsets of CD34+ cells (CD34+/CD33-, CD34+/CD38-, CD34+/DR- and CD34+/CD90+) and early and long-term hemoglobin, neutrophil and platelet counts were studied in a homogeneous series (for disease, pre-transplant chemotherapy, mobilization chemotherapy, conditioning regimen) of 26 AML patients after autologous PBSCT. Cell counts were performed before and after cryopreservation, but only after thawing were the cell counts used for correlation with early and long-term engraftment. The number of CD34+/CD38- cells infused correlated with the neutrophil (r = 0.88, p < 0.005) and platelet counts (r = 0.67, p < 0.05) at 12 months after PBSCT. This correlation was better than that for the total CD34+ cell dose at 12 months (r = 0.36, p = 0.09 for neutrophil count and r = 0.48, p = 0.06 for platelets count). The number of CD34+/CD90+ cells was also correlated with the platelet counts at 6 (r = 0.70, p < 0.05) and 12 months (r = 0.80, p = 0.005) after PBSCT. This correlation was better than the total dose of CD34+ cells at 6 (r = 0.31, p = 0.3) and 12 months (r = 0.48, p = 0.06) for the platelet counts. CD34+ subset analysis suggests that for early engraftment the total number of CD34+ cells infused is more strongly correlated than the CD34+ subsets, whereas the CD34+/CD38- and CD34+/CD90+ subsets may be associated with sustained long-term neutrophil and platelet engraftment. These findings may help to predict the repopulating capacity of PBSCs in AML patients after autologous PBSCT, especially when a relatively low number of CD34+ cells is infused.

Flow cytometric CD34+ stem cell enumeration: lessons from nine years' external quality assessment within the Benelux countries

BACKGROUND

A biannual external quality assurance (EQA) scheme for flow cytometric CD34+ haematopoietic stem cell enumeration has been operational in the Benelux countries since 1996. In an evaluation of the results of 16 send-outs, we studied the effects of the methods used on assay outcome and whether or not this exercise was effective in reducing between-laboratory variation.

METHODS

Data were analyzed using robust multivariate regression. This approach is relatively insensitive to outliers and is used to assess the effect of methodological aspects of CD34+ cell counting on the bias and variability.

RESULTS

Five variables were associated with significant bias of absolute CD34+ cell counts: (i) unique laboratory number (ULN), (ii) gating strategy; (iii) CD34 mAb fluorochrome; (iv) type of flow cytometer, and (v) method of sample preparation. In addition, ULN and platform methodology (i.e., single vs. dual) contributed significantly to the variability of this assay. Overall, the variability in results of CD34+ cell enumeration has declined with time; in particular, after a practical workshop in which participants were trained to use the "single platform ISHAGE protocol."

CONCLUSIONS

Between-laboratory variation in CD34+ cell enumeration can be reduced by standardization of methodologies between centres. Our approach, i.e., EQA with targeted training and feedback in response to reported results, has been successful in reducing the variability of CD34+ cell enumeration between participants.

CD34(+) CD38(-) and CD34(+) HLA-DR(-) cells in BM stem cell grafts correlate with short-term engraftment but have no influence on long-term hematopoietic reconstitution after autologous transplantation

BACKGROUND

Prior studies have demonstrated that relatively immature hematopoietic stem cells, including CD34(+) CD38(-) and CD34(+) HLA-DR(-) subsets, correlate with short-term hematopoietic reconstruction (SHR) after transplantation. The aim of this study was to investigate whether these immature CD34(+) subsets also correlate with long-term hematopoietic reconstitution (LHR) in recipients of ABMT.

METHODS

We examined stem cell grafts from 58 patients with B-cell lymphoma or CLL who underwent ABMT after myeloablative conditioning. We determined whether total mononuclear cell dose (MNC), colony-forming unit-granulocyte-monocyte (CFU-GM), CD34(+) cell dose and CD34(+) cell subsets (CD34(+) CD38(-) and CD34(+) HLA-DR(-) were associated with SHR and/or LHR. Time to neutrophil engraftment (TNE) and time to platelet engraftment (TPE) were used to measure SHR, while platelet counts at day 100 and 1 year post-ABMT were used as indicators for LHR.

RESULTS AND DISCUSSION

CD34(+) cell dose and CD34(+) cell subsets were significantly associated with SHR. However, at day 100 and 1 year post-transplant only total CD34(+) cell dose was associated with LHR. The association of total CD34(+) cell dose with LHR persisted after adjusting for age, sex and disease. None of the CD34(+) cell subsets analyzed showed evidence of significant association with LHR.

Overnight storage of autologous stem cell apheresis products before cryopreservation does not adversely impact early or long-term engraftment following transplantation

To reduce costs and avoid inconvenient overtime work, our institution changed policy in September 2000 so that autologous stem cell apheresis products were stored overnight before cryopreservation rather than immediately processed. This retrospective review was conducted to evaluate the possible impact of this policy change on hematopoietic engraftment following autologous stem cell transplantation (ASCT). In total, 229 consecutive lymphoma patients who underwent a single, unpurged ASCT in Calgary between January 1995 and November 2003 were evaluated. Of these patients, 131 patients' autografts underwent immediate processing and cryopreservation before September 2000, and 98 patients' autografts underwent next-day cryopreservation after overnight storage following this date. Results of univariate and multivariate analyses demonstrated no adverse effect of overnight storage before cryopreservation on the number of days to initial engraftment of platelets or neutrophils, on the proportion of patients with low blood counts 6 months post-ASCT, or on lymphoma relapse rates or overall survival post-ASCT. These data suggest that overnight storage of the autograft before cryopreservation does not adversely affect graft viability or influence long-term disease status, and support the continued use of overnight storage of stem cells before cryopreservation as a convenient, cost reduction measure.

Surface-aminated electrospun nanofibers enhance adhesion and expansion of human umbilical cord blood hematopoietic stem/progenitor cells

Interaction between hematopoietic stem/progenitor cells (HSPCs) and their extra cellular matrix components is an integral part of the signaling control for HSPC survival, proliferation and differentiation. We hypothesized that both substrate topographical cues and biochemical cues could act synergistically with cytokine supplementation to improve ex vivo expansion of HSPCs. In this study, we compared the ex vivo expansion of human umbilical cord blood CD34(+) cells on unmodified, hydroxylated, carboxylated and aminated nanofibers and films. Results from 10-day expansion cultures showed that aminated nanofiber mesh and film were most efficient in supporting the expansion of the CD34(+)CD45(+) cells (195-fold and 178-fold, respectively), as compared to tissue culture polystyrene (50-fold, p<0.05). In particular, aminated nanofiber meshes supported a higher degree of cell adhesion and percentage of HSPCs, as compared to aminated films. SEM imaging revealed the discrete colonies of cells proliferating and interacting with the aminated nanofibers. This study highlights the potential of a biomaterials approach to influence the proliferation and differentiation of HSPCs ex vivo.

Effect of dimethyl sulfoxide on post-thaw viability assessment of CD45+ and CD34+ cells of umbilical cord blood and mobilized peripheral blood

BACKGROUND

The effect of dimethyl sulfoxide (Me2SO) on enumeration of post-thaw CD45+ and CD34+ cells of umbilical cord blood (HPC-C) and mobilized peripheral blood (HPC-A) has not been systematically studied.

METHODS

Cells from leukapheresis products from multiple myeloma patients and umbilical cord blood cells were suspended in 1, 2, 5, or 10% Me2SO for 20 min at 22 degrees C. Cells suspended in Me2SO were then immediately assessed or assessed following removal of Me2SO. In other samples, cells were suspended in 10% Me2SO, cooled slowly to -60 degrees C, stored at -150 degrees C for 48 h, then thawed. The thawed cells in 10% Me2SO were diluted to 1, 2, 5, or 10% Me2SO, held for 20 min at 22 degrees C and then immediately assessed or assessed after the removal of Me2SO. CD34+ cell viability was determined using a single platform flow cytometric absolute CD34+ cell count technique incorporating 7-AAD.

RESULTS

The results indicate that after cryopreservation neither recovery of CD34+ cells nor viability of CD45+ and CD34+ cells from both post-thaw HPC-A and HPC-C were a function of the concentration of Me2SO. Without cryopreservation, when Me2SO is present recovery and viability of HPC-C CD34+ cells exposed to 10% Me2SO but not CD45+ cells were significantly decreased. Removing Me2SO by centrifugation significantly decreased the viability and recovery of CD34+ cells in both HPC-A and HPC-C before and after cryopreservation.

DISCUSSION

To reflect the actual number of CD45+ cells and CD34+ cells infused into a patient, these results indicate that removal of Me2SO for assessment of CD34+ cell viability should only be performed if the HPC are infused after washing to remove Me2SO.

Hematologic aspects of myeloablative therapy and bone marrow transplantation

The transplantation of bone marrow cells or isolated hematopoietic stem cells from the bone marrow or peripheral blood is a widely utilized form of therapy for patients with incurable diseases of the hematopoietic and immune systems. Successful engraftment of the transplanted stem cells in an adequately prepared recipient normally leads to bone marrow reconstitution over a period of several weeks, accompanied by more gradual reconstitution of the immune system. Since the recipient is profoundly ill during the initial treatment period, laboratory data is critical for monitoring engraftment, detecting residual/recurrent disease, and identifying problems that may delay bone marrow reconstitution or lead to other medical complications. Accurate blood cell counts are imperative, and most bone marrow transplantation patients undergo periodic monitoring with bone marrow aspirates and biopsies with cytogenetic, molecular, and multiparametric flow cytometric studies. The potential complications of bone marrow transplantation include engraftment failure and delayed engraftment, infection, residual bone marrow disease, acute and chronic graft versus host disease, myelofibrosis, therapy-related acute leukemia, post-transplant lympho-proliferative disorders, and toxic myelopathy.

Hematopoietic cellular therapy: implications for the flow cytometry laboratory

Advances in hematopoietic stem cell transplantation, gene therapy, and immunotherapy have necessitated a host of novel monitoring procedures. Cell sorting is also coming of age as a clinical procedure designed to organize hematopoietic grafts for specificity of cellular components designed for individual patients or diseases. This article has focused on these novel developments in their historical context. The next generation of transplantation flow cytometry promises to be an exciting one.

CD34+/CD90+ cells infused best predict late haematopoietic reconstitution following autologous peripheral blood stem cell transplantation

This study aimed to identify which graft product subset of cells might be the most predictive of late haematopoietic recovery (three to 12 months) following autologous peripheral blood stem cell transplantation (PBSCT). The relationships between the numbers of reinfused CD34+ cells and their immature subsets such as CD34+/CD90+, CD34+/AC133+, CD34+/CD38- and CD34+/HLA-DR- cells, and haemoglobin, white blood cell (WBC) and platelet counts at 3, 6, 9 and 12 months after PBSCT, were studied in 25 patients with haematological and solid malignancies. The total CD34+ cell number, as well as CD34+/CD90+ and CD34+/AC133+ cell numbers, correlated with platelet counts at 3, 6, 9 and 12 months after PBSCT, but the CD34+/CD90+ cells infused best predicted platelet recovery during the first 12 months after PBSCT (P < 0.0238 at any time-point). The CD34+/AC133+ cell dose also correlated with WBC counts at 3 months post PBSCT. In addition, all patients receiving more than 80 x 10(4) CD34+/CD90+ cells/kg showed platelet counts greater than 100 x 10(9)/l at all points after PBSCT, suggesting that this value of the CD34+/CD90+ cells infused was a threshold dose for durable haematopoietic engraftment after PBSCT.

Extensive early apoptosis in frozen-thawed CD34-positive stem cells decreases threshold doses for haematological recovery after autologous peripheral blood progenitor cell transplantation

Stem cell doses necessary for engraftment after myelo-ablative therapy as defined for fresh transplants vary largely. Loss of CD34+ cell quality after cryopreservation might contribute to this variation. With a new early apoptosis assay including the vital stain Syto16, together with the permeability marker 7-AAD, CD34+ cell viability in leucapheresis samples of 49 lymphoma patients receiving a BEAM regimen was analysed. After freeze-thawing large numbers of non-viable, early apoptotic cells appeared, leading to only 42% viability compared to 72% using 7-AAD only. Based on this Syto16 staining in the frozen-thawed grafts, threshold numbers for adequate haematological recovery of 2.8-3.0 x 10(6) CD34+ cells/kg body weight determined for fresh grafts, now decreased to 1.2-1.3 x 10(6) CD34+ cells/kg. In whole blood transplantation of lymphoma patients (n = 45) receiving a BEAM-like regimen, low doses of CD34+ cells were sufficient for recovery (0.3-0.4 x 10(6)CD34+ cells/kg). In contrast to freeze-thawing of leucapheresis material, a high viability of CD34+ cells was preserved during storage for 3 days at 4 degrees C, leaving threshold doses for recovery unchanged. In conclusion, the Syto16 assay reveals the presence of many more non-functional stem cells in frozen-thawed transplants than presumed thus far. This led to a factor 2.3-fold adjustment downward of viable CD34+ threshold doses for haematological recovery.

CD34(+) cell subsets and long-term culture colony-forming cells evaluated on both autologous and normal bone marrow stroma predict long-term hematopoietic engraftment in patients undergoing autologous peripheral blood stem cell transplantation

OBJECTIVE

The aim of this study was to evaluate which CD34(+) cell subset contained in leukapheresis products could be regarded as the most predictive of long-term hematopoietic recovery after autologous peripheral blood stem cell transplantation (auto-PBSCT).

MATERIALS AND METHODS

Based on data from 34 patients with hematologic malignancies, doses of CD34(+) cells and CD34(+) cell subsets, defined by the expression of HLA-DR, CD38, CD117 (c-kit/R), CD123 (alpha subunit of IL-3/R), CD133 (AC133), and CD90 (Thy-1) antigens, were correlated with the number of short-term (i.e., colony-forming cells [CFC]) and long-term culture CFC (LTC-CFC) (generated at week 5 of culture) and with the kinetics of hematopoietic engraftment following auto-PBSCT. The capacity of autologous stroma (AS), normal human bone marrow stroma, and M2-10B4 murine cell line to sustain CD34(+) cell growth was comparatively evaluated in the LTC assay.

RESULTS

Our data demonstrated that some of the most primitive progenitor subsets (CD34(+)CD117(-)HLA-DR(-), and CD34(+)CD38(+)HLA-DR(-)) showed the strongest correlation with LTC-CFC numbers generated within the AS, whereas no significant correlation was noted using normal bone marrow stroma. Multivariate analysis showed that the only CD34 cell subset independently associated with long-term (3 to 6 months) platelet engraftment after auto-bone marrow transplantation was the CD34(+)CD117(-)HLA-DR(-) phenotype; long-term erythrocyte engraftment was correlated with CD34(+)CD38(+)HLA-DR(-) cell content. The latter further influenced platelet engraftment in the first 3 months after auto-PBSCT. The most predictive parameters for neutrophil engraftment were CD34(+)CD38(+)HLA-DR(-) cell subtype and the total LTC-CFC quantity infused.

CONCLUSIONS

These data further support the hypothesis that the type of stromal feeders influences the frequency of LTC-CFC, possibly because they differ in their ability to interact with distinct subsets of hematopoietic stem cells. Furthermore, as the use of AS in LTC assay can mimic in vitro the human bone marrow microenvironment, it can be speculated that this culture system could be a useful means to study the kinetics of recovery of bone marrow stroma following chemotherapy and PBSCT. From these results, it can be concluded that some CD34(+) cell subsets appear to be more reliable predictors of long-term hematopoietic recovery rates than total CD34(+) cell quantity.

Generation of dendritic cells ex vivo: differences in steady state versus mobilized blood from patients with breast cancer, with lymphoma, and from normal donors

Dendritic cells (DC) are potent antigen-presenting cells that are integral to the initiation of T cell immunity. The ability to culture these cells in vitro has allowed DC immunotherapy to be investigated as a mechanism of enhancing immune responses against various malignancies. We examined the optimal time for generating DC and compared DC generated from normal donors for allogeneic blood stem cell transplantation, or patient's with non-Hodgkin's lymphoma or breast cancer undergoing high-dose chemotherapy and autologous stem cell transplantation. Experiments were conducted to compare DC cultured prior to and post mobilization chemotherapy. Blood was obtained from consenting patients prior to granulocyte colony-stimulating factor (G-CSF) administration with (non-Hodgkin lymphoma and breast cancer) or without (normal donors) chemotherapy. A sample of apheresis product (AP) was obtained at the time of apheresis. DC were generated from peripheral blood mononuclear cells by culturing the adherent cells in the presence of interleukin-4 and granulocyte-macrophage colony-stimulating factor. Resultant DC were harvested and examined for yield, morphology, phenotype, and function. All cell populations yielded highly pure DC, as assessed by light microscopy and flow cytometry. The average cellular yield was significantly greater from AP than steady-state blood in paired and unpaired samples. Yield did not correlate with the percentage of CD14(+) cells, and it negatively correlated with CD34 counts. DC from breast cancer patients functioned significantly better than DC from lymphoma patients in a mixed lymphocyte reaction. These data suggest that the optimal timing of culturing DC is after mobilization, and that differences may exist in the functional capabilities of DC derived from different patient populations.

G-CSF Primed Autologous Marrow Harvest and Transplantation in Cytapheresis "Mobilization Failure" Patients: A Descriptive Analysis; Bone Marrow Transplantation

Fifteen cancer patients, deemed blood HSC "mobilization failures" due to CD34 + cell yields of < 0.5 x 10(6) /kg from two consecutive daily cytaphereses, underwent G-CSF primed autologous bone marrow harvest in an attempt to obtain adequate hematopoietic support for subsequent autotransplantation. CD34 + cell yields from the primed marrow harvest were variable; however, some patients had > 5-fold increases in CD34 + cell yields in the marrow compared to cytapheresis, and 4 patients had CD34 + cell yields of > 1.0 (i.e., 1.2, 1.44, 1.61 and 2.45) x 10(6) /kg from the primed marrow harvest. None of the five patients previously exposed to stem cell toxins or fludarabine achieved > 0.85 x 10(6) /kg CD34 + cells with the primed marrow harvest. A significant difference was noted between G-CSF primed blood and marrow for CD34 + cells but not for GM-CFU ( p = 0.011 and p = 0.135, respectively, paired t-test). All evaluable patients engrafted; a median ANC > 0.5 x 10(9) /L recovery was achieved on D + 12 (range + 9 to + 17) in 12 of 13 evaluable patients - one died on D + 9 without recovery. The last day of platelet transfusion occurred at a median D + 13 (range + 8 to > + 66); only one patient remained platelet transfusion-dependent beyond D + 34. As anticipated, patients with higher numbers of CD34 + cells transplanted had somewhat more rapid recoveries. Although stem cell damage is obviously a key factor in mobilization failure patients, these findings raise the possibility that poor mobilization, at least in some patients, results from a mechanism other than, or in addition to, simple stem cell damage. Moreover, they raise the issue of the minimum number of marrow CD34 + - or more arguably other - cells needed for adequate short- and long-term reconstitution. The role of G-CSF in this situation, especially regarding dose and/or schedule, is intriguing but remains to be clarified. G-CSF primed marrow harvest is a potential option in certain poor mobilizers but, as fully expected, is frequently inadequate. Whether such is preferable to "steady-state" marrow harvest, continued or repeated G-CSF primed cytapheresis (with or without chemotherapy), or primed marrow with G-CSF in other schedules - or with other cytokines - is unclear and will be the subject of further study.

A European reference protocol for quality assessment and clinical validation of autologous haematopoietic blood progenitor and stem cell grafts

Recently, the regulatory authorities have begun to show interest in haematopoietic stem cell products. On a professional rather than a regulatory basis, the International Society for Hematotherapy and Graft Engineering (ISHAGE) has established the Foundation for the Accreditation of Haematopoietic Cell Therapy (FACHT), which has drawn up guidelines for standards and accreditation of such activity. In Europe, the regulatory environment with regard to haematopoietic stem cell grafts, processing and storage are currently less stringent. However, in 1998 the European Joint Accreditation Committee Euro-ISHAGE/EBMT (JACIE) prepared a regulatory document 'Standards for Blood and Marrow Progenitor Cell Collection, Processing and Transplantation' which was approved by the EBMT General Assembly. The major objectives were to promote quality of medical and laboratory practice in haematopoietic progenitor cell transplantation. The standards extend and detail the pre-existing activity of EBMT centres including all phases of collection, processing and administration of these cells. This is the platform for the proposed reference protocol for CD34(+) cell enumeration and clinical validation of quality assessment to ensure that appropriate standards of work and product quality are established and will be maintained.

Predictive factors for long-term engraftment of autologous blood stem cells

Data from 170 consecutive patients aged 19-66 years (median age 46 years) who underwent unmanipulated autologous blood stem cell transplant (ASCT) were analyzed to determine if total CD34+ cells/kg infused, CD34+ subsets (CD34+41+, CD34+90+, CD34+33-, CD34+38-, CD34+38-DR-), peripheral blood CD34+ cell (PBCD34+) count on first apheresis day, or various clinical factors were associated with low blood counts 6 months post ASCT. Thirty-four patients were excluded from analysis either because of death (n = 17) or re-induction chemotherapy prior to 6 months post ASCT (n = 13), or because of lack of follow-up data (n = 4). Of the remaining 136 patients, 46% had low WBC ( < 4 x 10(9)/l), 41% low platelets (<150 x 10(9)/l), and 34% low hemoglobin ( < 120 g/l) at a median of 6 months following ASCT. By Spearman's rank correlation, both the total CD34+ cell dose/kg and the PBCD34+ count correlated with 6 month blood counts better than any subset of CD34+ cells or any clinical factor. The PBCD34+ count was overall a stronger predictor of 6 month blood counts than was the total CD34+ cells/kg infused. Both factors retained their significance in multivariate analysis, controlling for clinical factors. In conclusion, subsets of CD34+ cells and clinical factors are inferior to the total CD34+ cell dose/kg and PBCD34+ count in predicting 6 month blood counts following ASCT.

Technical aspects and clinical impact of hematopoietic progenitor subset quantification

As high-dose therapy for malignancies is now being applied to newly diagnosed patients as adjuvant therapy, it has become a requirement that quality and safety assessment of hematopoietic stem cell grafts be evidence-based. This process has developed a new institution in medicine, the stem cell laboratory. In most cases this speciality has evolved from or within hematological research laboratories. However, the increased routine technologies applied in quality evaluation, ex vivo manipulation and safety assessment in stem cell handling naturally places this activity in transfusion medicine. Multiparametric flow cytometry can identify progenitor subsets in normal human bone marrow and peripheral blood, and such subset quantification has been used retrospectively to predict three-lineage engraftment following high-dose therapy for malignancies. Published single center data have suggested an impact on clinical outcome, and a standardized technique for subset enumeration needs to be established before prospective multicenter trials can be initiated to document the prognostic value of such quality assessment in autografting. Based on experiences of CD34 enumeration, which we consider to be the first step in quality assessment of hematopoietic stem cell grafts, this review discusses flow cytometry subset identification by lineage-specific differentiation markers, stromal-dependent adherence molecules, and regulatory growth factor receptors from a technical point of view. The aim of this review is:To recommend a simple method based on the experiences of the Nordic workshop III on subset identification; To present new molecular genetic-based methods for future use in quality assessment; and To propose new endpoints necessary for validation of the likely clinical impact of subsets in prospective trials. As sample differences between blood and marrow result in technical difficulties, this review only focuses on the methodology of identifying subsets in blood and leukapheresis products. Methods for subset analysis in diagnostic bone marrow samples will be covered in a forthcoming review.

The CD34+90+ cell dose does not predict early engraftment of autologous blood stem cells as well as the total CD34+ cell dose

CD90 or Thy-1 is an antigen co-expressed with CD34+ on putative immature hematopoietic stem cells. Peak mobilization of CD34+90+ cells into the blood occurs a few days earlier than peak mobilization of total CD34+ cells. Because it is not known which cell type best correlates with engraftment, the optimal timing of apheresis remains unclear. The purpose of the study was to determine if the CD34+90+ cell dose predicts engraftment of autologous blood stem cells independent of the total CD34+ cell dose/kg, the dose of other CD34+ cell subsets (CD34+33-, CD34+38-, CD34+41+), or various clinical factors. Data were analyzed on 125 consecutive patients ranging in age from 19 to 66 years (median 46) who underwent autologous blood stem cell transplantation (ABSCT) for breast cancer (54), lymphoma (59), or other malignancies (12). By univariate analysis, neutrophil (> or = 0.5 x 10(9)/l) and platelet (> or = 20 x 10(9)/l or > or = 100 x 10(9)/l) engraftment correlated better with the total CD34+ cell dose than with the CD34+90+ cell subset. Using Cox proportional hazards models, factors independently associated with both neutrophil engraftment (> or = 0.5 x 10(9)/l) and platelet engraftment (> or = 20 x 10(9)/l and > or = 100 x 10(9)/l) were higher total CD34+ dose/kg and high-dose regimen (melphalan-containing slower than other regimens). In conclusion, the total CD34+ dose/kg was a better predictor of hematopoietic engraftment following ABSCT than the dose of any CD34+ subset, including CD34+90+ cells. Apheresis should continue to be timed according to peak CD34+ levels.