Sixty as the new forty: considerations on older related stem cell donors

Decoupling blood telomere length from age in recipients of allogeneic hematopoietic cell transplant in the BMT-CTN 1202

The age of allogeneic hematopoietic cell transplant (HCT) donors and their hematopoietic cell telomere length (TL) might affect recipients’ outcomes. Our goals were to examine the possible effect of these donors’ factors on the recipients’ hematopoietic cell TL and quantify hematopoietic cell TL shortening in the critical first three-month post-HCT. We measured hematopoietic cell TL parameters in 75 recipient-donor pairs, from the Blood and Marrow Transplant Clinical Trials Network (protocol#1202), by Southern blotting (SB), the Telomeres Shortest Length Assay (TeSLA), and quantitative PCR (qPCR). Recipients’ hematopoietic cell TL parameters post-HCT correlated with donors’ age (p<0.001 for all methods), but not recipients’ own age, and with donors’ pre-HCT hematopoietic cell TL (p<0.0001 for all). Multivariate analyses showed that donors’ hematopoietic cell TL pre-HCT, independent of donors’ age, explained most of the variability in recipients’ hematopoietic cell TL post-HCT (81% for SB, 56% for TeSLA, and 65% for qPCR; p>0.0001 for all). SB and TeSLA detected hematopoietic cell TL shortening in all recipients post-HCT (mean=0.52kb and 0.47kb, respectively; >15-fold the annual TL shortening in adults; p<0.00001 for both), but qPCR detected shortening only in 57.5% of recipients. TeSLA detected a buildup of post-HCT of telomeres <3 kb in 96% of recipients (p<0.0001). In conclusion, HCT decouples hematopoietic cell TL in the recipients from their own age to reflect the donors’ age. The potential donors’ age effect on outcomes of HCT might be partially mediated by short hematopoietic cell TL in older donors. qPCR-based TL measurement is suboptimal for detecting telomere shortening post-HCT.

Basic characteristics and safety of donation in related and unrelated haematopoietic progenitor cell donors - first 10 years of prospective donor follow-up of Swiss donors

Since July 2007 prospective life-long follow-up (FU) for unrelated (URD) and related donors (RD) is mandatory in Switzerland and data on every allogeneic haematopoietic progenitor cell (HPC) donation are collected prospectively. We report the real-world experience of HPC donation during a 10-year study period (01.07.2007-30.06.2017) with basic characteristics and FU data. 1105 donors underwent 1155 HPC donation procedures. Eighty percent of first donations performed by 802 (73%) RDs and 303 (27%) URDs were peripheral blood stem cells (PBSC), 20% bone marrow (BM). Male donors were over-represented as URD (60% male vs 40% female). Main differences between RDs and URDs concerned age and pre-existing health disorders. RDs were significantly older at first donation (median age 48 years) compared to URD (34 years, p < 0.0001) and had more pre-existing health problems: 25% vs 9% in URD (p < 0.0001). No fatal complications occurred, collection related severe adverse events (SAE) after first donation were not significantly different between groups (RD 1.2%, URD 0.99%), incidence rates for neoplastic and autoimmune diseases did not exceed the rates of the general population. RDs are a more heterogeneous and potentially more vulnerable group, but if donor evaluation is performed appropriately, HPC donation is still safe.

Relationship of donor age and relationship to outcomes of haploidentical transplantation with posttransplant cyclophosphamide

Allogeneic blood or marrow transplantation (BMT) physicians seek to optimize all possible variables to improve outcomes. Selectable factors include conditioning, graft-versus-host disease (GVHD) prophylaxis, graft source, and donor. Many patients, especially those with eligible haploidentical (haplo) donors, will have multiple donor options. We seek to identify factors to optimize the choice of haplo donors when using posttransplantation cyclophosphamide (PTCy) GVHD prophylaxis. We evaluated the effect of modifiable donor characteristics (donor age and relationship) on outcomes following haplo BMT with a uniform nonmyeloablative conditioning and PTCy. From 2002 to 2017, 889 consecutive adult patients underwent nonmyeloablative haplo BMT with PTCy. Median follow-up among survivors was 2.5 years after BMT. Median recipient age was 59 (range: 18 to 76) years and median donor age was 40 (range: 13 to 79) years. Multivariable analyses demonstrated that increasing donor age by decade was associated with poorer overall survival (hazard ratio [HR], 1.13 [1.05, 1.22; P = .0015]), worse progression-free survival (HR, 1.09 [1.02, 1.16; P = .015]), and a higher risk for grade 2 to 4 and grade 3 to 4 GVHD (1.3 [1.06, 1.61; P = .013]), but not for chronic GVHD (HR, 1.06 [0.94, 1.2]; P = .37). These less-favorable results with older donors were attributable to worse nonrelapse mortality (HR, 1.19 [1.05, 1.34]; P = .006), not relapse. Parents were associated with inferior outcomes compared with sibling donors, whereas no significant differences were observed between parental donors. These data suggest that the youngest, adult-sized donors should be preferred when multiple haplo donors are available.

Age-Related Changes in Bone-Marrow Mesenchymal Stem Cells

The use of stem cells is part of a strategy for the treatment of a large number of diseases. However, the source of the original stem cells for use is extremely important and determines their therapeutic potential. Mesenchymal stromal cells (MSC) have proven their therapeutic effectiveness when used in a number of pathological models. However, it remains an open question whether the chronological age of the donor organism affects the effectiveness of the use of MSC. The asymmetric division of stem cells, the result of which is some residential stem cells acquiring a non-senile phenotype, means that stem cells possess an intrinsic ability to preserve juvenile characteristics, implying an absence or at least remarkable retardation of senescence in stem cells. To test whether residential MSC senesce, we evaluated the physiological changes in the MSC from old rats, with a further comparison of the neuroprotective properties of MSC from young and old animals in a model of traumatic brain injury. We found that, while the effect of administration of MSC on lesion volume was minimal, functional recovery was remarkable, with the highest effect assigned to fetal cells; the lowest effect was recorded for cells isolated from adult rats and postnatal cells, having intermediate potency. MSC from the young rats were characterized by a faster growth than adult MSC, correlating with levels of proliferating cell nuclear antigen (PCNA). However, there were no differences in respiratory activity of MSC from young and old rats, but young cells showed much higher glucose utilization than old ones. Autophagy flux was almost the same in both types of cells, but there were remarkable ultrastructural differences in old and young cells.

Prostaglandin E2 Enhances Aged Hematopoietic Stem Cell Function

Aging of hematopoiesis is associated with increased frequency and clonality of hematopoietic stem cells (HSCs), along with functional compromise and myeloid bias, with donor age being a significant variable in survival after HSC transplantation. No clinical methods currently exist to enhance aged HSC function, and little is known regarding how aging affects molecular responses of HSCs to biological stimuli. Exposure of HSCs from young fish, mice, nonhuman primates, and humans to 16,16-dimethyl prostaglandin E₂ (dmPGE₂) enhances transplantation, but the effect of dmPGE₂ on aged HSCs is unknown. Here we show that ex vivo pulse of bone marrow cells from young adult (3 mo) and aged (25 mo) mice with dmPGE₂ prior to serial competitive transplantation significantly enhanced long-term repopulation from aged grafts in primary and secondary transplantation (27 % increase in chimerism) to a similar degree as young grafts (21 % increase in chimerism; both p < 0.05). RNA sequencing of phenotypically-isolated HSCs indicated that the molecular responses to dmPGE₂ are similar in young and old, including CREB1 activation and increased cell survival and homeostasis. Common genes within these pathways identified likely key mediators of HSC enhancement by dmPGE₂ and age-related signaling differences. HSC expression of the PGE₂ receptor EP4, implicated in HSC function, increased with age in both mRNA and surface protein. This work suggests that aging does not alter the major dmPGE₂ response pathways in HSCs which mediate enhancement of both young and old HSC function, with significant implications for expanding the therapeutic potential of elderly HSC transplantation.

Modeling and Bioinformatics Identify Responders to G-CSF in Patients With Amyotrophic Lateral Sclerosis

Objective: Developing an integrative approach to early treatment response classification using survival modeling and bioinformatics with various biomarkers for early assessment of filgrastim (granulocyte colony stimulating factor) treatment effects in amyotrophic lateral sclerosis (ALS) patients. Filgrastim, a hematopoietic growth factor with excellent safety, routinely applied in oncology and stem cell mobilization, had shown preliminary efficacy in ALS. Methods: We conducted individualized long-term filgrastim treatment in 36 ALS patients. The PRO-ACT database, with outcome data from 23 international clinical ALS trials, served as historical control and mathematical reference for survival modeling. Imaging data as well as cytokine and cellular data from stem cell analysis were processed as biomarkers in a non-linear principal component analysis (NLPCA) to identify individual response. Results: Cox proportional hazard and matched-pair analyses revealed a significant survival benefit for filgrastim-treated patients over PRO-ACT comparators. We generated a model for survival estimation based on patients in the PRO-ACT database and then applied the model to filgrastim-treated patients. Model-identified filgrastim responders displayed less functional decline and impressively longer survival than non-responders. Multimodal biomarkers were then analyzed by PCA in the context of model-defined treatment response, allowing identification of subsequent treatment response as early as within 3 months of therapy. Strong treatment response with a median survival of 3.8 years after start of therapy was associated with younger age, increased hematopoietic stem cell mobilization, less aggressive inflammatory cytokine plasma profiles, and preserved pattern of fractional anisotropy as determined by magnetic resonance diffusion tensor imaging (DTI-MRI). Conclusion: Long-term filgrastim is safe, is well-tolerated, and has significant positive effects on disease progression and survival in a small cohort of ALS patients. Developing and applying a model-based biomarker response classification allows use of multimodal biomarker patterns in full potential. This can identify strong individual treatment responders (here: filgrastim) at a very early stage of therapy and may pave the way to an effective individualized treatment option.

Development of an Unrelated Donor Selection Score Predictive of Survival after HCT: Donor Age Matters Most

Donor factors, in addition to HLA matching status, have been associated with recipient survival in unrelated donor (URD) hematopoietic cell transplantation (HCT); however, there is no hierarchical algorithm that weights the characteristics of individual donors against each other in a quantitative manner to facilitate donor selection. The goal of this study was to develop and validate a donor selection score that prioritizes donor characteristics associated with better survival in 8/8 HLA-matched URDs. Two separate patient/donor cohorts, the first receiving HCT between 1999 and 2011 (n = 5952, c1), and the second between 2012 and 2014 (n = 4510, c2) were included in the analysis. Both cohorts were randomly spilt, 2:1, into training and testing sets. Despite studying over 10,000 URD transplants, we were unable to validate a donor selection score. The only donor characteristic associated with better survival was younger age, with 2-year survival being 3% better when a donor 10 years younger is selected. These results support previous studies suggesting prioritization of a younger 8/8 HLA-matched donor. This large dataset also shows that none of the other donor clinical factors tested were reproducibly associated with survival, and hence flexibility in selecting URDs based on other characteristics is justified. These data support a simplified URD selection process and have significant implications for URD registries.

T Cell Depletion as an Alternative Approach for Patients 55 Years or Older Undergoing Allogeneic Stem Cell Transplantation as Curative Therapy for Hematologic Malignancies

T cell-depleted (TCD) allogeneic hematopoietic stem cell transplantation (HSCT) is curative treatment for hematologic malignancies in adults, shown to reduce graft-versus-host disease (GVHD) without increased relapse. We retrospectively reviewed a single-center, 11-year experience of 214 patients aged ≥ 55 years to determine tolerability and efficacy in the older adult. Most patients (70%) had myeloid diseases, and most acute leukemias were in remission. Median age was 61 years, with related and unrelated donors ≥8/10 HLA matched. Hematopoietic cell transplantation-specific comorbidity index scores were intermediate and high for 84%. Conditioning regimens were all myeloablative. Grafts were peripheral blood stem cells (97%) containing CD3 dose ≤103-4/kg body weight, without pharmacologic GVHD prophylaxis. With median follow-up of 70 months among survivors, Kaplan-Meier estimates of overall and relapse-free survival were 44% and 41%, respectively (4 years). Cumulative incidence of nonrelapse mortality at day +100 was only 10%. Incidence of GVHD for acute (grades II to IV) was 9% at day +100 and for chronic was 7% at 2 and 4 years (8 extensive, 1 overlap). Median Karnofsky performance status for patients > 2 years post-transplant was 90%. As 1 of the largest reports for patients ≥2 aged ≥55 years receiving TCD HSCTs, it demonstrates curative therapy with minimal GVHD, similar to that observed in a younger population.