Hematopoietic Cell Transplant (HCT) in the Elderly: Myths, Controversies and Unknowns

Cognitive functioning of older adults prior to hematopoietic stem cell transplantation

Hematopoietic cell transplantation is increasingly used in older adults with hematological malignancies. Younger adult patients who undergo HCT have shown to commonly present with cognitive impairment and depression prior to transplant; however, little research has been done to understand the cognitive and emotional functioning of older adults undergoing HCT. This study aimed to investigate the rate of cognitive impairment in a retrospective sample of older adult HCT candidates prior to transplant using a comprehensive battery. Ninety-three patients over the age of 60 completed a neuropsychology test battery that assessed standard domains of cognitive and emotional functioning. Impairment was defined as z-scores = < -1.5 on at least two tests or a z score = < -2.0 on at least one test. Results indicated that over 68% of patients were impaired with nearly a third of the sample showing impairment in verbal learning and memory and approximately one fifth showing impairments in aspects of executive function, processing speed, and visual learning. Ten percent of the patients endorsed symptoms indicative of a clinical level of depression. Medical comorbidities nor depression predicted cognitive impairment. These findings suggest that older adults candidates for HCT are at risk for cognitive impairment prior to transplant and thus cognition should be a consideration when developing treatment plans.

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.