Endothelial transplantation rejuvenates aged hematopoietic stem cell function
Michael G. Poulos, … , Sina Y. Rabbany, Jason M. Butler
Michael G. Poulos, … , Sina Y. Rabbany, Jason M. Butler
Published October 16, 2017
Citation Information: J Clin Invest. 2017;127(11):4163-4178. https://doi.org/10.1172/JCI93940.
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Concise Communication

Endothelial transplantation rejuvenates aged hematopoietic stem cell function

Abstract

Age-related changes in the hematopoietic compartment are primarily attributed to cell-intrinsic alterations in hematopoietic stem cells (HSCs); however, the contribution of the aged microenvironment has not been adequately evaluated. Understanding the role of the bone marrow (BM) microenvironment in supporting HSC function may prove to be beneficial in treating age-related functional hematopoietic decline. Here, we determined that aging of endothelial cells (ECs), a critical component of the BM microenvironment, was sufficient to drive hematopoietic aging phenotypes in young HSCs. We used an ex vivo hematopoietic stem and progenitor cell/EC (HSPC/EC) coculture system as well as in vivo EC infusions following myelosuppressive injury in mice to demonstrate that aged ECs impair the repopulating activity of young HSCs and impart a myeloid bias. Conversely, young ECs restored the repopulating capacity of aged HSCs but were unable to reverse the intrinsic myeloid bias. Infusion of young, HSC-supportive BM ECs enhanced hematopoietic recovery following myelosuppressive injury and restored endogenous HSC function in aged mice. Coinfusion of young ECs augmented aged HSC engraftment and enhanced overall survival in lethally irradiated mice by mitigating damage to the BM vascular microenvironment. These data lay the groundwork for the exploration of EC therapies that can serve as adjuvant modalities to enhance HSC engraftment and accelerate hematopoietic recovery in the elderly population following myelosuppressive regimens.

Authors

Michael G. Poulos, Pradeep Ramalingam, Michael C. Gutkin, Pierre Llanos, Katherine Gilleran, Sina Y. Rabbany, Jason M. Butler

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Figure 1

Aged BM vasculature displays functional alterations in vivo.

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Aged BM vasculature displays functional alterations in vivo. (A) Represe...
(A) Representative longitudinal and inset images of femurs intravitally labeled with a vascular-specific VECAD antibody (red), showing morphological alterations in aged vasculature (white line demarcates cortical bone). Scale bars: 100 μm (longitudinal images) and 50 μm (insets). (B and C) Analysis of BM vascular leakiness in young and aged femurs. (B) Quantification of Evans blue dye extravasation (n = 5 mice/cohort). (C) Representative femurs injected with Evans blue dye. Noninjected controls were used to determine baselines (n = 5 mice/cohort). (D and E) Frequency of recoverable (D) VECAD+CD31+CD45–TER119– BM ECs and (E) VECAD–CD31–CD45–TER119– stroma in young and aged femurs (n = 5 mice/cohort). (F) Quantification of mean fluorescence intensity (MFI) and representative histogram of ROS in VECAD+CD31+CD45–TER119– ECs from young and aged femurs showing an increase in ROS in aged ECs (n = 3 mice/cohort). (G) MFI quantification and representative histogram of pimonidazole adducts as detected by an anti-pimonidazole antibody (HypoxyProbe) in VECAD+CD31+CD45–TER119– ECs from young and aged femurs, demonstrating an increased hypoxia state in aged ECs (n = 3 mice/cohort). (H) Representative immunofluorescence images of HypoxyProbe-stained young and aged femurs, showing local changes in hypoxia (white line demarcates cortical bone). Scale bar: 50 μm. Error bars represent the sample mean ± SEM. *P < 0.05 and ***P < 0.001, by unpaired, 2-tailed Student’s t test.