Netrin-1 promotes the expansion and function of human hematopoietic stem cells by supporting a pro-hematopoietic vascular niche

PROJECT SUMMARY
Adult hematopoietic stem cells (HSCs) are defined by their ability to undergo self-renewal and maintain the
capacity to generate all the types of mature hematopoietic cells within the blood and immune system. The
ultimate objective of the proposed research plan described herein is to establish a novel HSC expansion platform
to enable treating more patients with life-threatening disorders of blood and bone marrow than is currently
possible. This proposal seeks to greatly expand the availability of suitable donors for hematopoietic stem cell
transplantation (HSCT) and limit the duration of post-transplant cytopenia, which is the leading cause of
treatment-related death following HSCT. To tackle this issue, we have developed a novel physiological vascular
niche platform for ex vivo expansion of human HSCs with unprecedented potential to accelerate hematopoietic
recovery and avoid life-threatening infection and hemorrhage in patients treated with myeloablative or
myelosuppressive therapies. Our novel ex vivo HSC expansion technology will hopefully shorten the duration of
hospitalization and reduce the high of HSCT therapy. Indeed, this platform was successfully tested in a recently
completed Phase I clinical trial (Identifier: NCT03483324). The current research plan aims to build upon our
recent discoveries that the vascular niche provides the instructional cues that enable large-scale expansion of
HSCs, while preserving their self-renewal capabilities. We propose to utilize a pro-HSC factor we recently
discovered (PMID: 37037837), Netrin-1 (NTN1), to supplement our vascular niche/HSC co-culture assay to
enhance the functional output of ex vivo expanded human HSCs. This proposal will determine if NTN1 can
support the function of human blood products and begin to define novel angiocrine factors from a humanized in
vivo BM vascular niche that support human HSC and vascular function. To this end, we will: 1) determine if
supplementation of NTN1 improves the ex vivo expansion and in vivo engraftment of human HSPCs, 2)
determine if blocking NTN1 signaling interferes with the function of ex vivo expanded and transplanted HSPCs,
3) determine if NTN1 signaling support vascular function human hematopoietic recovery following
myelosuppressive insult, and 4) begin to identify candidate pro-HSC angiocrine factors from human ECs that
can improve human HSC function. The proposed experiments represent a continuum of pre-clinical research,
aimed at ultimately investigating the transplantation of expanded long-term repopulating HSCs in patients who
may benefit from an autologous BM or umbilical cord blood grafts. Successful HSC expansion will ultimately
extend access to HSCT for patients requiring a curative HSC replacement. Accomplishing these objectives will
ultimately benefit underserved patient populations, including ethnic and racial minorities as well as older patients
who lack suitably human leukocyte antigen matched sibling or adult unrelated volunteer donors for hematopoietic
transplantation and patients requiring engineered, engraftable HSCs for the correction of genetic disorders, but
for whom the number of available autologous HSCs is suboptimal.

Grant Number: 5R01HL177599-02
NIH Institute/Center: NIH
Principal Investigator: Jason Butler