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Research in the Butler Lab
Vascular Regulation of Hematopoietic Stem Cell Ontogeny
Our laboratory has focused on enhancing regeneration of the hematopoietic system in the context of hematological injuries (e.g., myelosuppression), leukemogenesis, and aging. Our commitment to studying the hematopoietic system is based on the discoveries by our group demonstrating that bone marrow endothelial cells (BM ECs) serve as instructive niche cells that are essential for the reconstitution of the hematopoietic system following radiation injury (Figure 1). Our approach proved that the cellular cross talk between the BM vascular niche and hematopoietic stem cells (HSCs) is largely dependent on the activation state of the ECs. These innovative concepts have led to a paradigm shift in vascular biology—demonstrating that BM ECs are not only essential for the delivery of oxygen, nutrients, and waste disposal, but also function as a specialized vascular niche that, upon proper activation, can instructively support the maintenance and reconstitution of normal HSCs. The concept that ECs provide an instructive fertile niche for maintenance of functional HSCs opens up new avenues for many aspects in stem cell biology and can be applied to multiple biosystems.
Figure 1. Model for HSC homeostasis by the endothelial niche. This model demonstrates that the activation of either the AKT or MAPK signaling pathway within ECs promotes the expansion and differentiation of HSCs, respectively.
Our laboratory is currently aiming to identify relevant paracrine factors and metabolites found within the BM vascular niche cells that modulate self-renewal and expansion of adult HSCs and to develop strategies to enhance hematopoietic reconstitution in the clinical arena. In addition to studying the role of the ECs in regulating adult hematopoiesis, we are interrogating the ability of embryonic vascular niches to induce and expand definitive HSCs from pluripotent stem cell (PSC) sources. In order to determine the optimal embryonic vascular niche for the induction and expansion of embryonic-stage hematopoietic stem/progenitor cells (HSPCs), we have developed methods to isolate and culture ECs from numerous fetal (e.g., E11 AGM, E10.5 placenta, E13.5 fetal liver) and adult (e.g., bone marrow) hematopoietic tissues. Furthermore, we have developed an effective, novel platform to expand adult BM macaque CD34+ LT-HSCs and iPSC-HSPCs on human ECs that have high levels of engraftment in NSG mice. This evidence substantiates our novel approach to enhance definitive HSPCs through direct contact cultures with pro-hematopoietic signals unique to ECs. It is our long-term goal to deconstruct the critical stage-specific signal pathways differentially required for induction and expansion of HSCs from embryonic sources as well as enabling the use of patient-specific cells to safely treat their hematological deficiencies.
Overall, our laboratory is dedicated to understanding the role of tissue-specific ECs in establishing unique instructive vascular niche cells that produce the correct milieu and stoichiometry of paracrine factors to direct organ regeneration, in particular within the BM microenvironment. We have assembled large transcriptional profiles from tissue-specific vascular niches that have revealed remarkable heterogeneity within the adult vasculature that is underscored by the production of tissue-specific paracrine factors which we believe are necessary for orchestrating the regeneration of their organ of origin. Based on these data, we are developing novel therapeutic applications and justification for the transplantation of genetically modified BMECs or other cellular sources that are directly reprogrammed into BMECs utilizing a unique set of transcription factors that establish BMEC identity to enhance the regeneration of the BM microenvironment. We hypothesize that reconstitution of hematopoiesis along with an increase in engrafted ECs will not only cooperatively augment both the stability and integrity of the newly formed vessels, but also via an inductive mechanism to promote tissue repair and multi-organ regeneration. We expect that the knowledge gained from our laboratory’s research goals will have a significant and positive impact on decreasing the morbidity and mortality associated with the life-threatening pancytopenia that is associated with hematopoietic dysfunction.
The long-term vision of our research is to demonstrate that ECs can rapidly and efficiently home and functionally engraft multiple organ-specific vascular beds. These findings will allow us to study the role of transplanted ECs in a vast array of biological systems that require the stimulation of organ regeneration. The proposed work is expected to challenge the scientific conceptualization of a monofunctional, relatively inert microvasculature by revealing a dynamic role for ECs in injury repair and regeneration. We are hopeful that the endless pursuit of our laboratory’s vision and potential fruitful collaborations throughout the scientific community will open up innovative avenues for translational cellular therapy.
- Poulos MG, Ramalingam P, Gutkin MC, Llanos P, Gilleran K, Rabbaby S, Butler JM. Endothelial transplantation rejuvenates aged hematopoietic stem cell function. The Journal of Clinical Investigation. 2017 Nov 1;127(11):4163-4178. doi: 10.1172/JCI93940. https://www.ncbi.nlm.nih.gov/pubmed/29035282
- Guo P, Poulos MG, Palikuqi B, Badwe CR, Lis R, Kunar B, Ding BS, Rabbany SY, Shido K, Butler JM*, Rafii S. Endothelial jagged-2 sustains hematopoietic stem and progenitor reconstitution after myelosuppression. The Journal of Clinical Investigation. 2017 Nov 1;127(11):4256-4178. doi: 10.1172/JCI92309. https://www.ncbi.nlm.nih.gov/pubmed/29058691
- Conversion of adult endothelium to immunocompetent haematopoietic stem cells. Lis R, Karrasch CC, Poulos MG, Barcia Duran JG, Schachterle W, Ginsberg M, Tabrizi AR, Shido K, Sandler V, Speck N, Butler JM, Scandura J, Rafii S. 2017 May 25; 545(7655):439-445. https://www.ncbi.nlm.nih.gov/pubmed/28514438
- Altered feto-placental vascularization, placenta malperfusion, and fetal growth restriction in mice with Egfl7 loss-of-function. Lacko LA, Hurtado R, Hinds S, Poulos MG, Butler JM, Stuhlmann H. 2017 May 19 pii: dev.147025 https://www.ncbi.nlm.nih.gov/pubmed/28526753
- A Common Origin for B-1a and B-2 Lymphocytes in Clonal Pre-Hematopoietic Stem Cells. Hadland BK, Varnum-Finney B, Mandal PK, Rossi DJ, Poulos MG, Butler JM, Rafii S, Yoder MC, Yoshimoto M, Bernstein ID. Stem Cell Reports. 2017 Jun 6; 8(6): 1563-1572. https://www.ncbi.nlm.nih.gov/pubmed/28479303.
- Endothelial-specific inhibition of NF-κB enhances functional haematopoiesis. Poulos MG, Ramalingam P, Gutkin MC, Kleppe M, Ginsberg M, Crowley MJ, Elemento O, Levine RL, Rafii S, Kitajewski J, Greenblatt MB, Shim JH, Butler JM. Nature communications. 2016; 7:13829. https://www.ncbi.nlm.nih.gov/pubmed/28000664
- Sinusoidal ephrin receptor EPHB4 controls hematopoietic progenitor cell mobilization from bone marrow. Kwak H, Salvucci O, Weigert R, Martinez-Torrecuadrada JL, Henkemeyer M, Poulos MG, Butler JM, Tosato G. The Journal of clinical investigation. 2016; 126(12): 4554. https://www.ncbi.nlm.nih.gov/pubmed/27820703
- Endothelial Cells Promote Expansion of Long-Term Engrafting Marrow Hematopoietic Stem and Progenitor Cells in Primates. Gori JL, Butler JM, Kunar B, Poulos MG, Ginsberg M, Nolan DJ, Norgaard ZK, Adair JE, Rafii S, Kiem HP. Stem cells translational medicine. 2016 https://www.ncbi.nlm.nih.gov/pubmed/27742844
- Spleen hypoplasia leads to abnormal stress hematopoiesis in mice with loss of Pbx homeoproteins in splenic mesenchyme. Zewdu R, Risolino M, Barbulescu A, Ramalingam P, Butler JM, Selleri L. (Co-Corresponding Author) Journal of anatomy. 2016; 229(1):153-69. https://www.ncbi.nlm.nih.gov/pubmed/27075259
- Distinct bone marrow blood vessels differentially regulate haematopoiesis. Itkin T, Gur-Cohen S, Spencer JA, Schajnovitz A, Ramasamy SK, Kusumbe AP, Ledergor G, Jung Y, Milo I, Poulos MG, Kalinkovich A, Ludin A, Kollet O, Shakhar G, Butler JM, Rafii S, Adams RH, Scadden DT, Lin CP, Lapidot T. 2016; 532(7599):323-8. https://www.ncbi.nlm.nih.gov/pubmed/27074509
- Regulation of the hematopoietic stem cell lifecycle by the endothelial niche. Ramalingam P, Poulos MG, and Butler JM. Current Opinion in Hematology. 2017; July 24(4): 289-299. https://www.ncbi.nlm.nih.gov/pubmed/28594660
- Transplantation of Endothelial Cells to Mitigate Acute and Chronic Radiation Injury to Vital Organs. Rafii S, Ginsberg M, Scandura J, Butler JM, Ding BS. Radiation research. 2016; 186(2):196-202. https://www.ncbi.nlm.nih.gov/pubmed/27459700
- Stem cells: Painkillers caught in blood-cell trafficking. Butler JM, Rafii S. 2013; 495(7441):317-8. https://www.ncbi.nlm.nih.gov/pubmed/23485972
- Generation of a vascular niche for studying stem cell homeostasis. Butler JM, Rafii S. Methods in molecular biology (Clifton, N.J.). 2012; 904:221- https://www.ncbi.nlm.nih.gov/pubmed/22890935
- Instructive role of the vascular niche in promoting tumour growth and tissue repair by angiocrine factors. Butler JM, Kobayashi H, Rafii S. Nature reviews. Cancer. 2010; 10(2):138-46. https://www.ncbi.nlm.nih.gov/pubmed/20094048