Der Einfluss von Hypoxie pathway Proteinen in Endothelzellen (PHD2 und Endoglin) auf das hämatopoetische System und seine Knochenmarknische

• Antragsteller: Professor Dr. Ben Wielockx, Ph.D.
• Fachliche Zuordnung: Hämatologie, Onkologie ; Anatomie und Physiologie ; Pathologie
• Förderung: Förderung von 2019 bis 2023
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 418871341

• Erstellungsjahr: 2023

Zusammenfassung der Projektergebnisse

Oxygen is one of the most important molecules required for the development and maintenance of life. An appropriate response to low O2 tension (hypoxia) is therefore required for the proper functioning of the majority of living organisms. The master regulators of the adaptive response to hypoxia are the hypoxia-inducible factors (HIFs), transcription factors that form heterodimers (the oxygen-sensitive HIFαs and a constitutive HIFβ subunit) and promote oxygen delivery and adaptive processes such as angiogenesis, anaerobic glycolysis, and hematopoiesis. Of note, HIF1α is ubiquitously expressed, whereas HIF2α is restricted to specific cell types such as endothelial cells. The oxygen sensing machinery relies on HIF prolyl hydroxylase domain-containing enzymes (PHD1-3). PHD2, a key oxygen sensor, hydroxylates HIFα, triggering binding to the von Hippel-Lindau complex, ubiquitination, and HIF inactivation. Research on PHD2 in particular spans different physiological and pathological contexts. In this project, we aimed to investigate the role of hypoxia pathway proteins (PHD2, HIF and endoglin) in the bone marrow (BM) and hematopoietic maintenance. The BM is a critical organ for hematopoiesis, housing hematopoietic stem and progenitor cells (HSPCs) in specialized niches known as the BM microenvironment. The BM vasculature, composed predominantly of endothelial cells (ECs), plays a pivotal role in supporting cell migration and nutrient transport within the niche, and PHDs/HIFs have been implicated in vascular remodeling and pathophysiological conditions in the past. In a first subproject, we used our EC-specific PHD2-deficient mouse line (Flk1:cre-PHD2f/f) to determine the impact of this oxygen sensor on the BM vasculature and beyond. Our work has shown that PHD2 controls HIF2α to define vascular morphology, leukocytosis and consequent dysregulation of hematopoietic progenitors, in addition to facilitating bone metastasis and neutrophil extravasation during skin inflammation. Furthermore, BM-EC transcriptome analysis and additional mouse models strongly suggest for a HIF2-downstream role for miR126-VCAM1. In a second subproject, our group elucidated the role of endoglin (CD105) in BM-EC. In a detailed kinetic study using an inducible transgenic mouse line (VE-cadh:cre-ERT2-Engf/f), we identified endoglin as a direct regulator of vascular integrity in the BM niche. Deletion of this protein resulted in angiogenesis defined by BM-EC proliferation (week 2-3) and subsequent apoptosis (week 4), leading to a completely remodeled vascular bed, increased leukocyte leakiness and dramatic modulation of the HSPC population dependent on β-integrins (from week 2). Taken together, these findings contribute to our understanding of the influence of hypoxia pathway proteins on the entire BM and shed light on potential implications for hematopoiesis, bone metastasis and inflammation.

Projektbezogene Publikationen (Auswahl)

• Hypoxia Pathway Proteins in Normal and Malignant Hematopoiesis. Cells, 8(2), 155.
  Wielockx, Ben; Grinenko, Tatyana; Mirtschink, Peter & Chavakis, Triantafyllos
  
• Hypoxia Pathway Proteins are Master Regulators of Erythropoiesis. International Journal of Molecular Sciences, 21(21), 8131.
  Watts, Deepika; Gaete, Diana; Rodriguez, Diego; Hoogewijs, David; Rauner, Martina; Sormendi, Sundary & Wielockx, Ben
  
• HIF-Prolyl Hydroxylase Domain Proteins (PHDs) in Cancer—Potential Targets for Anti-Tumor Therapy? Cancers, 13(5), 988.
  Gaete, Diana; Rodriguez, Diego; Watts, Deepika; Sormendi, Sundary; Chavakis, Triantafyllos & Wielockx, Ben
  
• Hypoxia Pathway Proteins and Their Impact on the Blood Vasculature. International Journal of Molecular Sciences, 22(17), 9191.
  Rodriguez, Diego; Watts, Deepika; Gaete, Diana; Sormendi, Sundary & Wielockx, Ben
  
• CD38 promotes hematopoietic stem cell dormancy via c-Fos. Cold Spring Harbor Laboratory.
  Ibneeva, Liliia; Singh, Sumeet Pal; Sinha, Anupam; Eski, Sema Elif; Wehner, Rebekka; Rupp, Luise; Pérez-Valencia, Juan Alberto; Gerbaulet, Alexander; Reinhardt, Susanne; Wobus, Manja; von Bonin, Malte; Sancho, Jaime; Lund, Frances; Dahl, Andreas; Schmitz, Marc; Bornhäuser, Martin; Chavakis, Triantafyllos; Wielockx, Ben & Grinenko, Tatyana
  
• Hypoxia signaling pathway: A central mediator in endocrine tumors. Frontiers in Endocrinology, 13.
  Watts, Deepika; Jaykar, Mangesh T.; Bechmann, Nicole & Wielockx, Ben