RESUMEN
Within the bone marrow microenvironment, endothelial cells (EC) exert important functions. Arterial EC support hematopoiesis while H-type capillaries induce bone formation. Here, we show that BM sinusoidal EC (BM-SEC) actively control erythropoiesis. Mice with stabilized ß-catenin in BM-SEC (Ctnnb1OE-SEC) generated by using a BM-SEC-restricted Cre mouse line (Stab2-iCreF3) develop fatal anemia. While activation of Wnt-signaling in BM-SEC causes an increase in erythroblast subsets (PII-PIV), mature erythroid cells (PV) are reduced indicating impairment of terminal erythroid differentiation/reticulocyte maturation. Transplantation of Ctnnb1OE-SEC hematopoietic stem cells into wildtype recipients confirms lethal anemia to be caused by cell-extrinsic, endothelial-mediated effects. Ctnnb1OE-SEC BM-SEC reveal aberrant sinusoidal differentiation with altered EC gene expression and perisinusoidal ECM deposition and angiocrine dysregulation with de novo endothelial expression of FGF23 and DKK2, elevated in anemia and involved in vascular stabilization, respectively. Our study demonstrates that BM-SEC play an important role in the bone marrow microenvironment in health and disease.
Asunto(s)
Anemia/genética , Médula Ósea/metabolismo , Moléculas de Adhesión Celular Neuronal/genética , Endotelio Vascular/metabolismo , Eritroblastos/metabolismo , Eritropoyesis/genética , beta Catenina/genética , Anemia/metabolismo , Anemia/mortalidad , Anemia/patología , Animales , Médula Ósea/irrigación sanguínea , Capilares/citología , Capilares/metabolismo , Moléculas de Adhesión Celular Neuronal/metabolismo , Diferenciación Celular , Células Endoteliales/clasificación , Células Endoteliales/citología , Células Endoteliales/metabolismo , Endotelio Vascular/citología , Eritroblastos/clasificación , Eritroblastos/citología , Femenino , Factor-23 de Crecimiento de Fibroblastos/genética , Factor-23 de Crecimiento de Fibroblastos/metabolismo , Regulación de la Expresión Génica , Trasplante de Células Madre Hematopoyéticas , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/metabolismo , Integrasas/genética , Integrasas/metabolismo , Péptidos y Proteínas de Señalización Intercelular/genética , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Masculino , Ratones , Ratones Transgénicos , Osteogénesis , Reticulocitos/citología , Reticulocitos/metabolismo , Análisis de Supervivencia , Vía de Señalización Wnt , beta Catenina/metabolismoRESUMEN
Endothelial wingless-related integration site (Wnt)-/ß-catenin signaling is a key regulator of the tightly sealed blood-brain barrier. In the hepatic vascular niche angiokine-mediated Wnt signaling was recently identified as an important regulator of hepatocyte function, including the determination of final adult liver size, liver regeneration, and metabolic liver zonation. Within the hepatic vasculature, the liver sinusoidal endothelial cells (LSECs) are morphologically unique and functionally specialized microvascular endothelial cells (ECs). Pathological changes of LSECs are involved in chronic liver diseases, hepatocarcinogenesis, and liver metastasis. To comprehensively analyze the effects of endothelial Wnt-/ß-catenin signaling in the liver, we used endothelial subtype-specific Clec4g-iCre mice to generate hepatic ECs with overexpression of Ctnnb1. In the resultant Clec4g-iCre tg/wt ;Ctnnb1(Ex3) fl/wt (Ctnnb1 OE-EC ) mice, activation of endothelial Wnt-/ß-catenin signaling resulted in sinusoidal transdifferentiation with disturbed endothelial zonation, that is, loss of midzonal LSEC marker lymphatic vessel endothelial hyaluronic acid receptor 1 (Lyve1) and enrichment of continuous EC genes, such as cluster of differentiation (CD)34 and Apln. Notably, gene set enrichment analysis revealed overrepresentation of brain endothelial transcripts. Activation of endothelial Wnt-/ß-catenin signaling did not induce liver fibrosis or alter metabolic liver zonation, but Ctnnb1 OE-EC mice exhibited significantly increased plasma triglyceride concentrations, while liver lipid content was slightly reduced. Ctnnb1 overexpression in arterial ECs of the heart has been reported previously to cause cardiomyopathy. As Clec4g-iCre is active in a subset of cardiac ECs, it was not unexpected that Ctnnb1 OE-EC mice showed reduced overall survival and cardiac dysfunction. Altogether, balanced endothelial Wnt-/ß-catenin signaling in the liver is required for normal LSEC differentiation and for maintenance of normal plasma triglyceride levels.
