Different cardiovascular and pulmonary phenotypes for single- and double-knock-out mice deficient in BMP9 and BMP10

Abstract

Aims BMP9 and BMP10 mutations were recently identified in patients with pulmonary arterial hypertension (PAH), but their specific roles in the pathogenesis of the disease are still unclear. We aimed to study the roles of BMP9 and BMP10 in cardiovascular homeostasis and pulmonary hypertension using transgenic mouse models deficient in Bmp9 and/or Bmp10. Methods and Results Single- and double-knockout mice for Bmp9 (constitutive) and/or Bmp10 (tamoxifen inducible) were generated. Single-KO mice developed no obvious age-dependent phenotype when compared with their wild-type littermates. However, combined deficiency in Bmp9 and Bmp10 led to vascular defects resulting in a decrease in peripheral vascular resistance and blood pressure and the progressive development of high-output heart failure (HOHF) and pulmonary hemosiderosis. RNAseq analysis of the lungs of the double-KO mice revealed differential expression of genes involved in inflammation and vascular homeostasis. We next challenged these mice to chronic hypoxia. After three weeks of hypoxic exposure, Bmp10-cKO mice showed an enlarged heart. However, although genetic deletion of Bmp9 in the single and double-KO mice attenuated the muscularization of pulmonary arterioles induced by chronic hypoxia, we observed no differences in Bmp10-cKO mice. Consistent with these results, endothelin-1 levels were significantly reduced in Bmp9 deficient mice but not Bmp10-cKO mice. Furthermore, the effects of BMP9 on vasoconstriction were inhibited by bosentan, an endothelin receptor antagonist, in a chick chorioallantoic membrane assay. Conclusions Our data show redundant roles for BMP9 and BMP10 in cardiovascular homeostasis under normoxic conditions (only combined deletion of both Bmp9 and Bmp10 was associated with severe defects) but highlight specific roles under chronic hypoxic conditions. We obtained evidence that BMP9 contributes to chronic hypoxia-induced pulmonary vascular remodeling, whereas BMP10 plays a role in hypoxia-induced cardiac remodeling in mice.

BMP9 and BMP10: Two close vascular quiescence partners that stand out

“…In our hands, the global KD of Bmp10 in adult Bmp9-KO mice leads to a phenotype that is partially in accordance with this work, characterized by vessel dilation, a decrease in blood pressure, and a larger heart. 108 Together these results indicate that blockade of Bmp10 at postnatal stage in Bmp9-KO mice leads to the death of these pups while loss of Bmp10 in adult Bmp9-KO mice is viable although these mice present many vascular problems. It is also interesting to note, that BMP10 ANF mice crossed with Bmp9-KO mice, which will lead to a rapid loss of BMP10 after birth as BMP10 is mainly expressed by the right atria at this stage, leads to viable mice underscoring a role for other sources of BMP10 (such as the liver) at postnatal stage.…”

“…It was shown that adult Bmp10 knockdown in the C57BL/6 background was not lethal and showed no obvious vascular phenotype. 107,108 More recently, a mouse model specifically deleted for Bmp10 in the right atrium was generated (Bmp10 ANF ). 109 These mice overcame embryonic cardiac lethality and were viable with no obvious phenotype, suggesting that cardiac BMP10 is not involved in postnatal vascular remodeling.…”

“…89 On the contrary, another group showed that ALK1-Fc induced severe PH in mice treated with hypoxia. 113 On the other hand, Bmp10-KD in adult mice do not seem to be protected from PH when challenged 108 supporting a specific role for BMP9 in lung remodeling in PH. These apparently contradictory results are further discussed below and have been very accurately discussed in the editorial from Ormiston et al 114 The role of BMP9 and BMP10 has also been addressed in the context of tumor angiogenesis.…”

“…After birth, BMP9 and BMP10 clearly play redundant roles in postnatal angiogenesis (retinal vascularization and closure of the ductus arteriosus 5,30,85 ) but also in adult vascular homeostasis (under physiological conditions) as only the double Bmp9/ Bmp10 deletion leads to a vascular phenotype. 108,109 Due to technical issues, the role of BMP9 has been addressed via a complete and constitutive KO while the role of BMP10 has been addressed via either neutralizing antibodies, or tamoxifen inducible knockdown in adult or tissue-specific deletion in the right atria in order to bypass cardiac embryonic lethality. In zebrafish, no transcriptional adaptation or genetic compensation was found for bmp9 or bmp10-like expression or in bmp10 mutants.…”

The Dual Effect of the BMP9–ALK1 Pathway in Blood Vessels: An Opportunity for Cancer Therapy Improvement?

“…The main effector pathway of BMP9 signaling is Smad1/5/8, although it can vary depending on the cell type and cellular context. BMP9 transduces signals through Smad1/5/8, as it has been described in numerous studies on endothelial cells [79,[96][97][98][99][100][101][102]. In the hepatocellular carcinoma cell line HepG2, BMP9 induces phospho-Smad1/5/8 phosphorylation leading to increased survival [103].…”