Overactive Tgf beta Signaling in Smooth Muscle Cells Induces Hypertension in Mice Through Increased Myogenic Tone and is Responsible for Increased Myogenic Tone in Resistance Vessels of Hypertensive Patients

Emilin1 (E1) is a protein of the extracellular matrix that regulates TGFβ activity through proteolysis of the proTGFβ. E1 KO mice are hypertensive, with increased TGFβ activation. As E1 is expressed in blood vessels starting from embryonic life to adulthood, is still unknown whether the E1 KO phenotype results from a developmental defect or lack of a homeostatic role exerted in the adult. To dissect this issue, we inactivated E1 in smooth muscle cells (VSMCs) of adult mice, by the use of floxed E1 and CreERT2 [a tamoxifen (TAM) inducible Cre recombinase] under the control of the smooth muscle myosin heavy chain (Smmhc) promoter. When Smmhc-CreERT2 E1fl/fl mice were given TAM, blood pressure significantly increased (124±1 vs basal condition 106±1 mmHg) as well as myogenic response in resistance arteries (16.3±0.7 vs basal condition 11.4±0.1 % at 125 mmHg). In order to evaluate the relevance of our findings in the human pathology, we enrolled 20 hypertensive and 20 normotensive patients that underwent neurosurgical intervention for primary lumbar hernia repair and dissected out resistance vessels from skeletal muscle biopsies. We analyzed the myogenic tone of human peripheral resistance vessels in a pressure myograph and randomized vessels to receive vehicle, a neutralizing antibody anti-TGFβ or a preimmune non relevant IgG. As first, we found that hypertensive patients had significantly increased myogenic tone as compared to normotensive (16.6±2.1% vs 10.5±0.4% at 125 mmHg). Moreover, the pretreatment of vessels with anti-TGFβ antibody normalized the myogenic tone of hypertensive patients (10.8±0.6%) to the levels of normotensives (11.8±1.3%). A pretreatment with the non relevant IgG did not modify the myogenic tone of hypertensives (17±0.6%), thus demonstrating that the effect was dependent of an increased TGFβ signaling in vessels of hypertensive patients. Overall, our results suggest that the TGFβ pathway in VSMC, is crucial for the myogenic tone of resistance arteries and is linked to the regulation of blood pressure. The data obtained in peripheral resistance vessels from hypertensive patients, that display an increased myogenic tone dependent on overactive TGFβ signaling, highlight the translational potential of our findings to the human pathology.