Tsc1 deficiency-mediated mTOR hyperactivation in vascular endothelial cells causes angiogenesis defects and embryonic lethality

Abstract

This is a study on the role of tuberous sclerosis complex1 (TSC1) mutation and mTOR activation in endothelial cells during angiogenic and embryonic development. Past studies had shown that Tsc1/Tsc2 mutant genes lead to overactivation of mTOR in the regulating pathways in developing fetus. We used conditional Cre-loxp gene knockout approach to delete Tsc1 in mice's endothelial cells in our experimental models. Similarly, activation of mTOR signaling in endothelial cells of these embryos (Tie2-Cre/Tsc1(-/-)) was found. Majority of Tie2-Cre/Tsc1(-/-) embryos died at embryonic day 14.5 in utero. Cardiovascular defects, subcutaneous edema and hemorrhage were present among them. Whole-mount immunostaining in these embryos revealed a disorganized vascular network, defective sprouting of vessels in yolk sac and thickening of the labyrinth layer in the placenta. A thinner ventricular wall with disorganized trabeculae was present in the hearts of Tie2-Cre/Tsc1(-/-) embryos. Endothelial cells in Tsc1-deficient mice showed defective mitochondrial and endoplasmic reticular morphology, but no significant change was observed in cell junctions. The mutant embryos displayed significantly reduced cell proliferation, increased apoptosis and disturbed expression of angiogenic factors. A cohort of mice was treated prenatally with mTOR inhibitor rapamycin. The offspring of these mutant mice survived up to 22 days after birth. It was concluded that physiological TSC1-mTOR signaling in endothelial cells is crucial for vascular development and embryogenesis. We postulated that disruption of normal angiogenic pathways through hyperactive mTOR signaling maybe the mechanism that lead to deranged vascular pathogenesis in the tuberous sclerosis complex.

DEPTOR Deficiency-Mediated mTORc1 Hyperactivation in Vascular Endothelial Cells Promotes Angiogenesis

“…IF staining indicated that DEPTOR expression was decreased in vascular ECs in KO mice comparing with WT mice as shown in Fig. 1C and D. Cluster of differentiation 31 (CD31) was used primarily to show the presence of endothelial cells, which helped to evaluate the degree of angiogenesis [22]. Taken together, the results showed that there was DEPTOR deficiency in ECs of Tek- Cre + /Deptor fl/fl mice compared with WT mice.…”

Neurotoxicity of cerebro-spinal fluid from patients with Parkinson’s disease on mesencephalic primary cultures as an in vitro model of dopaminergic neurons

“…Previous studies reported that the survival rate of dopaminergic neurons collected at embryonic day 14 was ~17-21%, which was higher than that of cells collected at embryonic day 16 or later, which was only 0.1-2.5% (18,19). In addition, a previous study confirmed that ~90% of dopaminergic neurons are clustered around a tissue region of 1.0 mm 3 in rostral mesencephalic tegmentum (20).…”

Percutaneous cryoablation for tuberous sclerosis-associated renal angiomyolipoma with neoadjuvant mTOR inhibition

“…Although there is a likely benefit to this treatment, reduction in hemorrhagic risk with mTORi has not been formally demonstrated since bleeding events were infrequent in randomised trials [3]. The specific effect of the mTORi on the vascular component of the AML is not known but experimental data suggest that mTORis could partially inhibit the vascular pathogenesis of TSC [7]. …”