Abstract
Rationale: Tsc2 is an important negative regulator for mTOR pathway. Loss of functional mutation of Tsc2 causes tuberous sclerosis complex, which includes lymphangioleiomyomatosis (LAM).The mesenchymal function of Tsc2 during organ development and tissue homeostasis and its relationship to LAM pathogenesis has not been investigated.
Method: By crossing Dermo1-cre driver mouse line with floxed-Tsc2 mouse line, we have successfully developed Tsc2 knockout mice specifically in mesoderm-derived cells. All tissue samples were harvested at postnatal day (P) 1, P7, P14, P21 for histology, western blot, cell proliferation, cell differentiation and immunofluorescence analyses. In vivo EdU labeling was used to evaluate cell proliferation.
Results: The Dermo1-Cre driven Tsc2 conditional knockout mice were born without obvious abnormal phenotypes. However, that alveolar growth of the Tsc2 conditional knockout mice was significantly retarded. Reductions of cell proliferation and differentiation, as well as elastin expression/deposition were detected in the Tsc2 conditional knockout lungs compared to the wild type littermate controls. In addition to lung, alteration in kidney structure was identified, in which polycystic lesion starts from the 2nd week after birth, and became much severe with significant enlargement by gross-view about 3 weeks of age. Of note, most of the Tsc2 conditional knockout mice died around P21, possibly due to renal failure. Increased mTOR signaling was detected in both lung and kidney tissues of the Tsc2 conditional knockout mice.
Conclusion: Appropriate Tsc2-mTOR signaling in mesenchymal cells is essential for normal lung alveolar growth and kidney structural maintenance.
- Copyright ©the authors 2016