Cellular Characteristics of Lymphangioleiomyomatosis

Abstract

Lymphangioleiomyomatosis (LAM) is a rare lung disease in young women. Dysfunction of the tuberous sclerosis gene complex (TSC)-1 and TSC2 contributes to the manifestations of enhanced proliferation and migration of smooth muscle-like cells (LAM cells), elevated matrix metalloproteinase (MMP) activity and increased lymphangiogenesis. Currently there is no effective treatment for this fatal disease. This study aimed to assess the effectiveness of potential pharmacotherapies (doxycycline, statins and lamstatin) in targeting the different pathological aspects of LAM. Studies in this thesis examined the effects of doxycycline in human LAM cells and in a cellular model for LAM. Doxycycline had no effect on cell proliferation, but reduced elevated MMP2 activity, migratory capability and wound closure. In addition, doxycycline reduced cell migration through the inhibition of RhoA-GTPase and focal adhesion kinase (FAK), proteins that are involved in the regulation of cell motility. These findings were extended to show that the combination of doxycycline and rapamycin (inhibitor of the mammalian target of rapamycin compelx 1 [mTORC1] which is a potent inhibitor of cell proliferation) exhibited an additive effect on the inhibition of wound closure compared to the individual drugs alone. MMP profiles in people with LAM were also examined and confirmed previous findings of elevated serum MMP2 and MMP9. In addition elevated serum levels of MMP1 and MMP3 were identified. The effectiveness of statins as a treatment for LAM was examined in studies which investigated their effects on the enhanced proliferation, migration, wound closure and MMP2 activity in TSC2-deficient cells. All parameters were reduced by simvastatin and fluvastatin. The anti-lymphangiogenic protein lamstatin (NC1 domain of collagen IV α5) is absent in the lungs of people with LAM. Results showed that lamstatin and its consensus peptide, CP17 inhibited the proliferation, migration and wound closure in a cellular model of LAM. These studies have enhanced our understanding of the disease mechanisms underlying LAM and have revealed potential molecular targets for future therapy in this disease.