Role of TRPM7-Mediated Signaling in Vascular Remodeling in Abdominal Aortic Aneurysm - Project Abstract Abdominal aortic aneurysm (AAA) affects 1–2% of the elderly population and, when ruptured, often causes fatal hemorrhage. As AAA enlarges, the rupture risk increases, yet no pharmacological therapy exists to slow its progression, posing a major challenge, especially for patients ineligible for surgery. A key feature of AAA is vascular smooth muscle cell (VSMC) reprogramming from a contractile to a synthetic state, driven primarily by Kruppel-like factor 4 (KLF4). While Ca2+-dependent pathways induce KLF4 expression, the precise mechanism of its aberrant activation in AAA remains unclear. TRPM7 is a unique chanzyme (ion channel with kinase activity) abundantly expressed in VSMCs. TRPM7 is negatively regulated by ADP-ribosylation factor-like protein 15 (ARL15), but its biological significance is completely unknown. TRPM7-mediated ionic signaling and TRPM7 kinase play a critical role in enhancing inflammatory responses. Considering AAA is featured by the chronic inflammatory conditions of the aortic wall, I propose to investigate the contribution of TRPM7 activity in VSMCs reprogramming and AAA pathogenesis. In Aim 1, the expression and regulation of TRPM7 and ARL15 in human VSMCs and human AAA samples will be examined. The pathogenesis of human AAA will be investigated using the latest snRNA-seq technology, which offers more than twice the resolution of previous methods. Additionally, the role of VSMC’s TRPM7 in aneurysmal remodeling will be comprehensively evaluated through scRNA-seq and CITE-seq using my HA- TRPM7 transgenic mouse strain, and VSMC-specific TRPM7 knockout mouse strain with lineage tracing experiments. To elucidate the role of ARL15, the endogenous inhibitor of TRPM7, in AAA development, I will modulate its expression in vivo through overexpression or knockdown using adenoviral or AAV delivery systems. In Aim 2, the molecular mechanisms underlying TRPM7-induced AAA pathogenesis will be investigated. To determine whether TRPM7’s channel or kinase function is responsible for AAA progression, I have generated an inducible channel-dead TRPM7 (TRPM7E1047K) knock-in mice, which will be paired with kinase-dead TRPM7 (TRPM7K1646R) knock-in mice. The involvement of TRPM7-mediated ionic signaling pathways, including Ca2+, Mg2+, or Zn2+, will also be explored. Finally, I am generating inducible gain-of-function TRPM7N1098Q knock-in mice to directly assess whether TRPM7 overactivation serves as a primary driver of AAA pathogenesis or merely contributes secondarily to AAA related vascular remodeling. In summary, my goal is to elucidate the mechanisms underlying AAA and establish TRPM7 overactivation as a key driver of vascular remodeling and AAA pathogenesis, providing a foundation for potential future therapeutic strategies to limit AAA progression. Additionally, the development of inducible gain-of-function and channel-dead TRPM7 knock-in mouse strains will facilitate broader investigations into TRPM7’s role in other physiological and pathological processes, enabling future collaborations with other research groups.
