Sequential senolytic clearance of MMP-secreting senescent VSMCs followed by combined recombinant tropoelastin substra...

IF a sequenced, two-phase "clear-then-build" protocol — Phase 1: intermittent oral dasatinib (5 mg/kg) plus quercetin (50 mg/kg) by gavage for 3 consecutive days every 2 weeks to eliminate senescent vascular cells; Phase 2 (initiated at week 2, overlapping with Phase 1 cycling): subcutaneous recombinant human tropoelastin (100 μg, twice weekly) plus oral minoxidil (10 mg/kg, twice weekly) to provide monomeric elastin substrate and upregulate lysyl oxidase (LOX) crosslinking capacity — is administered to 20-month-old male C57BL/6J mice over 12 weeks,

THEN thoracic aortic desmosine/isodesmosine (DES/IDE) crosslink content will increase by ≥30% versus aged vehicle controls (LC-MS/MS), pulse wave velocity will decrease by ≥20% (Doppler ultrasound), Verhoeff-Van Gieson (VVG) elastic fiber integrity scores will improve by ≥1.5 points on a 0–4 scale, biaxial tensile strength will increase by ≥25%, and MMP-9/MMP-12 aortic activity will decrease by ≥40% versus vehicle, with the combination arm significantly exceeding either monotherapy arm on all endpoints — will be observed,

BECAUSE the following causally ordered, mechanistically distinct steps operate in synergy:

1. Senescent vascular smooth muscle cells (VSMCs) accumulate in aged aorta and constitute the primary source of SASP-driven MMP-9 and MMP-12 overexpression, which actively degrades existing elastic lamellae. Abdominal aortic tissue in aged mice undergoes structural and molecular remodeling characterized by loss of smooth muscle cell markers, increased inflammation, and accumulation of senescent cells; senolytic agents directly attenuate these features (Senolytic agents lessen the severity of abdominal aortic aneurysm in aged mice)[https://doi.org/10.1016/j.exger.2021.111416].

2. D+Q senolytic treatment eliminates p16^Ink4a^/p21^Cip1^-positive senescent VSMCs via their SCAPs (BCL-2/BCL-xL/PI3K/AKT dependence), reducing the SASP-derived proteolytic burden and creating a matrix-protective microenvironment. Dasatinib (5 mg/kg) plus quercetin (50 mg/kg) by oral gavage on an intermittent schedule reduces senescent cell burden, lowers circulating cf-mtDNA, and attenuates downstream inflammatory responses in aged C57BL/6J mice (Senolytics prevent mt-DNA-induced inflammation and promote the survival of aged organs following transplantation)[https://doi.org/10.1038/s41467-020-18039-x].

3. [SPECULATIVE] Circulating cell-free mitochondrial DNA (cf-mtDNA) released by senescent VSMCs activates cGAS-STING innate immune signaling in neighboring non-senescent VSMCs, and this signaling cascade suppresses endogenous ELN (elastin) and LOX transcription in those cells via NF-κB and IRF3-mediated epigenetic repression, creating a bystander elastogenic block that D+Q — by reducing cf-mtDNA — would lift. The mechanistic link between D+Q, cf-mtDNA reduction, and resolution of inflammatory T-cell activation is established (Senolytics prevent mt-DNA-induced inflammation)[https://doi.org/10.1038/s4146...

SENS category: GlycoSENS

Key references: • doi.org/10.1016/j.exger.2021.111416]. • doi.org/10.1038/s41467-020-18039-x]. • doi.org/10.1038/s41467-020-18039-x]; • doi.org/10.7554/elife.75492]. • doi.org/10.1126/science.abe4832],