# Novel Role of Thrombospondin-1 in Protection against Rupture of Abdominal Aortic Aneurysm

> **NIH NIH R01** · UNIVERSITY OF WISCONSIN-MADISON · 2021 · $513,693

## Abstract

Abdominal aortic aneurysm (AAA) is the progressive weakening and dilation of the aorta. A substantial
knowledge gap exists in the understanding of molecular mechanisms responsible for aneurysm rupture, the
major cause of mortality among AAA patients. Following our prior report of elevated thrombospondin-1 (TSP1)
in human and mouse aneurysmal tissues, we conducted single-cell RNA sequencing (scRNA-seq) analysis and
identified macrophages (Mɸs) being the primary source of elevated TSP1 in mouse aneurysmal aorta. We
subsequently generated Mɸ-specific Thbs1 knockout mice (Thbs1∆Mɸ) by crossing Lyz2-Cre with our newly
constructed Thbs1flox/flox mice. When subjected to aneurysm induction by angiotensin II (Ang II) coupled with
hypercholesterolemia, over 60% of Thbs1∆Mɸ died due to AAA rupture, an incidence that was 2.6 times higher
than Thbs1wt. Intriguingly, Thbs1∆Mɸ mice that survived to the end of 28-day Ang II infusion showed less aneurysm
dilation than Thbs1wt. Smaller aneurysmal expansion was also found when Thbs1∆Mɸ mice were challenged with
perivascular application of CaCl2, an AAA model that does not produce rupture. We propose two specific aims
to delineate the mechanisms through which Mɸ-specific Thbs1 gene deletion differentially affects aortic
dilation and rupture with an emphasis on AAA rupture. Specific Aim 1 devotes to establishing the rupture-
preventive function of Mɸ TSP1. Specifically, we will determine the aortic responses proceeding lethal rupture in
male and female Thbs1∆Mɸ mice in the Ang II model followed by identifying rupture-associated molecular
signatures through scRNA-seq, in situ hybridization and immunostaining. Furthermore, we will examine the
effects of Mɸ-specific Thbs1 knockout using a different murine model that produces rupture in advanced stages
of aneurysm, which is more relevant to human AAA than the early rupture produced by the Ang II model. Specific
Aim 2 focuses on investigating molecular mechanisms of aneurysm rupture. Preliminary studies showed that
compared to wildtype, Thbs1-/- Mɸs had significantly reduced ability to migrate or to engulf apoptotic cells as well
as neutrophil extracellular traps (NETs). We will test whether Mɸ TSP1 promotes NET clearance through CD47-
mediated actin polymerization. Next, we will establish the causal effect of impaired Mɸ migration and
phagocytosis on aneurysm rupture of Thbs1∆Mɸ mice. We will first determine whether NET burden is increased
in Thbs1∆Mɸ died from rupture, and the spatial relationship between NETs and Mɸs. Second, we will test whether
restoring Mɸ migration in Thbs1∆Mɸ reduces NET accumulation via adoptive transfer strategies. Furthermore, we
will examine whether enhancing or attenuating NET clearance affect aneurysm rupture in Thbs1∆Mɸ. Lastly, we
will analyze TSP1 expression and its association with Mɸ and NET accumulation in ruptured and non-ruptured
human AAA tissues. By dissecting the multifaceted functions of Mɸs through TSP1 manipulations, this proje...

## Key facts

- **NIH application ID:** 10234366
- **Project number:** 1R01HL158073-01
- **Recipient organization:** UNIVERSITY OF WISCONSIN-MADISON
- **Principal Investigator:** Bo Liu
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $513,693
- **Award type:** 1
- **Project period:** 2021-05-01 → 2025-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10234366

## Citation

> US National Institutes of Health, RePORTER application 10234366, Novel Role of Thrombospondin-1 in Protection against Rupture of Abdominal Aortic Aneurysm (1R01HL158073-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10234366. Licensed CC0.

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