Abstract Body: Aortic aneurysm (AA) is a life-threatening vascular disease with >95% mortality upon rupture. Human AA studies have been limited to end-stage human aneurysmal tissue, which undergoes compensatory molecular and cellular changes during aneurysm progression. Moreover, preclinical animal models have shown cross-species discrepancies. This underscores the urgent unmet need for a predictive human cell-based disease model to capture human AA pathogenesis and therapeutic responses.
To address this critical gap, I developed the first functional human AA model by implanting bioengineered vessel grafts (BVGs) derived from induced pluripotent stem cells (iPSCs)-smooth muscle cells (SMCs) of Loeys-Dietz syndrome (TGFBR1 variant) patients into nude rats (Fig. 1A)¹. The in vivo patency and inner diameter change were monitored for 8 weeks (Fig. 1B). To investigate the impact of other genetic variants associated with aneurysm formation, we generate implantable BVGs using iPSCs carrying COL3A1 [alpha-1(III) chain of type III collagen] variants. Mutations in COL3A1 are primarily linked to the severe, life-threatening vascular Ehlers-Danlos syndrome (vEDS). After 8 weeks’ in vitro culture, BVGs are harvested for in vitro properties tests. The morphology of the BVGs is recorded. We measure burst pressure and tensile stress of BVGs.
For in vitro disease modeling of vEDS, we used healthy donor cells (WT) and generated integration-free hiPSC carrying c.G970A mutation by CRISPR-Cas9 gene editing (COL3A1^+/-, Fig. 1C). Both WT and COL3A1^+/- BVGs appeared opaque at the end of in vitro culture period (Fig. 1D). Next, we characterized the mechanical properties of WT and COL3A1^+/- BVGs using burst pressure and tensile tests. The WT BVGs demonstrated a burst pressure of 968±142 mmHg. However, the BVGs generated from COL3A1^+/- clone displayed significantly lower burst pressure (601±99 mmHg, P < 0.001) (Fig. 1E). We measured tensile stress of the BVGs and generated stress-strain plots. We observed lower ultimate tensile stress of COL3A1^+/- BVGs (0.71±0.16 MPa) compared with isogenic control BVGs (1.42±0.29 MPa) and similar failure strain for both conditions (Fig. 1F and G).
We established a functional human aneurysm model using BVGs to mimic human TAA formation, which represents the first human aortic aneurysm model in an animal host. Our study offers an avenue to develop novel therapeutic approaches for the prevention and treatment of aortic aneurysm as an alternative to surgical repair.