Induced elastin regeneration by chronically activated smooth muscle cells for targeted aneurysm repair

Elastin breakdown in vascular aneurysms is mediated by cytokines such as tumor necrosis factor α (TNF-α, which induces vascular smooth muscle cell (SMC) activation and regulates their deposition of matrix. We previously demonstrated that exogenous supplementation with TGF-β1 (1 ng ml−1) and hyaluronan oligomers (0.786 kDa, 0.2 μg ml−1) cues the upregulation of elastin matrix synthesis by healthy cultured SMCs. Here, we determine whether these cues likewise enhance elastin matrix synthesis and assembly by TNF-α-stimulated SMCs, while restoring their healthy phenotype. Adult rat aortic SMCs were treated with TNF-α alone or together with TGF-β1/hyaluronan oligomeric cues and the release of inflammatory markers were monitored during over a 21 day culture. Biochemical analysis was used to quantify cell proliferation, matrix protein synthesis and cross-linking efficiency, while immunofluorescence and electron microscopy were used to analyze the elastin matrix quality. It was observed that SMC activation with TNF-α (10 ng ml−1) induced matrix calcification and promoted production of elastolytic MMP-2 and MMP-9. However, these effects were attenuated by the addition of TGF-β1 and HA oligomer cues to TNF-α-stimulated cultures, which also enhanced tropoelastin and collagen production, improved elastin matrix yield and cross-linking, promoted elastin fiber formation and suppressed elastase activity, although the release of MMP-2 and MMP-9 was not affected. Overall, the results suggest that TGF-β1 and HA oligomers are potentially useful in suppressing SMC activation and inducing regenerative elastin repair within aneurysms.