| Popis: |
Elastic fibers (EFs), containing elastin protein are the major structural extracellular matrix component of the aorta wall that imparts it stretch and recoil properties. Following injury stimuli to the aorta wall, EFs are disrupted by chronically overexpressed proteolytic enzymes. This leads to loss of wall elasticity, and vessel bulging to form rupture-prone abdominal aortic aneurysms (AAAs). AAA growth arrest or regression to a healthy state requires restoration of elastin homeostasis in the aorta wall which is limited by very poor elastogenicity of adult and aneurysmal vascular smooth muscle cells (SMCs). Based on their purported role in developmental elastogenesis, we explored use of stem cell-derived SMCs in therapeutically augmenting elastogenesis in the AAA wall. In study 1, we differentiated adult rat bone marrow mesenchymal stem cells (BM-MSCs) into SMCs (BM-SMCs), demonstrated their robust capacity for elastin synthesis and significant pro-elastogenic effects on rat aneurysmal SMCs (EaRASMCs). In study 2, we sought to identify phenotypic subtypes of derived BM-SMCs that are most elastogenic. BM-SMCs generated in low glucose (3.1g/L) and high serum (10% v/v) media containing transforming growth factor-beta (TGFß) and platelet-derived growth factor (PDGF) exhibited both synthetic and contractile properties that constituted their enhanced synthesis of elastin precursors, elastic matrix, and the desmosine crosslinks within the elastic matrix. In study 3, these BM-SMCs were co-cultured with EaRASMCs within 3-D collagen constructs. We observed significant increases in elastic matrix synthesis and fiber formation relative to EaRASMCs alone or in co-culture with healthy rat aortic SMCs. Proteomic analysis indicated presence of several unique and upregulated elastogenic growth factors in BM-SMC secretome. In study 4, we sought to render the BM-SMCs magnetically mobile for efficient delivery to the aorta wall for regenerative cell therapy. We showed that incorporating super paramagnetic iron oxide nanoparticles (SPIONs) within BM-SMCs imparted them significant magnetic responsiveness in an externally-applied magnetic field and not adversely impact their beneficial properties. We showed significantly higher uptake and retention of SPION-labeled BM-SMCs within matrix-injured arteries perfused ex vivo. Overall, our work has established an alternative elastogenic cell source that is promising towards in situ elastic matrix regenerative therapy. |
