Utility of Stem Cell-Derived Smooth Muscle Cells for Elastin Regenerative Repair in Aortic Aneurysms

Objective: Abdominal aortic aneurysms (AAAs) are aortal expansions resulting from proteolysis of wall collagen and elastin. Restoring elastin homeostasis, critical to arresting AAAs is impeded by poor elastogenicity of adult... [ view full abstract ]

Objective: Abdominal aortic aneurysms (AAAs) are aortal expansions resulting from proteolysis of wall collagen and elastin. Restoring elastin homeostasis, critical to arresting AAAs is impeded by poor elastogenicity of adult SMCs. In this context, we showed that bone marrow mesenchymal stem cell (BM-MSC)-derived SMCs (BM-SMCs) are significantly more elastogenic than healthy and AAA-SMCs and provide pro-elastogenic & anti-proteolytic stimuli. We now investigate if BM-SMC phenotype influences their regenerative effects, and if they maintain these properties a) in a 3D milieu, and b) in culture free of differentiation growth factors (GFs).

Methods: Rat BM-MSCs were differentiated on fibronectin (Fn) in presence/ absence of PDGF-BB in 2%v/v and 10%v/v FBS in low/high glucose DMEM/F12 containing TGFβ1 and propagated on a)Fn/GFs, b)no Fn or GFs, and c)3D collagen gels, co-seeded with rat aneurysmal SMCs; aneurysmal and healthy SMCs served as controls. BM-SMC phenotype was assessed using RT-PCR, western blot, and Immuno-Fluorescence. Fastin (elastin) and desmosine (for crosslinks) assays and IF assessed elastin deposited by BM-SMCs in 2D cultures and their effects on matrix synthesis by AAA-SMCs in collagen gels.
Results: Elastic matrix amounts, fiber assembly, and crosslinking were most increased in cultures of BM-SMCs derived with low glucose, 10%v/v serum conditions with TGF-β1 & PDGF-BB vs. controls. These BM-SMCs maintained their phenotype in long-term GF/FN-free culture and significantly augmented elastin synthesis and crosslinking by AAA-SMCs, and their contractility within collagen gels.

Conclusions: Our results strongly suggest utility of BM-SMCs cell therapy aimed at in situ elastic matrix regeneration for AAA repair.