(149c) Comparing the Effects of Mechanical Stimulation On Bone Marrow and Hair-Follicle Mesenchymal Stem Cells: Vascular Tissue Engineering

Adult stem cells such as mesenchymal stem cells (MSC) show significant proliferation and differentiation potential; however these capacities decrease significantly with donor aging. This problem is further compounded by culture senescence limiting their culture time to about 8-10 passages. This is a major concern as patients mostly in need for vascular grafts and cellular therapies are elderly.

In the present study we compared adult and neonatal ovine hair-follicle MSC (aHF,nHF) to adult and neonatal bone-marrow MSC (aBM, nBM) in 2D culture examining their susceptibility to culture senescence as well as their differentiation potential to smooth muscle cell (SMC) lineage. We concluded that aHF/nHF and nBM do not show significant cellular senescence and also demonstrate increased cell proliferation compared to aBM. This was confirmed by long term proliferation experiments and β-galactosidase activity staining. aHF/nHF also showed significantly higher clonogenic potential compared to nBM, while nBM showed significantly higher clonogenic potential compared to aBM isolations.

We then generated fibrin based Tissue Engineered Vascular constructs (TEVs) using these cell isolations and compared their vasoreactive response to receptor and non-receptor mediated pathways under static and pulsed conditions. Pulsation was induced in a dose response fashion for one week at (2%, 3.6% and 5.5% distention) after culturing the vascular constructs statically for one week. To accomplish this task a 24 well- pulsation plate (24-PP) was designed, capable of mechanically conditioning 24 TEVs at the same time. Under static conditions all aHF/nHF isolations demonstrated superior vasoreactive responses when compared to aBM/nBM isolations. However, mechanical properties and vasoreactive responses were either unchanged or diminished when aHF/nHF were pulsed, while BM isolations showed improvements. Young’s Modulus increased significantly following pulsation for aBM/nBM and Ultimate Tensile Stress also increased significantly for aBM isolations following pulsation. Collagen content was measured from static and pulsed TEV constructs to determine the extent of ECM remodeling and it was found there were significant improvements for aBM/nBM isolations, while aHF/nHF isolations were unchanged or diminished. In summary we concluded that there are significant similarities and differences between HF and BM MSCs. Developing a stronger understanding on these similarities and differences will aid us in the further development and optimization for the use of MSCs in vascular tissue engineering.