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Bioreactor Conditioning of Valve Scaffolds Seeded Internally with Adult Stem Cells.

ABSTRACT: The goal of this study was to test the hypothesis that stem cells, as a response to valve-specific extracellular matrix "niches" and mechanical stimuli, would differentiate into valvular interstitial cells (VICs). Porcine aortic root scaffolds were prepared by decellularization. After verifying that roots exhibited adequate hemodynamics in vitro, we seeded human adipose-derived stem cells (hADSCs) within the interstitium of the cusps and subjected the valves to in vitro pulsatile bioreactor testing in pulmonary pressures and flow conditions. As controls we incubated cell-seeded valves in a rotator device which allowed fluid to flow through the valves ensuring gas and nutrient exchange without subjecting the cusps to significant stress. After 24 days of conditioning, valves were analyzed for cell phenotype using immunohistochemistry for vimentin, alpha-smooth muscle cell actin (SMA) and prolyl-hydroxylase (PHA). Fresh native valves were used as immunohistochemistry controls. Analysis of bioreactor-conditioned valves showed that almost all seeded cells had died and large islands of cell debris were found within each cusp. Remnants of cells were positive for vimentin. Cell seeded controls, which were only rotated slowly to ensure gas and nutrient exchange, maintained about 50% of cells alive; these cells were positive for vimentin and negative for alpha-SMA and PHA, similar to native VICs. These results highlight for the first time the extreme vulnerability of hADSCs to valve-specific mechanical forces and also suggest that careful, progressive mechanical adaptation to valve-specific forces might encourage stem cell differentiation towards the VIC phenotype.

SUBMITTER: Kennamer A

PROVIDER: S-EPMC6170839 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Bioreactor Conditioning of Valve Scaffolds Seeded Internally with Adult Stem Cells.

Kennamer Allison A Sierad Leslie L Pascal Richard R Rierson Nicholas N Albers Christopher C Harpa Marius M Cotoi Ovidiu O Harceaga Lucian L Olah Peter P Terezia Preda P Simionescu Agneta A Simionescu Dan D

Tissue engineering and regenerative medicine 20161020 5

The goal of this study was to test the hypothesis that stem cells, as a response to valve-specific extracellular matrix "niches" and mechanical stimuli, would differentiate into valvular interstitial cells (VICs). Porcine aortic root scaffolds were prepared by decellularization. After verifying that roots exhibited adequate hemodynamics <i>in vitro</i>, we seeded human adipose-derived stem cells (hADSCs) within the interstitium of the cusps and subjected the valves to <i>in vitro</i> pulsatile b ...[more]

PMID: 30337944

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Project description:INTRODUCTION:Articular cartilage (AC) is a viscoelastic tissue with a limited regenerative capability because of the lack of vasculature. Mechanical stimulation contributes to the homeostasis of functional AC since it promotes the delivery of nutrients, cytokines and growth factors between the distant chondrocytes. We hypothesized that biomechanical stimulation might enhance mobilization of endogenous mesenchymal stem/stromal cells (MSCs) from neighboring niches as the bone marrow. AIM:This study aimed to introduce a bioreactor for inducing mobilization of MSCs from one compartment to another above by mechanical stimulation in vitro. METHODS:A novel mechanical system for evaluating mobilization of cells in a 3D context in vitro is presented. The system consists of a compression bioreactor able to induce loading on hydrogel-based scaffolds, custom-made software for settings management and data recording, and image based biological evaluation. Intermittent load was applied under a periodic regime with frequency of 0.3 Hz and unload phases of 10 seconds each 180 cycles over 24 hours. The mechanical stimulation acted on an alginate scaffold and a cell reservoir containing MSCs below it. The dynamic compression exerted amplitude of 200 ?m as 10% strain regarding the original height of the scaffold. RESULTS:The bioreactor was able to stimulate the scaffolds and the cells for 24.4 (±1.7) hours, exerting compression with vertical displacements of 185.8 (±17.8) ?m and a force-amplitude of 1.87 (±1.37; min 0.31, max 4.42) N. Our results suggest that continuous mechanical stimulation hampered the viability of the cells located at the cell reservoir when comparing to intermittent mechanical stimulation (34.4 ± 2.0% vs. 66.8 ± 5.9%, respectively). Functionalizing alginate scaffolds with laminin-521 (LN521) seemed to enhance the mobilization of cells from 48 (±21) to 194 (±39) cells/mm3 after applying intermittent mechanical loading. CONCLUSION:The bioreactor presented here was able to provide mechanical stimulation that seemed to induce the mobilization of MSCs into LN521-alginate scaffolds under an intermittent loading regime.

Dataset Information

Bioreactor Conditioning of Valve Scaffolds Seeded Internally with Adult Stem Cells.

Publications

Bioreactor Conditioning of Valve Scaffolds Seeded Internally with Adult Stem Cells.

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