Abstract
The efficacy of cell therapy is limited by low retention and survival of transplanted cells in the target tissues. In this work, we hypothesize that pharmacological preconditioning with celastrol, a natural potent antioxidant, could improve the viability and functions of mesenchymal stromal cells (MSC) encapsulated within an injectable scaffold. Bone marrow MSCs from rat (rMSC) and human (hMSC) origin were preconditioned for 1 hour with celastrol 1 μM or vehicle (DMSO 0.1% v/v), then encapsulated within a chitosan-based thermosensitive hydrogel. Cell viability was compared by alamarBlue and live/dead assay. Paracrine function was studied first by quantifying the proangiogenic growth factors released, followed by assessing scratched HUVEC culture wound closure velocity and proliferation of HUVEC when cocultured with encapsulated hMSC. In vivo, the proangiogenic activity was studied by evaluating the neovessel density around the subcutaneously injected hydrogel after one week in rats. Preconditioning strongly enhanced the viability of rMSC and hMSC compared to vehicle-treated cells, with 90% and 75% survival versus 36% and 58% survival, respectively, after 7 days in complete media and 80% versus 64% survival for hMSC after 4 days in low serum media (p < 0.05). Celastrol-treated cells increased quantities of proangiogenic cytokines compared to vehicle-pretreated cells, with a significant 3.0-fold and 1.8-fold increase of VEGFa and SDF-1α, respectively (p < 0.05). The enhanced paracrine function of preconditioned MSC was demonstrated by accelerated growth and wound closure velocity of injured HUVEC monolayer (p < 0.05) in vitro. Moreover, celastrol-treated cells, but not vehicle-treated cells, led to a significant increase of neovessel density in the peri-implant region after one week in vivo compared to the control (blank hydrogel). These results suggest that combining cell pretreatment with celastrol and encapsulation in hydrogel could potentiate MSC therapy for many diseases, benefiting particularly ischemic diseases.
Highlights
Cardiovascular disease (CVD) is a leading cause of mortality, and of these deaths, 85% are due to ischemic events [1, 2]
We demonstrate that combining both cell encapsulation and pharmacological preconditioning enhances the viability and the proangiogenic paracrine function of Mesenchymal stromal cell (MSC) in vitro and in vivo and could be used to improve the outcomes of cell therapy for ischemic diseases
The preliminary proof of concept was performed with MSC cultured in 2D and covered by a 3 mm thick hydrogel layer, which limits nutrient diffusion
Summary
Cardiovascular disease (CVD) is a leading cause of mortality, and of these deaths, 85% are due to ischemic events [1, 2]. Clinical management includes fibrinolytic therapy, primary percutaneous coronary intervention, or bypass graft surgery to restore blood flow [3,4,5,6,7] These interventions cannot regenerate dead cells and scar tissues. The efficacy of cell therapy remains limited due to the poor retention, diminished survival, and poor functionality of cells, especially when transplanted in such ischemic, inflammatory, and oxidative microenvironments [16, 17]. In this context, injectable scaffolds have been proposed to localize, anchor, and protect cells in the target tissues [20,21,22,23,24]. We propose to combine encapsulation with cell preconditioning to improve cell retention, survival, and function
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