Hyaluronic acid-serum hydrogels rapidly restore metabolism of encapsulated stem cells and promote engraftment

Abstract

Background Cell death due to anoikis, necrosis and cell egress from transplantation sites limits functional benefits of cellular cardiomyoplasty. Cell dissociation and suspension, which are a pre-requisite for most cell transplantation studies, lead to depression of cellular metabolism and anoikis, which contribute to low engraftment. Objective We tissue engineered scaffolds with the goal of rapidly restoring metabolism, promoting viability, proliferation and engraftment of encapsulated stem cells. Methods The carboxyl groups of HA were functionalized with N-hydroxysuccinimide (NHS) to yield HA succinimidyl succinate (HA-NHS) groups that react with free amine groups to form amide bonds. HA-NHS was cross-linked by serum to generate HA:Serum (HA:Ser) hydrogels. Physical properties of HA:Ser hydrogels were measured. Effect of encapsulating cardiosphere-derived cells (CDCs) in HA:Ser hydrogels on viability, proliferation, glucose uptake and metabolism was assessed in vitro. In vivo acute intra-myocardial cell retention of 18FDG-labeled CDCs encapsulated in HA:Ser hydrogels was quantified. Effect of CDC encapsulation in HA:Ser hydrogels on in vivo metabolism and engraftment at 7 days was assessed by serial, dual isotope SPECT-CT and bioluminescence imaging of CDCs expressing the Na-iodide symporter and firefly luciferase genes respectively. Effect of HA:Ser hydrogels +/− CDCs on cardiac function was assessed at 7 days & 28 days post-infarct. Results HA:Ser hydrogels are highly bio-adhesive, biodegradable, promote rapid cell adhesion, glucose uptake and restore bioenergetics of encapsulated cells within 1 h of encapsulation, both in vitro and in vivo. These metabolic scaffolds can be applied epicardially as a patch to beating hearts or injected intramyocardially. HA:Ser hydrogels markedly increase acute intramyocardial retention (~6 fold), promote in vivo viability, proliferation, engraftment of encapsulated stem cells and angiogenesis. Conclusion HA:Ser hydrogels serve as ‘synthetic stem cell niches’ that rapidly restore metabolism of encapsulated stem cells, promote stem cell engraftment and angiogenesis. These first ever, tissue engineered metabolic scaffolds hold promise for clinical translation in conjunction with CDCs and possibly other stem cell types.

Changing Metabolism in Differentiating Cardiac Progenitor Cells—Can Stem Cells Become Metabolically Flexible Cardiomyocytes?

“…Hydrogels have also been shown to induce cell maturation and differentiation which makes them an attractive system for basic studies of cardiac development and potential for the delivery of therapeutics to the heart ( 273 , 274 ). Suspension of CDCs in a hydrogel formed from serum and the glycosoaminoglycan hyaluronic acid, increased the oxygen consumption rate from that of cells in suspension and increased cell retention after transplantation in vivo ( 275 ). Porous scaffolds can be generated by freeze-drying suspensions poured in molds ( 267 , 276 ).…”

Cardiosphere-Derived Cells Demonstrate Metabolic Flexibility That Is Influenced by Adhesion Status

“…This study demonstrates that SPECT, which is a widely available clinical imaging modality, and 99m Tc-pertechnetate, a clinically approved tracer, could be used in conjunction with NIS gene expression to monitor/maximize energetics and thus increase engraftment of transplanted cells in future preclinical studies of cell transplantation. We have previously demonstrated, using SPECT imaging, that intramyocardial transplantation of suspended cells leads to a low SPECT signal at 1 to 3 h post-transplantation (when compared with 24 h) (3) , whereas cell encapsulation in HA:Ser hydrogels prior to epicardial transplantation leads to a high SPECT signal (similar to 24 h signal) (25) . We attributed differences in the SPECT signal early post-transplantation in the suspended and hydrogel conditions to differences in cellular energetics, but direct proof for this hypothesis was lacking.…”

“…Cell metabolism was monitored using a Seahorse Bioscience XF instrument (Agilent Technologies, Santa Clara, California) 3 , 12 , 25 . We measured the rate of change of dissolved O 2 in each well (oxygen consumption rate [OCR], which reflects OxPhos) and change in pH (extracellular acidification rate [ECAR], which reports glycolysis).…”

“…Dual isotope SPECT/CT imaging was performed at 1 and 24 h following transplantation. As described previously 3 , 20 , 25 , 99m Tc-pertechnetate and 201 TlCl were injected intravenously 1 h prior to imaging to visualize transplanted NIS + CDCs and myocardium, respectively, by SPECT. Two groups of rats were studied: group 1 consisted of NIS + CDCs encapsulated in hydrogels, and group 2 consisted of adherent NIS + CDCs pre-treated with a reversible Akt inhibitor for 1 h followed by washout, prior to dissociation and encapsulation in hydrogels.…”

Kinin B2-Receptor in human iPSC differentiation into cardiomyocytes

“…In addition to this, genetically engineered mice are frequently employed in arrhythmia studies (2,3). Further, animals have repeatedly been recipients of cell grafts in studies that seek optimizing the technology of cell therapy (4)(5)(6)(7).…”