Nutritional nanoparticles provide self-feeding properties enabling long-term stem cell functionality under anoxia
M. Gurian* (TNW-DBE), N.G.A. Willemen (TNW-DBE), I.R. Porsul (TNW-DBE), S. Jeong (Harvard Medical School), S.R. Shin (Harvard Medical School), and J. Leijten (TNW-DBE)
Abstract
Background
The engineering of tissues is limited to small sizes due to the metabolic constraints caused by diffusion limitations of oxygen and nutrients. Current approaches try to overcome this challenge by in situ oxygen generation from solid peroxides or glucose release from enzymatic conversion of polysaccharides. However, these methods depend on xenogeneic enzymes to either reduce cytotoxicity or release nutrients. These xenogeneic enzymes illicit immunogenic responses, and show a reduced efficiency within the host.
Here, we report for the first time on the use of glycogen, an autologous nutritional nanoparticle that reversibly stores glucose, which we explored for providing metabolic support to human mesenchymal stem cells (hMSC) in clinically relevant sized engineered tissues.
Methods
Glycogen loaded dextran-tyramine core-shell microparticles were prepared using droplet microfluidics combined with a timed enzymatic outside-in crosslink to allow for controlled glucose release. hMSC were maintained within nutrient-free DMEM supplemented with formulated glycogen under anoxia. Cell functionality was determined by hMSC viability, metabolic activity, and growth factor secretion.
Results & Conclusion
Extracellular glycogen maintained cell functionality for a clinically relevant time period of four weeks. Additionally, this associated with pro-angiogenic protein secretion. The natural size of glycogen allowed for stable retention into core-shell microparticles, allowing for a self-regulated controlled release of nutrients, as glycogen degradation was driven by cell-secreted enzymes. The first of its kind long-term self-feeding properties of glycogen in combination with its straightforward incorporation in engineered tissues offers excellent control over cell function under anoxic conditions to bridge the prevascular phase of living implants.