Engineering of hybrid spheroids of mesenchymal stem cells and drug depots for immunomodulating effect in islet xenotransplantation

Abstract

Immunomodulation is an essential consideration for cell replacement procedures. Unfortunately, lifelong exposure to nonspecific systemic immunosuppression results in immunodeficiency and has toxic effects on nonimmune cells. Here, we engineered hybrid spheroids of mesenchymal stem cells (MSCs) with rapamycin-releasing poly(lactic- co -glycolic acid) microparticles (RAP-MPs) to prevent immune rejection of islet xenografts in diabetic C57BL/6 mice. Hybrid spheroids were rapidly formed by incubating cell-particle mixture in methylcellulose solution while maintaining high cell viability. RAP-MPs were uniformly distributed in hybrid spheroids and sustainably released RAP for ~3 weeks. Locoregional transplantation of hybrid spheroids containing low doses of RAP-MPs (200- to 4000-ng RAP per recipient) significantly prolonged islet survival times and promoted the generation of regional regulatory T cells. Enhanced programmed death-ligand 1 expression by MSCs was found to be responsible for the immunomodulatory performance of hybrid spheroids. Our results suggest that these hybrid spheroids offer a promising platform for the efficient use of MSCs in the transplantation field.

Scalable and Uniform Fabrication of Dexamethasone-Eluting Depot-Engineered Stem Cell Spheroids as a Microtissue Construct to Target Bone Regeneration

“…A previous study showed that syngeneic MSCs can be rejected as early as 7 days after injection . We have recently demonstrated that co-injection of syngeneic MSCs with an immunosuppressive drug depot can improve MSC retention in the injected site for around 3–4 weeks . Given that DEXA is a potent immunosuppressive drug, we expect that this drug delivery system could protect syngeneic MSCs for certain time.…”

“…52 We have recently demonstrated that co-injection of syngeneic MSCs with an immunosuppressive drug depot can improve MSC retention in the injected site for around 3−4 weeks. 7 Given that DEXA is a potent immunosuppressive drug, we expect that this drug delivery system could protect syngeneic MSCs for certain time. Currently, our data showed clear improvement in new bone formation after implantation of the MFS loaded with PD-DEXA/MP-conjugated spheroids at 4 weeks, but the new bone did not completely fill the defect at 8 weeks.…”

“…MSCs were cultured in the growth medium until they reached approximately 90% confluency. MSCs within 3–6 passages were used for the experiments …”

“…However, monotherapy with MSCs has shown low effectiveness and biased outcomes due to low cell viability and engraftment in harsh injection sites. − Although treatment outcomes could be improved with multiple doses of MSCs, this approach significantly increases the treatment fee and patient discomfort . Therefore, enhancing the MSC potency is essential for the successful translation of MSC therapy in clinical settings . Synchronous delivery of therapeutic agents with MSCs has shown potential for achieving such effects.…”

“…5 Therefore, enhancing the MSC potency is essential for the successful translation of MSC therapy in clinical settings. 7 Synchronous delivery of therapeutic agents with MSCs has shown potential for achieving such effects. Current approaches involve seeding MSCs in drug-eluting rigid scaffolds or soft hydrogels, encapsulating MSCs and drug depots into heterospheroids, or internalizing drug depots into MSCs.…”