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

Potentiation of stem cell potency is critical for successfultissueengineering, especially for bone regeneration. Three-dimensional cellculture and bioactive molecule co-delivery with cells have been proposedto achieve this effect. Here, we provide a uniform and scalable fabricationof osteogenic microtissue constructs of mesenchymal stem cell (MSC)spheroids surface-engineered with dexamethasone-releasing polydopamine-coatedmicroparticles (PD-DEXA/MPs) to target bone regeneration. The microparticleconjugation process was rapid and cell-friendly and did not affectthe cell viability or key functionalities. The incorporation of DEXAin the conjugated system significantly enhanced the osteogenic differentiationof MSC spheroids, as evidenced by upregulating osteogenic gene expressionand intense alkaline phosphatase and alizarin red S staining. In addition,the migration of MSCs from spheroids was tested on a biocompatiblemacroporous fibrin scaffold (MFS). The result showed that PD-DEXA/MPswere stably anchored on MSCs during cell migration over time. Finally,the implantation of PD-DEXA/MP-conjugated spheroid-loaded MFS intoa calvarial defect in a mouse model showed substantial bone regeneration.In conclusion, the uniform fabrication of microtissue constructs containingMSC spheroids with drug depots shows a potential to improve the performanceof MSCs in tissue engineering.

Automated summary

Potentiation of stem cell potency is crucial for successful bone regeneration in tissue engineering. This study demonstrates a uniform and scalable method to fabricate osteogenic microtissue constructs of mesenchymal stem cell (MSC) spheroids surface-engineered with dexamethasone-releasing polydopamine-coated microparticles (PD-DEXA/MPs). The incorporation of DEXA significantly enhances the osteogenic differentiation of MSC spheroids, and the microparticles remain stable during cell migration. Implantation of these constructs in a mouse model shows substantial bone regeneration.