Zinc-Releasing Fibrous Scaffolds Modulate Fibroblast, Endothelial, and Macrophage Interactions for Vascularized Tissue Engineering

Fibrous scaffolds are emerging as key biomaterials in regenerative medicine, which provide structural and biochemical support for tissue repair. Despite new advancements in the field, many fibrous scaffolds still face intrinsic limitations, including suboptimal biodegradability, inadequate bioactivity, and limited control over therapeutic release, all of which hinder their broader biomedical applications. To address these challenges, we fabricated electrospun poly(glycolic-<i>co</i>-lactic acid) (PLGA) fibrous scaffolds embedded with various weight percentages (wt %) of zinc nanoparticles (Zn NPs), and then their physicochemical and biocompatibility properties were evaluated. The scaffold containing 1.0 wt % Zn NPs (PLZ2) exhibited controlled release of Zn²⁺, followed by a downward linear trend up to day 8. Afterward, the release rate became relatively steady over time, up to day 14, thereby avoiding burst toxicity while supporting vascularized tissue formation. The bioactivity of these scaffolds was systematically evaluated using multiple cell types, such as human dermal fibroblasts (HDFn), human umbilical vein endothelial cells (HUVECs), and RAW264.7 macrophages, showing important properties in wound healing and angiogenesis. Further, indirect coculture of HUVECs and HDFn was studied to assess cell-to-cell interactions. The controlled release of Zn²⁺ from PLZ2 promoted fibroblast-to-myofibroblast differentiation significantly, indicated by increased vimentin and α-smooth muscle actin expression and enhanced secretion of angiogenic growth factors-vascular endothelial growth factor (1.34-fold) and basic fibroblast growth factor (1.47-fold) at day 7. These soluble growth factors stimulated HUVECs' survival, enhanced their migration, and promoted the formation of capillary-like networks. Simultaneously, scaffolds promoted the transformation of macrophages into M1 and M2 phenotypes, identified through the immunostaining of macrophage polarization markers, inducible nitric oxide synthase (iNOS) and Arg1, and further confirmed by Western blot analysis. In addition, endothelial functionality was further supported by CD31 and VE-cadherin upregulation. These findings indicate that the indirect coculture system in conditioned culture medium with Zn²⁺ effectively stimulates HUVECs and may also influence other cell types to generate capillary-like structures. This approach holds promise for tissue regeneration and applications where vascularization is essential.