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

## TL;DR

Zinc-releasing fibrous scaffolds improve tissue engineering by promoting cell interactions needed for blood vessel formation and healing.

## Contribution

A novel zinc-releasing fibrous scaffold is developed to enhance vascularized tissue regeneration through controlled zinc ion release.

## Key findings

- PLZ2 scaffolds with 1.0 wt% Zn NPs showed controlled Zn2+ release without burst toxicity.
- Zn2+ release promoted fibroblast differentiation and increased angiogenic growth factor secretion.
- Scaffolds supported macrophage polarization and endothelial cell functionality for vascularization.

## Abstract

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-co-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.