Enhancing soft tissue regeneration with a 3D-printed Exos@GelMA+PCL biohybrid scaffold via M2 macrophage polarization

Abstract Three-dimensional (3D)-printed breast scaffolds have attracted increased attention for soft tissue reconstruction. However, the polymeric porous scaffolds commonly cause fibrous tissue ingrowth due to their limited immunomodulatory capabilities. In this study, we integrated polycaprolactone (PCL) scaffolds with adipose-derived mesenchymal stem cell (ADSC) exosome-laden Gelatin Methacrylate (GelMA) hydrogels (Exos@GelMA+PCL) to promote macrophage M2 polarization and adipose regeneration. The biohybrid scaffolds exhibited sustained Exo release, with a cumulative release of >80% by day 14. Internalized Exos enhanced RAW264.7 macrophage M2 polarization in vitro , as confirmed by immunofluorescence and real-time quantitative PCR. Conditioned medium from scaffold-macrophage cocultures enhanced the proliferation, migration, and adipogenic differentiation of ADSCs. In vivo , Exos@GelMA+PCL biohybrid scaffolds significantly increased the proportion of M2 macrophages compared to controls (GelMA+PCL and PCL scaffolds). At 12 weeks, the biohybrid scaffolds achieved markedly higher adipose tissue area percentages (46.26 ± 4.55%) compared to GelMA+PCL scaffolds (23.76 ± 1.90%) and PCL scaffolds (26.14 ± 2.55%). This strategy offers an innovative immunomodulatory approach to enhance soft tissue regeneration in breast reconstruction by regulating the microenvironment.