Fig. 6
Histological evaluation. Samples harvested at 6 weeks after the calvarial defects were transplanted with a 3D-PLA scaffold or b 3D-PLA + human gingival mesenchymal stem cells (hGMSCs). Left panels (1): The images at low magnification (4×) showed 3D-PLA and 3D-PLA + hGMSCs integrated smoothly with the host tissue. Middle panels (2): High-magnification images (10×) showing the contact area between 3D-PLA and 3D-PLA + hGMSCs with bone calvaria grafted at 6 weeks postsurgery. Right panels (3): Images obtained at 40× objective showing the connective tissue between 3D-PLA and 3D-PLA + hGMSCs and bone host tissue. Samples harvested at 6 weeks after the calvarial defects was transplanted with c 3D-PLA + extracellular vesicles (EVs) scaffold or d 3D-PLA + EVs + hGMSCs. Left panels (1): The images at low magnification (4×) showed 3D-PLA + EVs and 3D-PLA + EVs + hGMSCs integrated smoothly with the host. Middle panels (2): High-magnification images (10×) showing the new bone formation stained with acid fuchsin in both samples grafted at 6 weeks postsurgery. Right panels (3): Images obtained at 40× objective showed a zone with new mineralized matrix inside 3D PLA scaffold for both samples. In particular, in the 3D-PLA + EVs (c3) sample in the contact zone some blood vessels are valuable. Samples harvested at 6 weeks after the calvarial defects was transplanted with e 3D-PLA + polyethyleneimine (PEI)-EVs scaffold or f 3D-PLA + PEI-EVs + hGMSCs. Left panels (1): The images at low magnification (4×) showed 3D-PLA + PEI-EVs and 3D-PLA + PEI-EVs + hGMSCs integrated smoothly with the host. Middle panels (2): High-magnification images (10×) showing the new bone formation stained with acid fuchsin in both samples grafted at 6 weeks postsurgery. Right panels (3): Images obtained at 40× objective showed new bone formation inside the scaffold structure. In particular, in 3D-PLA + PEI-EVs there were numerous blood vessels present around the new bone deposition area. Scale bars = 10 μm. *, scaffold; V, vessels; B, new bone. Acid fuchsin-toluidine blue staining