3D Printed PLATMC Scaffolds Induce Consistent Host Immune Response

Objectives: Significant effort has been devoted to fabrication techniques used to design scaffold with suitable properties for bone regeneration. Highly porous and degradable scaffolds are conventionally fabricated from Poly(L-lactide-co-trimethylenecarbonate) (PLATMC) using salt-leaching methods. 3D-printing technology enables control over the mechanical properties and porosity of the material, which enhances the regenerative potential of the scaffold by improving cell attachment and distribution.
The aim of the present experimental in vivo study was to investigate the host response to 3D-printed PLATMC scaffolds in comparison to salt-leaching scaffolds.
Methods: PLATMC scaffolds were enrolled in a subcutaneous model in Lewis rats and harvested at 4 days and 8 weeks. Twenty-three relevant chemokines were investigated using Bioplex protein assay (BIORAD). Histological analysis was performed on formalin-fixed paraffin-embedded sections. Immunohistochemical (IHC) staining for macrophages (CD68) was quantified as percent positive pixels using Color-Deconvolution Algorithm (Aperio). Distribution of chemokine data in 3D-printed and salt-leached scaffolds were investigated by principal component analysis. Linear regression models were constructed to compare chemokine and macrophage levels according to scaffold fabrication method. Data analysis was conducted in R v4.2.0 with 0.05 set as the significance limit.
Results: 3D-printed group showed less variation in chemokine expression levels than the salt leaching group. However, three chemokines were significantly downregulated: KC/Gro (neutrophil activating protein, p=0.018), Interferon gamma (INF- γ) inducing factor (natural killer cell chemoattractant, p=0.014), and IFN-γ(macrophage activating factor, p=0.03). Similarly, Histological examination revealed less infiltration by mononuclear inflammatory and multinucleated foreign-body giant (MNFG) cells and lower CD68 signal in the 3D-printed group (p<0.001).
Conclusions: 3D-printing of scaffolds offered more consistent host immune response in comparison to salt-leaching. However, the resulting response is characterized by low infiltration of immune cells. Further investigations are needed to improve the immunogenicity of 3D-printed PLATMC scaffolds.