ANALYSIS OF THE INTERACTION BETWEEN STEM CELLS AND POLYLACTIC ACID (PLA) SCAFFOLDS FOR APPLICATIONS IN TISSUE ENGINEERING

Background Tissue engineering is a branch of regenerative medicine which comprises the combination of biomaterials, cells and bioactive molecules to regenerate tissues. Biomaterial scaffolds can be solid or porous and are used to reproduce the extracellular matrix acting as substrate for cells, directing the formation of the new tissue. The ideal biomaterial is chosen based on its biocompatibility, biodegradability and properties that must be similar to the biological tissue. Other important factors that influence cells’ responses are the size and interconnectivity of the pores. To better understand how 3D structures affect cell behavior in culture we combined different 3D printed polylactic acid (PLA) scaffolds with mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs). Methods PLA scaffolds presenting two different pore sizes (1,27 ± 0,06 and 0,7 ± 0,02 mm) were printed using a commercial 3D printer. Adipose tissue derived MSCs and umbilical cord blood derived EPCs were cultured on the scaffolds until 7 days. Cell adhesion was observed through fluorescence microscopy and scanning electron microscopy was used to analyze cell morphology. Cell cycle, proliferation and immunophenotype was evaluated by flow cytometry. The angiogenic potential of 3D cultured EPCs were evaluated in vitro. Results Both cell types were able to adhere on the scaffolds while also maintaining their characteristic morphologies. In comparison with a 2D culture, after 48h of 3D cultures the percentage of MSCs in G2 phase of the cell cycle was higher (12,53% ±1,84 vs. 19,78% ±1,64), whereas the EPC population suffered a delay in the cell cycle, resulting in a lower percentage of proliferating cells (25,8% ± 7,8 vs. 15,65% ± 2,4). However, between the scaffolds with distinct pore sizes there were no differences in any of the phases of the cell cycle after 2 and 7 days of culture. While MSCs maintained their undifferentiated profile after being cultured on the scaffolds, EPCs presented reduction of the von Willebrand factor (vWF), which did not affect the cells’ angiogenic potential. Conclusion These results indicate that the 3D environment had different effects on each cell type and that the difference in pore sizes did not affect cell behavior in the terms of adherence, cell cycle, proliferation and immunophenotype. Furthermore, they reinforce the importance of studying how cells respond to 3D culture when considering the scaffold approach for tissue engineering.