Cell Loaded 3D Bioprinted GelMA Hydrogels for Corneal Stroma Engineering
Tissue engineering aims to replace missing or damaged tissues and restore their functions. Three dimensional (3D) printing has been gaining more attention because it enables the researchers to design and produce cell loaded constructs with predetermined shapes, sizes, and interior architecture. In the present study a 3D bioprinted corneal stromal equivalent was designed to substitute for the native tissue. Reproducible outer and inner organization of the stroma could be obtained by optimizing printing conditions in terms the nozzle speed in x-y direction the spindle speed. 3D printed GelMA hydrogels were highly stable in PBS during three weeks of incubation (8% weight loss). Live-Dead cell viability assay showed 98% cell viability on Day 21 indicating that printing conditions were suitable for keratocyte printing. Mechanical properties of the cell loaded 3D printed hydrogels increased 2 folds during this incubation period and approached that of native cornea (ca. 20 kPa vs 27 kPa, respectively). Expression of collagens (types I and V), and proteoglycan (decorin) representative of keratocytes indicates maintenance of the phenotype in the hydrogels. Transparency of cell-loaded and cell-free hydrogels were over 80% (at 700 nm) during the three week culture and comparable to that of the native cornea (85%) at the same wavelength. Thus, GelMA hydrogels bioprinted with keratocytes could mimic the biological and physical properties of the corneal stroma with its excellent transparency, adequate mechanical strength, and high cell viability.