Bioengineered Cornea: 3D Bioprinting Using A Biomimetic Hydrogel

Corneal wounding, due to infection, injury or inflammation, heals by stromal scarring and opacification, which is a significant cause of blindness affecting millions worldwide. This study tries to address the unmet clinical need for a biomaterial that can be used as a corneal stromal equivalent for transplantation and to prevent the development of stromal scarring.

This study reports the development of a biomimetic hydrogel composed of decellularized extracellular matrix (dECM) derived from non-transplant grade human cadaveric corneas from eye banks and from bovine corneas, discarded from slaughterhouses. This hydrogel was used to 3D Bioprint custom corneal construct and transplant it in rabbits in sutureless fashion. 

 A thorough in-vitro characterization was performed followed by in-vivo validation of the hydrogel by testing its application in a unique rabbit corneal scar model and compared with collagen and sham controls using in vivo imaging techniques to assess corneal thickness, curvature, densitometry. The hydrogel was then optimised by assessing its rheological properties to develop a bioink. Customized 3-D CAD models of cornea were generated and extrusion-based 3-D bioprinting was used to print corneal stromal constructs after optimising the bioprinting parameters. These constructs were transplanted in the rabbit corneas post-wounding.

Both human and bovine hydrogels retained the major extra-cellular matrix components, demonstrated physical, chemical, and environmental stability, and was tested as non-pyrogenic and non-immunogenic. Our in-vivo study revealed that, while the control group developed corneal opacification, the prophylactic application of hydrogels derived from both bovine and human sources could effectively prevent corneal scarring and opacification, which was evaluated objectively using in-vivo imaging. The human dECM bioprinted constructs had good print fidelity,  showed repithelialization, biointegration at day 90 post-transplantation. Transparency improved serially over the period of follow up and thickness, curvature restored to normal in vivo.

These findings suggest that the application of decellularized corneal matrix hydrogel could be a new promising therapeutic approach in the clinic as a minimally invasive and easily performable procedure in preventing scaring, as well as a potential source for a bioink to print corneal volume constructs as stromal equivalents to aid in corneal transplantation.