Corneal Donor Profile and Evolution of Corneal Donation in a Brazilian State Where the Number of Individuals on the Waiting List Reached Zero But Increased Again

Disparities in Access to Corneal Tissue in the Developing World

Corneal disease is a leading cause of blindness worldwide. For most blinding corneal conditions, keratoplasty is the only way of restoring sight. Unfortunately, access to corneal transplantation is widely variable, most notably due to the lack of suitable donor material. There exists significant disparity between the developed and developing world when it comes to access to cornea tissue, with supply often inversely proportional to burden of disease. The purpose of this review is to identify the current disparities in supply and demand of corneal donor tissue, understand how to access corneal tissue, and propose solutions that promote equitable care for patients with severe corneal disease.

High-Resolution Bioprinting of Recombinant Human Collagen Type III

The development of commercial collagen inks for extrusion-based bioprinting has increased the amount of research on pure collagen bioprinting, i.e., collagen inks not mixed with gelatin, alginate, or other more common biomaterial inks. New printing techniques have also improved the resolution achievable with pure collagen bioprinting. However, the resultant collagen constructs still appear too weak to replicate dense collagenous tissues, such as the cornea. This work aims to demonstrate the first reported case of bioprinted recombinant collagen films with suitable optical and mechanical properties for corneal tissue engineering. The printing technology used, aerosol jet® printing (AJP), is a high-resolution printing method normally used to deposit conductive inks for electronic printing. In this work, AJP was employed to deposit recombinant human collagen type III (RHCIII) in overlapping continuous lines of 60 µm to form thin layers. Layers were repeated up to 764 times to result in a construct that was considered a few hundred microns thick when swollen. Samples were subsequently neutralised and crosslinked using EDC:NHS crosslinking. Nanoindentation and absorbance measurements were conducted, and the results show that the AJP-deposited RHCIII samples possess suitable mechanical and optical properties for corneal tissue engineering: an average effective elastic modulus of 506 ± 173 kPa and transparency ≥87% at all visible wavelengths. Circular dichroism showed that there was some loss of helicity of the collagen due to aerosolisation. SDS-PAGE and pepsin digestion were used to show that while some collagen is degraded due to aerosolisation, it remains an inaccessible substrate for pepsin cleavage.

Factors influencing endothelial cell density of corneas for transplantation

To evaluate factors affecting corneal endothelial cell density (ECD) under enucleation and preservation time studies at Eye Bank of the Federal District of Brazil. We conducted a case-control study collecting data from 1128 corneas where death-to-enucleation time and enucleation-to-preservation time were within 24 h. Low cell count were those corneas with an ECD less than 2000 cells/mm² and high cell count was defined as those with ECD greater than 2000 cells/mm². We calculated the independent risk factors related to: cause of death, donor age, death-to-enucleation time, enucleation-to-preservation time and primary graft failure. Correlation analysis was used to assess which parameters influence ECD: death-to-enucleation time, enucleation-to-preservation time, average cell area (AVE), coefficient of variation and percentage of hexagonal cells. Of the total number of corneas, 1004 had ECD data and were selected for the study. 87.4% (n = 877) had high cell counts with 2699 ± 412 cells/mm². The mean donor age was 38.8 ± 16 years. The most common causes of death were external causes (48.6%, n = 488). Longer times from death-to-enucleation, up to 24 h were not associated with a decrease in ECD (OR 0.58; P = 0.44) or risk of graft survival (P = 0.74). Enucleation-to-preservation intervals greater than 12 h showed increased risk of graft survival (P = 0.04). AVE was the main parameter for ECD (R² = 0.96, P < 0.001). The overall graft survival rate was 98.2% (n = 761). Donors with 40 years of age and above did not present a higher risk of graft survival (P = 0.09). We suggest that the maximum time from death-to-enucleation should be 24 h, assuming the body has been refrigerated after 6 h; and from enucleation-to-preservation time of 12 h, followed by proper processing and cornea morphology examination.