Considering 3D topography of endothelial folds to improve cell count of organ cultured corneas

Corneal endothelial validation in the eye bank: differences in automated methods and repeatability

PURPOSE

To evaluate reproducibility of endothelial cell density (ECD) measurements using the Konan Cell Check D in donor corneas by two different ophthalmologists and to compare the two automated cell count methods (center and flex-center) available in the software of this specular microscope.

METHODS

ECD values were quantified in 54 donor corneas by two independent investigators using the Cell Check D (Konan Medical USA Inc) with both automated cell count methods. In the center method, at least 30 contiguous cells are marked. For the flex-center method, an area is delineated and only the cells within the designated area are counted.

RESULTS

The mean ECD was 2473.81±378.22 cells/mm2. Good ECD intergrader reproducibility for the center (ICC=0.821) and the flex-center method (ICC=0.784) were noted. Poor reliability was observed for coefficient of variation and hexagonality (ICC≤0.265). When both methods for ECD analysis were compared, a moderate correlation for the two independent graders using the two manual (center and flex-center) methods was detected (correlation coefficient of 0.678 and 0.745 for each of the investigators). Comparison between methods yielded significantly higher ECD with the flex-center method (P=0.013). When corneas were divided by ECD, those under 2200 cells/mm2 and those between 2200 and 2700 cells/mm2 also had significantly higher ECD with the flex-center method (P<0.022).

CONCLUSIONS

ECD values are reproducible with both methods, although the flex-center method ECDs tend to be higher, particularly in cases of low ECD. Eye banks and surgeons should exercise caution in making decisions based only on small differences in ECD.

Specular Microscopy of Human Corneas Stored in an Active Storage Machine

Purpose: Unlike corneas stored in cold storage (CS) which remain transparent and thin, corneas stored in organoculture (OC) cannot be assessed by specular microscopy (SM), because edema and posterior folds occur during storage and prevent from specular reflection. We previously developed an active storage machine (ASM) which restores the intraocular pressure while renewing the storage medium, thus preventing major stromal edema. Its transparent windows allow multimodal corneal imaging in a closed system. Aim: to present SM of corneas stored in this ASM. Methods: Ancillary study of two preclinical studies on corneas stored for one and three months in the ASM. A prototype non-contact SM was developed (CMOS camera, ×10 objective, collimated LED source, micrometric stage). Five non-overlapping fields (935 × 748 μm) were acquired in exactly the same areas at regular intervals. Image quality was graded according to defined categories (American Cornea Donor Study). The endothelial cell density (ECD) was measured with a center method. Finally, _SMECD was also compared to Hoechst-stained cell nuclei count (_HoechstECD). Results: The 62 corneas remained thin during storage, allowing SM at all time points without corneal deconditioning. Image quality varied depending on donors and days of control but, overall, in the 1100 images, we observed 55% of excellent and 30% of good quality images. _SMECD did not differ from _HoechstECD (p = 0.084). Conclusions: The ASM combines the advantages of CS (closed system) and OC (long-term storage). Specular microscopy is possible at any time in the ASM with a large field of view, making endothelial controls easy and safe.

Corneal endothelial cell therapy: feasibility of cell culture from corneas stored in organ culture

In 2013, a clinical trial was initiated to investigate cell therapy for the treatment of corneal endothelial decompensation. Cultivating human corneal endothelial cells (CECs) while maintaining their functional phenotype is challenging; therefore, establishment of a confirmed protocol is pivotal for obtaining approval from regulatory authorities for use of cellular therapy products. In this study, we evaluated organ culture (OC) as a storage method for donor corneas used as a raw material for establishing CEC cultures. OC allows storage of corneal tissue for conventional corneal transplantation at 31-37 °C for up to 5 weeks, whereas storage at 4 °C is limited to 2 weeks. We investigated 20 pairs of corneas: one cornea of each pair was stored in OC and the other in cold storage for one week before CEC culture. In 15/20 cases, the CECs assumed a hexagonal sheet-like monolayer structure and expressed endothelial function-related markers. CECs were also obtained from OC corneas that had been stored for 1 (n = 19) and 2 (n = 7) months. As a further test, CECs were cultivated from 5 OC corneas that had been transported from France to Japan. In all cases, these corneas, even after international transport, generated CECs that formed hexagonal monolayers with clinically applicable and sufficiently high cell densities. In conclusion, the CEC cultures required for endothelial cell therapy can be obtained from OC corneas without changing the standard storage operating procedures of the eye banks.

Significant differences between specular microscopy and corneal bank endothelial cell counts - a pilot study

BACKGROUND

It was shown recently that endothelial cell count performed by cornea banks overestimates the real number of endothelial cells. The aim of this study was to investigate the internal quality of preclinical ECD in human donor corneas using two widely used methods for endothelial cell counting, transmitted light microscopy used in organ culture tissue bank and clinically used specular microscopy.

METHODS

Twenty human donor corneas that could not be transplanted were included in this analysis. Differences in evaluating endothelial cell density (ECD) and hexagonal endothelial cell ratio (HEX) between clinical specular microscopy (CSM) and corneal bank transmitted light microscope (CBLM) were evaluated as well as differences between automated and manual cell counts.

RESULTS

Automated CBLM showed a higher ECD of 31.85% compared to automated CSM, while manual CBLM counting is 10.51% higher compared to manual CSM (p < 0.01). Further, higher average ECD values result in a higher difference between CSM and CBLM measurements. The manual CBLM ECDs were significantly higher compared to automated derived ECD from CSM (p < 0.01). However, no systematic bias can be detected when comparing the differences of the measurements with the average ECD measurements of both methods.

CONCLUSION

This preclinical pilot study confirmed a significant higher ECD using transmitted light microscopy in organ culture compared to clinical specular microscopy. This indicates that the early rapid decrease of EC universally observed after surgery might be partly artefactual.

Innovative corneal active storage machine for long-term eye banking

Optimal ex vivo corneal storage in eye banks is crucial to increase both the number of corneas suitable for graft and their intrinsic quality, mainly the number of viable endothelial cells, which dictates graft survival in recipients. With both passive storage methods used worldwide (short-term cold storage in the United States, long-term organ culture in Europe), significant endothelial cell loss is inevitable. Here we show that, with an active storage machine, also called a bioreactor, which restores 2 fundamental physiological parameters, intraocular pressure and medium renewal, endothelial cell survival is improved by 23% compared with organ culture after 4 weeks' storage. Also observed in the bioreactor is a 4-fold higher expression of Na⁺ /K⁺ ATPase, which supports one of the major endothelial cell pumping functions. In addition, corneas remain thin and transparent, so they are suitable for surgery at any time. This new active eye banking method may help to reduce the severe global scarcity of donor corneas.