Air toxicity for primary human-cultured corneal endothelial cells: an in vitro model

Safety of air tamponade versus corneal hydration for sealing clear corneal incisions in cataract surgery

PURPOSE

To compare safety of wound hydration to anterior chamber air tamponade for securing watertight closure of clear corneal incisions, during uneventful cataract surgery.

METHODS

Prospective, comparative case-control series. Patients undergoing phacoemulsification were assigned to receive either anterior chamber air bubble (Group A) or intrastromal wound hydration with balanced salt solution (Group B) at the end of the procedure. Two high-volume surgeons operated equal number of cases in each group employing identical surgical technique, except for corneal side incision management. Patients were assessed pre- and postoperatively at day 1, day 4, day 9, and day 30 after surgery.

RESULTS

One hundred eyes of 100 patients were enrolled, of which 2 were lost to follow-up. The two groups were comparable in terms of preoperative risk factor assessment, baseline central corneal thickness (CCT), preoperative endothelial cell density, as well as cumulative dissipated energy and duration of phacoemulsification (p > 0.05). Mean CCT and best-corrected visual acuity were better in Group B on the first postoperative day, but did not differ between the two groups at all other timepoints. Surgically induced astigmatism was comparable in the two groups (p > 0.05). Endothelial cell density loss at 1 month postoperatively was greater in Group A (34.06%) compared to Group B (16.45%).

CONCLUSIONS

Wound sealing with intrastromal hydration proved to be safer than air tamponade in terms of preserving endothelial cell density and function.

A Novel Pulse Damper for Endothelial Cell Flow Bioreactors

PURPOSE

Peristaltic pumps (PP) are favored in flow bioreactors for their non-contact sterile design. But they produce pulsatile flow, which is consequential for the cultured cells. A novel pulse damper (PD) is reported for pulsatility elimination.

METHODS

The PD design was implemented to target static pressure pulsatility and flow rate (velocity) pulsatility from a PP. Damping effectiveness was tested in a macro-scale, closed-loop recirculating bioreactor mimicking the aortic arch at flow rates up to (4 L/min). Time-resolved particle image velocimetry was used to characterize the velocity field. Endothelial cells (EC) were grown in the bioreactor, and subjected to continuous flow for 15 min with or without PD.

RESULTS

The PD was found to be nearly 90% effective at reducing pulsatility. The EC exposed to low PP flow without PD exhibited distress signaling in the form of increased ERK1/2 phosphorylation (2.5 folds) when compared to those exposed to the same flow with PD. At high pump flow without PD, the cells detached and did not survive, while they were perfectly healthy with PD.

CONCLUSIONS

Flow pulsatility from PP causes EC distress at low flow and cell detachment at high flow. Elevated temporal shear stress gradient combined with elevated shear stress magnitude at high flow are believed to be the cause of cell detachment and death. The proposed PD design was effective at minimizing the hemodynamic stressors in the pump's output, demonstrably reducing cell distress. Adoption of the proposed PD design in flow bioreactors should improve experimental protocols.

The toxic effect of air on primary human retinal pigment epithelium cells

PURPOSE

To investigate the toxic effect of air on primary human retinal pigment epithelium cells (RPE) over time.

METHODS

RPE cultures were retrieved from six donor eyes and cultivated at 37 °C in 5% CO(2) and 95% humidified air. The RPE were divided in six groups with each group containing four samples. Six groups of RPE cultures were set up and four samples were enclosed in each group: group 1 consisted of samples in which RPE were exposed to air for 1 hour. Group 2 consisted of RPE exposed to air for 3 hours, group 3 for 6 hours group 4 for 12 hours group 5 for 24 hours and group 6 for 36 hours respectively.

RESULTS

Six hours after exposure, the morphology of the cells was still intact. At 12 hours few cells appeared enlarged. 24 hours after exposure to air the cells started losing their typical morphology and appeared deformed. Viability was higher than 95% in groups 1-3 while for groups 4-6 was 75.5%, 15.5% and 7.3%, respectively.

CONCLUSION

The toxic effect of air for the studied in vitro model of RPE is not significant for the first 6 hours. The morphology of the cells progressively changed after 12 hours of exposure and almost all cells appeared apoptotic at 36 hours.

Morphological changes and viability of primary cultured human ocular trabecular meshwork cells after exposure to air

PURPOSE

To investigate the possible toxic effect of air exposure for an in vitro model of primary human ocular trabecular meshwork cells (HTM).

METHODS

HTM were isolated from five donor eyes and cultivated at 37 °C. After reaching confluence the cells were seeded on two well chamber slides. The chamber slides were turned upside down in a Petri culture dish full of culture medium and filled with air using a 5 ml syringe, starting this way the exposure of the cells to the air. Subsequently they were placed in the incubation chamber at 37 °C. Six groups of HTM cultures were set up: group 1 consisted of samples in which HTM were exposed to air for 30 min, group 2 for 1 h, group 3 for 3 h, group 4 for 6 h, group 5 for 12 h and group 6 for 24 h.

RESULTS

At 3 h after exposure, the morphology of the cells was still intact, at 6 h few cells appeared deformed and exhibited characteristics of more senescent cells. At 12 h after exposure to air the HTM cells started losing their typical morphology and appeared enlarged and compromised. Viability was superior to 94% in groups 1-3 while for groups 4, 5, 6 it was 82.7%, 39.5% and 12.7% respectively.

CONCLUSION

The toxic effect of air exposure for the studied in vitro model of HTM is not significant for the time period of one to three hours. However it starts reducing viability and alternating morphology 6 h after exposure until the time period of 24 h, where the percentage of living cells is drastically decreased. Therefore, we suggest that the use of an air bubble especially in glaucomatous patients should be applied with caution.