Gerd Geerling

Porcine decellularized conjunctiva (PDC) represents a promising alternative source for conjunctival reconstruction. Methods of its re-epithelialization in vitro with primary human conjunctival epithelial cells (HCEC) have already been established. However, a long-term storage method is required for a simplified clinical use of PDC. This study investigates the influence of several storage variants on PDC. PDC were stored in (1) phosphate-buffered saline solution (PBS) at 4 °C, (2) in glycerol-containing epithelial cell medium (EM/gly) at −80 °C and (3) in dimethyl sulfoxide-containing epithelial cell medium (EM/DMSO) at −196 °C in liquid nitrogen for two and six months, respectively. Fresh PDC served as control. Histological structure, biomechanical parameters, the content of collagen and elastin and the potential of re-epithelialization with primary HCEC under cultivation for 14 days were compared (n = 4–10). In all groups, PDC showed a well-preserved extracellular matrix without structural disruptions and with comparable fiber density (p ≥ 0.74). Collagen and elastin content were not significantly different between the groups (p ≥ 0.18; p ≥ 0.13, respectively). With the exception of the significantly reduced tensile strength of PDC after storage at −196 °C in EM/DMSO for six months (0.46 ± 0.21 MPa, p = 0.02), no differences were seen regarding the elastic modulus, tensile strength and extensibility compared to control (0.87 ± 0.25 MPa; p ≥ 0.06). The mean values of the epithelialized PDC surface ranged from 51.9 ± 8.8% (−196 °C) to 78.3 ± 4.4% (−80 °C) and did not differ significantly (p ≥ 0.35). In conclusion, all examined storage methods were suitable for storing PDC for at least six months. All PDC were able to re-epithelialize, which rules out cytotoxic influences of the storage conditions and suggests preserved biocompatibility for in vivo application.

Background: Preliminary clinical work indicates that increasing eyelid tension improves the function of the meibomian glands. The aim of this study was to optimize laser parameters for a minimally invasive laser treatment to increase eyelid tension by coagulation of the lateral tarsal plate and canthus. Methods: Experiments were performed on a total of 24 porcine lower lids post mortem, with six lids in each group. Three groups were irradiated with an infrared B radiation laser. Laser-induced lower eyelid shortening was measured and the increase in eyelid tension was assessed with a force sensor. A histology was performed to evaluate coagulation size and laser-induced tissue damage. Results: In all three groups, a significant shortening of the eyelids after irradiation was noticed (p < 0.0001). The strongest effect was seen with 1940 nm/1 W/5 s, showing −15.1 ± 3.7% and −2.5 ± 0.6 mm lid shortening. The largest significant increase in eyelid tension was seen after placing the third coagulation. Conclusion: Laser coagulation leads to lower eyelid shortening and an increase in lower eyelid tension. The strongest effect with the least tissue damage was shown for laser parameters of 1470 nm/2.5 W/2 s. In vivo studies of this effect have to confirm the efficacy of this concept prior to clinical application.