P33-A110†Ex vivo models of corneal epithelial regeneration in bioreactor: respective roles of limbal, conjunctival and corneal epithelia.

PURPOSE: Human corneas preserved in bioreactor (BR) are characterized by not only a better endothelial viability, but also a more differentiated and stratified epithelium compared to corneas preserved in organoculture. By using corneal preservation in BR, we aimed to analyze the respective contribution of corneal (C), limbal (L), and conjunctival (Conj) epithelia in corneal epithelial regeneration. METHODS: Five pairs of corneas from body donation to Science were used with a death-to-collection time <20 hours. A 3- to 5-mm-wide conjunctival flange was kept intact. Five patterns were set up by complete mechanical removal of 1, 2, or 3 epithelia (-): C-L+Conj+, C-L-Conj+, C-L+Conj-, C+L-Conj-, C-L-Conj- (control) (n=2 for each pattern). The L epithelia was destroyed by scraping and thermocoagulation. Corneas were then kept in BR (21mmHg, 2.5µl/min of Corneamax Eurobio, 31°C) for 3 weeks to allow epithelial regeneration. The epithelium was then analyzed using immunofluorescence (IF) on flat mounted cornea by targeting CK12 (corneal epithelium) and CK15 (limbal epithelium). Cell nuclei were counterstained with DAPI. Corneal transparency was quantified using a transparometer. RESULTS: No epithelium was reconstituted in the C-L-Conj- control group. In the other 4 models including the C-L-Conj+ group, the cornea was transparent and covered by a pluristratified corneal epithelium, characterized by CK12 expression. CONCLUSION: In this BR model, conjunctival epithelial cells alone allowed the regeneration of a typical corneal epithelium whereas corneal epithelium was able to migrate to the limbus and conjunctiva. We hypothesize that all 3 ocular surface epithelia contain stem cells or progenitors able to migrate throughout the cornea and restore the corneal epithelium independently of each other. The main difference between our ex vivo model and in vivo situation is the absence of neovascularization. This suggests that the main cause of limbic insufficiency is due to the loss of the anti-angiogenic barrier rather than the loss of limbic stem cells.

Investigating the Role of TGF-ß Signaling Pathways in Human Corneal Endothelial Cell Primary Culture.

Corneal endothelial diseases are the leading cause of corneal transplantation. The global shortage of donor corneas has resulted in the investigation of alternative methods, such as cell therapy and tissue-engineered endothelial keratoplasty (TEEK), using primary cultures of human corneal endothelial cells (hCECs). The main challenge is optimizing the hCEC culture process to increase the endothelial cell density (ECD) and overall yield while preventing endothelial-mesenchymal transition (EndMT). Fetal bovine serum (FBS) is necessary for hCEC expansion but contains TGF-ßs, which have been shown to be detrimental to hCECs. Therefore, we investigated various TGF-ß signaling pathways using inhibitors to improve hCEC culture. Initially, we confirmed that TGF-ß1, 2, and 3 induced EndMT on confluent hCECs without FBS. Using this TGF-ß-induced EndMT model, we validated NCAM as a reliable biomarker to assess EndMT. We then demonstrated that, in a culture medium containing 8% FBS for hCEC expansion, TGF-ß1 and 3, but not 2, significantly reduced the ECD and caused EndMT. TGF-ß receptor inhibition had an anti-EndMT effect. Inhibition of the ROCK pathway, notably that of the P38 MAPK pathway, increased the ECD, while inhibition of the ERK pathway decreased the ECD. In conclusion, the presence of TGF-ß1 and 3 in 8% FBS leads to a reduction in ECD and induces EndMT. The use of SB431542 or LY2109761 may prevent EndMT, while Y27632 or Ripasudil, and SB203580 or SB202190, can increase the ECD.

Technique of flat-mount immunostaining for mapping the olfactory epithelium and counting the olfactory sensory neurons.

The pathophysiology underlying olfactory dysfunction is still poorly understood, and more efficient biomolecular tools are necessary to explore this aspect. Immunohistochemistry (IHC) on cross sections is one of the major tools to study the olfactory epithelium (OE), but does not allow reliable counting of olfactory sensory neurons (OSNs) or cartography of the OE. In this study, we want to present an easy immunostaining technique to compensate for these defects of IHC. Using the rat model, we first validated and pre-screened the key OSN markers by IHC on cross sections of the OE. Tuj-1, OMP, DCX, PGP9.5, and N-cadherin were selected for immunostaining on flat-mounted OE because of their staining of OSN dendrites. A simple technique for immunostaining on flat-mounted septal OE was developed: fixation of the isolated septum mucosa in 0.5% paraformaldehyde (PFA) preceded by pretreatment of the rat head in 1% PFA for 1 hour. This technique allowed us to correctly reveal the olfactory areas using all the 5 selected markers on septum mucosa. By combining the mature OSN marker (OMP) and an immature OSN marker (Tuj-1), we quantified the mature (OMP+, Tuj-1-), immature (OMP-, Tuj-1+), transitory (OMP+, Tuj-1+) and total OSN density on septal OE. They were respectively 42080 ± 11820, 49384 ± 7134, 14448 ± 5865 and 105912 ± 13899 cells per mm2 (mean ± SD). Finally, the same immunostaining technique described above was performed with Tuj-1 for OE cartography on ethmoid turbinates without flat-mount.