Transplantation of cultured mucosal epithelium: an experimental study

Oral mucosal graft with amniotic membrane transplantation for total limbal stem cell deficiency

PURPOSE

To report the results of oral mucosal graft for reconstruction of corneas with total limbal stem cell deficiency.

DESIGN

Retrospective, interventional case series.

METHODS

Seven patients (7 eyes) with total limbal stem cell deficiency caused by chemical burn (4 eyes), Stevens-Johnson syndrome / toxic epidermal necrolysis (1 eye), ocular cicatricial pemphigoid (1 eye), and multiple cryotherapies and application of mitomycin C for conjunctival melanoma (1 eye) were enrolled in this study. Oral mucosal graft was transplanted as a surrogate limbus together with amniotic membrane transplantation with a follow-up of at least 8 months. Symptomatic relief, restoration of a stable epithelium, corneal clarity, and the best-corrected visual acuity were assessed.

RESULTS

Limbal stem cell deficiency was confirmed by impression cytology in all eyes, among which 6 were bilateral while 1 was unilateral. All 7 patients presented with severe loss of vision, photophobia, pain, chronic inflammation, and corneal vascularization and scarring. For 30 ± 19.8 months, pain and photophobia were resolved in all 7 eyes; 6 eyes exhibited a stable epithelium with regressed corneal vascularization and reduced chronic inflammation. Visual acuity was improved in all 7 eyes. One eye developed partial limbal stem cell deficiency due to exposure at 47 months follow-up and was reoperated. Five eyes had peripheral corneal vascularization.

CONCLUSIONS

Oral mucosal graft is a viable alternative for treating total limbal stem cell deficiency in eyes where transplantation of allogeneic limbal stem cells has failed or is not feasible.

In vivo behavior of complete human oral mucosa equivalents: characterization in athymic mice

BACKGROUND AND OBJECTIVE

The interest in tissue engineering as a way to achieve repair of damaged body tissues has led to the carrying out of many studies whose results point to the potential effectiveness of these methods. In a previous study, we reported the obtaining of complete autologous oral mucosa equivalents (CAOMEs), characterized by oral immature keratinocytes and stem cells on an autologous plasma and fibroblast scaffold. The purpose of this study is to show their behavior in vivo, by using them as free grafts in experimental animals, and to demonstrate their potential capacity to regenerate oral mucosa.

MATERIAL AND METHODS

We engineered CAOMEs, as previously described. All CAOMEs thus obtained were used as free grafts in nu/nu mice. To assess their evolution in vivo, we studied their histological and immunohistochemical features by using AE1/AE3 pancytokeratin, the 5/6 cytokeratin pair, cytokeratin 13, laminin 5, collagen IV, vimentin, p-63 and Ki-67, at 7, 14 and 21 d.

RESULTS

The structure became progressively closer to that of oral mucosa samples. Cytokeratin 5/6 staining became increasingly intense in the basal and suprabasal layers, and cytokeratin 13 was exclusively positive in the superficial layers. The basal membrane was completed in 21 d. Vimentin showed a correct formation of the chorion. The increasingly positive staining of p-63 and Ki-67 indicated that the regeneration process was taking place.

CONCLUSION

The present study shows the potential regenerative capacity of the CAOMEs by their ability to reach maturity similar to that seen in oral mucosa.

In vitro cultured autologous pre-confluent oral keratinocytes for experimental prefabrication of oral mucosa

The reconstruction of large defects after head and neck cancer resection often requires composite tissue transfer to replace a combination of bone, muscle and mucosa. Thus, tissue engineering techniques may be useful for oral mucosal reconstructive surgery to prefabricate mucosal tissue on the muscle flap in vivo, instead of using conventional skin-bearing composite flaps. The aim of this study was to investigate whether autogenous pre-confluent oral keratinocytes (PCOK) cultured in vitro can create mucosal coverage on muscle in vivo, in a single grafting procedure. In 30 Wistar rats, with a small piece of oral mucosa (2 mm x 5 mm), oral keratinocytes were isolated and then seeded on a hydrophilic PTFE membrane (n = 50) in serum-free culture condition. After 48 h, the membrane, together with the PCOK, was transplanted onto the gracilis muscle to fabricate a mucosal flap in vivo. The wound bed was closed primarily until the time of examination. Biopsies were carried out 1, 2, 3, and 4 weeks, respectively, after transplantation and were evaluated immunohistochemically (AE1/AE3 anti-pancytokeratin, cytokeratin 5/6, collagen IV, laminin, lectin-specific labeling of N-acetylglucosamine oligomeres of endothelial cells) with relation to the following criteria: (1) graft acceptance; (2) inflammatory signs; (3) structural changes and keratinocyte lining; (4) expression of basement membrane components; and (5) vascularization. Ninety-one percent of the grafts showed uniform epithelial layers. The mean number of reconstructed epithelial cell layers was 1.7, 2.0, 1.85 and 2.7 at 1, 2, 3 and 4 weeks, respectively after transplantation (P = 0.342). Collagen IV, laminin and lectin-specific capillaries developed between the neoepithelium and the underlying muscular layer. Only two specimens showed signs of infection 2 weeks after transplantation. In conclusion, this experiment demonstrated that PCOK grafts on muscle in vivo can achieve uniform multi-layered oral epithelial coverage in a short period of time. This technique may be a useful alternative tool for oropharyngeal reconstructive surgery and is also worth considering for further clinical studies.

Successful culture and sustainability in vivo of gene-modified human oral mucosal epithelium

Human oral mucosal cells are an attractive site for tissue engineering because they are the most accessible cells in the body and easy to manipulate in vitro. They thus have possibilities for targeting by somatic gene therapy. We examined the efficiency of retrovirus-mediated gene transfer and the construction of mucosal epithelium in vivo. Human oral mucosal cells were transduced with a retroviral vector carrying the lacZ gene at high efficiency and constructed epithelium after G418 selection with 3T3 cells in vitro. The cultured oral mucosal epithelium membrane was then grafted onto immunodeficient mice. Beta-Gal expression was detected histochemically in vivo 5 weeks after grafting. Furthermore, we transduced factor IX cDNA into the mucosal epithelium membrane, and it was then transplanted into nude mice. Between 0.6 and 1.8 ng of human factor IX per milliliter was found in mouse plasma, and the production was continued for 23 days in vivo. These results confirmed that the oral mucosal epithelium is an ideal target tissue for gene therapy or tissue engineering.