Transplantation for severe OSD

Cultivated oral mucosal epithelial transplantation (COMET) is a very effective surgical modality that avoids graft rejection and complications when treating patients with severe ocular surface diseases such as Stevens-Johnson syndrome, ocular cicatricial pemphigoid or chemical injury, according to Tsutomu Ben Inatomi MD, PhD. “It works very well for these severe cases. The transplantation of oral mucosal epithelium maintains the original characteristics of the tissue and is beneficial for stabilisation and conjunctival reconstruction. However, very strict postoperative follow-up of the reconstructed ocular surface is essential for a successful long-term prognosis,” Dr Inatomi said at the World Ophthalmology Congress 2020 Virtual. Dr Inatomi, a researcher at the Kyoto Prefectural University of Medicine, Kyoto, Japan, said that cicatrising ocular surface disorders are typically very difficult to treat because of the loss of the stem cells and the scarring of the tissue. “To overcome these issues, we have developed several advanced approaches such as intraoperative mitomycin C to inactivate the fibroblasts, amniotic membrane transplantation to promote epithelialisation, and also cultivated epithelial sheet transplantation, which has yielded some promising results for these difficult cases,” he said. The advantages of cultivated epithelial sheet transplantation include rapid wound healing of the ocular surface, and easy expansion of large cell numbers from a small biopsy, said Dr Inatomi. “The sheet can contain a high content of progenitor cells, which is very helpful for ocular surface maintenance, and also if we use non-ocular cells as with COMET, we can treat bilateral disease with autologous tissue. Since we are using amniotic membrane substrate, we can prevent corneal scarring at the same time,” he said. Auto-corneal epithelial transplantation is ideal for cases of unilateral disease, whereas either allo-corneal epithelial transplantation or auto-oral mucosal epithelial transplantation are better options for bilateral cases, said Dr Inatomi. The COMET procedure entails harvesting a small amount of oral mucosa by biopsy, which is then cultured on amniotic membrane with feeder cells. “Since these are autologous tissue non-ocular cells there is no risk of rejection. Oral mucosa is a very easy region for biopsy, and it can be repeated many times. The oral tissue has a high potential for proliferation, and there are a lot of phenotypic similarities between the oral and corneal epithelial surfaces,” he said. Dr Inatomi said that his group has been using COMET for various types of ocular reconstruction in recent years and has obtained good results with this approach. “It is useful, for instance, to treat acute stem cell loss because of rapid epithelisation, cicatrising ocular surface diseases with stem cell deficiency and conjunctival reconstruction,” he said. COMET can also be used in conjunction with various keratoplasty techniques in order to obtain better visual recovery and a stable ocular surface. Limbal-supported hard contact lenses can also be used to correct irregular astigmatism, added Dr Inatomi.

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