Comparative analysis of long-term results of three epithelial cell transplantation procedures for treating limbal stem cell deficiency

This study compared the long-term outcome of different epithelial transplantation techniques to treat limbal stem cell deficiency (LSCD). We conducted a retrospective 15-year comparative systematic cohort study of patients with LSCD who underwent either cultivated limbal epithelial transplantation (CLET), simple limbal epithelial transplantation (SLET), or cultivated oral mucosal epithelial transplantation (COMET). We reviewed the demographic data, etiology, LSCD severity, best-corrected visual acuity, surgical outcomes, and complications. A total of 103 eyes of 94 patients (mean age, 45.0 ± 16.4 years) with LSCD were enrolled. The most common cause of LSCD was chemical injury (42.7 %). The median follow-up time was 75 months. The success rates of CLET, SLET, and COMET were 45.5 %, 77.8 %, and 57.8 %, respectively. The 7-year survival rates after CLET, SLET, and COMET were 50.0 %, 72.2 %, and 53.2 %, respectively. Steven-Johnson syndrome (SJS) had a significantly lower survival rate than other causes (p < 0.001), but SLET had a significantly higher survival rate than CLET (p = 0.018) and COMET (p = 0.047). Visual improvement of more than four Snellen lines was achieved in 53.1 % of successful cases and 28.2 % of failed cases. SJS, Schirmer I test <5 mm, and the presence of postoperative recurrent epithelial defects were significant risk factors for a failed surgery. All epithelial transplantation techniques had favorable long-term surgical outcomes. More than half of the patients achieved a stable ocular surface and visual acuity improvement up to 7 years postoperatively. SLET tends to have a better surgical outcome than CLET and COMET, especially in patients with SJS.

Focus on limbal stem cell deficiency and limbal cell transplantation

Limbal stem cell deficiency (LSCD) causes severe vision impairment and can lead to blindness, representing one of the most challenging ocular surface disorders. Stem cell deficiency can be congenital or, more often, acquired. The categorization of ocular surface transplantation techniques is crucial to achieving treatment homogeneity and quality of care, according to the anatomic source of the tissue being transplanted, genetic source, autologous or allogenic transplantation (to reflect histocompatibility in the latter group), and cell culture and tissue engineering techniques. The aim of this minireview is to provide a summary of the management of LSCD, from clinical characteristics and therapeutic outcomes to the development of novel therapeutic approaches. The manuscript also briefly summarizes recent findings in the current literature and outlines the future challenges to overcome in the management of the major types of ocular surface failure.

Insights into the clinical development of regenerative medical products through a comparison of three cell-based products recently approved for limbal stem cell deficiency

Three regenerative medical products for limbal stem cell deficiency (LSCD), a rare and intractable ocular surface disease, have recently been approved in Japan. To our knowledge, this is the first time multiple stem-cell-based medical products have been approved for the same ocular disease. Development plans and study designs for each product differ, resulting in differences in indications. Since cell-based products have a heterogeneous formulation and often target rare diseases, they require a flexible approach to development. This review article describes the status and prospects of the clinical development of regenerative medical products by summarizing the issues of the three products from the Pharmaceuticals and Medical Devices Agency (PMDA) standpoint. Implementing stem cell-based products is challenging, requiring scientific and flexible review by regulatory authorities. To overcome these issues in the development process, developers and regulatory authorities need to communicate and fully discuss study protocols from the early stage of development.

Long-term outcome of allogeneic cultivated limbal epithelial transplantation for symblepharon caused by severe ocular burns

Background

The therapeutic effects of allogeneic cultivated limbal epithelial transplantation (CLET) for symblephara at different degrees caused by ocular burns were evaluated in this study.

Methods

A series of interventional cases were involved in this retrospective study. Eighty eyes (80 patients) with symblephara underwent CLET and the success rates of surgical treatment as well as corneal conditions and risk factors for recurrent symblepharon were analyzed.

Results

The average age of patients was 32.4 ± 13.7 years (ranged from 4 to 60 years). The average follow-up time was 26.4 ± 13.6 months (ranged from 12 to 60 months). Symblepharon cases were caused by chemical burns (36 eyes) or thermal burns (44 eyes). The first surgical intervention achieved complete success in 40 eyes (50%), partial success in 25 eyes (31.3%), and failure in 15 eyes (18.8%). The rate of complete success was 85.0% in eyes with grade I/II symblephara, 51.5% in eyes with grade III eyes and 22.2% in eyes grade IV symblephara (P = 0.001). The treatment was completely successful in 23.1% of eyes with moderate or severe preoperative inflammatory action and 63.0% of eyes with mild or no inflammation (P = 0.000). The corneal conditions were improved in 43 eyes (53.8%), of which 21 eyes had improved visual acuity. The recurrence of symblepharon after the first CLET was positively correlated with symblepharon length (P = 0.003), preoperative inflammatory activity (P = 0.016) as well as postoperative cicatricial entropion and trichiasis (P = 0.038).

Conclusions

CLET was effective on the recovery of anatomically deep fornixes in eyes caused by symblephara and corneal surface condition could be improved simultaneously. The success of surgical treatment was dependent on the effective control of inflammation and timely management of eyelid abnormalities.

Limbal stem cell and oral mucosal epithelial transplantation from ex vivo cultivation in LSCD-induced rabbits: histology and immunologic study of the transplant epithelial sheet

PURPOSE

To evaluate the results of cultivated limbal epithelial and oral mucosal epithelial transplantation (CLET and COMET) in limbal stem cell deficiency (LSCD)-induced rabbit model.

MATERIALS AND METHODS

Six New Zealand white rabbits were divided into two groups of three rabbits each. Limbal tissue was harvested from the first group, and oral mucosal biopsy was obtained from the second group. The tissues were cultured using an explant technique with amniotic membrane as a substrate and co-culture with the 3T3 fibroblast and air-lifting method. The right eye of each rabbit was induced to have LSCD using alkali burns. After three weeks, the LSCD-induced rabbit eyes were transplanted with the cultivated limbal and oral mucosal epithelial sheet in the first and second group, respectively. The transplanted eye was evaluated weekly post-operation. After 2 months, all transplanted eyes were enucleated and the epithelial morphology and phenotype of ocular surfaces were studied and compared with normal corneal and oral mucosal tissue.

RESULTS

At 2-month post-transplantation, the eyes of four animals recovered with corneal transparency, one partially recovered, and one failed. The histology of the majority of transplanted eyes was stratified layers of corneal epithelia similar to normal rabbit cornea with some different findings such as goblet cells in the limbal region. Corneal epithelial thickening and stromal vascularization in two animals were observed. Phenotypic characterization of transplanted eyes showed a similar pattern of marker expression with the absence of p63 expression in the limbal or corneal epithelium in the COMET group.

CONCLUSIONS

The histology and phenotype of transplanted eyes after CLET and COMET were most likely to have similar characteristics as a normal healthy rabbit eye even though the COMET eyes have some inferior characteristics to the CLET eyes.