Corneal Epithelial Stem Cells Repopulate the Donor Area within 1 Year from Limbus Removal for Limbal Autograft

Technique for the Management of Extensive Ocular Surface Lipodermoid Involving the Cornea of Children

PURPOSE

Ocular surface lipodermoids with corneal involvement may require surgical intervention; if deep, ocular surface reconstruction with lamellar corneal tissue or amniotic membrane may be needed. We describe a staged technique using autologous ipsilateral simple limbal epithelial transplantation.

METHODS

After verifying sparing of Descemet membrane, the conjunctival portion of the lipodermoid was debulked in the first stage. Six weeks later, the corneal portion was excised, followed by autologous ipsilateral simple limbal epithelial transplantation to promote rapid reepithelialization of the residual stromal bed. Temporary tarsorrhaphy was used for patient comfort and to expedite ocular surface healing.

RESULTS

Three eyes of 3 children with grade III large ocular surface lipodermoids that encroached the visual axis and hindered proper eyelid closure underwent surgery without complications. In all cases, the visual axis was cleared and eyelid closure was improved. At the last follow-up (mean 35.7 months, median 36.0 months), the bed of the original dermoid showed minimal haze in 1 case, while 2 eyes developed small pseudopterygium; best spectacle-corrected visual acuity improved from 20/200 to 20/70 in the first case, from fix and follow to 20/50 in the second case, and remained fix and follow in the last case, but this child had congenital hydrocephalus with severe developmental delay.

CONCLUSIONS

This surgical technique is a promising option for children with grade III large ocular surface lipodermoids given its effectiveness in clearing the visual axis and in improving eyelid closure. Moreover, it does not require lamellar corneal transplantation or intervention to the fellow eye.

Surgical Management and Recent Advances in Chemical Injury: A 5-year Review

Purpose: To review the surgical management options in ocular chemical burn, including newer advances.Methods: Online literature search of published articles over last 5 years on surgical management of ocular chemical burn and newer advances were performed on December 30, 2020.Results: Following literature search and screening using adequate filters, 67 review articles on surgical management of ocular chemical burns were retrieved. The review talks about the surgical management options starting from Debridement in acute stage to various visual rehabilitative procedures in the chronic stage. The review also highlights the evolving surgical advances in this field.Conclusion: It is imperative to choose adequate surgical tool wherever applicable; current review discusses the role of each surgical option at different clinical stages in detail.

Time-course single-cell RNA sequencing reveals transcriptional dynamics and heterogeneity of limbal stem cells derived from human pluripotent stem cells

BACKGROUND

Human pluripotent stem cell-derived limbal stem cells (hPSC-derived LSCs) provide a promising cell source for corneal transplants and ocular surface reconstruction. Although recent efforts in the identification of LSC markers have increased our understanding of the biology of LSCs, much more remains to be characterized in the developmental origin, cell fate determination, and identity of human LSCs. The lack of knowledge hindered the establishment of efficient differentiation protocols for generating hPSC-derived LSCs and held back their clinical application.

RESULTS

Here, we performed a time-course single-cell RNA-seq to investigate transcriptional heterogeneity and expression changes of LSCs derived from human embryonic stem cells (hESCs). Based on current protocol, expression heterogeneity of reported LSC markers were identified in subpopulations of differentiated cells. EMT has been shown to occur during differentiation process, which could possibly result in generation of untargeted cells. Pseudotime trajectory analysis revealed transcriptional changes and signatures of commitment of hESCs-derived LSCs and their progeny-the transit amplifying cells.

CONCLUSION

Single-cell RNA-seq revealed time-course expression changes and significant transcriptional heterogeneity during hESC-derived LSC differentiation in vitro. Our results demonstrated candidate developmental trajectory and several new candidate markers for LSCs, which could facilitate elucidating the identity and developmental origin of human LSCs in vivo.

In Vivo Confocal Microscopy of the Corneal-Conjunctival Transition in the Evaluation of Epithelial Renewal after SLET

Examination of the corneal surface by in vivo confocal microscopy (IVCM) allows for objective identification of corneal and conjunctival cell phenotypes to evaluate different epithelialization patterns. Detection of a corneal-conjunctival epithelial transition could be considered as a sign of restored epithelial function following simple limbal epithelial transplantation (SLET). This is a prospective, interventional case series. We assessed patients with limbal stem cell deficiency (LSCD) by IVCM, preoperatively and at monthly intervals following SLET. Sectors in the central and peripheral cornea were scanned. Immediately upon detection of multi-layered cells with the epithelial phenotype in the central cornea and confirmation of epithelial transition in all corneal sectors, the decision for keratoplasty was taken. Ten patients were enrolled. After SLET, epithelial phenotype in the central cornea and an epithelial transition were identified within six and nine months in seven and one patients, respectively. One patient was a partial success and one failed. Five patients underwent keratoplasty, with stable results up to 12 months. Identification of the epithelial transition zone by IVCM permits assessment of the efficacy of SLET, enabling subsequent planning of keratoplasty for visual rehabilitation. The stability of the corneal surface following keratoplasty confirms that the renewal of the corneal epithelium was effectively retained.

Limbal niche cells: a novel feeder cell for autologous cultivated oral mucosal epithelial transplantation

AIM

To establish a culture system using conspecific limbal niche cells (LNCs) as feeders for autologous cultivated oral mucosal epithelial transplantation (COMET).

MATERIALS & METHODS

Rabbit oral epithelial sheets, harvested from culture systems containing LNCs or 3T3 cells, were transplanted onto limbal stem cell-deficient rabbit eyes (COMET-3T3 or COMET-LNCs).

RESULTS

After COMET, corneas were relatively restored, with the exception of mild neovascularization in one cornea of the COMET-3T3 group. CD34 was detected in COMET-3T3 group corneas. Corneas of the COMET-LNCs group expressed high levels of PEDF and sFlt-1, but low levels of bFGF, compared with expression in COMET-3T3 corneas.

CONCLUSION

The culture system containing conspecific LNC feeders could substitute for the 3T3 cell system and decrease the risk of neovascularization after COMET.

Corneal epithelial stem cells for corneal injury

INTRODUCTION

Ocular surface diseases with limbal insufficiency represent a therapeutic challenge for restoring vision. This corneal deficiency includes both classical ocular diseases (as chemical burns) and rare ocular diseases (as congenital aniridia and ocular cicatricial pemphigoid).

AREAS COVERED

Our understanding of limbal epithelial stem cells (LESCs) has increased the potential for treatment options. Pharmacological treatment strategies (as regenerating agent ophthalmic solutions) and especially surgical treatment strategies are available. Isolated LESCs can be produced by limbal primary cultures obtained from explants or cell suspensions. We review the latest cornea surgery techniques.

EXPERT OPINION

The adjunction of human limbal mesenchymal cells as a support for limbal stem cell primary cultures appears to be of great interest. Recently, human-induced pluripotent stem cells have allowed the generation of minicorneal organoids. This potential means of creating a three-dimensional cornea with in vitro maturation opens up important research areas for corneal regeneration therapy.

Simple limbal epithelial transplantation: a review on current approach and future directions

Simple limbal epithelial transplantation is a recently developed technique for treating limbal stem cell deficiency caused by ocular burns. A small limbal biopsy from the donor eye, usually from the patient's healthy eye, is excised and dissected into multiple pieces. An amniotic membrane is atttached using fibrin glue on the diseased eye after removing the conjunctivalized pannus from the corneal surface. The limbal biopsy pieces are placed onto the amniotic membrane, fixed with fibrin glue, followed by bandaging of the ocular surface with a contact lens. This technique (auto simple limbal epithelial transplantation) offers easier surgical manipulations and economic advantages over other techniques for the treatment of limbal stem cell deficiency. We therefore review simple limbal epithelial transplantation along with recent modifications in the technique and case studies, including challenges and failures.

Repairing the corneal epithelium using limbal stem cells or alternative cell-based therapies

INTRODUCTION

The corneal epithelium is maintained by limbal stem cells (LSCs) that reside in the basal epithelial layer of the tissue surrounding the cornea termed the limbus. Loss of LSCs results in limbal stem cell deficiency (LSCD) that can cause severe visual impairment. Patients with partial LSCD may respond to conservative therapies designed to rehabilitate the remaining LSCs. However, if these conservative approaches fail or, if complete loss of LSCs occurs, transplantation of LSCs or their alternatives is the only option. While a number of clinical studies utilizing diverse surgical and cell culture techniques have shown favorable results, a universal cure for LSCD is still not available. Knowledge of the potential risks and benefits of current approaches, and development of new technologies, is essential for further improvement of LSCD therapies.

AREAS COVERED

This review focuses on cell-based LSCD treatment approaches ranging from current available clinical therapies to preclinical studies of novel promising applications.

EXPERT OPINION

Improved understanding of LSC identity and development of LSC expansion methods will influence the evolution of successful LSCD therapies. Ultimately, future controlled clinical studies enabling direct comparison of the diverse employed approaches will help to identify the most effective treatment strategies.

Long-Term Ocular Surface Stability in Conjunctival Limbal Autograft Donor Eyes

PURPOSE

To investigate the incidence of limbal stem cell deficiency (LSCD) in donor eyes after conjunctival limbal autograft (CLAU).

METHODS

An observational retrospective review was performed on all patients who underwent CLAU alone, combined keratolimbal allograft with CLAU ("Modified Cincinnati Procedure"), or combined living-related conjunctival limbal allograft (lr-CLAL) with CLAU having ≥6 months of follow-up after surgery. The outcome measures were best-corrected visual acuity (BCVA) and ocular surface status.

RESULTS

The inclusion criteria were fulfilled by 45 patients. Of these, 26 patients underwent CLAU, 18 underwent combined keratolimbal allograft/CLAU, and 1 underwent combined lr-CLAL/CLAU. Mean age at the time of surgery was 39.6 years. Mean logMAR preoperative BCVA was -0.08. There were no operative complications. The mean follow-up duration after surgery was 48.3 months (range 8.3-181.5 mo). At last follow-up, all eyes maintained a stable ocular surface, and mean logMAR BCVA was -0.05.

CONCLUSIONS

With the advent of newer ocular surface transplantation methods, there has been concern that CLAU carries the theoretical risk of inducing LSCD. Our long-term clinical results following donor eyes after CLAU demonstrate no signs of LSCD.

Conjunctival-limbal autograft

PURPOSE OF REVIEW

To provide an overview of conjunctival-limbal autografting (CLAU) for ocular surface rehabilitation with emphasis on more recent literature detailing outcomes of the procedure over the last 2 decades as well as technique variations and adjuvant techniques.

RECENT FINDINGS

Limbal autografting initially described in 1964 by Barraquer and Strampelli and later popularized by Kenyon and Tseng is considered the best option for restoration of corneal phenotype in unilateral limbal stem-cell deficiency. Although there have been developments in alternative limbal epithelial stem-cell techniques including ex-vivo tissue engineering methods, because of the benefit of immunohistocompatability, this procedure still provides better long-term outcomes. As autograft donor tissue is valuable, optimization of the recipient eye preoperatively with good lid closure and reduction of inflammation is vital for success as is close postoperative follow-up. Variations in the technique described have included the modified Cincinnati technique combining CLAU with cadaveric keratolimbal allograft to avoid conjunctivalization. In addition, simple limbal epithelial autograft transplantation, a less-invasive technique combined with amniotic membrane transplantation, has shown promise.

SUMMARY

In spite of the development of new epithelial transplant techniques, in unilateral limbal stem-cell deficiency, CLAU from a healthy unaffected fellow eye remains the best option available for restoration of corneal phenotype.