Consecutive Expansion of Limbal Epithelial Stem Cells from a Single Limbal Biopsy

In Vivo Confocal Microscopy in Limbal Stem Cell Deficiency After Mesenchymal Stem Cell Transplantation: A Sub-analysis from a Phase I-II Clinical Trial

INTRODUCTION

The aim of this work is to evaluate the effect of mesenchymal stem cell transplantation (MSCT) and cultivated limbal epithelial transplantation (CLET) therapies on the limbus of patients suffering from limbal stem cell deficiency (LSCD).

METHODS

A sub-analysis of a phase I-II randomized, controlled, and double-masked clinical trial was performed to assess the changes in the anatomical structures of the limbus. In vivo confocal microscopy (IVCM) analysis was carried out in LSCD eyes before and 12 months after allogeneic MSCT or CLET. Epithelial phenotype of the central cornea, as well as the presence of transition zones and palisades of Vogt in the limbus, were assessed using Wilcoxon test.

RESULTS

Twenty-three LSCD (14 MSCT and nine CLET) eyes were included. The epithelial phenotype of the central cornea improved significantly (p < 0.001) from 15 (eight MSCT, seven CLET) and eight (six MSCT, two CLET) LSCD eyes showing conjunctival and mixed phenotypes, respectively, to eight (five MSCT, three CLET), five (two MSCT, three CLET), and ten (seven MSCT, three CLET) eyes showing conjunctival, mixed, and corneal phenotypes, respectively. Transition areas and palisades of Vogt were observed in at least one quadrant in nine (five MSCT, four CLET) and 16 (nine MSCT, seven CLET), and in four (two MSCT, two CLET) and six (three MSCT, three CLET) LSCD eyes before and after surgery, respectively. Changes in the transition zones and palisades were solely significant (p = 0.046) for the nasal and inferior quadrants, respectively.

CONCLUSIONS

MSCT and CLET improved the central corneal epithelial phenotype despite only minor changes in the anatomical structures of the limbus, as detected by IVCM technology.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT01562002.

Interleukin-13 increases the stemness of limbal epithelial stem cells cultures

This study aimed to determine the effect of interleukin-13 (IL13) on the stemness, differentiation, proliferation, clonogenicity, and morphology of cultured limbal epithelial cells (LECs). Human limbal explants were used to culture LECs up to the second passage (P0-P2) with or without IL13 (IL13+ and IL13-, respectively). Cells were analyzed by qPCR (for the expression of ΔNp63α, BMI-1, keratin (K) 3, K7, K12, K14, K17, mucin 4, and MKI67) and immunofluorescence staining for p63α. The clonogenic ability was determined by colony-forming assay (CFA), and their metabolic activity was measured by WST-1 assay. The results of the CFA showed a significantly increased clonogenic ability in P1 and P2 cultures when LECs were cultured with IL13. In addition, the expression of putative stem cell markers (ΔNp63α, K14, and K17) was significantly higher in all IL13+ cultures compared to IL13-. Similarly, immunofluorescence analysis showed a significantly higher percentage of p63α positive cells in P2 cultures with IL13 than without it. LECs cultures without IL13 lost their cuboidal morphology with a high nucleocytoplasmic ratio after P1. The use of IL13 also led to significantly higher proliferation in P2, which can be reflected by a higher ability to reach confluence in P2 cultures. On the other hand, IL13 had no effect on corneal epithelial cell differentiation (K3 and K12 expression), and the expression of the conjunctival marker K7 significantly increased in all IL13+ cultures compared to the respective cell culture without IL13. This study showed that IL13 enhanced the stemness of LECs by increasing the clonogenicity and the expression of putative stem cell markers of LECs while maintaining their stem cell morphology. We established IL13 as a culture supplement for LESCs, which increases their stemness potential in culture, even after the second passage, and may lead to the greater success of LESCs transplantation in patients with LSCD.

Progress in the use of plasma rich in growth factors in ophthalmology: from ocular surface to ocular fundus

Introduction: The use of blood derivatives and especially Plasma rich in growth factors (PRGF), for regenerative purposes has been a common trend along the last decades in the field of oral surgery, dermatology, orthopedics, and more recently in ophthalmology.Areas covered: PRGF is a type of platelet-rich plasma that is being explored for the treatment of ocular injuries. The present review article highlights 50 ophthalmology-related publications about the application of PRGF in the treatment of acute and chronic pathologies in ophthalmology as well as most relevant challenges and future prospects.Expert opinion: PRGF technology provides a wide range of formulations that can be used therapeutically in many different acute and chronic ocular pathologies. In addition to eye drops enriched with autologous growth factors, PRGF enables the preparation of both immunologically safe and fibrin-based formulations. Recent advances in the field have promoted PRGF storage for 12 months under freezing conditions, its daily use for 7 days at room temperature and the freeze-dried formulation. The thermally treated immunosafe formulation has shown promising clinical results for the treatment of several diseases such as Sjögren syndrome, graft versus host disease or cicatrizing conjunctivitis. In addition, several fibrin formulations have been preclinically evaluated and clinically incorporated as an adjuvant to ocular surface or glaucoma surgeries, dermal fat graft procedures, limbal stem cell expansion and retinal surgeries. The present review explores the latest scientific and clinical data, current challenges, and main prospects of this technology for the treatment of several ocular injuries.

Optimization of Human Limbal Stem Cell Culture by Replating a Single Limbal Explant

Cultured limbal epithelial stem cell transplantation is a clinical procedure used to regenerate the corneal epithelium in patients with limbal stem cell deficiency. The protocols used to expand limbal epithelial cells in vitro need to be optimized, since the scarcity of human ocular tissue donors is limiting the potential use of this procedure. Here, we describe a method to consecutively expand a single human limbal explant. With this method it is possible to obtain up to three limbal epithelial primary cultures from the same explant, thus increasing the efficiency of the in vitro cell culture.

A proof-of-concept clinical trial using mesenchymal stem cells for the treatment of corneal epithelial stem cell deficiency

Ocular stem cell transplantation derived from either autologous or allogeneic donor corneoscleral junction is a functional cell therapy to manage extensive and/or severe limbal stem cell deficiencies that lead to corneal epithelial failure. Mesenchymal stem cells have been properly tested in animal models of this ophthalmic pathology, but never in human eyes despite their potential advantages. We conducted a 6- to 12-month proof-of-concept, randomized, and double-masked pilot trial to test whether allogeneic bone marrow-derived mesenchymal stem cell transplantation (MSCT], n = 17) was as safe and as equally efficient as allogeneic cultivated limbal epithelial transplantation (CLET), (n = 11) to improve corneal epithelial damage due to limbal stem cell deficiency. Primary endpoints demanded combination of symptoms, signs, and the objective improvement of the epithelial phenotype in central cornea by in vivo confocal microscopy. This proof-of-concept trial showed that MSCT was as safe and efficacious as CLET. Global success at 6-12 months was 72.7%-77.8% for CLET cases and 76.5%-85.7% for MSCT cases (not significant differences). Central corneal epithelial phenotype improved in 71.4% and 66.7% of MSCT and CLET cases, respectively at 12 months (P = 1.000). There were no adverse events related to cell products. This trial suggests first evidence that MSCT facilitated improvement of a diseased corneal epithelium due to lack of its stem cells as efficiently as CLET. Consequently, not only CLET but also MSCT deserves more preclinical investigational resources before the favorable results of this proof-of-concept trial could be transformed into the larger numbers of the multicenter trials that would provide stronger evidence. (ClinicalTrials.gov number, NCT01562002.).

Characterization and comparison of human limbal explant cultures grown under defined and xeno-free conditions

Human limbal epithelial cells (LECs) intended for treatment of limbal stem cell deficiency are commonly cultivated on a 3T3 feeder layer with complex culture medium supplemented with fetal bovine serum (FBS). However, FBS is a xenogeneic component containing poorly characterised constituents and exhibits quantitative and qualitative lot-to-lot variations. Human limbal explants were plated on untreated or fibrin coated plastic plates and cultured in two non-xenogeneic media (supplemented with either human serum or platelet lysate only). Our aim was to find out whether the characteristics of harvested LEC cultures are comparable to those of LEC cultivated in the gold standard - FBS-supplemented complex medium. The growth kinetics, cell proliferation, differentiation, stemness maintenance, apoptosis and contamination by other cell types were evaluated and compared among these conditions. In all of them LECs were successfully cultivated. Stemness was preserved in both xeno-free media. However, cells cultured with human serum on the fibrin-coated plates had the highest growth rate and cell proliferation and very low fibroblast-like cell contamination. These data suggest that xeno-free cell culture conditions can replace the traditional FBS-supplemented medium and thereby provide a safer protocol for ex vivo cultured limbal stem cell transplants.

Autologous method for ex vivo expansion of human limbal epithelial progenitor cells based on plasma rich in growth factors technology

PURPOSE

Develop an autologous culture method for ex vivo expansion of human limbal epithelial progenitor cells (LEPCs) using Plasma Rich in Growth Factors (PRGF) as a growth supplement and as a scaffold for the culture of LEPCs.

METHODS

LEPCs were cultivated in different media supplemented with 10% fetal bovine serum (FBS) or 10% PRGF. The outgrowths, total number of cells, colony forming efficiency (CFE), morphology and immunocytochemistry against p63- α and cytokeratins 3 and 12 (CK3-CK12) were analyzed. PRGF was also used to elaborate a fibrin membrane. The effects of the scaffold on the preservation of stemness and the phenotypic characterization of LEPCs were investigated through analysis of CK3-CK12, ABCG-2 and p63.

RESULTS

LEPCs cultivated with PRGF showed a significantly higher growth area than FBS cultures. Moreover, the number of cells were also higher in PRGF than FBS, while displaying a better morphology overall. CFE was found to be also higher in PRGF groups compared to FBS, and the p63-α expression also differed between groups. LEPCs cultivated on PRGF membranes appeared as a confluent monolayer of cells and still retained p63 and ABCG-2 expression, being negative for CK3-CK12.

CONCLUSIONS

PRGF can be used in corneal tissue engineering, supplementing the culture media, even in a basal media without any other additives, as well as providing a scaffold for the culture.

Successful Consecutive Expansion of Limbal Explants Using a Biosafe Culture Medium under Feeder Layer-Free Conditions

PURPOSE

Transplantation of in vitro cultured limbal epithelial stem cells (LESCs) is a treatment widely used for LESC deficiency. However, the number of limbal tissue donors is limited, and protocols for LESC cultivation often include compounds and/or feeder layers that can induce side effects and/or increase the cost of the culture procedure. We investigated the feasibility of obtaining more than one limbal primary culture (LPC) from the same biopsy using a culture medium in which several potentially harmful compounds were replaced at the same time by biosafe supplements, allowing the LESC cultivation without feeder layers.

MATERIALS AND METHODS

We established feeder layer-free LPCs with three culture media: (1) a modified supplemental hormonal epithelial medium, containing potential harmful components (cholera toxin, dimethylsulfoxide, and fetal bovine serum [FBS]), (2) IOBA-FBS, a medium with FBS but with no other harmful supplements, and (3) IOBA-HS, similar to IOBA-FBS but with human serum instead of FBS. Additionally, the same limbal explant was consecutively cultured with IOBA-HS producing three cultures. LPCs were characterized by real-time reverse transcription polymerase chain reaction and/or immunofluorescence.

RESULTS

LPCs cultured with the three media under feeder layer-free conditions showed cuboidal cells and no significant differences in the percentage of positive cells for limbal (ABCG2, p63, and K14) and corneal (K3, K12) proteins. Except for ABCG2, the relative mRNA expression of the LESC markers was significantly higher when IOBA-FBS or IOBA-HS was used. LPC1 showed characteristics similar to LPC0, while LPC2 cell morphology became elongated and the expression of some LESC markers was diminished.

CONCLUSION

IOBA-HS enables the culturing of up to two biosafe homologous LPCs from one limbal tissue under feeder layer-free conditions. The routine use of this culture medium could improve both the biosafety and the number of available LPCs for potential clinical transplantation, as well as decrease the expense of the culture procedure.

Long-Term Cultures of Human Cornea Limbal Explants Form 3D Structures Ex Vivo - Implications for Tissue Engineering and Clinical Applications

Long-term cultures of cornea limbal epithelial stem cells (LESCs) were developed and characterized for future tissue engineering and clinical applications. The limbal tissue explants were cultivated and expanded for more than 3 months in medium containing serum as the only growth supplement and without use of scaffolds. Viable 3D cell outgrowth from the explants was observed within 4 weeks of cultivation. The outgrowing cells were examined by immunofluorescent staining for putative markers of stemness (ABCG2, CK15, CK19 and Vimentin), proliferation (p63α, Ki-67), limbal basal epithelial cells (CK8/18) and differentiated cornea epithelial cells (CK3 and CK12). Morphological and immunostaining analyses revealed that long-term culturing can form stratified 3D tissue layers with a clear extracellular matrix deposition and organization (collagen I, IV and V). The LESCs showed robust expression of p63α, ABCG2, and their surface marker fingerprint (CD117/c-kit, CXCR4, CD146/MCAM, CD166/ALCAM) changed over time compared to short-term LESC cultures. Overall, we provide a model for generating stem cell-rich, long-standing 3D cultures from LESCs which can be used for further research purposes and clinical transplantation.

Stem Cell Therapy for Corneal Epithelium Regeneration following Good Manufacturing and Clinical Procedures

Objective. To evaluate outcomes of cultivated limbal epithelial transplantation (CLET) for management of ocular surface failure due to limbal stem cell deficiency (LSCD). Design. Prospective, noncomparative, interventional case series and extensive comparison with recent similar studies. Participants. Twenty eyes with LSCD underwent CLET (11 autologous; 9 allogeneic) and were followed up for 3 years. Etiologies were divided into 3 prognostic categories: Group 1, chemical injuries (7 eyes); Group 2, immune-based inflammation (4 eyes); and Group 3, noninflammatory diseases (9 eyes). Intervention. Autologous and allogeneic limbal epithelial cells were cultivated on amniotic membranes and transplanted. Evaluations were based on clinical parameters, survival analysis, and in vivo confocal microscopy (IVCM). European Union Tissues/Cells Directive and good manufacturing procedures were followed. Main Outcome Measures. Improved clinical parameters, absence of epithelial defects, and improved central corneal epithelial phenotype. Results. Success rate was 80% at 1-2 years and 75% at 3 years. Autografts and allografts had similar survival. Success rate was significantly lower in prognostic Group 1 (42.9%) than in Groups 2-3 (100% each). All clinical parameters improved substantially. By IVCM, 80% of cases improved in epithelial status. Conclusions. CLET improved corneal epithelium quality, with subsequent improvement in symptoms, quality of life, and vision. These results confirm that CLET is a valid therapy for ocular surface failure.

Comparison of Explant and Enzyme Digestion Methods for Ex Vivo Isolation of Limbal Epithelial Progenitor Cells

PURPOSE

To compare the effectiveness of two isolation systems for stemness, proliferation and mesenchymal contamination of ex vivo cultured limbal epithelial cells (LECs).

METHODS

Whole explant and dispase digestion methods were used to isolate LECs. For whole explant isolation, one limbal explant was cultivated up to four consecutive times (through LEC1 to LEC4). The performance of LECs isolated with both systems was evaluated according to the following parameters: immunofluorescent staining for adenosine 5'-triphosphate-binding cassette member 2 (ABCG2), p63, cytokeratin 3 (K3), Ki67, and vimentin, and flow cytometry analysis for ABCG2, Ki67 and vimentin.

RESULTS

Twelve LEC cultures were established using whole explant isolation, and nine LEC cultures were established using dispase digestion isolation. In immunofluorescent staining analysis, the ABCG2, p63 and Ki67 expressions were higher in LECs isolated with dispase compared to any LECs isolated with explant. Only the differences in ABCG2 and Ki67 were statistically significant. Further, LEC4 isolated with explant had the highest percentage of cells positive for vimentin, and LEC1 had the highest percentage of cells positive for K3. However, no significant differences were detected. In flow cytometry analysis, the expressions of ABCG2 and Ki67 were statistically higher for LECs isolated with dispase compared to any LECs isolated with explant.

CONCLUSION

Dispase digestion isolation technique was significantly superior to explant isolation techniques in terms of progenitor and proliferative cell contents.

Keeping an eye on decellularized corneas: a review of methods, characterization and applications

The worldwide limited availability of suitable corneal donor tissue has led to the development of alternatives, including keratoprostheses (Kpros) and tissue engineered (TE) constructs. Despite advances in bioscaffold design, there is yet to be a corneal equivalent that effectively mimics both the native tissue ultrastructure and biomechanical properties. Human decellularized corneas (DCs) could offer a safe, sustainable source of corneal tissue, increasing the donor pool and potentially reducing the risk of immune rejection after corneal graft surgery. Appropriate, human-specific, decellularization techniques and high-resolution, non-destructive analysis systems are required to ensure reproducible outputs can be achieved. If robust treatment and characterization processes can be developed, DCs could offer a supplement to the donor corneal pool, alongside superior cell culture systems for pharmacology, toxicology and drug discovery studies.