Successful restoration of corneal surface integrity with a tissue-engineered allogeneic implant in severe keratitis patients.

OBJECTIVES: Corneal diseases are among the main causes of blindness, with approximately 4.6 and 23 million patients worldwide suffering from bilateral and unilateral corneal blindness, respectively. The standard treatment for severe corneal diseases is corneal transplantation. However, relevant disadvantages, particularly in high-risk conditions, have focused the attention on the search for alternatives. METHODS: We report interim findings of a phase I-II clinical study evaluating the safety and preliminary efficacy of a tissue-engineered corneal substitute composed of a nanostructured fibrin-agarose biocompatible scaffold combined with allogeneic corneal epithelial and stromal cells (NANOULCOR). 5 subjects (5 eyes) suffering from trophic corneal ulcers refractory to conventional treatments, who combined stromal degradation or fibrosis and limbal stem cell deficiency, were included and treated with this allogeneic anterior corneal substitute. RESULTS: The implant completely covered the corneal surface, and ocular surface inflammation decreased following surgery. Only four adverse reactions were registered, and none of them were severe. No detachment, ulcer relapse nor surgical re-interventions were registered after 2 years of follow-up. No signs of graft rejection, local infection or corneal neovascularization were observed either. Efficacy was measured as a significant postoperative improvement in terms of the eye complication grading scales. Anterior segment optical coherence tomography images revealed a more homogeneous and stable ocular surface, with complete scaffold degradation occurring within 3-12 weeks after surgery. CONCLUSIONS: Our findings suggest that the surgical application of this allogeneic anterior human corneal substitute is feasible and safe, showing partial efficacy in the restoration of the corneal surface.

Genetic Polymorphisms in VEGFR Coding Genes (FLT1/KDR) on Ranibizumab Response in High Myopia and Choroidal Neovascularization Patients.

A severe form of myopia defined as pathologic/high myopia is the main cause of visual impairment and one of the most frequent causes of blindness worldwide. It is characterized by at least 6 diopters or axial length (AL) of eyeball > 26 mm and choroidal neovascularization (CNV) in 5 to 10% of cases. Ranibizumab is a humanized recombinant monoclonal antibody fragment targeted against human vascular endothelial growth factor A (VEGF-A) used in the treatment of CNV. It acts by preventing VEGF-A from interacting with its receptors (VEGFR-1 and -2) encoded by the FLT1 and KDR genes. Several studies found that the KDR and FLT1 genotypes may represent predictive determinants of efficacy in ranibizumab-treated neovascular age-related macular degeneration (nAMD) patients. We performed a retrospective study to evaluate the association of single nucleotide polymorphisms (SNPs) in VEGFR coding genes with the response rate to ranibizumab in patients with high myopia and CNV. In the association study of genotypes in FLT1 with the response to ranibizumab, we found a significant association between two FLT1 variants (rs9582036, rs7993418) with ranibizumab efficacy at the 12-month follow-up. About the KDR gene, we found that two KDR variants (rs2305948, rs2071559) are associated with best-corrected visual acuity (BCVA) improvement and KDR (rs2239702) is associated with lower rates of BCVA worsening considering a 12-month follow-up period.

Genetic Polymorphisms Affecting Ranibizumab Response in High Myopia Patients.

High myopia is an ophthalmic pathology that affects half of the young adults in the United States and Europe and it is predicted that a third of the world's population could be nearsighted at the end of this decade. It is characterized by at least 6 diopters or axial length > 26 mm and, choroidal neovascularization (CNV) in 5 to 11% of cases. Ranibizumab is a recombinant humanized monoclonal antibody fragment. It is an anti-vascular endothelial growth factor (anti-VEGF) drug used in the treatment of CNV. Many genetic polymorphisms have been associated with interindividual differences in the response to ranibizumab, but these associations were not yet assessed among patients with high myopia and CNV. We performed a retrospective study assessing the association of genetic polymorphisms with response to ranibizumab in patients with CNV secondary to high myopia (mCNV). We included genetic polymorphisms previously associated with the response to drugs used in CNV patients (bevacizumab, ranibizumab, aflibercept, and photodynamic therapy (PDT)). We also included genetic variants in the VEGFA gene. Based on our results, ARMS2 (rs10490924) and CFH (rs1061170) are associated with response to ranibizumab in high myopia patients; and, included VEGFA genetic polymorphisms are not associated with ranibizumab response in our population but might be related to a higher risk of CNV.

Genetic Variants Affecting Anti-VEGF Drug Response in Polypoidal Choroidal Vasculopathy Patients: A Systematic Review and Meta-Analysis.

Polypoidal choroidal vasculopathy (PCV) is usually regarded as a subtype of choroidal neovascularization (CNV) that is secondary to age-related macular degeneration (AMD) characterized by choroidal vessel branching, ending in polypoidal lesions. Despite their close association, PCV and neovascular AMD have shown differences, especially regarding patients' treatment response. Currently, antivascular endothelial growth factor (anti-VEGF) drugs, such as ranibizumab, bevacizumab and aflibercept, have demonstrated their efficacy in CNV patients. However, in PCV, anti-VEGF treatments have shown inconclusive results. Many genetic polymorphisms have been associated with a variable response in exudative/wet AMD patients. Thus, the aim of this study is to explore the genetic variants affecting anti-VEGF drug response in PCV patients. In this regard, we performed a systematic review and meta-analysis. We found four variants (CFH I62V, CFH Y402H, ARMS2 A69S, and HTRA1-62A/G) that have been significantly related to response. Among them, the ARMS2 A69S variant is assessed in our meta-analysis. In conclusion, in order to implement anti-VEGF pharmacogenetics in clinical routines, further studies should be performed, distinguishing physio-pathogenic circumstances between PCV and exudative AMD and the combined effect on treatment response of different genetic variants.

Successful development and clinical translation of a novel anterior lamellar artificial cornea.

Blindness due to corneal diseases is a common pathology affecting up to 23 million individuals worldwide. The tissue-engineered anterior human cornea, which is currently being tested in a Phase I/II clinical trial to treat severe corneal trophic ulcers with preliminary good feasibility and safety results. This bioartificial cornea is based on a nanostructured fibrin-agarose biomaterial containing human allogeneic stromal keratocytes and cornea epithelial cells, mimicking the human native anterior cornea in terms of optical, mechanical, and biological behavior. This product is manufactured as a clinical-grade tissue engineering product, fulfilling European requirements and regulations. The clinical translation process included several phases: an initial in vitro and in vivo preclinical research plan, including preclinical advice from the Spanish Medicines Agency followed by additional preclinical development, the adaptation of the biofabrication protocols to a good manufacturing practice manufacturing process, including all quality controls required, and the design of an advanced therapy clinical trial. The experimental development and successful translation of advanced therapy medicinal products for clinical application has to overcome many obstacles, especially when undertaken by academia or SMEs. We expect that our experience and research strategy may help future researchers to efficiently transfer their preclinical results into the clinical settings.

Construction of a complete rabbit cornea substitute using a fibrin-agarose scaffold.

PURPOSE: To construct a full-thickness biological substitute of the rabbit cornea by tissue engineering. METHODS: Ten rabbit corneas were surgically excised, and the three main cell types of the cornea (epithelial, stromal, and endothelial cells) were cultured. Genetic profiling of the cultured cells was performed by RT-PCR for the genes COL8 and KRT12. To develop an organotypic rabbit cornea equivalent, we used a sequential culture technique on porous culture inserts. First, endothelial cells were seeded on the base of the inserts. Then, a stroma substitute made of cultured keratocytes entrapped in a gel of human fibrin and 0.1% agarose was developed. Finally, cultured corneal epithelial cells were grown on the surface of the scaffold. Stratification of the epithelial cell layer was promoted by using an air-liquid culture technique. Corneal substitutes were analyzed by light and electron microscopy. RESULTS: All three types of corneal cells were efficiently cultured in the laboratory, expanded, and used to construct a full-thickness cornea substitute. Gene expression analyses confirmed that cultured endothelial cells expressed the COL8 gene, whereas epithelial cells expressed KRT12. Microscopic evaluation of the cornea substitutes demonstrated that epithelial cells tended to form a normal stratified layer and that stromal keratocytes proliferated rapidly in the stromal substitute. The endothelial monolayer exhibited a pattern similar to a normal corneal endothelium. CONCLUSIONS: These findings suggest that development of a full-thickness rabbit cornea model is possible in the laboratory and may open new avenues for research.