Corneal epithelial stem cells residing within the annular limbal crypts regulate adult tissue homeostasis. Autologous limbal grafts and tissue engineered corneal epithelial cell sheets have been widely used in the treatment of various ocular surface defects. In case of bilateral limbal defects, pluripotent stem cell (PSC) derived corneal epithelial cells are now being explored as an alternative to allogeneic limbal grafts. We report here an efficient method to generate complex three dimensional corneal organoids from human PSCs. The eye field primordial (EFP) clusters that emerged from differentiating PSCs developed into whole eye ball-like, self-organized, three dimensional, miniature structures consisting of retinal primordia (RP), corneal primordia (CP), primitive eye lid-like outer covering and ciliary margin zone-like adnexal tissues in a step-wise maturation process within 15 weeks. These minicorneal organoids recapitulate the early developmental events in vitro and displayed similar anatomical features and marker expression profiles as that of adult corneal tissues and offers an alternative tissue source for regenerating different layers of the cornea and eliminates the need for complicated cell enrichment procedures.

Region specific brain organoids are brain organoids derived by patterning protocols using extrinsic signals as opposed to cerebral organoids obtained by self-patterning. The main focus of this review is to discuss various region-specific brain organoids developed so far and their application in modeling neurodevelopmental disease. We first discuss the principles of neural axis formation by series of growth factors, such as SHH, WNT, BMP signalings, that are critical to generate various region-specific brain organoids. Then we discuss various neurodevelopmental disorders modeled so far with these region-specific brain organoids, and findings made on mechanism and treatment options for neurodevelopmental disorders (NDD).

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Purpose: The sub-retinal injections are not very commonly performed procedures in vitreoretina, but form a crucial step in any cell replacement therapy for retinal diseases. The purpose of this study is to describe the learning curve of a trained vitreo-retinal surgeon in sub-retinal injections in a rat model and its implications in future clinical trials. Methods: This is an in-vivo retrospective animal study using Wistar rats. All ARVO guidelines regarding animal handling were followed. After anesthetization, aspectic preparation and dilating the pupils with 1% tropicamide eye drops, subretinal injection of 10 μl saline was done via a limbal entry. Data recorded included time taken for the procedure, success of injection, associated complications, post-operative infections and complications. The rats were followed up for 1 month post procedure. A trend analysis was done for the above factors to look for improvement in ease of procedure, reduction in procedure time and reduction in complications for the clinician using a novel objective scale. Results: About 20 eyes were studied. Mean weight of the rats was 188 ± 12.82 gram. Mean time taken for the procedure was 14.1 ± 5.07 minutes. There was a significant inverse co-relation between the serial number of the eye and time taken for the procedure (r = −0.89, P < 0.0001). Comparative complications noted between the first ten and the last ten eyes were: conjunctival tear 30% versus 10% ( P = 0.27), lens touch 50% versus 10% ( P = 0.05), subretinal hemorrhage 40% versus 0% ( P = 0.13), vitreous loss 30% versus 0% ( P = 0.06). The successful subretinal injection without intraocular complications was achieved in 40% versus 90% ( P = 0.02). There was a significant co-relation between the serial number of the eye and ease of the procedure (r = 0.87, P < 0.0001). Post operatively none of the eyes had any infection. Six eyes (12%) developed cataract and 3 eyes (6%) had non-resolving retinal detachment at the last examination visit. Conclusion: Subretinal injections in rats have a definite learning curve even for a trained vitreoretinal surgeon. This should be accounted for and resources allocated accordingly to achieve good technical comfort and negate confounding by the surgeon factor in the results of future clinical trials