Differentiation Induction of Human Stem Cells for Corneal Epithelial Regeneration

Abstract

Deficiency of corneal epithelium causes vision impairment or blindness in severe cases. Transplantation of corneal epithelial cells is an effective treatment but the availability of the tissue source for those cells is inadequate. Stem cells can be induced to differentiate to corneal epithelial cells and used in the treatment. Multipotent stem cells (mesenchymal stem cells) and pluripotent stem cells (embryonic stem cells and induced pluripotent stem cells) are promising cells to address the problem. Various protocols have been developed to induce differentiation of the stem cells into corneal epithelial cells. The feasibility and efficacy of both human stem cells and animal stem cells have been investigated for corneal epithelium regeneration. However, some physiological aspects of animal stem cells are different from those of human stem cells, the protocols suited for animal stem cells might not be suitable for human stem cells. Therefore, in this review, only the investigations of corneal epithelial differentiation of human stem cells are taken into account. The available protocols for inducing the differentiation of human stem cells into corneal epithelial cells are gathered and compared. Also, the pathways involving in the differentiation are provided to elucidate the relevant mechanisms.

An efficient simplified method for the generation of corneal epithelial cells from human pluripotent stem cells

“…Among the chemical inhibitors for Wnt/ β-catenin inhibition, IWP-2 and IWR-1 endo have been extensively reported in many differentiation protocols, involving neuron cells [30][31], cardiomyocytes [32], and retinal and corneal cells, where both compounds have an equivalent inhibition potency [33]. For the inhibition of TGF-β kinase/activin receptor, several compounds are commonly reported in the differentiation of the forehead and eye lineage, such as SB431542 [34], SB505124 [35], and A83-01 [33], where the inhibition potency of A83-01 is much greater than that of other TGF-β/R inhibitors [36]; thus, we selected A83-01 to be combined with IWR-1 endo and bFGF for the initiation of differentiation toward the corneal epithelium lineage. In this process, we noticed two important factors for the success of the protocol: 1.…”

“…Smad signaling has been shown to be critical in the recovery of wounds in many tissues, including the lens and retina of the eye [33]. To confirm the necessity these pathways in the maturation stage of corneal epithelial cells, we compared the expression of TGF-β and Wnt/βcatenin signaling genes in K1-CEpC-D20 at D20 versus hPCEpC.…”

Goals and Challenges of Stem Cell-Based Therapy for Corneal Blindness Due to Limbal Deficiency

“…Since the reprogramming technique was described, great efforts have been made to generate corneal and limbal epithelial cells from hiPSCs. This technology could provide an unlimited supply of limbal and corneal epithelial cells without any ethical issue for treating patients with LSCD (reviewed in [ 183 , 184 , 185 ]).…”

“…This same research group later published another reproducible and clinical compatible differentiation method using xeno-free conditions to generate limbal epithelial stem cells from hiPSCs [ 190 ]. Apart from the ones already mentioned, several other methods have been published with the aim to generate functional corneal and limbal epithelial cells from hiPSCs (reviewed in [ 183 , 184 , 185 ]). However, before translating these methodologies to clinical applications, further improvements must be made on the derivation protocols because they are extremely expensive.…”

“…However, there are no studies that compare the outcomes obtained among the different methodologies, and as a consequence, there are no standardized differentiation protocols. Therefore, efforts should be made to elaborate standard and reproducible differentiation protocols for each of the different types of stem cells [ 185 ]. There is also a need to develop cell culture techniques with chemically defined xeno-free culture media that meet the clinical grade requirements.…”