Limbal Stromal Tissue Specific Stem Cells and Their Differentiation Potential to Corneal Epithelial Cells

Current perspectives of limbal-derived stem cells and its application in ocular surface regeneration and limbal stem cell transplantation

Limbal stem cells are involved in replenishing and maintaining the epithelium of the cornea. Damage to the limbus due to chemical/physical injury, infections, or genetic disorders leads to limbal stem cell deficiency (LSCD) with partial or total vision loss. Presently, LSCD is treated by transplanting limbal stem cells from the healthy eye of the recipient, living-related, or cadaveric donors. This review discusses limbal-derived stem cells, the importance of extracellular matrix in stem cell niche maintenance, the historical perspective of treating LSCD, including related advantages and limitations, and our experience of limbal stem cell transplantation over the decades.

Stem Cell Niche Microenvironment: Review

The cornea comprises a pool of self-regenerating epithelial cells that are crucial to preserving clarity and visibility. Limbal epithelial stem cells (LESCs), which live in a specialized stem cell niche (SCN), are crucial for the survival of the human corneal epithelium. They live at the bottom of the limbal crypts, in a physically enclosed microenvironment with a number of neighboring niche cells. Scientists also simplified features of these diverse microenvironments for more analysis in situ by designing and recreating features of different SCNs. Recent methods for regenerating the corneal epithelium after serious trauma, including burns and allergic assaults, focus mainly on regenerating the LESCs. Mesenchymal stem cells, which can transform into self-renewing and skeletal tissues, hold immense interest for tissue engineering and innovative medicinal exploration. This review summarizes all types of LESCs, identity and location of the human epithelial stem cells (HESCs), reconstruction of LSCN and artificial stem cells for self-renewal.

Decellularized Human Stromal Lenticules Combine with Corneal Epithelial-Like Cells: A New Resource for Corneal Tissue Engineering

The lack of donor corneal tissue or the immunological rejection remains a challenge for individuals with limbal stem cell deficiency (LSCD) who are treated with keratoplasty. Numerous lenticules which were extracted by small incision lenticule extraction (SMILE) appear to be useful materials for keratoplasty. In order to reduce the incidence of allograft rejection, lenticules would be decellularized. Lenticules which were treated with liquid nitrogen and nucleases had no cellular and nuclear materials remained. Human induced pluripotent stem cells (iPSCs) can be generated from the patient who requires keratoplasty, offering an autologous alternative and eliminating the risk of graft rejection. We found that BMP-4, RA, N-2 supplement, hEGF, B27, decellularized human stromal lenticules, conditioned medium, or induction medium promoted the differentiation of human iPSCs with high purity. The results showed that human iPSCs cultured for 4 days in differentiation medium A, 14 days in condition medium, and 1 week in induction medium on decellularized human stromal lenticules developed markedly higher expression of the markers P63, CK3, and CK12 than did those in the other methods. The level of gene expression of the epithelial and pluripotency markers and analysis by scanning electron microscopy and immunohistochemistry also showed successful differentiation. After inducing differentiation in vitro, corneal epithelial-like cells were induced. In the study, we investigated the possibility of a new resource for corneal tissue engineering.

Strategies for reconstructing the limbal stem cell niche

The epithelial cell layer that covers the surface of the cornea provides a protective barrier while maintaining corneal transparency. The rapid and effective turnover of these epithelial cells depends, in part, on the limbal epithelial stem cells (LESCs) located in a specialized microenvironment known as the limbal niche. Many disorders affecting the regeneration of the corneal epithelium are related to deficiency and/or dysfunction of LESCs and the limbal niche. Current approaches for regenerating the corneal epithelium following significant injuries such as burns and inflammatory attacks are primarily aimed at repopulating the LESCs. This review summarizes and assesses the clinical feasibility and efficacy of current and emerging approaches for reconstruction of the limbal niche. In particular, the application of mesenchymal stem cells along with appropriate biological scaffolds appear to be promising strategies for long-term revitalization of the limbal niche.

Therapeutic effect of urine-derived stem cells for protamine/lipopolysaccharide-induced interstitial cystitis in a rat model

Background

Interstitial cystitis (IC) is a chronic inflammation disorder mainly within the submucosal and muscular layers of the bladder. As the cause of IC remains unknown, no effective treatments are currently available. Administration of stem cell provides a potential for treatment of IC.

Methods

This study was conducted using urine-derived stem cells (USCs) for protamine/lipopolysaccharide (PS/LPS)-induced interstitial cystitis in a rodent model. In total, 60 female Sprague–Dawley rats were randomized into three experimental groups (n = 5/group): sham controls; IC model alone; and IC animals intravenously treated with USCs (1.2 × 10⁶ suspended in 0.2 ml phosphate-buffered saline (PBS).

Results

Our data showed that the bladder micturition function was significantly improved in IC animals intravenously treated with USCs compared to those in the IC model alone group. The amount of antioxidants and antiapoptotic protein biomarkers heme oxygenase (HO)-1, NAD(P)H quinine oxidoreductase (NQO)-1, and Bcl-2 within the bladder tissues were significantly higher in IC animals intravenously treated with USCs and lower in the sham controls group as assessed by Western blot and immunofluorescent staining. In addition, the expression of autophagy-related protein LC3A was significantly higher in the IC model alone group than that in IC animals intravenously treated with USCs. Inflammatory biomarkers and apoptotic biomarkers (interleukin (IL)-6, tumor necrosis factor (TNF)α, nuclear factor (NF)-κB, caspase 3, and Bax) and the downstream inflammatory and oxidative stress biomarkers (endoplasmic reticulum stress and autophagy-related protein (GRP78, LC3, Beclin1)) in the bladder tissue revealed statistically different results between groups.

Conclusions

USCs restored the bladder function and histological construction via suppressing oxidative stress, inflammatory reaction, and apoptotic processes in a PS/LPS-induced IC rodent model, which provides potential for treatment of patients with IC.