Transplantation of tissue-engineered human corneal epithelium in limbal stem cell deficiency rabbit models

Limbal epithelial stem cell sheets from young donors have better regenerative potential

To investigate the stemness of limbal epithelial stem cell sheets in relation to the donor’s age. Human limbal explants from cadaveric donors were set on human amniotic membrane scaffolds with the xeno-free medium. We evaluated limbal epithelial sheet size, expression of stem/progenitor cell markers, and colony formation efficiency from donors of different age groups (age ≤ 45, age 45–65, and age > 65). Expression of the proliferation marker Ki67, stem/progenitor cell markers p63α and ABCG2, cornea specific marker PANCK, and differentiation marker CK12 were evaluated. To determine the effect of donor age on the storage period of limbal explant sheets, the limbal explant outgrowth sheets were stored in 4 °C for 2 days and analyzed for JC-1, p63α, and PANCK with FACS on each day. From days 6 to 12, the outgrowth area of the limbal epithelial stem cell sheet was significantly larger in the age ≤ 45 groups (296 ± 54.7 mm², day 9) compared to the other two age groups [age 45–65 group (278 ± 62.6 mm²), age > 65 group (257 ± 44.0 mm²), day 9] (p < 0.01). In terms of stemness, outgrowth cells from aged donors (age > 65) showed lower expression of stem/progenitor cell markers p63α and ABCG2 and decreased CFE compared to the other two groups. There were significantly more p63α+ cells in outgrowth cells in the age ≤ 45 group (18.2 ± 3.6%) compared to the age > 65 group (14.1 ± 4.6%; p < 0.01). Limbal explant outgrowth sheet on the age ≤ 45 group (32.7 ± 7.5%) had higher percentages of cells resisting staining by JC-1 compared with sheets under the age > 65 groups (25.7 ± 7.1%, p < 0.01) (JC-1^low). Cells from the age ≤ 45 group showed a higher clonogenic capacity than those from the other two age groups (45 < Age ≤ 65 CFE ratio = 0.7 ± 0.16, p < 0.01; 65 < Age CFE ratio = 0.3 ± 0.06, p < 0.01, vs. Age ≤ 45). In the age > 65 group, positive cells of p63α on D0, 1, and 2 were significantly lower compared to those in the age ≤ 45 group on the storage period (p < 0.01, respectively). Our results imply that donors younger than 65 years of age are a better source of limbal epithelial stem cell sheet generation with high regeneration potential.

Cytotoxic effect and possible mechanisms of Tetracaine on human corneal epithelial cells in vitro

AIM

To demonstrate the cytotoxic effect and possible mechanisms of Tetracaine on human corneal epithelial (HCEP) cells in vitro.

METHODS

In vitro cultured HCEP cell were treated with Tetracaine hydrochloride at different doses for different times, and their morphology, viability, and plasma membrane permeability were detected by light microscopy, methyl thiazolyl tetrazolium (MTT) assay, and acridine orange (AO)/ethidium bromide (EB) staining, respectively. Their cell cycle progression, phosphatidylserine orientation in plasma membrane, and mitochondrial membrane potential (MTP) were assessed by flow cytometry. DNA fragmentation, ultrastructure, caspase activation, and the cytoplasmic apoptosis inducing factor (AIF) and cytochrome c (Cyt. c) along with the expression of B-cell lymphoma-2 (Bcl-2) family proteins were examined by gel electrophoresis, transmission electron microscope, enzyme linked immunosorbent assay (ELISA), and Western blot, respectively.

RESULTS

After exposed to Tetracaine at doses from 10.0 to 0.3125 g/L, the HCEP cells showed dose- and time-dependent morphological abnormality and typical cytopathic effect, viability decline, and plasma membrane permeability elevation. Tetracaine induced phosphatidylserine externalization, DNA fragmentation, G1 phase arrest, and ultrastructural abnormality and apoptotic body formation. Furthermore, Tetracaine at a dose of 0.3125 g/L also induced caspase-3, -9 and -8 activation, MTP disruption, up-regulation of the cytoplasmic amount of Cyt. c and AIF, the expressions of Bax and Bad, and down-regulation of the expressions of Bcl-2 and Bcl-xL.

CONCLUSION

Tetracaine above 0.3125 g/L (1/32 of its clinical applied dosage) has a dose- and time-dependent cytotoxicity to HCEP cells in vitro, with inducing cell apoptosis via a death receptor-mediated mitochondrion-dependent pathway.

An Ultra-thin Amniotic Membrane as Carrier in Corneal Epithelium Tissue-Engineering

Amniotic membranes (AMs) are widely used as a corneal epithelial tissue carrier in reconstruction surgery. However, the engineered tissue transparency is low due to the translucent thick underlying AM stroma. To overcome this drawback, we developed an ultra-thin AM (UAM) by using collagenase IV to strip away from the epithelial denuded AM (DAM) some of the stroma. By thinning the stroma to about 30 μm, its moist and dry forms were rendered acellular, optically clear and its collagen framework became compacted and inerratic. Engineered rabbit corneal epithelial cell (RCEC) sheets generated through expansion of limbal epithelial cells on UAM were more transparent and thicker than those expanded on DAM. Moreover, ΔNp63 and ABCG2 gene expression was greater in tissue engineered cell sheets expanded on UAM than on DAM. Furthermore, 2 weeks after surgery, the cornea grafted with UAM based cell sheets showed higher transparency and more stratified epithelium than the cornea grafted with DAM based cell sheets. Taken together, tissue engineered corneal epithelium generated on UAM has a preferable outcome because the transplanted tissue is more transparent and better resembles the phenotype of the native tissue than that obtained by using DAM for this procedure. UAM preserves compact layer of the amniotic membrane and maybe an ideal substrate for corneal epithelial tissue engineering.

Use of Mesothelial Cells and Biological Matrices for Tissue Engineering of Simple Epithelium Surrogates

Tissue-engineering technologies have progressed rapidly through last decades resulting in the manufacture of quite complex bioartificial tissues with potential use for human organ and tissue regeneration. The manufacture of avascular monolayered tissues such as simple squamous epithelia was initiated a few decades ago and is attracting increasing interest. Their relative morphostructural simplicity makes of their biomimetization a goal, which is currently accessible. The mesothelium is a simple squamous epithelium in nature and is the monolayered tissue lining the walls of large celomic cavities (peritoneal, pericardial, and pleural) and internal organs housed inside. Interestingly, mesothelial cells can be harvested in clinically relevant numbers from several anatomical sources and not less important, they also display high transdifferentiation capacities and are low immunogenic characteristics, which endow these cells with therapeutic interest. Their combination with a suitable scaffold (biocompatible, degradable, and non-immunogenic) may allow the manufacture of tailored serosal membranes biomimetics with potential spanning a wide range of therapeutic applications, principally for the regeneration of simple squamous-like epithelia such as the visceral and parietal mesothelium vascular endothelium and corneal endothelium among others. Herein, we review recent research progresses in mesothelial cells biology and their clinical sources. We make a particular emphasis on reviewing the different types of biological scaffolds suitable for the manufacture of serosal mesothelial membranes biomimetics. Finally, we also review progresses made in mesothelial cells-based therapeutic applications and propose some possible future directions.

Construction of corneal epithelium with human amniotic epithelial cells and repair of limbal deficiency in rabbit models

This study aims to evaluate the effect of a human amniotic epithelial cell (HAEC)-rabbit corneal stroma tissue-engineered cornea on ocular reconstruction in three different animal models. HAECs were isolated from human placenta, seeded onto rabbit corneal stroma. HAECs-rabbit corneal stroma tissue engineering cornea transplantation was examined in three distinct rabbit models: transplantation of cornea constructed (1) with lamellar corneal HAECs and rabbit corneal stroma, (2) with central corneal HAECs and rabbit corneal stroma, or (3) with full-thickness corneal HAECs and rabbit corneal stroma. In the tissue engineering corneal transplantation groups in all three models, the mean number of days to corneal epithelial healing was significantly shorter than that in the control group and the mean number of days to corneal neovascularization was significantly greater than in the control group. In addition, in the tissue engineering corneal transplantation groups in the central lamellar cornea model and the full-thickness corneal transplantation model neovascularization, corneal turbidity, and epithelial fluorescence were significantly less than in the control groups. HAECs can be induced to differentiate into corneal epithelial cells, which may be suitable for the reconstruction of the corneal epithelium in cases of limbal stem cell deficiency.