Isolation, Culture, and Quality Assessment of Clinical-Grade Corneal Stromal Stem Cells.

The challenge of treating corneal scarring through keratoplasties lies in the limited availability of donor tissue. Various studies have shown the therapeutic use of cultivated corneal stromal stem cells (CSSCs) to mitigate tissue inflammation and suppress fibrosis and scar tissue formation in preclinical corneal wound models. To develop CSSC therapy for clinical trials on patients with corneal scarring, it is necessary to generate clinical-grade CSSCs in compliant to Good Manufacturing Practice (GMP) regulations. This chapter elucidates human CSSC isolation, culture, and cryopreservation under GMP-compliant conditions. It underscores quality assessment encompassing morphological traits, expression of stemness markers, anti-inflammatory activity, and keratocyte differentiation potency.

Focal Adhesion Maturation Responsible for Behavioral Changes in Human Corneal Stromal Fibroblasts on Fibrillar Substrates.

The functioning of the human cornea heavily relies on the maintenance of its extracellular matrix (ECM) mechanical properties. Within this context, corneal stromal fibroblasts (CSFs) are essential, as they are responsible for remodeling the corneal ECM. In this study, we used a decellularized human amniotic membrane (dHAM) and a custom fibrillar collagen film (FCF) to explore the effects of fibrillar materials on human CSFs. Our findings indicate that substrates like FCF can enhance the early development of focal adhesions (FAs), leading to the activation and propagation of mechanotransduction signals. This is primarily achieved through FAK autophosphorylation and YAP1 nuclear translocation pathways. Remarkably, inhibiting FAK autophosphorylation negated the observed changes. Proteome analysis further confirmed the central role of FAs in mechanotransduction propagation in CSFs cultured on FCF. This analysis also highlighted complex signaling pathways, including chromatin epigenetic modifications, in response to fibrillar substrates. Overall, our research highlights the potential pathways through which CSFs undergo behavioral changes when exposed to fibrillar substrates, identifying FAs as essential mechanotransducers.

Bioprinting of anisotropic functional corneal stroma using mechanically robust multi-material bioink based on decellularized cornea matrix.

Corneal scarring is a common cause of blindness, affecting millions globally each year. A huge gap between the demand and supply of donor tissue currently limits corneal transplantation, the only definitive therapy for patients with corneal scarring. To overcome this challenge, researchers have harnessed the efficacy of 3D bioprinting to fabricate artificial corneal stromal constructs. With all the different bioinks available, the decellularized corneal matrix-based bioprinted construct can fulfill the required biological functionality but is limited by the lack of mechanical stiffness. Additionally, from a biophysical standpoint, it is necessary for an ideal corneal substitute to mimic the anisotropy of the cornea from the central optic zone to the surrounding periphery. In this study, we enhanced the mechanical robustness of decellularized cornea matrix (DCM) hydrogel by blending it with another natural polymer, sonicated silk fibroin solution in a defined ratio. Although hybrid hydrogel has an increased complex modulus than DCM hydrogel, it has a lower in vitro degradation rate and increased opaqueness due to the presence of crystalline beta-sheet conformation within the hydrogel. Therefore, we used this multi-material bioink-based approach to fabricate a corneal stromal equivalent where the outer peripheral corneal rim was printed with a mechanically robust polymeric blend of DCM and sonicated silk fibroin and the central optic zone was printed with only DCM. The bioprinted corneal stroma thus maintained its structural integrity and did not break when lifted with forceps. The two different bioinks were encapsulated with human limbus-derived mesenchymal stem cells (hLMSC) individually and 3D bioprinted in different patterns (concentric and parallel) to attain a native-like structure in terms of architecture and transparency. Thus, the bilayer cornea constructs maintained high cell viability and expressed keratocyte core proteins indicating optimal functionality. This approach helped to gain insight into bioprinting corneas with heterogeneous mechanical property without disturbing the structural clarity of the central optic zone.

Alternative cryoprotective agent for corneal stroma-derived mesenchymal stromal cells for clinical applications.

Cryopreservation of human corneal stroma-derived mesenchymal stromal cells (hCS-MSCs) with dimethylsulfoxide (DMSO) as a cryoprotective agent (CPA) has not been previously compared to that with glycerol under standard conditions. The hCS-MSCs were hereby cryopreserved with both compounds using a freezing rate of 1 °C/minute. The CPAs were tested by different concentrations in complete Minimum Essential Medium (MEM) approved for good manufacturing practice, and a medium frequently used in cell laboratory culturing-Dulbecco's modified eagle serum. The hCS-MSCs were isolated from cadaveric human corneas obtained from the Norwegian Eye Bank, and immunophenotypically characterized by flow cytometry before and after cryopreservation. The survival rate, the cellular adhesion, proliferation and cell surface coverage after cryopreservation of hCS-MSCs has been studied. The hCS-MSCs were immunofluorescent stained and examined for their morphology microscopically. The results showed that cryopreservation of hCS-MSCs in MEM with 10% glycerol gives a higher proliferation rate compared to other cryopreserving media tested. Based on the results, hCS-MSCs can safely be cryopreserved using glycerol instead of the traditional use of DMSO.

Dynamic changes of endothelial and stromal cilia are required for the maintenance of corneal homeostasis.

Primary cilia are distributed extensively within the corneal epithelium and endothelium. However, the presence of cilia in the corneal stroma and the dynamic changes and roles of endothelial and stromal cilia in corneal homeostasis remain largely unknown. Here, we present compelling evidence for the presence of primary cilia in the corneal stroma, both in vivo and in vitro. We also demonstrate dynamic changes of both endothelial and stromal cilia during corneal development. In addition, our data show that cryoinjury triggers dramatic cilium formation in the corneal endothelium and stroma. Furthermore, depletion of cilia in mutant mice lacking intraflagellar transport protein 88 compromises the corneal endothelial capacity to establish the effective tissue barrier, leading to an upregulation of α-smooth muscle actin within the corneal stroma in response to cryoinjury. These observations underscore the essential involvement of corneal endothelial and stromal cilia in maintaining corneal homeostasis and provide an innovative strategy for the treatment of corneal injuries and diseases.

ROCK 1 and 2 affect the spatial architecture of 3D spheroids derived from human corneal stromal fibroblasts in different manners.

The objective of the current study was to examine the roles of ROCK1 and 2 on the spatial architecture of human corneal stroma. We examined the effects of a pan-ROCK inhibitor (pan-ROCK-i), ripasudil, and a ROCK2 inhibitor (ROCK2-i), KD025 on the expression of genes that encode for ECM proteins including collagen (COL) 1, 4, 6, and fibronectin (FN), their regulators, a tissue inhibitor of metalloproteinase (TIMP) 1-4, matrix metalloproteinase (MMP) 2, 9 and 14, and ER stress-related factors of two- and three-dimensional (2D and 3D) cultures of human corneal stroma fibroblasts (HCSFs), and the physical properties of 3D HCSF spheroids. A gene expression analysis using ROCK-is indicated that KD025 (ROCK2 selective ROCK inhibitor) induced more significant changes than Rip (ripasudil, pan-ROCK inhibitor), suggesting that ROCK2 might be more extensively involved in the metabolism of ECM proteins and cell architectures of the 2D cultured HCSFs than ROCK1. In terms of the physical properties, size and stiffness of the 3D HCSFs spheroids, Rip caused a significant enlargement and this enhancement was concentration-dependent while KD025 also exerted a similar but less pronounced effect. In contrast, Rip and KD025 modulated physical stiffness differently, in that Rip caused a substantial decrease and KD025 caused an increase. Such diverse effects between Rip and KD025 were also observed for the gene expressions of ECM proteins, their regulators, and ER-stress related factors. The findings presented herein suggest that the ROCK1 and 2 influence the spatial architecture of 3D HCFS spheroids in different manners.

Isolation and Propagation of Human Corneal Stromal Keratocytes for Tissue Engineering and Cell Therapy.

The human corneal stroma contains corneal stromal keratocytes (CSKs) that synthesize and deposit collagens and keratan sulfate proteoglycans into the stromal matrix to maintain the corneal structural integrity and transparency. In adult corneas, CSKs are quiescent and arrested in the G0 phase of the cell cycle. Following injury, some CSKs undergo apoptosis, whereas the surviving cells are activated to become stromal fibroblasts (SFs) and myofibroblasts (MyoFBs), as a natural mechanism of wound healing. The SFs and MyoFBs secrete abnormal extracellular matrix proteins, leading to corneal fibrosis and scar formation (corneal opacification). The issue is compounded by the fact that CSK transformation into SFs or MyoFBs is irreversible in vivo, which leads to chronic opacification. In this scenario, corneal transplantation is the only recourse. The application of cell therapy by replenishing CSKs, propagated in vitro, in the injured corneas has been demonstrated to be efficacious in resolving early-onset corneal opacification. However, expanding CSKs is challenging and has been the limiting factor for the application in corneal tissue engineering and cell therapy. The supplementation of serum in the culture medium promotes cell division but inevitably converts the CSKs into SFs. Similar to the in vivo conditions, the transformation is irreversible, even when the SF culture is switched to a serum-free medium. In the current article, we present a detailed protocol on the isolation and propagation of bona fide human CSKs and the morphological and genotypic differences from SFs.

Different mRNA expression patterns in keratoglobus and pellucid marginal degeneration keratocytes.

PURPOSE: Alike keratoconus (KC), keratoglobus (KG) and pellucid marginal degeneration (PMD) belong to ectatic corneal diseases. While there are numerous studies on keratoconus pathophysiology, there is no exact knowledge on genetic and pathophysiological background of KG and PMD, so far. It is not yet clarified, whether KG and PMD are independent clinical entities or represent different stages of the same disease. Our purpose was to investigate key parameters concerning collagen synthesis, intracellular LOX expression and inflammation in corneal stromal cells of KG and PMD subjects, in vitro. METHODS: Normal human keratocytes of corneas from the LIONS Cornea Bank Saar-Lor-Lux, Trier/Westpfalz and human keratocytes of KG and PMD patients were isolated and cultured as keratocytes. To examine Collagen I and V (Col I, Col V), heat shock protein 47 (Hsp47), Lysyl Oxidase (LOX), nuclear factor kappa B (NF-κB) mRNA and protein expression in all cell types, quantitative PCR and Western blot analysis has been performed. RESULTS: Col5A1 mRNA expression was significantly lower in KG and PMD keratocytes and LOX mRNA expression was significantly higher in KG-keratocytes, compared to controls. Col1A1, Hsp47 and NF-κB mRNA expression and the analyzed protein expressions did not differ from controls, in KG or PMD. CONCLUSIONS: Col5A1 mRNA expression is decreased in KG and PMD and LOX mRNA expression is increased in KG. Therefore, the pathophysiology of KG and PMD differs from KC and these seem to be from KC independent entities. The explanation of the peripheral corneal thinning in KG and PMD must be investigated in further studies.

Membranes Prepared from Recombinant RGD-Silk Fibroin as Substrates for Human Corneal Cells.

A recombinant formulation of silk fibroin containing the arginine-glycine-aspartic acid (RGD) cell-binding motif (RGD-fibroin) offers potential advantages for the cultivation of corneal cells. Thus, we investigated the growth of corneal stromal cells and epithelial cells on surfaces created from RGD-fibroin, in comparison to the naturally occurring Bombyx mori silk fibroin. The attachment of cells was compared in the presence or absence of serum over a 90 min period and analyzed by quantification of dsDNA content. Stratification of epithelial cells on freestanding membranes was examined by confocal fluorescence microscopy and optimized through use of low molecular weight poly(ethylene glycol) (PEG; 300 Da) as a porogen, the enzyme horseradish peroxidase (HRP) as a crosslinking agent, and stromal cells grown on the opposing membrane surface. The RGD-fibroin reduced the tendency of stromal cell cultures to form clumps and encouraged the stratification of epithelial cells. PEG used in conjunction with HRP supported the fabrication of more permeable freestanding RGD-fibroin membranes, that provide an effective scaffold for stromal-epithelial co-cultures. Our studies encourage the use of RGD-fibroin for corneal cell culture. Further studies are required to confirm if the benefits of this formulation are due to changes in the expression of integrins, components of the extracellular matrix, or other events at the transcriptional level.

Morphofunctional Properties of Corneal Stromal Cells.

Human corneal stromal cells were isolated by enzymatic digestion from a new source, lenticules obtained during laser vision correction by the ReLEx SMILe method. The resulting culture was mainly presented by fibroblast-like cells with a phenotype CD90-/CD73+/CD105+/keratocan-/lumican-/ALDH1A1+ that differentiate into keratocytes in a specialized medium. The concentration of fetal calf serum-derived growth factors affects the rate of proliferation, production of erythropoietin and brain neurotrophic factor by corneal fibroblasts, and to a lesser extent, their migration activity and production of extracellular matrix components. Thus, the high functional potential of fibroblast-like cells isolated from stromal lenticles can be used to develop cell technologies in ophthalmology.

Human platelet lysate as a replacement for fetal bovine serum in human corneal stromal keratocyte and fibroblast culture.

The isolation and propagation of primary human corneal stromal keratocytes (CSK) are crucial for cellular research and corneal tissue engineering. However, this delicate cell type easily transforms into stromal fibroblasts (SF) and scar inducing myofibroblasts (Myo-SF). Current protocols mainly rely on xenogeneic fetal bovine serum (FBS). Human platelet lysate (hPL) could be a viable, potentially autologous, alternative. We found high cell survival with both supplements in CSK and SF. Cell numbers and Ki67+ ratios increased with higher fractions of hPL and FBS in CSK and SF. We detected a loss in CSK marker expression (Col8A2, ALDH3A1 and LUM) with increasing fractions of FBS and hPL in CSK and SF. The expression of the Myo-SF marker SMA increased with higher amounts of FBS but decreased with incremental hPL substitution in both cell types, implying an antifibrotic effect of hPL. Immunohistochemistry confirmed the RT-PCR findings. bFGF and HGF were only found in hPL and could be responsible for suppressing the Myo-SF conversion. Considering all findings, we propose 0.5% hPL as a suitable substitution in CSK culture, as this xeno-free component efficiently preserved CSK characteristics, with non-inferiority in terms of cell viability, cell number and proliferation in comparison to the established 0.5% FBS protocol.

Cellular Contractility Profiles of Human Diabetic Corneal Stromal Cells.

Diabetic keratopathy is a corneal complication of diabetes mellitus (DM). Patients with diabetic keratopathy are prone to developing corneal haze, scarring, recurrent erosions, and significant wound healing defects/delays. The purpose of this study was to determine the contractility profiles in the diabetic human corneal stromal cells and characterize their molecular signatures. Primary human corneal fibroblasts from healthy, Type 1 DM (T1DM), and Type 2 DM (T2DM) donors were cultured using an established 3D collagen gel model. We tracked, measured, and quantified the contractile footprint over 9 days and quantified the modulation of specific corneal/diabetes markers in the conditional media and cell lysates using western blot analysis. Human corneal fibroblasts (HCFs) exhibited delayed and decreased contractility compared to that from T1DMs and T2DMs. Compared to HCFs, T2DMs demonstrated an initial downregulation of collagen I (day 3), followed by a significant upregulation by day 9. Collagen V was significantly upregulated in both T1DMs and T2DMs based on basal secretion, when compared to HCFs. Cell lysates were upregulated in the myofibroblast-associated marker, α-smooth muscle actin, in T2DMs on day 9, corresponding to the significant increase in contractility rate observed at the same time point. Furthermore, our data demonstrated a significant upregulation in IGF-1 expression in T2DMs, when compared to HCFs and T1DMs, at day 9. T1DMs demonstrated significant downregulation of IGF-1 expression, when compared to HCFs. Overall, both T1DMs and T2DMs exhibited increased contractility associated with fibrotic phenotypes. These findings, and future studies, may contribute to better understanding of the pathobiology of diabetic keratopathy and ultimately the development of new therapeutic approaches.

Effect of prolactin on normal and keratoconus human corneal stromal fibroblasts in vitro.

PURPOSE: To examine the effect of prolactin (PRL) on human corneal stromal fibroblasts (CSFs), derived from healthy individuals and from keratoconus (KC) patients, in vitro, specifically assessing physiological and elevated PRL concentrations as apparent during pregnancy. METHODS: Eye bank corneas of 3 female and 3 male healthy individuals as well as the corneal buttons of 3 female and 3 male KC patients were utilized for this study. The endothelium of the cornea was removed with sterile surgical scalpels, the probes were washed repeatedly with Dulbecco's PBS and corneoscleral rims were trimmed off. Subsequently the corneal stroma was digested with collagenase type I and the harvested CSFs were cultured. We then examined (1) cell proliferation, (2) cell viability and (3) cytokine release of CSFs upon exposure to prolactin in vitro. RESULTS: With respect to viability and proliferation our experiments did not show significant differences between CSFs exposed to different PRL concentrations. Our data show a significantly lower IL-8 concentration in normal CSFs exposed to 10ng/ml PRL compared to 0ng/ml and 1000ng/ml at 5 hours post exposition. Moreover, we can report significantly lower secretion of IL-8, IL-6, HGF, VEGF and FGFb in KC CSFs compared to normal CSFs, independent of PRL exposure, as determined by cytokine ELISA. CONCLUSION: Our data in part points towards corneal cytokine secretion as a possible link between altered stromal PRL concentrations and KC progression. However, in our small dataset a significant influence of PRL concentration on cytokine secretion can only be described for IL-8 in normal CSFs. Further our results contribute to existing reports on the importance of cytokines in KC development, with an emphasis on significantly lower cytokine secretion in KC CSFs compared to normal controls.

Penetrating Keratoplasty in Dogs using Acellular Porcine Corneal Stroma (BioCorneaVet™): A prospective pilot study of five cases.

OBJECTIVE: This prospective pilot study was conducted to evaluate the outcome of a commercially available corneal stroma substitute, Acellular Porcine Corneal Stroma (APCS), in dogs undergoing penetrating keratoplasty (PK) to restore corneal integrity after having deep ulcers. METHOD: Five dogs (1 eye in each dog) underwent a PK using APCS (BioCorneaVet™) as a graft. The surgical procedure and peri- and postoperative treatment were standardized. All cases required a minimum 6 months follow-up. Ease of keratoprosthetic tissue handling, graft survival, anterior chamber stability, corneal opacity, neovascularization and re-epithelialization were noted. Presence of secondary uveitis was investigated. RESULTS: BioCorneaVet™ was easy to handle and, at all-time points, provided adequate tectonic support. Graft survival was achieved in all 5 cases. A minimum follow-up period of 10 months was available for the five eyes (22 months maximum). Degree and area of corneal graft opacity progressively improved resulting in minimal to moderate loss of transparency in all cases but one, where it was severe. Neovascularization degree was most severe 0.5-1 month after surgery and fully resolved 4-6 months post-surgery. Re-epithelialization was complete in the majority of grafts in 1 month. Secondary uveitis was not detected at any time in 4 of 5 dogs. CONCLUSION: BioCorneaVet™ seems to be an effective graft for PK in the dog. In this case series, APCS was convenient to handle during surgery and provided excellent tectonic support. The material showed good tissue biocompatibility and resulted in the majority of cases in minimal to moderate graft opacity, that ameliorates with time.

A decellularized human corneal scaffold for anterior corneal surface reconstruction.

Allogenic transplants of the cornea are prone to rejection, especially in repetitive transplantation and in scarred or highly vascularized recipient sites. Patients with these ailments would particularly benefit from the possibility to use non-immunogenic decellularized tissue scaffolds for transplantation, which may be repopulated by host cells in situ or in vitro. So, the aim of this study was to develop a fast and efficient decellularization method for creating a human corneal extracellular matrix scaffold suitable for repopulation with human cells from the corneal limbus. To decellularize human donor corneas, sodium deoxycholate, deoxyribonuclease I, and dextran were assessed to remove cells and nuclei and to control tissue swelling, respectively. We evaluated the decellularization effects on the ultrastructure, optical, mechanical, and biological properties of the human cornea. Scaffold recellularization was studied using primary human limbal epithelial cells, stromal cells, and melanocytes in vitro and a lamellar transplantation approach ex vivo. Our data strongly suggest that this approach allowed the effective removal of cellular and nuclear material in a very short period of time while preserving extracellular matrix proteins, glycosaminoglycans, tissue structure, and optical transmission properties. In vitro recellularization demonstrated good biocompatibility of the decellularized human cornea and ex vivo transplantation revealed complete epithelialization and stromal repopulation from the host tissue. Thus, the generated decellularized human corneal scaffold could be a promising biological material for anterior corneal reconstruction in the treatment of corneal defects.

L-carnitine suppresses transient receptor potential vanilloid type 1 activity and myofibroblast transdifferentiation in human corneal keratocytes.

Corneal stromal wound healing is a well-balanced process promoted by overlapping phases including keratocyte proliferation, inflammatory-related events, and tissue remodeling. L-carnitine as a natural antioxidant has shown potential to reduce stromal fibrosis, yet the underlying pathway is still unknown. Since transient receptor potential vanilloid 1 (TRPV1) is a potential drug target for improving the outcome of inflammatory/fibrogenic wound healing, we investigated if L-carnitine can mediate inhibition of the fibrotic response through suppression of TRPV1 activation in human corneal keratocytes (HCK). We determined TRPV1-induced intracellular calcium transients using fluorescence calcium imaging, channel currents by planar patch-clamping, and cell migration by scratch assay for wound healing. The potential L-carnitine effect on TRPV1-induced myofibroblast transdifferentiation was evaluated by immunocytochemical detection of alpha smooth muscle actin. RT-PCR analysis confirmed TRPV1 mRNA expression in HCK. L-carnitine (1 mmol/l) inhibited either capsaicin (CAP) (10 µmol/l), hypertonic stress (450 mOsmol/l), or thermal increase (>43 °C) induced Ca2+ transients and corresponding increases in TRPV1-induced inward and outward whole-cell currents. This was accompanied by suppression of injury-induced increases in myofibroblast transdifferentiation and cell migration. In conclusion, L-carnitine contributes to inhibit stromal scarring through suppressing an injury-induced intrinsic TRPV1 activity that is linked with induction of myofibroblast transdifferentiation in HCK cells.

In Vivo Effect of RSH-12, a Novel Selective MMP-9 Inhibitor Peptide, in the Treatment of Experimentally Induced Dry Eye Model.

PURPOSE: To investigate the efficacy of RSH-12, a novel selective matrix metalloproteinase 9 (MMP-9) inhibitor peptide in rabbit models of dry eye syndrome (DES). METHODS: In vitro toxicity of RSH-12 on cultured human corneal fibroblasts was investigated with MTT. Ocular toxicity of RSH-12 was investigated by clinical examinations, histology, and TUNEL assay. Experimental model of dry eye was induced by 1.0% atropine sulfate administration followed after 15 min by treatment with PBS, RSH-12, and Restasis in individual groups, three times a day for 7 days. In addition to performing Schirmer's test for evaluating basic tear secretion and tear break-up time test for investigating tear stability, the occurrence of superficial punctate keratopathy was also investigated in the study groups. RESULTS: MTT assay demonstrated that RSH-12 was not toxic to human corneal fibroblasts in different concentrations. During the administration of atropine, TBUT values and tear volume were decreased in vehicle group while these indices improved significantly in groups treated with RSH-12 in a promising manner. RSH-12 increased the mean value of tear volume from 4.85 to 10.75 mm (P = .0001) and mean of TBUT values from 20.3 s to 34.5 s (P = .0001) compared with the vehicle. In contrast to the presence of severe superficial punctate keratopathy in the controls, no significant dotted staining was observed in the RSH-12 and Restasis groups. CONCLUSIONS: These outcomes propose that RSH-12 has a therapeutic effect in the rabbit model of dry eye and might be a potential treatment for severe DES.

Effect of porcine corneal stromal extract on keratocytes from SMILE-derived lenticules.

Propagating large amounts of human corneal stromal cells (hCSCs) in vitro while maintaining the physiological quality of their phenotypes is necessary for their application in cell therapy. Here, a novel medium to propagate hCSCs obtained from small incision lenticule extraction (SMILE)-derived lenticules was investigated and the feasibility of intrastromal injection of these hCSCs was assessed. Primary hCSCs were cultured in porcine corneal stroma extract (pCSE) with RIFA medium including ROCK inhibitor Y27632, insulin-transferrin-selenium, fibroblast growth factor 2, L-ascorbate 2-phosphate and 0.5% FBS (RIFA medium + pCSE). Protein profiling of the pCSE was identified using nanoscale liquid chromatography coupled to tandem mass spectrometry (nano LC-MS/MS). After subculturing in RIFA medium + pCSE or 10% FBS normal medium (NM), hCSCs at P4 were transplanted into mouse corneal stroma. Compared with NM, ALDH3A1, keratocan and lumican were significantly more expressed in the RIFA medium + pCSE. ALDH3A1 was also more expressed in the RIFA medium + pCSE than in the RIFA medium. Fibronectin and α-SMA were less expressed in the RIFA medium + pCSE than in the NM. Using Metascape analysis, the pCSE with its anti-fibrosis, pro-proliferation and anti-apoptosis activities, was beneficial for hCSC cultivation. The intrastromally implanted hCSCs in the RIFA medium + pCSE had positive CD34 expression but negative CD45 expression 35 days after injection. We provide a valuable new medium that is advantageous for the proliferation of hCSCs with the properties of physiological keratocytes. Intrastromal injection of hCSCs in RIFA medium + pCSE has the potential for clinical cell therapy.

Effect of isolation method on human corneal stromal cell behaviour.

Current research on healthy corneal stromal cells will typically use primary cells as they are the most representative of in vivo behaviour. Primary cells are normally isolated from the limbus of discarded donor peripheral corneal tissue left over from transplantation (due to its relative abundance). Therefore, the central part of the cornea is less used in research as this tissue is usually used for transplantation. In some cases, although rare, the whole cornea, can become available for research. It is important to keep in mind that these corneas often have longer storage time, but the use of the central tissue for research is even more interesting, as knowing what cells are being transplanted into recipients would be highly relevant. To this end, stromal cells were extracted from both the limbus and central button of healthy corneas donated for research. This allowed for important comparison between central and limbal cells in culture. Of interest here was the extraction method of stromal cells from the donor tissue. The two most common methods of extraction are enzyme digestion and explant migration. However, no work has been done to understand how each method relatively affects the extracted cells. The extraction method and location from which stromal cells are harvested seems to have a significant effect on the cell adherence, survival, and gene expression of the stromal cells in culture. Enzyme digested cells showed that limbal and central cells had different gene expressions prior to culture, with gene such as ALDH3A1 being much more expressed in limbal cells. Enzyme digesting the limbal ring seems to yield the hardiest populations of stromal cells, a desirable trait in the culture of primary cells.

Role of inhibitor of differentiation 3 gene in cellular differentiation of human corneal stromal fibroblasts.

Purpose: Inhibitor of differentiation (Id) proteins are helix-loop-helix (HLH) transcriptional repressors that modulate a range of developmental and cellular processes, including cell differentiation and cell cycle mobilization. The inhibitor of differentiation 3 (Id3) gene, a member of the Id gene family, governs the expression and progression of transforming growth factor beta (TGFß)-mediated cell differentiation. In the face of mechanical, chemical, or surgical corneal insults, corneal keratocytes differentiate into myofibroblasts for wound repair. Excessive development or persistence or both of myofibroblasts after wound repair results in corneal haze that compromises corneal clarity and visual function. The objective of this study was to investigate whether Id3 overexpression in human corneal stromal fibroblasts governs TGFß-driven cellular differentiation and inhibits keratocyte to myofibroblast transformation. Methods: Primary human corneal stromal fibroblast (h-CSF) cultures were generated from donor human corneas. Human corneal myofibroblasts (h-CMFs) were produced by growing h-CSF in the presence of TGFß1 under serum-free conditions. The Id3 gene was cloned into a mammalian expression vector (pcDNA3 mCherry LIC cloning vector), and the nucleotide sequence of the vector constructs was confirmed with sequencing as well as through restriction enzyme analysis. The Id3 mammalian overexpression vector was introduced into h-CSFs using a lipofectamine transfection kit. The expression of Id3 in selected clones was characterized with quantitative real-time PCR (qRT-PCR), immunocytochemistry, and western blotting. Phase contrast microscopy and trypan blue exclusion assays were used to evaluate the effects of the transfer of the Id3 gene on the hCSF phenotype and viability, respectively. To analyze the inhibitory effects of the Id3 gene transfer on TGFß-induced formation of h-CMFs, expression of the mRNA and protein of the myofibroblast marker alpha smooth muscle actin (α-SMA) was examined with qRT-PCR, western blotting, and immunocytochemistry. Student t test, analysis of variance (ANOVA), and Bonferroni adjustment for repeated measures were used for statistical analysis. Results: The results indicate that Id3 overexpression does not alter the cellular phenotype or viability of h-CSFs. Overexpression of the Id3 gene in h-CSF cells grown in the presence of TGFß1 under serum-free conditions showed a statistically significant decrease (76.3±4.3%) in α-SMA expression (p<0.01) compared to the naked-vector transfected or non-transfected h-CSF cells. Id3-transfected, naked-vector transfected, and non-transfected h-CSF cells grown in the absence of TGFß1 showed the expected low expression of α-SMA (0-5%). Furthermore, Id3 overexpression statistically significantly decreased TGFß-induced mRNA levels of profibrogenic genes such as fibronectin, collagen type I, and collagen type IV (1.80±0.26-, 1.70±0.35- and 1.70±0.36-fold, respectively; p<0.05) that a play role in stromal matrix modulation and corneal wound healing. Results of the protein analysis with western blotting indicated that Id3 overexpression in h-CSF cells effectively slows TGFß-driven differentiation and formation of h-CMFs. Results for subsequent overexpression studies showed that this process occurs through the regulation of E2A, a TATA box protein. Conclusions: Id3 regulates TGFß-driven differentiation of h-CSFs and formation of h-CMFs in vitro. Targeted Id3 gene delivery has potential to treat corneal fibrosis and reestablish corneal clarity in vivo.