Fibroblast growth factor-1 receptor messenger RNA expression in corneal cells

Acceleration of Regeneration of the Corneal Endothelial Layer After Descemet Stripping Induced by the Engineered FGF TTHX1114 in Human Corneas in Organ Culture

PURPOSE

Descemet stripping only (DSO, descemetorhexis without endothelial keratoplasty) is increasing in clinical use but can impose long recovery times. The objective of this research was to determine whether TTHX1114, an engineered analog of FGF1, could accelerate healing in corneas after DSO.

METHODS

Corneas obtained from eye banks were placed into suspension culture and subjected to DSO with a procedure comparable with that used clinically. The healing of the stripped area and the regeneration of the corneal endothelial cell (CEC) layer were evaluated intermittently for 14 days using trypan blue staining, alizarin red staining, and immunohistochemistry.

RESULTS

Corneas subjected to DSO showed about 30% of the stripped area healed after 14 days in culture while those treated with TTHX1114 healed 81%. The healed area was similar in both normal corneas and corneas judged by the eye banks to be dystrophic. The regeneration of the endothelial layer in the stripped area was substantially more complete in TTHX1114-treated corneas, most of which demonstrated a contiguous monolayer of CECs expressing ZO-1 at the cell-cell junctions. In corneas not subject to DSO, incorporation of EdU, a marker of proliferation, was stimulated by TTHX1114 treatment.

CONCLUSIONS

The corneal organ culture model recapitulated clinical observations of DSO, only with much more rapid recovery. Within the immediate postsurgical time frame of 2 weeks, treatment with TTHX1114 stimulated near-total regeneration of the CEC layer, suggesting that TTHX1114 may be useful as an adjunct to DSO.

Proliferation of Human Corneal Endothelia in Organ Culture Stimulated by Wounding and the Engineered Human Fibroblast Growth Factor 1 Derivative TTHX1114

Purpose: Corneal endothelial dystrophies are characterized by endothelial cell loss and dysfunction. Recent evidence suggests that corneal endothelial cells (CECs) can regenerate although they do not do so under normal conditions. This work sought to test whether CECs can be stimulated to proliferate in organ culture by wounding and/or by treatment with the engineered human fibroblast growth factor 1 (FGF1) derivative TTHX1114.

Methods: Human donor corneas obtained from eye banks were maintained in organ culture in the presence or absence of TTHX1114. Wounds in the corneas were created by quartering the corneas. The CEC monolayer was identified as a regular layer by Hoechst staining of the nuclear DNA with cell outlines delineated by immunohistochemical identification of ZO-1. Nuclei and nuclei incorporating 5-ethynyl-2′-deoxyuridine (EdU) were counted using ImageJ.

Results: CECs in normal corneas in undisturbed monolayers had low, but measurable, rates of proliferation. CECs at the edge of a wound had higher rates of proliferation, probably due to the release of contact inhibition. TTHX1114 increased proliferation at wound edges. After 7 days of culture, proliferating CECs formed contiguous groups of labeled cells that did not migrate away from one another. TTHX1114-treated cells, including the EdU labeled proliferating cells, retained normal morphology, including cell/cell junction ZO-1 staining.

Conclusions: Proliferation of CECs in organ-cultured corneas is low, but can be stimulated by wounding or by the administration of TTHX1114 with the effects of each being additive. The CEC monolayer appears to have a population of progenitor cells that are susceptible to stimulation.

An Engineered Human Fibroblast Growth Factor-1 Derivative, TTHX1114, Ameliorates Short-term Corneal Nitrogen Mustard Injury in Rabbit Organ Cultures

Purpose

Organ cultures of rabbit corneas have been used to ascertain the effectiveness of a human fibroblast growth factor (FGF)-1 derivative (TTHX1114), lacking cysteine residues, to protect against and/or repair epithelial lesions following exposure to nitrogen mustard (NM).

Methods

Rabbit corneas were exposed to NM and cultured for up to 14 days, with or without drug (TTHX1114). At specified times, tissue was examined by histopathology and graded by a novel composite scale. Proliferation was measured by 5-ethynyl-2'-deoxyuridine (EdU) incorporation, and the expression of native FGF-1 and ADAM-17 after NM exposure was determined by immunofluorescence.

Results

Rabbit corneas, exposed to a single dose of NM, showed a nearly complete loss of epithelial cells by day 6 but were significantly regenerated by day 14. When treated continuously with TTHX1114 following vesicant exposure, the losses remained at day 2 levels. The loss of keratocytes in the stroma was not affected by TTHX1114. EdU incorporation over the same time course showed a steady increase in tissue that had not been treated with TTHX1114, while corneas that were treated with the drug showed a higher percent incorporation initially, which then decreased, indicating the strong proliferative response to TTHX1114. ADAM-17 was not significantly altered by TTHX1114 treatment. Corneal epithelial FGF-1 disappeared after only 1 day following exposure to NM.

Conclusions

TTHX1114 is protective against NM-induced damage of the corneal epithelium, possibly by supplying an NM-resistant source of trophic support and by stimulating regeneration of new epithelial cells. These responses underscore the potential value of TTHX1114 as an anti-vesicant therapeutic.

Proliferative capacity of corneal endothelial cells

The corneal endothelial monolayer helps maintain corneal transparency through its barrier and ionic "pump" functions. This transparency function can become compromised, resulting in a critical loss in endothelial cell density (ECD), corneal edema, bullous keratopathy, and loss of visual acuity. Although penetrating keratoplasty and various forms of endothelial keratoplasty are capable of restoring corneal clarity, they can also have complications requiring re-grafting or other treatments. With the increasing worldwide shortage of donor corneas to be used for keratoplasty, there is a greater need to find new therapies to restore corneal clarity that is lost due to endothelial dysfunction. As a result, researchers have been exploring alternative approaches that could result in the in vivo induction of transient corneal endothelial cell division or the in vitro expansion of healthy endothelial cells for corneal bioengineering as treatments to increase ECD and restore visual acuity. This review presents current information regarding the ability of human corneal endothelial cells (HCEC) to divide as a basis for the development of new therapies. Information will be presented on the positive and negative regulation of the cell cycle as background for the studies to be discussed. Results of studies exploring the proliferative capacity of HCEC will be presented and specific conditions that affect the ability of HCEC to divide will be discussed. Methods that have been tested to induce transient proliferation of HCEC will also be presented. This review will discuss the effect of donor age and endothelial topography on relative proliferative capacity of HCEC, as well as explore the role of nuclear oxidative DNA damage in decreasing the relative proliferative capacity of HCEC. Finally, potential new research directions will be discussed that could take advantage of and/or improve the proliferative capacity of these physiologically important cells in order to develop new treatments to restore corneal clarity.

Enhanced survival in vitro of human corneal endothelial cells using mouse embryonic stem cell conditioned medium

Purpose

To determine whether mouse embryonic stem cell conditioned medium (ESC-CM) increases the proliferative capacity of human corneal endothelial cells (HCECs) in vitro.

Methods

Primary cultures of HCECs were established from explants of the endothelial cell layer, including the Descemet’s membrane. Cells were cultured in human corneal endothelium medium (CEM) containing 25% ESC-CM for the experimental group and CEM alone for the control group. Phase-contrast microscopy and reverse-transcription polymerase chain reaction (RT–PCR) were used to identify HCECs. The eruption time and HCEC morphology were observed under phase-contrast microscopy. We detected the protein expression of zona occludens protein-1 (ZO-1; a tight junction protein) and the Na⁺-K⁺-ATPase by western blot analysis and immunocytochemistry. The mRNA expression of the Na⁺-K⁺-ATPase, voltage-dependent anion channel 3 (VDAC3), solute carrier family 4, sodium bicarbonate cotransporter member 4 (SLC4A4), and chloride channel protein 3 (CLCN3) were detected by RT–PCR. To explore the proliferation capacity of HCECs, the colony forming efficiency (CFE) was determined by Giemsa staining and the cellular proliferation marker of Ki-67 protein (Ki-67) positive cells were detected by immunocytochemistry and flow cytometry. Progression of the cell cycle and apoptosis were analyzed by flow cytometry. Negative regulation of the cell cycle, as measured by cyclin-dependent kinase inhibitor p21 (p21) levels, was detected by western blot analysis and immunocytochemistry.

Results

In primary culture, HCECs in the 25%ESC-CM group erupted with polygonal appearance on day 2, while those in the CEM group erupted with slightly larger cells on day 3–4. HCECs in the 25%ESC-CM group could be subcultured until passage 6 without enlargement of cell volume, while those in the CEM group were enlarged and lost their polygonal appearance by passage 2. HCECs in both the 25%ESC-CM and CEM groups expressed ZO-1, Na⁺-K⁺-ATPase, VDAC3, SLC4A4, and CLCN3. The number of Ki67 positive cells, CFE, and percentage of cells entering the S and G₂ phases were higher in the 25%ESC-CM group than in the CEM group. The number of apoptotic cells and p21 protein expression both decreased in the 25%ESC-CM group.

Conclusions

Use of 25%ESC-CM significantly increased the number of proliferating cells. These effects may be achieved through inhibition of p21 expression and apoptosis. These results suggested that 25%ESC-CM may be a new tool for cultivating HCECs for transplantation.

New prognostic histological parameter of invasive ductal carcinoma of the breast: clinicopathological significance of fibrotic focus

Immunohistochemistry, DNA ploidy analysis and molecular genetics have made it possible to predict the outcome of breast cancer more precisely than routine histological examination alone. However, in routine practice, it is difficult to incorporate these methodologies in all cases. If certain histological parameters can accurately predict the outcome of patients with breast cancer, they would be more practical for routine use. We showed that the presence of fibrotic focus (FF) in invasive ductal carcinoma (IDC) is closely associated with c-erbB-2 or p53 protein expression, high proliferative activity, and high angiogenesis of the tumors. Furthermore, multivariate analyses with well-known prognostic parameters for IDC demonstrated that the presence of FF is the most useful independent parameter to predict IDC patient outcome. In addition, our data suggested that the interaction between tumor cells and stromal fibroblasts may play an important role in the formation of FF in IDC based on growth factor and growth factor receptor protein expression in the tumor cells and fibroblasts forming FF. Based on the results of our clinicopathological studies, we propose a new prognostic classification scheme for the prediction of IDC patient outcome, which consists of FF, nuclear atypia, and fat invasion. This classification has superior predicting power to existing prognostic classifications.

Significance of basic fibroblast growth factor and fibroblast growth factor receptor protein expression in the formation of fibrotic focus in invasive ductal carcinoma of the breast

A fibrotic focus (FF) is a scar-like area within invasive ductal carcinoma (IDC) of the breast, and has been shown to be a marker of high aggressiveness of IDC. In order to investigate the mechanism of FF formation in IDC, expression of basic fibroblast growth factor (bFGF) and fibroblast growth factor receptor (FGFR) was studied. One hundred and forty-nine IDCs were divided into solid tumors and scirrhous tumors. Immunohistochemistry was used to determine the expression of bFGF and FGFR proteins in both tumor cells and fibroblasts forming FF. Scirrhous tumors with FF showed a significantly higher frequency of bFGF protein expression than those without (P = 0.017), whereas, in solid tumors, the presence of FF was not significantly associated with the frequency of bFGF protein expression (P = 0.143). In addition, scirrhous tumors showed a significantly higher frequency of FGFR protein expression than solid tumors (P = 0.001). Among IDCs having FF and expressing bFGF protein, a significantly larger number of fibroblasts expressing FGFR protein within FF was observed in scirrhous tumors than in solid tumors (P = 0.016). The results of this study suggest that in scirrhous tumors the interaction between tumor cells and stromal fibroblasts plays an important role in the formation of FF, and that there is a paracrine mechanism between bFGF protein from tumor cells and FGFR protein in fibroblasts.

Corneal endothelium and growth factors

Human corneal endothelium is characterized by a low regenerative capacity, mainly because of a low mitotic activity, and therefore complete regeneration of the endothelial layer after injury is precluded. A decrease in endothelial cell density and an abnormal cell mosaic, which may occur after many conditions, can compromise the integrity of the endothelial monolayer, resulting in corneal decompensation with reduced vision and eventual need for penetrating keratoplasty. It would be beneficial to have growth factors that can help to maintain or restore the integrity of this delicate endothelial monolayer by maintaining or increasing the endothelial cell density or to stimulate the regeneration during wound healing. Growth factors represent a group of signalling peptides which influence diverse cellular processes, including cell proliferation, differentiation, migration and survival. One of the areas that has received great interest is its enhancement of wound healing. In this review the effects of three most effective growth factors (EGF, PDGF, FGF) on corneal endothelium, especially on wound healing in human corneal buttons, will be discussed.

Orientation and directed migration of cultured corneal epithelial cells in small electric fields are serum dependent

Reorientation and migration of cultured bovine corneal epithelial cells (CECs) in an electric field were studied. Electric field application was designed to model the laterally directed, steady direct current electric fields which arise in an injured corneal epithelium. Single cells cultured in media containing 10% foetal bovine serum showed significant galvanotropism, reorienting to lie perpendicular to electric field vector with a threshold field strength of less than 100 mV/mm. Cells cultured in serum-free medium showed no reorientation until 250 mV/mm. Addition of EGF, bFGF or TGF-beta 1 singly or in combination to serum free medium significantly restored the reorientation response at low field strengths. Both the mean translocation rate and directedness of cell migration were serum dependent. Cultured in medium with serum or serum plus added EGF, single cells showed obvious cathodal migration at 100 mV/mm. Increasing electric field strength enhanced the cathodal directedness of single cell migration. Supplementing serum free medium with growth factors restored the cathodal directed migration of single cells and highest directedness was found for the combination of EGF and TGF-beta 1. Corneal epithelial sheets also migrated towards the cathode in electric fields. Serum or individual growth factors stimulated CEC motility (randomly directed). Applied fields did not further augment migration rates but added a vector to stimulated migration. Electric fields which are present in wounded cornea interact with other environmental factors and may impinge on CECs migration during wound healing. Therapies which combine the application of growth factors and electric fields may be useful clinically.