Interactions of corneal cells with transforming growth factor β2‐modified poly dimethyl siloxane surfaces

Abstract

The downgrowth of corneal epithelial cells at the interface of an artificial cornea and the host eye tissue poses a significant problem to be overcome in developing a successful implant. As a means of inhibiting the proliferation of corneal epithelial cells on the stromal surface of the implant, we examined the immobilization of transforming growth factor beta-2 (TGF-beta2) via a bifunctional poly ethylene glycol (PEG) spacer to poly dimethyl siloxane (PDMS) surfaces. Growth factor immobilization was confirmed by modification with (125)I-labeled TGF-beta 2. The modified surfaces were also characterized by advancing water contact angles, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Although the amount of growth factor covalently bound to the surface was difficult to quantify apparently due to strong interactions between the growth factor and the PEG layer and high levels of adsorption, differences in the modified surfaces, suggestive of the presence of a significant amount of TGF-beta 2, were found. In vitro interactions of the modified surfaces with human corneal epithelial and stromal cells were examined. Growth factor surface concentrations as well as culture in the absence and presence of serum and other adhesive proteins were examined. Corneal stromal and epithelial cells cultured on the TGF-beta 2-modified surfaces consistently gave results opposite to those expected. Likely, the most notable and surprising result was the almost complete lack of adhesion of the stromal cells, with coverage averaging between 3 and 5%. In comparison, corneal epithelial cell growth appeared to be promoted by the presence of the immobilized growth factor, with cell coverage averaging 50-60% at 7 days of culture. A TGF-beta 2 concentration effect was noted with both cell types in the absence of serum, with increases in the coverage at higher TGF-beta 2 concentrations. The observed cell growth appeared to be the result of interactions between the cells and active growth factor, because the addition of anti-TGF-beta 2 to the culture medium reduced cell coverage to levels similar to those noted on control surfaces. Therefore, although TGF-beta 2-modified surfaces may not be suitable as corneal epithelial cell inhibiting surfaces, interactions of surface immobilized growth factor and corneal cells are complex and should be further examined.

The Development of a Tissue-Engineered Cornea: Biomaterials and Culture Methods

“…Future work will address the effect of EGF on the production of ECM proteins. PDMS surfaces were also modified with transforming growth factor ␤2 (TGF␤2) to stimulate stromal proliferation while inhibiting the proliferation of corneal epithelial cells (46). Contrary to expected results, corneal stromal cells exhibited very low adhesion to TGF␤2 coated surfaces (3-5%) while epithelial cells exhibited high levels of adhesion (50 -70%) after one week of culture.…”

Regenerative Approaches as Alternatives to Donor Allografting for Restoration of Corneal Function

“…However, the results observed on TGFβ-modified PDMS surfaces in vitro were opposite to those expected; keratocyte adhesion was inhibited and epithelial cell growth was enhanced by surface treatment, indicating the complex nature of growth factor-cell interactions. 31 Grafting of PEG to poly(methyl methacrylate) (PMMA) implants, which typically exhibit high protein deposition and cell adhesion associated with retroprosthetic membrane formation, was investigated. 32 The modification resulted in decreased keratocyte and inflammatory cell adhesion on the polymer surface in vitro and in rabbit experiments.…”

Silk fibroin/cartilage extracellular matrix scaffolds with sequential delivery of TGF-β3 for chondrogenic differentiation of adipose-derived stem cells

“…21,22 To regulate the release of factors, loading microparticle containing factors into the scaffolds 23 and covalently binding the factors to the scaffolds have been used in recent research of chondrogenesis. 24,25 However, the effect of microspheres themselves on cell differentiation and covalent binding on the activity of factors cannot be well controlled, so both methods do not mimic the natural presentation of the factors in vitro. 26 In addition, the preparation of these controlled release systems is relatively complicated.…”