Establishment of a standardized assay system of fibronectin activity using fibronectin-mediated cell adhesion

Ocular Surface Findings in Hallopeau-Siemens Subtype of Dystrophic Epidermolysis Bullosa

PURPOSE

This article describes the clinical features and long-term changes in corneal sensitivity, tear function, and impression cytology findings in a patient with recessive dystrophic epidermolysis bullosa (DEB).

METHODS

The patient underwent best-corrected Landolt visual acuity measurements, slit-lamp examinations, anterior segment photography, Schirmer test with anesthesia, tear film break-up time, corneal fluorescein and Rose-Bengal staining, assessment of corneal sensitivity, and conjunctival impression cytology at the initial and final visits.

RESULTS

The patient had a recurrent corneal erosion in the right eye and a painful corneal blister with extensive superficial punctuate keratopathy in the left eye, which remained refractory to treatment with patching, lubricants, and antibiotic ointments for 10 weeks. The corneal disease in both eyes responded swiftly to topical fibronectin, topical nonpreserved tears, vitamin A ointment, and therapeutic soft contact lenses. Maintenance treatment was continued with preservative-free topical tear drops and vitamin A ointment. Corneal disease did not recur in the patient during the follow-up of 29 months. The mean corneal sensitivity and tear film break-up time were decreased initially in both eyes and attained normal values with treatment. Impression cytology revealed squamous metaplasia, loss of cellular cohesion, and total absence of goblet cells before treatment, all of which were observed to be normalized at the final follow-up.

CONCLUSIONS

The ocular surface disease in DEB was characterized by low corneal sensitivity, disorder of tear quality, decreased cellular cohesion, squamous metaplasia of the conjunctiva, and goblet cell loss. Close follow-up for ocular complications in DEB is essential and a pathophysiology-oriented approach to the epithelial disease may not only provide rapid healing but might prevent recurrences as well.

Fibronectin facilitates adhesion of K562 leukemic cells normally growing in suspension to cationic surfaces

The role of protein adsorption in the forced adhesive growth of K562 leukemic cells onto a cationic surface composed of polylysine was investigated. Numerous studies have demonstrated that adhesion in anchorage-dependent cells is mediated in vitro by adsorption of serum proteins [particularly proteins of the extracellular matrix (ECM) such as fibronectin and vitronectin] present in the growth medium. Specifically, adhesion has been shown to occur when ECM proteins attach to the substratum and act as ligands for specific receptors located on the surface of cells. K562 cells are human erythroleukemic cells that normally grow in suspension. These cells are not involved in the same cell adhesion processes as anchorage-dependent cells and do not need to be attached to ECM proteins in order to survive and grow. Thus, with these systems, it is possible to better determine the role of protein adsorption in the adhesion of cells, growing in suspension such as blood cells, onto charged surfaces. The results presented show that adhesion of K562 cells onto the positively charged polylysine surface in the presence of serum is mediated through specific interactions between fibronectin receptors present on K562 cells and fibronectin adsorbed onto that cationic surface. Specifically, determination of cell adhesion under different experimental conditions indicates that nonspecific charge interactions do not take place directly between the cells and polylysine, but rather take place between polylysine and fibronectin, which adsorbs onto the cationic polymer. In addition, flow cytometric analyses reveal that only fibronectin receptors are present on these cells and, consequently, only fibronectin can be responsible for the actual adhesion of these cells onto the cationic surface. In view of the data presented, the possibility should be considered that ECM components adsorbed onto surfaces with specific charges and/or belonging to certain functional groups are involved in structural and functional modifications in cells. These cells grow in suspension and are normally not involved in adhesion phenomena, though these components should be considered. These considerations should be made especially when designing biomaterials that can modulate the response of cells growing in suspension, such as blood cells, and also in tissue engineering of blood substitutes.