Characterization of human corneal collagenase

Profiles of matrix metalloproteinase activity in equine tear fluid during corneal healing in 10 horses with ulcerative keratitis

OBJECTIVE

Levels of tear film matrix metalloproteinases (MMPs) activity are significantly elevated in horses with ulcerative keratitis and contribute to the excessive breakdown of stromal collagen. Changes in the amount of proteolytic activity in horse tear film during corneal healing and stromal remodeling have not yet been reported, but we hypothesize they should decrease. In the present study we analyzed serial tear fluid from horses with ulcerative keratitis to identify any changes in MMP activity during corneal healing and stromal remodeling.

PROCEDURES

Samples of tear fluid were obtained from both eyes of 10 horses with ulcerative keratitis on the day of admission (day 1) at the hospital and then at various time points until complete healing of the cornea. Tear film MMP2 and MMP9 activity was determined by quantitative gelatin zymography. In all cases medical treatment included topical applications of equine serum, antibiotics, atropine and systemic administration of anti-inflammatory drugs. Surgical procedures were performed in several cases on day 2 in addition to the medical treatment.

RESULTS

The mean total MMP activity (+/- SD) measured in relative standard units (RSU) in the tear fluid of the ulcerated eye (2.44 +/- 1.44) of the 10 horses was significantly higher than the mean in the contralateral eye (0.81 +/- 0.68) (P = 0.006), on the day of admission at the VMTH. The mean MMP activity in these ulcerated eyes significantly decreased (-82.4%) between the first day of admission and the day when the ulcer had completely healed (P = 0.0002). The activity level in the healed eye (0.43 +/- 0.17) was not significantly different to the one in the contralateral eye (0.36 +/- 0.18) on the day of complete corneal healing (P = 0.374). The level of MMP activity in the contralateral eye also decreased from 0.81 +/- 0.68-0.36 +/- 0.18 but this decrease (56%) was not significant (P = 0.069).

CONCLUSIONS

Ulcerative keratitis in horses is associated with initially high levels of tear film proteolytic activity that decrease as the ulcers heal. The success of medical and surgical treatment of the corneal ulcers is reflected by the enzyme activity in tears. In horses successful treatment does lead to a rapid reduction in tear film proteolytic activity that corresponded with the improvement in the clinical signs of corneal ulceration. Measurement of MMP activity in the tear film might represent a way to monitor the progression of corneal healing in horses with ulcerative keratitis.

Connective tissue growth factor in tear film of the horse: detection, identification and origin

BACKGROUND

Healing of corneal ulcers in horses is often associated with profound corneal stromal fibrosis and scar formation resulting in visual impairment. Connective tissue growth factor (CTGF) is a fibrogenic cytokine involved in wound healing and scarring. The purpose of this study was to determine whether CTGF was present in the tear fluid of normal horse eyes and the eyes of horses with corneal ulcers in order to evaluate the role of CTGF in corneal wound healing and corneal scar formation.

METHODS

Tear fluid samples were collected from 65 eyes of 44 horses; 32 samples from normal eyes, 21 samples from eyes with corneal ulceration, and 12 samples from the unaffected contralateral eyes of horses with ulcers. CTGF levels in the tears were determined by enzyme immunoassay using goat IgG against human CTGF. Antigenetic similarity of human and horse CTGF was established in a bio-equivalence assay. The identity of horse CTGF was confirmed by western blot. Lacrimal and nictitating membrane glands were investigated by immunohistochemistry in the attempt to clarify the origin of tear fluid CTGF.

RESULTS

CTGF was detected in tear film of 23 normal unaffected eyes (72%) and 8 normal contralateral eyes (67%), with the mean CTGF levels (+/- SEM) being 51.5+/-19.2 and 13.4+/-3.9 ng/ml respectively. CTGF was found in 8 eyes with corneal ulcers (38%) with the mean CTGF concentration of 26.3+/-14.8 ng/ml. Western blot identified the protein detected as CTGF. The identification of CTGF in lacrimal glands suggests a major role of these glands in the presence of CTGF in tears.

CONCLUSIONS

CTGF is present in horse tear fluid and derives, at least partly, from the lacrimal gland. Equine CTGF has strong antigenic similarity with human CTGF. Corneal disease leads to a decrease of CTGF concentrations in tears. The possible role of CTGF in the healing process of ocular surface requires further investigation.

Immune cells in a case of postherpetic marginal trophic ulcer

The corneal surface was examined by means of replica histology, and the excised limbic conjunctiva was examined by routine histological and immunohistochemical methods with monoclonal antibodies directed against major histocompatibility class II antigens, lymphocyte subsets, Langerhans cells (HLA-DR, OKT4-Leu3a, OKT8, BA1, B1, and OKT6) and immunoglobulins A, G, M, and D. The findings were compared with those found in normal conjunctiva. No inflammatory cells were present in the replica of the corneal surface. An inflammatory infiltrate composed of B lymphocytes and null cells, in addition to T lymphocytes, Langerhans cells, and polymorphs, was present in the epithelium as well as in the stroma of the limbic conjunctiva. The composition of the infiltrate points towards the involvement of cell mediated immunity as well as humoral immunity. No immunoglobulins were bound to the conjunctival epithelium.

Regulation of corneal collagenase production: stimulation of serially passaged stromal cells by blood mononuclear cells

After three or more passages, stromal cell outgrowths from explants of normal rabbit corneas and from corneas previously burned with alkali did not produce collagenase until they were stimulated by the addition of rabbit blood-derived mononuclear cells or media conditioned by them. Normal stromal cells required stimulation by lymphocytes or their products from alkali-burned animals, whereas those from alkali-burned corneas were stimulated by lymphocytes from either normal or alkali-burned rabbits.

Ulceration of the cornea in rheumatoid arthritis

Five patients with melting of the cornea in association with rheumatoid arthritis are described. The arthritis was often inactive and without systemic manifestations, in contrast to that seen in association with scleritis. In 3 there was evidence of reduced tear formation, but in none was tear production absent. In 3 patients the lesions healed during treatment with azathioprine or penicillamine.

Herpes simplex eye infections: clinical manifestations, pathogenesis and management

Herpes infection of the eye may be acquired as the patient's first exposure to the virus (primary infection) or as involvement of a new anatomical site (the eye) in a patient with previous HSV infection. In either case, patients with herpetic eye infection risk recurrent eye disease throughout their lives. The infective lesions of the corneal epithelium (dendritic and geographic ulcers) occasionally develop into noninfective indolent or trophic ulcers, particularly under the influence of cauterizing chemicals or corticosteroids. Inflammation of the corneal stroma may accompany herpetic epithelial lesions or occur independently. Stromal keratitis probably represents the host's immune response to viral antigens filtering down from epithelial lesions or from viral replication in stromal cells. The clinical manifestations of ocular HSV infection are reviewed, pathogenesis and possible pathways of the infection are analyzed, and some practical guidelines for management and prevention are presented.

Collagenolysis of rat tail tendons by crude corneal collagenase and clostridiopeptidase A

An experimental apparatus, which uses freshly collected, nondenatured rat tail tendons as substrate against crude corneal collagenase from alkali-burned rabbit corneas and clostridiopeptidase A, is introduced. The apparatus makes it possible to compare the collagenolytic activity of the two enzymes directly on intact connective tissue similar to intact corneal tissue. It was found that the two enzymes were able to reduce the tensile strength of rat tail tendons to less than 100 g in less than 5 h. The two enzymes attacked the tendons in structurally the same manner, estimated from a statistical model. The conclusion drawn is that crude corneal collagenase can degradate intact connective tissue indicating that it can attack the intact cornea.