Tear Matrix Metalloproteinases and Myeloperoxidase Levels in Patients With Boston Keratoprosthesis Type I

Abstract

Purpose: To investigate the tear levels of matrix metalloproteinases (MMPs), myeloperoxidase (MPO), and tissue inhibitor of metalloproteinase-1 in eyes after Boston keratoprosthesis type I (B-KPro) implantation and to correlate these markers with the established B-KPro prognostic categories.

Methods: Tear washes were collected from 40 patients (7 with autoimmune disease, 2 with chemical burn, and 31 with other noncicatrizing diagnoses). Tear levels of MMPs, MPO, and tissue inhibitor of metalloproteinase-1 were quantified using multianalyte bead-based enzyme-linked immunosorbent assays. The total MMP activity was determined using a fluorimetric assay. The analytes were compared to the underlying diagnosis and other clinical factors.

Results: The MMP-8, MMP-9, and MPO levels were markedly elevated in the eyes with B-KPro (80 ± 31, 291 ± 77, and 244 ± 33 pg/μg, respectively). Chemical burn was associated with significantly higher tear MMP-8 (474 ± 376 pg/μg) and MMP-9 levels (1300 ± 635 pg/μg) compared with noncicatrizing diseases (MMP-8: 41 ± 15 pg/μg, P = 0.02 and MMP-9: 196 ± 57 pg/μg, P = 0.02) and higher MMP-9 levels compared with autoimmune diseases (MMP-8: 96 ± 65 pg/μg, P = 0.21 and MMP-9: 306 ± 196 pg/μg, P = 0.04). Similar analyte levels were observed in the B-KPro eye and the contralateral non-B-KPro eye of patients with bilateral diseases. MMP-8, MMP-9, and total MMP activities correlated strongly with each other.

Conclusions: In the eyes with B-KPro, tear MMP-8 and MMP-9 levels seem to be related to the underlying ocular surface pathology and not significantly influenced by the presence of the prosthesis.

Figures

Figure 1

Bar graph showing the means of A) matrix metalloproteinase (MMP)-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-12, myeloperoxidase (MPO) and tissue inhibitor of MMP-1 (TIMP-1) and B) total MMP activity in the tears of eyes with Boston keratoprosthesis type I (B-KPro). The eyes are grouped according to the established prognostic hierarchy based on underlying diagnosis leading to corneal blindness and B-KPro implantation. All values were standardize to total protein: A) picograms per microgram of total protein (pg/µg) and B) relative fluorescent units per minute per microgram of total protein (RFU/min/µg). Levels were compared across all 3 diagnostic groups using the Kruskal-Wallis test ({) while group pairs were compared using the Mann-Whitney U test ([). * P

Figure 2

Scatter graphs illustrating the association between A) matrix metalloproteinase (MMP)-8 and MMP-9; B) MMP-9 and myeloperoxidase (MPO) and C) MMP-8 and MPO. The Spearman rank correlation coefficient (rs) and p value for all eyes is shown in the upper left corner of each graph while values for each diagnostic category are shown down and to the right ((autoimmune disease (♦); chemical burn (■); non-cicatrizing disease (●)).

Figure 3

Bar graph showing the means of A) matrix metalloproteinase (MMP)-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-12, myeloperoxidase (MPO) and tissue inhibitor of metalloproteinase-1 (TIMP-1) and B) total MMP activity in the tears of patients with bilateral disease but unilateral Boston keratoprosthesis type I (B-KPro). All values were standardized to total protein: A) picograms per microgram of total protein (pg/µg) and B) relative fluorescent units per minute per microgram of total protein (RFU/min/µg). Levels were compared between paired eyes of the same patient using the Wilcoxon matched-pairs signed-rank test. *P

Figure 4

Slit lamp photographs of eyes with Boston keratoprosthesis type I (B-KPro) and clinically detectable melt on the day of tear collection. The tear level of matrix metalloproteinase (MMP) -8, MMP-9 and myeloperoxidase (MPO) are shown. A) A 43-year old male with Stevens Johnson syndrome (SJS) developed active melting by postoperative 1 month when tear collection was performed. The MMP-9 level was above the detection limit of the assay (at least 1 489 pg/µg total protein). B) A 62-year old male with aniridia and bilateral B-KPro developed corneal melting with extensive exposure of the back plate on the day of first tear collection. Shortly after, the patient underwent repeat B-KPro. Tear collection was performed one year later when the patient had a stable ocular surface with no sign of melt. Tear MMP-8, MMP-9 and MPO levels, at 3, 22 and 131 pg/µg total protein, were very similar to those seen in the presence of active melt. C) A 75-year old female with SJS had mild thinning superiorly and contact lens deposits on the day of tear collection.