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Characterization of membranes removed during open-sky vitrectomy
Abstract:
Membranes removed during open-sky vitrectomy have been characterized by electron microscopy, reaction with anti-human fibrinogen, susceptibility to enzymatic digestion, amino acid analysis, and electrophoresis in sodium dodecyl sulfate. There were significant differences between longstanding and newly formed membranes. Longstanding membranes contained substantial amounts of hydroxyproline, glycine, and hydroxylysine, were capable of digestion by collagenase but not by plasmin, yielded faint positive results with anti-human fibrinogen, and showed fibrils characteristic of collagen by electron microscopy. After digestion with pepsin, electrophoresis revealed bands that migrated the same distance as vitreous collagen chains. This type of membrane is evidently collagenous in nature. A second type of membrane, which developed in the course of vitrectomy, contained no hydroxyproline, only traces of hydroxylysine, and relatively small amounts of glycine, was digested by plasmin, yielded strong positive results with anti-human fibrinogen, and showed fibers that were not characteristic of collagen by electron microscopy. Electrophoresis demonstrated bands similar to authentic fibrin in these newly formed membranes. These data suggest that this second type of membrane is composed largely of fibrin. Prevention of the formation of this second type of membrane during vitrectomy may require the addition of agents that inhibit fibrin formation.
Insights
Vitrectomy membranes differ structurally. Newly formed membranes are primarily fibrin, while longstanding ones are collagenous, suggesting strategies to inhibit fibrin formation during surgery.
Area of Science:
- Ophthalmology
- Biochemistry
- Materials Science
Background:
- Membranes form during vitrectomy surgery.
- Understanding membrane composition is crucial for surgical outcomes.
Purpose of the Study:
- To characterize and differentiate longstanding and newly formed membranes removed during open-sky vitrectomy.
- To elucidate the biochemical composition of these membranes.
Main Methods:
- Electron microscopy
- Immunological assays (anti-human fibrinogen)
- Enzymatic digestion (collagenase, plasmin, pepsin)
- Amino acid analysis
- Electrophoresis (SDS-PAGE)
Main Results:
- Longstanding membranes showed collagen characteristics (hydroxyproline, collagenase digestion, collagen fibrils).
- Newly formed membranes were rich in fibrinogen, digested by plasmin, and showed fibrin-like bands on electrophoresis.
- Newly formed membranes lacked hydroxyproline and contained minimal hydroxylysine.
Conclusions:
- Two distinct membrane types exist: collagenous (longstanding) and fibrin-based (newly formed).
- Newly formed membranes are likely composed of fibrin.
- Inhibiting fibrin formation during vitrectomy may prevent the development of these secondary membranes.