Time Course of Lens Epithelial Cell Behavior in Rabbit Eyes following Lens Extraction and Implantation of Intraocular Lens

Abstract

Background: After cataract surgery, some lens epithelial cells (LECs) transdifferentiate into myofibroblast-like cells, which causes fibric posterior capsule opacification (PCO). Residual LECs differentiate into lens fiber cells, forming Elschnig pearls with PCO. This study was carried out to identify the time course of both types of LEC behavior in rabbit eyes following lens extraction and implantation of an intraocular lens (IOL).

Methods: Phacoemulsification and implantation of posterior chamber IOLs were performed in rabbit eyes. Following enucleation, immunohistochemical methods were used to detect α-smooth muscle actin (α-SMA), a marker for myofibroblast-like cells, in the pseudophakic rabbit eyes. A mouse monoclonal antibody against α-SMA was used.

Results: Soon after the operation, the LECs migrated and covered the lens capsule. Thereafter, the LECs around the anterior capsular margin were always positive for α-SMA. However, the distributions of these cells were not consistent. In some specimens, α-SMA-positive LECs were present around the IOL optic early after surgery, but most of them had disappeared several weeks after the surgery. The residual cells induced fibrotic PCO. In the other specimens, most LECs around the IOL optic except the anterior capsular margin were negative for α-SMA. In the peripheral region covered by the peripheral anterior and posterior capsules, LECs on the posterior capsule always differentiated into lens fiber cells and formed a Soemmering ring. Thereafter, migration of lens fiber cells from the Soemmering ring and differentiation of LECs in situ on the central posterior capsule consisted of Elschnig pearls type of PCO.

Conclusions: Although postoperative LEC behavior is not consistent, residual α-SMA-positive LECs induced fibrotic PCO. The lens fiber cells that migrated from the peripheral capsular bag or that were differentiated in situ covered the central posterior capsule, forming Elschnig pearls with PCO.

Figure 1

Immunolocalization of α-SMA in pseudophakic rabbit eyes 3 days after cataract surgery. A monolayer of LECs covers the inner surface of the anterior and central posterior capsules (arrows). These LECs are negative for α-SMA, although the sphincter muscles of the iris are positive for α-SMA. bar = 200 μm. The inset shows a higher power view of LECs on the central posterior capsule. Bar = 50 μm. Sections were stained with 3-3'-diaminobenzidine hydrochloride and counterstained with hematoxylin. The asterisk indicates the IOL optic.

Figure 2

Immunolocalization of α-SMA in pseudophakic rabbit eyes 5 days after cataract surgery. The flattened and multilayered LECs are positive for α-SMA. The specimens could be divided into two groups according to the distribution of these α-SMA-positive LECs around the IOL optics. (a) Surrounding type: LECs positive for α-SMA surround the IOL optic. The anterior and posterior capsules around such LECs appear wrinkled (open arrows) except for the posterior capsule under the IOL optic (arrows). The inner surface of the peripheral anterior and posterior capsule is covered by a monolayer of LECs, with these two surfaces being attached to each other like a zipper (arrowheads), which are separated from the IOL optic by α-SMA-positive LECs around the IOL optic edge. These LECs are negative for α-SMA. Bar = 250 μm. (b) Higher power view of (a): the central posterior capsule under the IOL optic is covered by α-SMA-positive LECs without wrinkling of the capsule. (c) Restricted type: LECs positive for α-SMA are present only around the margin of the anterior capsule (arrow). Other LECs around the IOL optics are negative for α-SMA, with most of them forming a monolayer. The inner surface of the peripheral anterior and posterior capsule is also covered by a monolayer of α-SMA-negative LECs (arrowheads). Bar = 400 μm. (d) Higher power view of (c): the margin of the anterior capsule is covered with α-SMA-positive, flattened LECs (arrows). Bar = 75 μm. (e); higher power view of (c): LECs around the edge of the IOL optic and on the inner surface of the peripheral anterior and posterior capsules are α-SMA-negative (arrowheads). Bar = 75 μm. (f) Restricted type: LECs positive for α-SMA are present around the margin of the anterior capsule and on small areas of the posterior capsule (arrows). Bar = 200 μm. (a–f) Sections were stained with 3-3'-diaminobenzidine hydrochloride and counterstained with hematoxylin. The asterisks indicate the IOL optic.

Figure 3

Immunolocalization of α-SMA in pseudophakic rabbit eyes 10 days after cataract surgery. (a) Surrounding type: The flattened and α-SMA-positive LECs cover some parts of the anterior and posterior capsules around the IOL optics. The other parts of the anterior and posterior capsules around the IOL optics have no LECs (arrows). The LECs on the peripheral posterior capsule begin to differentiate and form the Soemmering ring and are negative for α-SMA (large arrowheads), which are separated from the IOL optic by α-SMA-positive LECs around the IOL optic edge (small arrowheads). Bar = 250 μm. (b) Higher power view of (a): although there are some α-SMA-positive LECs on the anterior and posterior capsules (arrows), LECs are absent from other areas of these capsules (arrowheads). Bar = 50 μm. (c) Restricted type: the LECs on the posterior capsules begin to differentiate into lens fiber cells (arrows). Bar = 400 μm. (d) Higner power view of (b): the margin of the anterior capsule is covered with α-SMA-positive, flattened LECs (arrowheads), whereas LECs on the posterior capsule begin to differentiate into lens fibers (arrows). Bar = 125 μm. (a–d) Sections were stained with 3-3'-diaminobenzidine hydrochloride and counterstained with hematoxylin. Asterisks indicate the IOL optic.

Figure 4

Immunolocalization of α-SMA in pseudophakic rabbit eyes 14 days after cataract surgery. (a) Surrounding type: most of the capsules around the IOL optics are devoid of LECs (arrows). Some posterior capsules are wrinkled without LECs (small arrowheads). Some α-SMA-positive LECs are present on the capsules, and the Soemmering ring has increased in size. The separation between the IOL optic and the Soemmering ring is lost. Part of the Soemmering ring has begun to attach to the IOL optic (large arrowheads). Bar = 200 μm. (b) Restricted type: the differentiation of LECs under the IOL optic has progressed to form the Elschnig pearls type of opacification (arrows). Bar = 200 μm. (c) Higher power view of (b): the differentiated lens fiber cells are recognizable. Bar = 50 μm. (a–c) Sections were stained with 3-3'-diaminobenzidine hydrochloride and counterstained with hematoxylin. Asterisks indicate the IOL optic.

Figure 5

Immunolocalization of α-SMA in pseudophakic rabbit eyes 1 month after cataract surgery. (a) The capsular bag is filled with lens fibers. Differentiated LECs are also present between the anterior surface of the IOL optic and the anterior capsule. Some of these lens fibers migrated beyond the anterior capsule margin and formed posterior synechia to the iris (arrow). The lens fibers migrated onto the posterior capsule from the periphery to the center (arrowhead), which showed no LECs. Bar = 800 μm. (b) Higher power view of LECs around the margin of the anterior capsule (arrow). The arrowhead indicates the posterior synechia of the lens fibers to the iris. Bar = 250 μm. (c) Higher power view of lens fibers on the central posterior capsule. Differentiated LECs, which form the Elschnig pearls type of opacification, are present over the α-SMA-positive LECs attached to the wrinkled posterior capsule (arrows). Bar = 250 μm. (a–c) Sections were stained with 3-3'-diaminobenzidine hydrochloride and counterstained with hematoxylin. The asterisks indicate the IOL optic.