Iris Movement Works as a Mechanical Factor to Induce Pupillary Membrane Regression in Rats

Abstract

[Background] It has been reported that pupillary membrane (PM), a transient vascular network surrounded by iris, regresses by apoptotic process. In our previous study, we found that the PM regression occurred following the initiation of iris movement in rats and the transient cessation of PM blood flow took place in miosis. Therefore, we hypothesized that iris movement works as a mechanical factor of PM regression by induction of apoptosis.
[Methods ] Rat littermates (n = 10) were divided into three groups and instilled each eyedrop from postnatal day 7 (P7) to P12: (1) Control: saline, (2) Stimulation of iris movement: 0.005% physostigmine, and (3) Inhibition of iris movement: 1% atropine sulphate. At P12, we quantified the degree of PM regression by counting the number of vascular junctions of PM. We evaluated apoptotic vascular endothelial cell (VEC) of PM in groups 1 and 3.
[Results] The inhibition of iris movement group (group 3) showed the significant persistence of PM when compared with group 1 and 2 and decreased in the number of apoptotic VECs comparing with group 1.
[Conclusions] The iris movement triggers PM regression by inducing apoptosis. [Jpn J Physiol 54 Suppl:S227 (2004)]