Abstract
Purpose:
To determine the functional morphology of the mouse ciliary muscle and outflow pathways, focusing on the connections between the ciliary muscle, trabecular meshwork (TM), Schlemm’s canal (SC) and choroid.
Methods:
Immunohistochemical studies of histological sections and whole mounts using antibodies against α-SM-Actin, elastin, and the neuronal markers: vesicular acetylcholine transporter (VACHT), nitric oxide synthase (NOS), vasoactive intestinal peptide (VIP), tyrosine hydroxylase (TH) as well as semi- and ultrathin serial sections in sagittal and tangential planes were performed in eyes of BALB/c- and C57BL/6 mice.
Results:
The mouse TM, similar to human TM, contains an elastic fiber network present within the TM lamellae and juxtacanalicular TM (JCT). Elastic fibers are located at the center of the TM lamellae, which are continuous with the anterior surface of the ciliary body/iris stroma. The JCT consists of around four layers of TM cells and surrounding connective tissue including the elastic fiber network. The network is connected to SC inner wall endothelium and JCT cells.The mouse ciliary muscle consists of mainly longitudinally oriented, branching smooth muscle cells, laterally connected to each other by junctional complexes. Anteriorly, the muscle cells form elastic tendons inserting into the subendothelial elastic net and into the elastic fibers at the center of the TM lamellae. Posteriorly, the elastic tendons of the cilliary muscle insert into the elastic net of the choroid and into the basement membrane of the choriocapillaris. Ciliary muscle fibers are surrounded by VACHT-positive varicosities. No staining for NOS, VIP or TH was seen within the ciliary muscle. TM cells (most of them staining for α-SM-Actin) were in contact with VACHT- and TH-positive varicosities.
Conclusions:
In mice, as in human, the cholinergic innervated ciliary muscle forms elastic tendons inserting anteriorly into the TM and inner wall of SC and posteriorly into the choroid. Contraction of the mouse ciliary muscle may act to open SC, pull the ciliary body/iris inwardly, and potentially increase outflow facility.
Keywords: 735 trabecular meshwork •
456 ciliary muscle •
554 immunohistochemistry