In the posterior chamber, podoplanin immunoreactivity was detected on the anterior margin of the ciliary body, namely the irido-ciliary trabeculum, with a sharp stop at the anterior margin of the ciliary muscle fibers. This immunopositive signal could not be unequivocally attributed to a cellular structure, nor any CD31 positive- or any other luminal structure (
Fig. 3A). Nevertheless, within the ciliary body, individual podoplanin immunoreactive cells were detectable in the connective tissue gaps of neighbored ciliary muscle fibers (
Fig. 3B). Further, LYVE-1–positive cells were detected here (
Fig. 3C) and these LYVE-1+ cells were lacking podoplanin (
Figs. 3C, 3D). In the same set of experiments applying LYVE-1 and podoplanin, structures reminiscent on vessels (i.e., forming a true lumen or at least appear as double line of two adjacent endothelial cell layers in the sense of a collapsed vessel) were never found. Nevertheless, occasionally an immunopositive signal has been detected with pseudovessel appearance (i.e., forming a one-sided endothelial-like border around a cell free area,
Fig. 3C; or cell-filled area,
Fig. 3D). These pseudovessels were never colocalized with LYVE-1, nor were similar structures positive for LYVE-1–only detected; also, an association with PROX1-positive nuclei was never detected (
Fig. 3E). Double-labeling experiments with VEGFR3 and α-SMA revealed numerous VEGFR3-positive structures at the iris root, just anteriorly of the ciliary muscle (
Fig. 3E). In combination with a DAPI nuclear staining, these structures were identified as VEGFR3-positive cells, with round nucleus and cell size between 10 and 15 μm (
Fig. 3F). Further, the ciliary muscle showed immunoreactivity for VEGFR3, but again a PROX1- immunoreactive nucleus was not detectable here (
Fig. 3G). Within the ciliary muscle, structures were identified displaying VEGFR-immunoreactivity bordering a cell-free lumen, thus possibly representing a lymphatic vessel. However, these lumina were not associated with PROX1- nor CCL21-immunopositive signals (
Fig. 3H). Instead, these structures displayed also immunoreactivity for CD31, and were thus identified as blood-vessels (
Fig. 3I). Again, few VEGFR3-immunoreactive cells were present within the muscle (
Fig. 3I). Combining VEGFR3 with CCL21 revealed that the latter was also expressed in ciliary muscle fibers (
Fig. 3J). Occasionally, also CCL21-positive cells were detected within the ciliary body, being VEGFR3-negative (
Fig. 3K). Further, few LYVE-1–positive cells were found, displaying a FOXC2-immunoreactive nucleus, but lacking a PROX1 nuclear signal (
Fig. 3L). Because aforementioned cell populations were only occasionally found and their overall amount was very low, we resisted to further classify these cells.