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Andrea Trost, Falk Schroedl, Alexandra Kaser-Eichberger, Barbara Bogner, Daniela Bruckner, Christian Runge, Karolina Motloch, Ludwig M Heindl, Herbert Reitsamer; Lymphatic markers in the normal and lesioned rat optic nerve. Invest. Ophthalmol. Vis. Sci. 2016;57(12):229.
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© ARVO (1962-2015); The Authors (2016-present)
Only few tissues lack lymphatic supply, such as the CNS or the inner eye. However, lymphatics are detected in the eye, if the scleral border is compromised due to trauma or tumor. Since the situation in the optic nerve (ON), part of the CNS, is not clear, the aim of this study is to screen for the presence of lymphatic, glial and blood vascular markers in the healthy and lesioned ON.
Brown Norway rats (n=5) received an defined ON crush (ONC), leaving the dura intact. Lesioned ONs and contralateral controls were analyzed 7 days after ONC, followed by immunohistochemistry against: PDGFRb (pericyte), Iba1 (microglia), CD31, RECA (endothelial cell, EC) as well as LYVE-1 and podoplanin (PDPN; lymphatic markers). Rat skin served as positive control, confocal microscopy was used for documentation.
In healthy ONs, PDGFRb is detected in vessel-like structures which co-localize for CD31 and RECA. Some of these structures are closely associated with LYVE-1. Homogenous PDPN-immunoreactivity was detected in healthy ON, without vascular appearance and was not co-localized with LYVE-1 or PDGFRb. However, in rat skin controls PDPN-immunoreactivity was co-localized with LYVE-1 and further with CD31 in vessel-like structures. In lesioned ONs, numerous PDGFRb+ cells were detected with network-like appearance. The majority of these PDGFRb+ cells were not associated with RECA and CD31-immunoreactivity, but were immunopositive for Iba1. Further, single LYVE-1+ cells were detected here, lacking vessel-like appearance. These LYVE-1+ cells were PDPN negative and PDPN-immunoreactivity was also clearly absent within the lesion site. LYVE-1+ and PDPN+ structures were both unaltered outside the lesion.
In healthy ON, few PDGFRb+ structures were associated with LYVE-1+ structures, suggesting that LYVE-1 most likely labels blood ECs, as reported earlier for other systems. In the lesioned area, PDGFRb+/Iba1+ network-like cells without vascular association might represent a subtype of microglia, potentially involved in repair and phagocytosis. Although PDPN is exclusively expressed in lymphatics in rat skin controls, it is extensively detected in non-lymphatic structures in the healthy ON, but absent in the lesion site. This observed PDPN staining pattern is inverse to the PDGFRb+ one, the functional meaning of which is unknown. The role of these structures in repair/regeneration mechanims need further investigation.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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