# Aquaporins in the Capillaries of the Dura Mater of Pigs

## TL;DR

This study compares capillary density and aquaporin expression in the dura mater of pigs, finding higher vascular activity in cranial regions.

## Contribution

The study provides the first systematic analysis of capillary architecture and aquaporin expression in porcine cranial and spinal dura mater.

## Key findings

- Cranial dura mater has 3–4 times higher capillary density than spinal dura.
- AQP1 and AQP4 are expressed in capillary walls, with higher levels in cranial regions.
- Lymphatic vessels are found adjacent to capillaries, suggesting a dual-system for fluid exchange.

## Abstract

Dura mater plays a critical role in neurofluid homeostasis, yet comparative data on capillary network density and organization between cranial and spinal regions remain limited. This study addresses this gap by systematically analyzing capillary architecture and aquaporin (AQP) expression in porcine cranial (parietal, falx) and spinal dura mater. Immunofluorescence labeling and confocal microscopy were used to assess capillary density, spatial distribution, and AQP1/AQP4 expression patterns across over 1000 capillaries in these regions. Cranial dura exhibited a 3–4 times higher capillary density compared to spinal dura, with capillaries predominantly localized to meningeal–dural border cell interfaces in cranial regions and a more dispersed distribution in spinal dura. Both AQP1 and AQP4 were detected as discrete clusters within capillary walls, with higher expression in cranial compared to spinal dura. Lymphatic vessels (PDPN-positive) were also observed adjacent to capillaries, supporting a dual-system model for fluid and waste exchange. These findings highlight the dura’s region-specific vascular specialization, with cranial regions favoring dense, structured capillary networks suited for active fluid exchange. This work establishes a foundation for investigating capillary-driven fluid dynamics in pathological states like subdural hematomas or hydrocephalus.