The ultrastructure of subarachnoid trabeculae in non-human primates varies by tissue region within the central nervous system

The subarachnoid space (SAS) plays an important role in central nervous system (CNS) physiology, housing cerebrospinal fluid (CSF), providing nutrients, clearing waste, and protecting CNS tissues from injury. The SAS also contains an intricate arrangement of collagenous fibers, known as subarachnoid trabeculae, which serve as biomechanical support for the subarachnoid space and modulate the flow of CSF. Despite their myriad of roles in health and disease, the ultrastructure of trabeculae is incompletely described, with a specific gap in understanding how fiber structure varies across different regions of the CNS. In this work, we used optimized fixation techniques and scanning electron microscopy (SEM) imaging to study ultrastructural differences in trabeculae that were obtained from different regions of the nonhuman primate (NHP) brain and spinal cord. Qualitative assessments included evaluation of the relative prevalence of different kinds of fiber networks by region, leading us to a redefinition of terminology for fiber morphology. Quantitative measurements yielded dramatic differences in fiber diameter, density, and network porosity between different regions of the CNS. Broadly, trabeculae supporting cauda equina, cervical spinal cord, and exiting nerve roots were observed to have a very high density of small diameter fibers, whereas larger fibers and more complex arrangements were observed in other regions of the CNS. These data contribute to a growing field understanding of CNS-region specific differences in tissue ultrastructure.