Cerebrospinal Fluid Characterization in Cynomolgus Monkeys, Beagle Dogs, and Göttingen Minipigs

Abstract

Intrathecal administration is an important route for drug delivery, and in pharmacology and toxicology studies, cerebrospinal fluid (CSF) collection and analysis is required for evaluating blood–brain barrier penetration and central nervous system exposure. The characteristics of CSF in commonly used nonrodent models are lacking. The purpose of this study is to evaluate and provide some insights into normal cellular and biochemical composition of CSF as well as diffusion potential following intrathecal injection across several nonrodent species. Cerebrospinal fluid samples were collected from the cerebellomedullary cistern of beagle dogs, cynomolgus monkeys, and Göttingen minipigs and analyzed for clinical chemistry and cytological evaluation. Diffusion into the intrathecal space following intrathecal injection was assessed following administration of a contrast agent using fluoroscopy. The predominant cell types identified in CSF samples were lymphocytes and monocytoid cells; however, lymphocytes were represented in a higher percentage in dogs and monkeys as opposed to monocytoid cells in minipigs. Clinical chemistry parameters in CSF revealed higher Cl− concentrations than plasma, but lower K+, Ca2+, phosphorus, glucose, creatinine, and total protein levels consistent across all 3 species. Diffusion rates following intrathecal injection of iodixanol showed some variability with dogs, showing the greatest diffusion distance; however, the longest diffusion time through the intervertebral space, followed by monkeys and minipigs. Minimal diffusion was observed in minipigs, which could have been attributed to anatomical spinal constraints that have been previously identified in this species.

Pre-clinical delivery of gene therapy products to the cerebrospinal fluid: challenges and considerations for clinical translation

“…In addition to considering CSF volume and turnover rates when evaluating large animal models, it is also important to compare diffusion rates and composition of CSF between species. In one study, a differential cell count found a comparable ratio of lymphocyte to monocytoid cells in both cynomolgus monkeys and beagle dogs ( Ballesteros et al, 2020 ), but a significantly lower ratio in Gottingen minipigs. This same study also assessed diffusion rates after an intrathecal injection of a contrast agent and showed that beagle dogs had the longest diffusion times with the infusate covering the most distance, followed by NHPs, and lastly minipigs.…”

Tauopathy promotes spinal cord-dependent production of toxic amyloid-beta in transgenic monkeys

“…The CSF sample collection and assay followed standard protocols and have been described previously. 49 In short, after monkeys fasted for at least 8 h, a lumbar puncture was performed at the intervertebral space L3-L4 or L4-L5 using a standard needle. CSF was collected into a 1.5 ml sterile microtube (Axygen, MCT-150-C) and immediately frozen at −80 °C.…”