Acute brain slice elastic modulus decreases over time

Abstract

A common benchmark in the brain tissue mechanics literature is that the properties of acute brain slices should be measured within 8 h of the experimental animal being sacrificed. The core assumption is that—since there is no substantial protein degradation during this time—there will be no change to elastic modulus. This assumption overlooks the possibility of other effects (such as osmotic swelling) that may influence the mechanical properties of the tissue. To achieve consistent and accurate analysis of brain mechanics, it is important to account for or mitigate these effects. Using atomic force microscopy (AFM), tissue hydration and volume measurements, we find that acute brain slices in oxygenated artificial cerebrospinal fluid (aCSF) with a standard osmolarity of 300 mOsm/l experience rapid swelling, softening, and increases in hydration within the first 2 hours after slicing. Reductions in elastic modulus can be partly mitigated by addition of chondroitinase ABC enzyme (CHABC). Increasing aCSF osmolarity to 400 mOsm/l does not prevent softening but may hasten equilibration of samples to a point where measurements of relative elastic modulus are consistent across experiments.

Fast Metabolic Glycan Labeling for Click-Labeling and Imaging of Sialoglycans in Living Acute Brain Slices from Mice and Human Patients

“…Prolonging the lifespan of acute brain slices by improving the preparation procedures and culture conditions is currently an active area of interest . Nevertheless, many important properties of the brain tissue such as cell viability, gene expression, and elastic modulus deviate from the physiological state very quickly over time . Similarly, organotypic slices as an alternative tissue culture can provide a longer culture time ( e.g.…”

“…18 Nevertheless, many important properties of the brain tissue such as cell viability, gene expression, and elastic modulus deviate from the physiological state very quickly over time. 19 Similarly, organotypic slices as an alternative tissue culture can provide a longer culture time (e.g., up to 14 days); however, the organotypic slices typically deviate from the physiological state during long-term culturing. 50,51 In addition, fast labeling and imaging of sialoglycans in acute brain slices may find applications in surgical pathological analysis on tissues from patients during surgery to help with disease diagnosis and treatment.…”

“…Living acute brain slices have emerged as a practical and powerful ex vivo platform for studying neuronal functions and neurological diseases at the tissue level for patient samples. , Besides, even for animal studies, acute slice culturing is cost-effective, easy to use, and animal welfare-friendly. However, the acute brain slices have a limited lifespan, typically 6–12 h, thus only amenable to short-term studies. − In contradiction to the short lifespan of acute slices, MGL of sialoglycans normally requires culturing of cells with unnatural sugars such as N -azidoacetylmannosamine (ManNAz) for 2–3 days or administration of mice or rats via intravenous injection for 3–7 days. As an azido analogue of N -acetylmannosamine (ManNAc), the precursor for sialic acid biosynthesis, ManNAz is accepted by the underlying enzymes and goes through the pathway producing azido sialic acid (SiaNAz)-incorporated sialoglycans.…”