Preservatives for postmortem brain tissue in biomechanical testing: A pilot study

• Published in: Journal of anatomy Vol. 245; no. 3; pp. 501 - 509
• Main Authors: Mallory, Ann, Wetli, Alaine, Neuroth, Lucas M., Rhule, Heather, Moorhouse, Kevin, Satterfield, Kelly, Thomas, Colton, Tesny, Angela, Kang, Yun‐Seok
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.09.2024; John Wiley and Sons Inc
• Subjects: Aged; Antibiotics; Antifungal activity; Antifungal agents; antimicrobial; Biomechanical Phenomena; Biomechanics; Brain - drug effects; Brain injury; Brain research; brain tissue stiffness; Brief Communication; Cerebrospinal fluid; Cold storage; Humans; Male; Pilot Projects; Postmortem Changes; Preservatives; Sodium; Sodium bicarbonate; Sodium Bicarbonate - pharmacology; Storage conditions; storage temperature; Temperature tolerance; tissue preservatives; Traumatic brain injury; antimicrobial; brain tissue stiffness; tissue preservatives; biomechanics; antibiotics; sodium bicarbonate; storage temperature
• ISSN: 0021-8782; 1469-7580; 1469-7580
• DOI: 10.1111/joa.14069

Postmortem human subject (PMHS) studies are essential to brain injury research in motor vehicle safety. However, postmortem deterioration reduces the similarity between postmortem test results and in vivo response in material testing of brain tissue and in biomechanical testing of the whole head. This pilot study explores the effect of potential preservatives on brain tissue breakdown to identify promising preservatives that warrant further investigation. To identify preservatives with potential to slow postmortem degradation, samples from an initial PMHS were refrigerated at 10°C to qualitatively compare tissue breakdown from 58 to 152 h postmortem after storage in candidate solutions. On brain tissue samples from a second PMHS, compressive stiffness was measured on six samples immediately after harvest for comparison to the stiffness of 23 samples that were stored at 10°C in candidate solutions for 24 h after harvest. The candidate solutions were artificial cerebrospinal fluid (ACSF) without preservatives; ACSF with a combination of antibiotics and antifungal agents; ACSF with added sodium bicarbonate; and ACSF with both the antibiotic/antifungal combination and sodium bicarbonate. Results were analyzed using multiple linear regression of specimen stiffness on harvest lobe and storage solution to investigate potential differences in tissue stiffness. Qualitative evaluation suggested that samples stored in a solution that contained both the antibiotic/antifungal combination and sodium bicarbonate exhibited less evidence of tissue breakdown than the samples stored without preservatives or with only one of those preservatives. In compression testing, samples tested immediately after harvest were significantly stiffer than samples tested after 24 h of storage at 10°C in ACSF (difference: −0.27 N/mm, 95% confidence interval (CI): −0.50, −0.05) or ACSF with antibiotics/antifungal agents (difference: −0.32 N/mm, 95% CI: −0.59, −0.04), controlling for harvest lobe. In contrast, the stiffness of samples tested after storage in either solution containing sodium bicarbonate was not significantly different from the stiffness of samples tested at harvest. There was no significant overall difference in the mean tissue stiffness between samples from the frontal and parietal lobes, controlling for storage solution. Given the importance of PMHS studies to brain injury research, any strategy that shows promise for helping to maintain in vivo brain material properties has the potential to improve understanding of brain injury mechanisms and tolerance to head injury and warrants further investigation. These pilot study results suggest that sodium bicarbonate has the potential to reduce the deterioration of brain tissue in biomechanical testing. The results motivate further evaluation of sodium bicarbonate as a preservative for biomechanical testing using additional test subjects, more comprehensive material testing, and evaluation under a broader set of test conditions including in whole‐head testing. The effect of antibiotics and antifungal agents on brain tissue stiffness was minimal but may have been limited by the cold storage conditions in this study. Further exploration of the potential for microbial agents to preserve tissue postmortem would benefit from evaluation of the effects of storage temperature. Biomechanical testing of postmortem brain is complicated by tissue deterioration after death. This pilot study explored antibiotics, anti‐fungal agents, and sodium bicarbonate as brain tissue preservatives for experimental biomechanics studies. Compression testing of tissue specimens after storage in solutions with and without these candidate preservatives showed that sodium bicarbonate shows particular promise for slowing postmortem softening of brain tissue.