ABSTRACT
Death initiates a cascade of physiological and biochemical alterations in organs and tissues, resulting in microscopic changes that challenge the histopathological evaluation. Moreover, the brain is particularly susceptible to artifacts owing to its unique composition and its location within the cranial vault. The aim of this study was to compile and illustrate the microscopic changes in the central nervous system (CNS) of rats subjected to delayed postmortem fixation. It also scrutinizes the influence of exsanguination and cooling methods on the initiation and progression of these alterations. Twenty-four Wistar Han outbred rats (RccHan™: WIST) were sacrificed and stored either at room temperature (18-22°C) or under refrigeration (2-4°C). Necropsies were conducted at different time points postmortem (i.e., 0.5 h, 1 h, 4 h, 8 h, 12 h, 24 h, 36 h, 48 h, 7 days and 14 days). Brain sections underwent simultaneous digital evaluation by 14 pathologists until a consensus was reached on terminology, key findings, and intensity levels. Microscopic observations varied among cell types. Glial cells were similarly affected throughout the CNS and showed pericellular halo, chromatin condensation and nuclear shrinkage. Neurons showed two types of postmortem changes as most of them showed progressive shrinkage, cytoplasmic dissolution and karyorrhexis whereas others acquired a dark-neuron-like appearance. Neuronal changes showed marked differences among neuroanatomical locations. Additional postmortem changes encompassed: granulation and microcavitation in neuropil and white matter; retraction spaces; detachment of ependyma, choroid plexus, and leptomeninges. Severity of findings after 48 h at room temperature was higher than after seven days under refrigeration and similar to or slightly lower than after 14 days under refrigeration. No clear differences were observed related to the sex or weight of the animals or their exsanguination status. This work elucidates the onset and progression of autolytic changes in the brains of Wistar Han rats, offering insights to accurately identify and enhance the histopathological evaluation.
ABSTRACT
PURPOSE: The PDDD is a ratchet-based, unidirectional expandable rod to treat adolescent idiopathic scoliosis (AIS), primarily by correcting scoliotic deformity without full spinal fusion. We hypothesized that the device will be fully tolerated by the host and, if aseptic screw loosening occurs, it will be unrelated to wear particle formation. METHODS: This study comprised tissue samples from seven patients from a prospective study (NCT04296903) to assess the PDDD's safety and benefits, reoperated due to complications. Host response was assessed from histological slides (four levels/implant) in accordance with GLP and ISO10993-6:2016. The elementary chemical composition of wear particles present in tissue sections was quantified by energy dispersive X-ray spectroscopy (EDX). RESULTS: Host reaction was minor, characterized by low levels of diverse inflammatory cells, mild fibrosis, occasional small necrotic foci, neovascularization, hemorrhage, and, rarely, small bone fragments. Twenty-four of 28 tissue sections displayed varying degrees of wear particles (black discoloration), and most sections (17) were scored as 1 (< 25% of the sample). The discoloration observed corresponded to black-appearing, fine granular pigment. EDX analysis confirmed particles were composed of titanium, aluminum, and vanadium. Twenty-six of 28 samples were scored zero for necrosis and 2/28 were scored 1. Eleven samples were scored zero for fibrosis, 12 as 1, and five as 2. No aseptic screw loosening occurred. CONCLUSION: The PDDD induced minimal host reaction with little or no degeneration, inflammation or fibrosis. No changes present could be expected to promote device failure. The PDDD implant for treating AIS is well-tolerated and locally safe.
