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Temporal Sequence of Post-Mortem Autolysis in the Mouse Retina
John Finnie1, Jim Manavis1, Glyn Chidlow2
1Discipline of Anatomy and Pathology, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia.
Journal of Comparative Pathology
|September 10, 2021
Summary
Post-mortem changes in mouse retinas, including detachment and cell degeneration, depend on the time after death and the fixative used. Understanding these changes is crucial for accurately interpreting retinal histology and differentiating ante-mortem from post-mortem events.
Area of Science:
- Veterinary Pathology
- Ocular Pathology
- Forensic Science
Background:
- Histological examination of retinal changes is vital for determining cause of death and differentiating ante-mortem injuries from post-mortem autolysis.
- Standardized methods are needed to accurately assess the post-mortem interval (PMI) in ocular tissues.
Purpose of the Study:
- To systematically investigate the temporal sequence of post-mortem retinal autolysis in a controlled mouse model.
- To evaluate the influence of different fixatives (Davidson's vs. formalin) on the rate and characteristics of post-mortem retinal changes.
- To establish reliable histological criteria for distinguishing ante-mortem retinal lesions from post-mortem artifacts.
Main Methods:
- A controlled study using a single strain, age, and sex of mice maintained at a constant ambient temperature.
- Eyes collected at various time points up to 72 hours post mortem.
- Immersion fixation in either Davidson's fixative or 10% neutral buffered formalin.
- Standard paraffin embedding, sectioning, and Hematoxylin and Eosin staining.
Main Results:
- Retinal detachment and folding were early autolytic changes, occurring immediately post mortem in formalin-fixed eyes and at 2 hours in Davidson's-fixed eyes.
- Fixative type significantly impacted the progression of retinal detachment; formalin led to rapid and complete separation, while Davidson's resulted in slower, segmental changes.
- Photoreceptor disruption, nuclear pyknosis in the inner nuclear layer, and ganglion cell alterations (swelling, shrinkage, basophilia, pyknosis) were observed with increasing post-mortem intervals.
- Rod outer segment homogenization was noted early (30 min to 4 h) in Davidson's-fixed retinas.
Conclusions:
- The histological appearance of post-mortem retinal changes is significantly influenced by the post-mortem interval and the fixative employed.
- Davidson's fixative appears to preserve retinal structure for a longer period compared to formalin, delaying the onset of complete retinal detachment.
- These findings highlight the critical importance of considering both the PMI and fixative type when interpreting retinal histology to avoid misdiagnosis of ante-mortem lesions.
