Program Enhancement Core Services

The Geropathology Research Resource is led by Dr. Tim Snider, Professor of Pathology, Department of Veterinary Pathobiology, College of Veterinary Medicine, Oklahoma State University. Dr. Snider is a Diplomate of the American College of Veterinary Pathologists with over 20 years of experience in diagnostic and experimental pathology of animal models used in research. Dr. Snider was involved in the Geropathology Research Network and the development of the Geropathology Grading Platform.

The Geropathology Research Resource uses the Geropathology Grading Platform (GGP), recently developed by the Geropathology Research Network (Ladiges et al., 2016; 2017a,b), which allows investigators to assess biological aging in mice by measuring the pathological status of a wide range of organs and tissues.  The GGP is based on a standardized set of guidelines developed by the Geropathology Research Network to (1) detect the presence or absence of low-impact histopathological lesions that occur with age and (2) determine the level of severity of high-impact lesions in tissues of aged mice.  The GGP allows one to generate a numerical score for each lesion in a tissue, which is then summed to give a score for the total lesions in the tissue that are averaged for the mice in the cohort such that a composite lesion score for that tissue, as well as a composite lesion score for the whole animal is obtained.  In other words, the composite lesion score gives one a numerical value for the burden of lesions, which can be compared to similar values from other mice of other cohorts to measure changes with age or with an aging intervention.

Ladiges et al. (2017a) showed that the composite lesion score for heart, lung, kidney, and liver increased dramatically with age in two strains of mice.  They also reported that rapamycin treatment, which has been shown to increase the lifespan of mice, reduced the composite lesion score in multiple tissues.  Using the GGP, Dr. Snider (Snider et al., 2018) evaluated the pathological status of a mouse model of accelerated aging, mice lacking Cu/Zn-superoxide dismutase (Sod1-/- mice).  The composite lesion score was 2- to 3.5-fold higher for Sod1-/- mice compared wild type mice, demonstrating that the GGP was able to predict the accelerated aging phenotype observed in the Sod1-/- mice, even at a relatively young age.   These data also suggest that that GGP can be used to assess the healthspan of mice because the increase in the composite lesion score for the whole animal mirrors the decline in physiological functions that have been observed in Sod1-/- mice.  Thus, the GGP is a new paradigm for evaluating the effect of an intervention on the pathological status of an animal as well as the healthspan of the mice.

References:

Ladiges W, Ikeno Y, Niedernhofer L, McIndoe RA, Ciol MA, Ritchey J, Liggitt D (2016) The Geropathology Research Network: an interdisciplinary approach for integrating pathologyInto research on aging. J Gerontol A Biol Sci Med Sci 71:431-434.

Ladiges W, Snyder JM, Wilkinson E, Imai DM, Snider T, Ge X, Ciol M, Pettan-Brewer C, Pillai SPS, Morton J, Quarles E, Rabinovitch P, Niedernhofer L, Liggitt D (2017a) A new preclinical paradigm for testing anti-aging therapeutics. J Gerontol A Biol Sci Med Sci 72:760-762.

Ladiges W (2017b) The emerging role of geropathology in preclinical aging studies. Pathobiol Aging Age Relat Dis 7:1304005.

Snider T, Richardson A, Stoner JA, Deepa, S (2018) The geropathology grading platform demonstrates that mice null for Cu/Zn-superoxide dismutase show accelerated biological aging. GeroScience 40:97-103.

Following an appropriate fixation (approximately one week), tissues are processed, e.g., paraffin embedded, sectioned via microtomy at 4 microns, stained with haemotoxylin and eosin, and coverslipped.   Slides are labeled by mouse and group number; however, the identifying details of groups are blinded to the scoring pathologist.

Currently, we analyze a full complement of organs subjected to observation and scoring, which include: heart, lung, liver, kidney, spleen, pancreas, small intestine, stomach, salivary gland, reproductive tissues appropriate to gender, mesenteric lymph node, and spinal cord.  Organs are scored as visualized on H&E-stained slides via light microscopy by an ACVP board certified pathologist.

A pre-determined repertoire of scoreable lesions is assessed and scored in each organ; this repertoire has been determined by the Geropathology Grading Committee.  It should be emphasized that the Geropathology Grading Committee responsible for the development of the Geropathology Grading Platform is currently refining the final platform.  Currently, we are using the following scoring system:  significant lesions within organs are scored 0-3 (0=absent, 1=mild, 2=moderate, 3=severe) and insignificant or incidental lesions are scored 0-1 (0=absent, 1=present) or 0-2 (0=absent, 1=present in rare foci, 2= present in multiple foci).  A full description of the scoreable parameters, typical lesions, and grades seen in each organ is available from Dr. Snider.

Tissues of mice are immediately immersion-fixed in 10% buffered neutral formalin. In instances where pathological analysis is conducted on mice that die spontaneously, the carcass is opened on a ventral midline incision from chin to pubis and the whole animal immersed in 10% buffered neutral formalin. The tissues/carcass are sent to Dr. Snider at Oklahoma State University for processing.

Preparation of slides for pathological analysis ($75/animal):  tissues from the carcasses provide by the investigator are processed, e.g., paraffin embedded, sectioned, and stained with haemotoxylin and eosin.

Pathological Analysis of slides ($225/animal):  Dr. Snider and another pathologist will conduct a comprehensive analysis of the slides and develop a composite lesion score for each tissue analyzed.