Behavioral battery in mice to model age-associated changes in human motor function Jamie N. Justice, Ph.D. Department of Integrative Physiology, University of Colorado Boulder Assessing physical function across species: Mice, monkeys and man Gerontological Society of America, Nov 2013

Improve quality of clinical aging research Provide “common currency” Standardized batteries of physical function tests have long been in use in clinical practice & aging research in humans Improve quality of clinical aging research Provide “common currency”

Though rodent behavior has long been used in aging research... Analogous batteries in mice? Validate against human declines?

Mouse models in aging research: Mechanisms -access to tissue -signaling pathways -genetic knock outs -disease models Screen interventions -prevention -treatment -safety -efficacy Longitudinal Research -survival studies -optimal intervention time Translation

Physical Function Aim: Mouse Model Aim: To develop and assess the validity of a battery of tests to characterize motor function in mice Strength Endurance Locomotion Balance face validity wide spread use in behavioral testing established use in aging research economy of time and effort Justice JN, Carter CS, Beck HJ, Gioscia-Ryan RA, McQueen M, Enoka RM, Seals DR. AGE, 2013.

Mouse Model of Physical Function the ability to generate a maximal force against physical objects - NIH Toolbox Strength Endurance Locomotion Balance Grip Strength: average force at forepaw release

Mouse Model of Physical Function the ability to move from place to place -NIH Toolbox Strength Endurance Locomotion Balance Open Field Distance: Distance traveled over 5 min Rearing Counts: Number of rears over 3 min “Scurry” Speed: average speed to cover straight walking track

Mouse Model of Physical Function the ability to orient the body in space, maintain an upright posture under both static and dynamic conditions, and move and walk without falling -NIH Toolbox Strength Endurance Locomotion Balance Accelerating Rota-Rod: average latency to fall from accelerating rotating rod Hindlimb Grasp: latency to grasp tightrope with hind limbs once suspended by forepaws

Mouse Model of Physical Function how long a person (animal) can perform an activity at a particular intensity -NIH Toolbox Strength Endurance Locomotion Balance Tightrope: maximum time suspended from tightrope Rota-Rod Run: maximum time and distance run until falling off the rota-rod

3 month 20 month 26 month n = 87 n = 48 n = 42 Strength Locomotion Fore-paw grip strength (g) 130 ± 14 96.7 ± 15.1* 79.7 ± 13.3*† Grip strength per mass 5.58 ± 0.55 2.80 ± 0.44* 2.55 ± 0.44* Locomotion Open field distance (cm) 1859 ± 265 1740 ± 431 1357 ± 398*† Rearing counts 25.4 ± 6.7 10.6 ± 6.3* 8.6 ± 8.2* Walk speed (cm/s) 11.0 ± 4.2 - 8.2 ± 3.8* Balance Accelerating rota-rod time (s) 240 ± 57 181 ± 76* 164 ± 62* Latency to hindlimb grasp (s) 5.0 ± 2.4 8.3 ± 7.2* 16.7 ± 13.1* % capable of hindlimb grasp 100 77 36 Endurance Tightrope hang score (s) 84.0 ± 32.5 62.4 ± 34 23.6 ± 24.2*† Tightrope score per mass (s/g) 3.5 ± 1.4 1.8 ± 1.0* 0.8 ± 0.8*† Endurance run time (s) 864 ± 356 670 ± 478 461 ± 328* Endurance run distance (m) 24.4 ± 9.9 15.7 ± 8.6* 14.2 ± 11.6* 10

Normalized Scores (0-1 scale): 1 - (worst / current) 3 month 20 month 26 month Normalized Scores (0-1 scale): 1 - (worst / current) Strength Forepaw grip strength Grip strength per mass Locomotion Open field distance Rearing counts Walk speed Balance Avg accelerating rota-rod time Latency to hindlimb grasp Endurance Tightrope hang score Tightrope score per mass Endurance run time Endurance run distance Average Average Average Average

Physical function declines with age in mice * * * * *

Physical function declines with age How do these subdomains relate to declines seen in humans? Systematic Review 21 articles included with normative data from young and old humans Percent declines from young were calculated for humans and mice Determine relative lifespan points for mice and humans

Relative lifespans for mice and humans 100 75 Percentage of survivors 50% survivorship 50 25 1 6 12 18 24 30 36 Mouse age (months) Human age equivalents (years) 12 30 42.5 56 69 81 94 1 1 Adapted from “The Mouse in Biomedical Research: Normative Biology, Husbandry, and Models” 14

Physical function declines with age Strength Locomotion Human Mice Balance Endurance

Physical Function Strength Endurance Locomotion Balance

Rachel Gioscia-Ryan, M.S. Acknowledgements Christy Carter, Ph.D. Roger M. Enoka, Ph.D. Douglas R. Seals, Ph.D. Rachel Gioscia-Ryan, M.S. Hannah J. Beck Matthew McQueen, Ph.D.

Which tests are most reflective of Summary Score? Performance Score Part R2 Grip strength 0.16 0.83 Rota-rod distance 0.07 0.90 Tightrope time per mass 0.18 0.94 “Scurry” speed 0.97 Accelerating rota-rod 0.04 0.98 Rearing count 0.08 0.99 Rota-rod time Time to hindlimb grasp 1.00 Open field distance 0.05

Which subdomains are most reflective of Summary Score? Subdomain Score Part R2 Endurance 0.38 0.65 Strength 0.22 0.85 Locomotion 0.30 0.93 Balance / Coordination 0.23 0.98

Order of test presentation Day 1 Day 2 Day 3 Day 4 Open field distance Rearing Counts Accelerating rota-rod 1 Endurance rota-rod Scurry speed Tightrope Accelerating rota-rod 2 Grip strength Intro to Accelerating rota-rod Accelerating rota-rod 3

Thank you Jamie Justice, IPHY Colloquium Presentation, 2013 “Put a bird on it” Jamie Justice, IPHY Colloquium Presentation, 2013

Physical function at midlife is predictive of lifespan in rats Swim Speed & Incline Plane Task Dependency? Normalized Scores (0-1 scale): 1 - (worst / current) Best Worst Performance at Midlife Best Worst Best Carter CS, Sonntag WE, Onder G, Pahor M. J Gerontol A Biol Sci Med Sci, 2002