Rodent blast injury models provide a good way to study traumatic brain injury (TBI) from blast exposure. Three key points: 1) Blast exposure can cause a complex array of injuries through different mechanisms such as high vs low frequency waves. It also has various components like overpressure, shockwaves, and electromagnetic pulses. 2) Effective models must reproduce the key features of human blast injury through controlled and measurable mechanical forces. They should also show graded functional deficits related to injury severity. 3) Choosing the right model is important. Shock tubes can better focus blast energy but lack all injury factors, while free explosions are less controlled. Measurement of both physical factors and functional outcomes is needed.

1. Rodent Blast Injury Models – Good "Bang for the Buck"? Ibolja Cernak, M.D., M.E., Ph.D. Biomedicine Business Area; National Security Technology Department

2. 2 Complex Mechanisms of Injuries

3. Cernak I & Noble-Hauesslein L. Journal of Cerebral Blood Flow & Metabolism (2010) 30, 255–266 Complex Array of Injuries

4. FREQUENCY high frequency (0.5-1.5 kHz) low-amplitude stress waves: target mostly organs that contain abrupt density changes from one medium to other (for example, air/blood interface in the lungs or blood/parenchyma interface in the brain); low-frequency (<0.5 kHz) high-amplitude shear waves: disrupt tissue structures by generating local motions that overcome natural tissue elasticity (for example, at the contact of gray and white brain matter). OVERPRESSURE Peak; Duration of the peak; Number of peaks; Distance between peaks; Interaction between stress, expansion and refraction waves. BLAST WAVE COMPOUNDS EM Pulse

6. Direct interaction with the skull

7. Direct interaction with the spineBlast-induced neurological deficits and psychological impairments

9. Extreme cold

10. Sleep deprivation

11. Social challenges

12. Nutrition

13. High-altitude hypoxiaComplex Environment Decreased Resilience

14. In Vivo Models of Traumatic Brain Injury UNCLASSIFIED 7 CERNAK, I. Experimental models of traumatic brain injury. NeuroRx, 2(3): 410-422, 2005.

16. Essential hallmarks of blast injuries and BINT:

17. Position-dependent injury severity and injury pattern;

18. Graded functional (motor, cognitive, and behavioral) deficits;

19. Graded induction of molecular response in the brain;

22. Computational Fluid Modeling of Blast Conditions – Know the Physics of the Injurious Environment UNCLASSIFIED 11 © 2011 The Johns Hopkins University Applied Physics Laboratory All Rights Reserved.

24. maximize the amount of blast energy that impacts the test subject;

28. compressed air fails to expand as quickly as would an ideal gas when the membrane is ruptured (due in part to intermolecular forces strengthened during compression;

32. 15 Cernak I et al. Neurobiology of Disease 41(2011): 538-551 Sensor Locations DRIVEN DRIVER Example: JHU/APL Mouse BINT Model

33. UNCLASSIFIED 16 Reneer DV, Hisel RD, Hoffman JM, Kryscio RJ, Lusk BT, Geddes JW: J Neurotrauma JOURNAL 28:95–104 (January 2011 Example: The McMillan blast device (MBD) The Mylar membrane The reflected (face-on) pressure sensor (embedded in the dorsal surface of the polyurethane rat model The anesthetized rat is fitted with a Kevlar vest (not shown) and inserted into a mesh netting support. This is then loaded into a shock tube insert. A test article (i.e., animal) should present less than 5% area blockage in order to replicate free-field conditions

34. How to Measure Blast Injury Severity UNCLASSIFIED 17 Bowen’s Injury Risk Curve (number of animals in parentheses) (adapted from “Estimate of man’s tolerance to the direct effects of air blast,” Technical Progress Report, DASA-2113, Defense Atomic Support Agency, Department of Defense, Washington, DC, October 1968).

35. Blast Injury Severity Measurement UNCLASSIFIED 18 Problem: The Bowen criteria used lethality and lung (i.e.organ) damages as outcome measures in function of pressure and duration of the blast. As such, they are less reliable and/or useful for predicting functional deficits (such as memory deficits) as outcomes; The physiological and biological responses to injurious environment are specific and unique among the different animal species. Thus, physical scaling based on animals’ size and using pressure-duration factors will give unreliable and inconsistent information about functional changes due to blast.

36. 19 Koliatsos V, Cernak I, et al. Journal of Neuropathology and Experimental Neurology, 70(5): 399-416, 2011 Type, Severity and Frequency of Blast-induced Microscopic Lesions in Key Thoracic and Abdominal Organs Supine > Prone Prone > Supine

37. UNCLASSIFIED Cernak I et al. Neurobiology of Disease 41(2011): 538-551 Functional Deficits in BINT: Motor * * ** ** * *** * *** *** ** *** *** *** *** ** *** 20

38. UNCLASSIFIED Cernak I et al. Neurobiology of Disease 41(2011): 538-551 Functional Deficits in BINT: Cognitive * * ** ** ** *** *** *** *** *** *** *** *** *** *** *** *** 21

39. UNCLASSIFIED Cernak I et al. Neurobiology of Disease 41(2011): 538-551 Post-traumatic Depression: Open Field Test Pre-blast Post-blast (14 d) Post-blast (30 d) 22

40. Take Home Message #1: BINT is not “just” a blunt traumatic brain injury UNCLASSIFIED 23

41. Importance of Blast Transmission Pathways 24 Cernak I Frontiers in Neurology (2010); 1: 1-9 Head protection & Torso exposure Torso protection & Head exposure Whole-body exposure UNCLASSIFIED

43. This probe is offered in a ready-to-use format and measures myeloperoxidase (MPO) activity of activated phagocytes allowing for longitudinal tracking of MPO level and inflammation status in vivo;

44. Intraperitoneal (i.p.) injection at 200 mg/kg (150 μL /mouse*) and imaging 10 minutes post i.p. injection of the probe with exposure time of 5 minutes for better sensitivity.UNCLASSIFIED

45. Cernak I Frontiers in Neurology (2010); 1: 1-9 Blast with No Protection The injected bioluminescent marker labels myeloperoxidase in activated macrophages, and is imaged in real-time using the IVIS bioluminescent camera in mice after mild intensity blast . 1 Day 3 Days 7 Days 14 Days 30 Days Blast with Head Protection Blast with Body Protection

46. 27 Koliatsos V, Cernak I, et al. Journal of Neuropathology and Experimental Neurology, 70(5): 399-416, 2011 Axonal Pathology in Distinct CNS Tracts Based on Silver Degeneration Staining 0 – no pathology 1 – mild pathology (scattered axons) 2 – moderate pathology 3 – severe pathology (confluent axons) CC – corpus callosum Cing – cingulum AC – anterior commissure Frnx – fornix SM – stria medullaris MTT – mammilothalamic tract IC – internal capsule Low CST – low corticospinal tract Olf – olfactory tract Optic – optic tract ML – medial lemniscus LL – lateral lemniscus Crbl WM – cerebellar white matter Crbl Pedn – cerebellar peduncles Spt V – spinal tract of trigeminal nucleus VSCT – ventral spinocerebellar tract Whole-body exposure Torso protection & head exposure Head protection & torso exposure

47. UNCLASSIFIED 28 Take Home Message #2 Well characterized experimental models reproducing military relevant conditions and related symptoms should be used to develop reliable diagnosis, therapy, and prevention. vs

49. Farid A. Ahmed

50. Andrew C. Merkle

51. Quang Luong

52. Theresa Mahota

53. Howard Conner

54. Ian Wing

55. Michele Schaefer

56. Brock Wester

57. VassilisKoliatsos (JHU SOM)

58. LeyanXu (JHU SOM)

59. Stefan Plantman (KI, Stockholm)