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On the importance of long-term functional assessment after stroke to improve translation from bench to bedside

Abstract

Despite extensive research efforts in the field of cerebral ischemia, numerous disappointments came from the translational step. Even if experimental studies showed a large number of promising drugs, most of them failed to be efficient in clinical trials. Based on these reports, factors that play a significant role in causing outcome differences between animal experiments and clinical trials have been identified; and latest works in the field have tried to discard them in order to improve the scope of the results. Nevertheless, efforts must be maintained, especially for long-term functional evaluations. As observed in clinical practice, animals display a large degree of spontaneous recovery after stroke. The neurological impairment, assessed by basic items, typically disappears during the firsts week following stroke in rodents. On the contrary, more demanding sensorimotor and cognitive tasks underline other deficits, which are usually long-lasting. Unfortunately, studies addressing such behavioral impairments are less abundant. Because the characterization of long-term functional recovery is critical for evaluating the efficacy of potential therapeutic agents in experimental strokes, behavioral tests that proved sensitive enough to detect long-term deficits are reported here. And since the ultimate goal of any stroke therapy is the restoration of normal function, an objective appraisal of the behavioral deficits should be done.

Letter to the editor

Regarding functional evaluations, the first point to consider is the body weight. Monitoring body weight changes after a stroke is of prime importance since postoperative weight loss may indicate feeding difficulties. Aside from all ethical considerations, such postoperative weight loss has been shown by some authors to be correlated with the extent of the lesion (extensive corticostriatal damage [1], or the involvement of the external carotid artery territory in the lesion [2]). An easy measurement such as this can advise as to the severity of the lesion. Beyond the lesion per se, feeding difficulties may also result from a reduced consciousness level or poor mobility due to anesthesia and/or surgery. For example, a surgical approach in which the temporal muscle is injured, such as the Tamura model [3] may induce severe mastication impairments, resulting thus in higher body weight loss. Nevertheless, a poor nutritional intake (Dennis, 2000) can be a bias, since it has been shown in patients [2] as in animals to have a negative effect on functional outcomes after stroke [2]. Body weight monitoring of patients has even been recommended as an index of functional outcome [4]. Thus, investigating weight changes in preclinical studies has to be recommended for all authors in the field, since it gives an independent and unambiguous assessment of animal welfare and safety. Animals should be weighed at least once before surgery and then regularly after. This parameter, accessible to everyone and not only to behaviorists since it does not require any specific skill, can also give, in some ways, information on how animals recover from surgery and can even be a prognostic index for functional outcome.

Concerning functional evaluations, few studies consider crucial long-term evaluation, even though it has been highly recommended during the Stroke Therapy Academic Industry Roundtables [57]. As in clinical practice [8], animals display a large degree of spontaneous recovery within a short time after experimental cerebral ischemia [912]. Even though demanding sensorimotor and cognitive tasks are powerful in revealing tiny deficits, long-term studies addressing such behaviors are unfortunately not very abundant. The characterization of long-term functional recovery is critical for evaluating the efficacy of potential therapeutic agents in an experimental stroke. Both acute (few days) and long-term (several weeks or months) evaluations have to be addressed in order to demonstrate a stable neuroprotection, and not only a slowing down of the lesion evolution [13, 14]. The issue of including behavioral assessments in animal stroke studies becomes even more critical with the recent interest in neurorestorative strategies, which requires a longer period of administration than classical treatments. Effectiveness of such strategies is more likely observable via changes in synapse number and dendritic structure, for example, than by changes in infarct volume [15, 16]. Since the ultimate goal of any stroke therapy is the restoration of functions that allow for a normal daily life of patients; an objective appraisal of the behavioral deficits should be done. Stroke-induced functional impairments can be divided into acute (pointing out effects of drugs on the rate of recovery - days or weeks) and long-term (pointing out the effects of drugs on the extent of recovery - several weeks to months). Ideally, a set of several different tests has to be performed to gather complementary information (see table 1: behavioral tests and time-points are given as an indication, and need to be adjusted according to the species/strain and the stroke model used). Several behavioral tests have been applied to ischemia research in regards to clinical criteria, from the simplest which measures global neurological status or motor reflexes (i.e. neurological score [17], limb placing test [18], cylinder test [19] - useful to assess an acute phase after stroke) to more complex tests assessing sensory and motor functions (i.e. adhesive removal [20] and rotarod or staircase [19, 2125]) - that are more relevant for the long-term phase. Similarly, cognitive tests such as those assessing memory functions are preferentially used for later time points because they require normalized motor functions [19, 22, 2628]. These behavioral tests have to be carefully chosen in accordance with the drugs tested and the nature of the targeted cerebral structures. Except from that of Winter and colleagues [27], very few publications deal with stoke-induced disturbances in emotional behavior. Because anatomical and functional brain regions are affected on a different timescale, and because treatments may also differentially affect those regions, it is our view and that of others [29] that direct (cortex, striatum) or indirect (thalamus) anatomical substrates hit during stroke, rather than global brain lesions, may be critical determinants of behavioral impairments and outcome.

Table 1 Available and helpful sensorimotor tests assessing longitudinal and long-term functional recovery.

Whereas the correlation between acute histological lesions and early behavioral impairment is well documented[24], less is known about the long-term evolution of this relationship. Correlation studies have to take into account the different brain structures, primarily or secondarily affected by stroke, in order to bring a better understanding of their involvement in behavioral impairments [23, 25, 30]. Additionally, the development of non-invasive methods (such as MRI) allowing longitudinal assessment of the evolution of the lesion may bring new insights to understanding the mechanisms underlying spontaneous functional recovery [31]. Longitudinal correlations must then be promoted since therapeutic agents targeting those mechanisms will free us from the current mandatory 3 to 6 hour therapeutic window.

The use of clinically relevant models taking into account associated factors and/or pathologies (i.e. aging[32], arterial hypertension, diabetes, ..) have, moreover, to be reinforced in the incoming studies. As such, the post-ischemic recovery may be different, depending on the presence of these aggravating factors.

Conflict of interests

The authors declare that they have no competing interests.

References

  1. 1.

    Virtanen T, Jolkkonen J, Sivenius J: Re: External carotid artery territory ischemia impairs outcome in the endovascular filament model of middle cerebral artery occlusion in rats. Stroke 2004, 35: e9–10. author reply e9–10

    PubMed  Article  Google Scholar 

  2. 2.

    Dittmar M, Spruss T, Schuierer G, Horn M: External carotid artery territory ischemia impairs outcome in the endovascular filament model of middle cerebral artery occlusion in rats. Stroke 2003, 34: 2252–7. 10.1161/01.STR.0000083625.54851.9A

    PubMed  Article  Google Scholar 

  3. 3.

    Tamura A, Graham DI, McCulloch J, Teasdale GM: Focal cerebral ischaemia in the rat: 1. Description of technique and early neuropathological consequences following middle cerebral artery occlusion. J Cereb Blood Flow Metab 1981, 1: 53–60. 10.1038/jcbfm.1981.6

    CAS  PubMed  Article  Google Scholar 

  4. 4.

    Jonsson AC, Lindgren I, Norrving B, Lindgren A: Weight loss after stroke: a population-based study from the Lund Stroke Register. Stroke 2008, 918–23.

    Google Scholar 

  5. 5.

    Wahlgren NG, Ahmed N: Neuroprotection in cerebral ischaemia: facts and fancies--the need for new approaches. Cerebrovasc Dis 2004,17(Suppl 1):153–66.

    CAS  PubMed  Article  Google Scholar 

  6. 6.

    Green AR: Why do neuroprotective drugs that are so promising in animals fail in the clinic? An industry perspective. Clin Exp Pharmacol Physiol 2002, 29: 1030–4. 10.1046/j.1440-1681.2002.03767.x

    CAS  PubMed  Article  Google Scholar 

  7. 7.

    Fisher M, Hanley DF, Howard G, Jauch EC, Warach S: Recommendations from the STAIR V meeting on acute stroke trials, technology and outcomes. Stroke 2007, 38: 245–8. 10.1161/01.STR.0000255951.37434.aa

    PubMed  Article  Google Scholar 

  8. 8.

    Rothrock JF, Clark WM, Lyden PD: Spontaneous early improvement following ischemic stroke. Stroke 1995, 26: 1358–60. 10.1161/01.STR.26.8.1358

    CAS  PubMed  Article  Google Scholar 

  9. 9.

    Hunter AJ, Mackay KB, Rogers DC: To what extent have functional studies of ischaemia in animals been useful in the assessment of potential neuroprotective agents? Trends Pharmacol Sci 1998, 19: 59–66. 10.1016/S0165-6147(97)01157-7

    CAS  PubMed  Article  Google Scholar 

  10. 10.

    Roof RL, Schielke GP, Ren X, Hall ED: A comparison of long-term functional outcome after 2 middle cerebral artery occlusion models in rats. Stroke 2001, 32: 2648–57. 10.1161/hs1101.097397

    CAS  PubMed  Article  Google Scholar 

  11. 11.

    Zausinger S, Hungerhuber E, Baethmann A, Reulen H, Schmid-Elsaesser R: Neurological impairment in rats after transient middle cerebral artery occlusion: a comparative study under various treatment paradigms. Brain Res 2000, 863: 94–105. 10.1016/S0006-8993(00)02100-4

    CAS  PubMed  Article  Google Scholar 

  12. 12.

    Zhang L, Chen J, Li Y, Zhang ZG, Chopp M: Quantitative measurement of motor and somatosensory impairments after mild (30 min) and severe (2 h) transient middle cerebral artery occlusion in rats. J Neurol Sci 2000, 174: 141–6. 10.1016/S0022-510X(00)00268-9

    CAS  PubMed  Article  Google Scholar 

  13. 13.

    Valtysson J, Hillered L, Andine P, Hagberg H, Persson L: Neuropathological endpoints in experimental stroke pharmacotherapy: the importance of both early and late evaluation. Acta Neurochir (Wien) 1994, 129: 58–63. 10.1007/BF01400874

    CAS  Article  Google Scholar 

  14. 14.

    Corbett D, Nurse S: The problem of assessing effective neuroprotection in experimental cerebral ischemia. Prog Neurobiol 1998, 54: 531–48. 10.1016/S0301-0082(97)00078-6

    CAS  PubMed  Article  Google Scholar 

  15. 15.

    Biernaskie J, Corbett D: Enriched rehabilitative training promotes improved forelimb motor function and enhanced dendritic growth after focal ischemic injury. J Neurosci 2001, 21: 5272–80.

    CAS  PubMed  Google Scholar 

  16. 16.

    Kawamata T, Alexis NE, Dietrich WD, Finklestein SP: Intracisternal basic fibroblast growth factor (bFGF) enhances behavioral recovery following focal cerebral infarction in the rat. J Cereb Blood Flow Metab 1996, 16: 542–7.

    CAS  PubMed  Article  Google Scholar 

  17. 17.

    Bederson JB, Pitts LH, Tsuji M, Nishimura MC, Davis RL, Bartkowski H: Rat middle cerebral artery occlusion: evaluation of the model and development of a neurologic examination. Stroke 1986, 17: 472–6. 10.1161/01.STR.17.3.472

    CAS  PubMed  Article  Google Scholar 

  18. 18.

    De Ryck M, Van Reempts J, Borgers M, Wauquier A, Janssen PA: Photochemical stroke model: flunarizine prevents sensorimotor deficits after neocortical infarcts in rats. Stroke 1989, 20: 1383–90. 10.1161/01.STR.20.10.1383

    CAS  PubMed  Article  Google Scholar 

  19. 19.

    Bouet V, Freret T, Toutain J, Divoux D, Boulouard M, Schumann-Bard P: Sensorimotor and cognitive deficits after transient middle cerebral artery occlusion in the mouse. Exp Neurol 2007, 203: 555–67. 10.1016/j.expneurol.2006.09.006

    PubMed  Article  Google Scholar 

  20. 20.

    Bouet V, Boulouard M, Toutain J, Divoux D, Bernaudin M, Schumann-Bard P, Freret T: The adhesive removal test: a sensitive method to assess sensorimotor deficits in mice. Nat Protoc 2009, 4: 1560–4. 10.1038/nprot.2009.125

    CAS  PubMed  Article  Google Scholar 

  21. 21.

    Modo M, Stroemer RP, Tang E, Veizovic T, Sowniski P, Hodges H: Neurological sequelae and long-term behavioural assessment of rats with transient middle cerebral artery occlusion. J Neurosci Methods 2000, 104: 99–109. 10.1016/S0165-0270(00)00329-0

    CAS  PubMed  Article  Google Scholar 

  22. 22.

    Freret T, Bouet V, Leconte C, Roussel S, Chazalviel L, Divoux D, Schumann-Bard P, Boulouard M: Behavioral deficits after distal focal cerebral ischemia in mice: Usefulness of adhesive removal test. Behav Neurosci 2009, 123: 224–30.

    PubMed  Article  Google Scholar 

  23. 23.

    Freret T, Chazalviel L, Roussel S, Bernaudin M, Schumann-Bard P, Boulouard M: Long-term functional outcome following transient middle cerebral artery occlusion in the rat: correlation between brain damage and behavioral impairment. Behav Neurosci 2006, 120: 1285–98.

    PubMed  Article  Google Scholar 

  24. 24.

    Rogers DC, Campbell CA, Stretton JL, Mackay KB: Correlation between motor impairment and infarct volume after permanent and transient middle cerebral artery occlusion in the rat. Stroke 1997, 28: 2060–5. discussion 2066 10.1161/01.STR.28.10.2060

    CAS  PubMed  Article  Google Scholar 

  25. 25.

    Grabowski M, Brundin P, Johansson BB: Paw-reaching, sensorimotor, and rotational behavior after brain infarction in rats. Stroke 1993, 24: 889–95. 10.1161/01.STR.24.6.889

    CAS  PubMed  Article  Google Scholar 

  26. 26.

    Borlongan CV, Cahill DW, Sanberg PR: Locomotor and passive avoidance deficits following occlusion of the middle cerebral artery. Physiol Behav 1995, 58: 909–17. 10.1016/0031-9384(95)00103-P

    CAS  PubMed  Article  Google Scholar 

  27. 27.

    Winter B, Juckel G, Viktorov I, Katchanov J, Gietz A, Sohr R, Balkaya M, Hortnagl H, Endres M: Anxious and hyperactive phenotype following brief ischemic episodes in mice. Biol Psychiatry 2005, 57: 1166–75. 10.1016/j.biopsych.2005.02.010

    PubMed  Article  Google Scholar 

  28. 28.

    DeVries AC, Nelson RJ, Traystman RJ, Hurn PD: Cognitive and behavioral assessment in experimental stroke research: will it prove useful? Neurosci Biobehav Rev 2001, 25: 325–42. 10.1016/S0149-7634(01)00017-3

    CAS  PubMed  Article  Google Scholar 

  29. 29.

    Virley D, Beech JS, Smart SC, Williams SC, Hodges H, Hunter AJ: A temporal MRI assessment of neuropathology after transient middle cerebral artery occlusion in the rat: correlations with behavior. J Cereb Blood Flow Metab 2000, 20: 563–82.

    CAS  PubMed  Article  Google Scholar 

  30. 30.

    Hudzik TJ, Borrelli A, Bialobok P, Widzowski D, Sydserff S, Howell A, Gendron P, Corbett D, Miller J, Palmer GC: Long-term functional end points following middle cerebral artery occlusion in the rat. Pharmacol Biochem Behav 2000, 65: 553–62. 10.1016/S0091-3057(99)00243-9

    CAS  PubMed  Article  Google Scholar 

  31. 31.

    van Meer MP, van der Marel K, Wang K, Otte WM, El Bouazati S, Roeling TA, Viergever MA, Berkelbach van der Sprenkel JW, Dijkhuizen RM: Recovery of sensorimotor function after experimental stroke correlates with restoration of resting-state interhemispheric functional connectivity. J Neurosci 2010, 30: 3964–72. 10.1523/JNEUROSCI.5709-09.2010

    CAS  PubMed  Article  Google Scholar 

  32. 32.

    Moore TL, Killiany RJ, Pessina MA, Moss MB, Finklestein SP, Rosene DL: Recovery from ischemia in the middle-aged brain: a nonhuman primate model. Neurobiol Aging 2011.

    Google Scholar 

  33. 33.

    Encarnacion A, Horie N, Keren-Gill H, Bliss TM, Steinberg GK, Shamloo M: Long-term behavioral assessment of function in an experimental model for ischemic stroke. J Neurosci Methods 2011, 196: 247–57. 10.1016/j.jneumeth.2011.01.010

    PubMed Central  PubMed  Article  Google Scholar 

  34. 34.

    Dijkhuizen RM, Ren J, Mandeville JB, Wu O, Ozdag FM, Moskowitz MA, Rosen BR, Finklestein SP: Functional magnetic resonance imaging of reorganization in rat brain after stroke. Proc Natl Acad Sci USA 2001, 98: 12766–71. 10.1073/pnas.231235598

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  35. 35.

    Rogalewski A, Dittgen T, Klugmann M, Kirsch F, Kruger C, Pitzer C, Minnerup J, Schabitz WR, Schneider A: Semaphorin 6A improves functional recovery in conjunction with motor training after cerebral ischemia. PLoS One 2010, 5: e10737. 10.1371/journal.pone.0010737

    PubMed Central  PubMed  Article  Google Scholar 

  36. 36.

    Hicks AU, Hewlett K, Windle V, Chernenko G, Ploughman M, Jolkkonen J, Weiss S, Corbett D: Enriched environment enhances transplanted subventricular zone stem cell migration and functional recovery after stroke. Neuroscience 2007, 146: 31–40. 10.1016/j.neuroscience.2007.01.020

    CAS  PubMed  Article  Google Scholar 

  37. 37.

    Reitmeir R, Kilic E, Kilic U, Bacigaluppi M, ElAli A, Salani G, Pluchino S, Gassmann M, Hermann DM: Post-acute delivery of erythropoietin induces stroke recovery by promoting perilesional tissue remodelling and contralesional pyramidal tract plasticity. Brain 2011, 134: 84–99. 10.1093/brain/awq344

    PubMed  Article  Google Scholar 

  38. 38.

    Brown AW, Bjelke B, Fuxe K: Motor response to amphetamine treatment, task-specific training, and limited motor experience in a postacute animal stroke model. Exp Neurol 2004, 190: 102–8. 10.1016/j.expneurol.2004.07.005

    CAS  PubMed  Article  Google Scholar 

  39. 39.

    Hatinen S, Sairanen M, Sirvio J, Jolkkonen J: Improved sensorimotor function by rolipram following focal cerebral ischemia in rats. Restor Neurol Neurosci 2008, 26: 493–9.

    CAS  PubMed  Google Scholar 

  40. 40.

    Jin K, Wang X, Xie L, Mao XO, Greenberg DA: Transgenic ablation of doublecortin-expressing cells suppresses adult neurogenesis and worsens stroke outcome in mice. Proc Natl Acad Sci USA 2010, 107: 7993–8. 10.1073/pnas.1000154107

    CAS  PubMed Central  PubMed  Article  Google Scholar 

  41. 41.

    Ferrara A, El Bejaoui S, Seyen S, Tirelli E, Plumier JC: The usefulness of operant conditioning procedures to assess long-lasting deficits following transient focal ischemia in mice. Behav Brain Res 2009, 205: 525–34. 10.1016/j.bbr.2009.08.011

    PubMed  Article  Google Scholar 

  42. 42.

    Leconte C, Tixier E, Freret T, Toutain J, Saulnier R, Boulouard M, Roussel S, Schumann-Bard P, Bernaudin M: Delayed Hypoxic Postconditioning Protects Against Cerebral Ischemia in the Mouse. Stroke 2009.

    Google Scholar 

  43. 43.

    Freret T, Valable S, Chazalviel L, Saulnier R, Mackenzie ET, Petit E, Bernaudin M, Boulouard M, Schumann-Bard P: Delayed administration of deferoxamine reduces brain damage and promotes functional recovery after transient focal cerebral ischemia in the rat. Eur J Neurosci 2006, 23: 1757–65. 10.1111/j.1460-9568.2006.04699.x

    PubMed  Article  Google Scholar 

  44. 44.

    Baird AL, Meldrum A, Dunnett SB: The staircase test of skilled reaching in mice. Brain Res Bull 2001, 54: 243–50. 10.1016/S0361-9230(00)00457-3

    CAS  PubMed  Article  Google Scholar 

  45. 45.

    Tennant KA, Jones TA: Sensorimotor behavioral effects of endothelin-1 induced small cortical infarcts in C57BL/6 mice. J Neurosci Methods 2009, 181: 18–26. 10.1016/j.jneumeth.2009.04.009

    CAS  PubMed  Article  Google Scholar 

  46. 46.

    Haelewyn B, Freret T, Pacary E, Schumann-Bard P, Boulouard M, Bernaudin M, Bouet V: Long-term evaluation of sensorimotor and mnesic behaviour following striatal NMDA-induced unilateral excitotoxic lesion in the mouse. Behav Brain Res 2007, 178: 235–43. 10.1016/j.bbr.2006.12.023

    CAS  PubMed  Article  Google Scholar 

  47. 47.

    Wahl F, Allix M, Plotkine M, Boulu RG: Neurological and behavioral outcomes of focal cerebral ischemia in rats. Stroke 1992, 23: 267–72. 10.1161/01.STR.23.2.267

    CAS  PubMed  Article  Google Scholar 

  48. 48.

    Esneault E, Castagne V, Moser P, Bonny C, Bernaudin M: D-JNKi, a peptide inhibitor of c-Jun N-terminal kinase, promotes functional recovery after transient focal cerebral ischemia in rats. Neuroscience 2008, 152: 308–20. 10.1016/j.neuroscience.2007.12.036

    CAS  PubMed  Article  Google Scholar 

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Acknowledgements

Authors want to thank Kate Stanton for the English editing.

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Correspondence to Thomas Freret.

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Freret, T., Schumann-Bard, P., Boulouard, M. et al. On the importance of long-term functional assessment after stroke to improve translation from bench to bedside. Exp & Trans Stroke Med 3, 6 (2011). https://doi.org/10.1186/2040-7378-3-6

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Keywords

  • Potential Therapeutic Agent
  • Behavioral Impairment
  • Experimental Stroke
  • Stroke Therapy
  • Postoperative Weight Loss