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    Consider Using Diffusion Tensor Imaging in Geron Phase I Trial | American Journal of Neuroradiology  
    


















    


























    
  
  




    
    

  

      


    

      

  
  
  

    

  

    

  

                
    

      

  

    

  
      
  
  

    


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LetterLetter

  
      

  
      
Consider Using Diffusion Tensor Imaging in Geron Phase I Trial
  
    	
C.B. Patel

  
    	
American Journal of Neuroradiology August 2009,  30 (7) e97; DOI: https://doi.org/10.3174/ajnr.A1632 

  
  
  



  


  
  



  
      
  
  

    
The first-time approval of human embryonic stem cell (hESC)-based therapy by the US Food and Drug Administration has highlighted the application of regenerative medicine to human spinal cord injury (SCI). As a result, attention has recently focused on the potential promises and perils of Geron Corporation’s (Menlo Park, Calif) hESC-derived oligodendrocyte progenitor cells (OPCs) in the treatment of human SCI.1 The rationale for the OPC therapy is that remyelination (by oligodendrocytes) of damaged spinal cord axons may improve nerve conduction and, thereby, perhaps neuromotor recovery in patients with SCI. Although the end points for the Geron phase I multicenter SCI trial are primarily safety and secondarily efficacy,2 the addition of noninvasive diffusion tensor imaging (DTI) to track patients treated with OPCs would enhance assessment of the therapy.
DTI, a newer MR imaging technique, provides quantitative information about axonal structure. Of relevance to the recently approved Geron study, on the basis of rodent models of SCI, the DTI measure of transverse diffusivity has been shown to be correlated with demyelination,3 whereas the DTI measure of longitudinal diffusivity has been shown to be correlated with axonal damage.4 In animal models, research is underway to elucidate the sensitivity and specificity of DTI measures for the various pathologies caused by SCI. Given the correlations that exist between conventional MR imaging measures and the degree of myelination,5 longitudinally tracking DTI measures from baseline scan values could provide investigators with additional information about changes in the state of axonal integrity and myelination after OPC therapy.
In addition to the presence of skilled neurosurgical and neuroradiologic teams for the intraspinal injection of OPCs, the presence of human DTI scanning capability should be considered when selecting clinical sites for enrollment of study participants. Indeed, the use of MR imaging to monitor cell transplant therapies in human SCI is not new; Féron et al6 used conventional MR imaging to scan spinal cords 1 year posttransplantation of autologous olfactory ensheathing cells in patients with SCI. However, using DTI in conjunction with conventional MR imaging techniques to image and monitor the progress of this novel therapy would increase the assessment potential of its phase I trial.
References
  1. Couzin J. Biotechnology: celebration and concern over U.S. trial of embryonic stem cells. Science 2009;323:568
  2. Geron Corporation. Geron receives FDA clearance to begin world’s first human clinical trial of embryonic stem cell-based therapy. Available at: http://geron.com/grnopc1clearance/grnopc1-backgrounder.pdf. Accessed February 5,2009
  3. Herrera JJ, Chacko T, Narayana PA. Histological correlation of diffusion tensor imaging metrics in experimental spinal cord injury. J Neurosci Res 2008;86:443–47
  4. Budde MT, Kim JH, Liang HF, et al. Toward accurate diagnosis of white matter pathology using diffusion tensor imaging. Magn Res Med 2007;57:688–95
  5. Mori S, Zhang J. Principles of diffusion tensor imaging and its applications to basic neuroscience research. Neuron 2006;51:527–39
  6. Féron F, Perry C, Cochrane J, et al. Autologous olfactory ensheathing cell transplantation in human spinal cord injury. Brain 2005;128:2951–60
  


  
  



  



    

  



  

                
    

      

  

    

  
      
  
  

    


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