Pathologic findings in retinal pigment epithelial cell implantation for Parkinson's disease. Neurology 2009; 73:1095–1102

doi:10.5214/71

Annals of Neurosciences, Vol 16, No 4 (2009)

Journal club

Neurology 2009; 73:1095-1102

Pathologic findings in retinal pigment epithelial cell implantation for Parkinson's disease

Emad S. Farag, Harry V. Vinters, MD, FCAP, FRCP(C) and Jeff Bronstein, MD, PHD

UCLA Department of Neurology (E.S.F., H.V.V., J.B.); WLA VA Southwest PADRECC (E.S.F., J.B.), Los Angeles; and UCLA Section of Neuropathology (H.V.V.), Department of Pathology and Laboratory Medicine, Los Angeles, CA.

Correspondence : Dr. Emad Farag,Movement Disorders Program, UCLA Department of Neurology, 300 UCLA Medical Plaza Ste. B200,Los Angeles, CA 90095 efarag@mednet.ucla.edu

Tajinder Singh
Neuroscience Research Lab, Department of Neurology, Post Graduate Institute of Medical Education and Research, Chandigarh, India

Background

Parkinson disease (PD) is a movement disorder that results in muscle rigidity and tremors. Dopaminergic neuron loss in the substantia nigra region of brain is one of the many known causes of this disease. L-dopa therapy is routinely used in clinics to manage the symptoms of PD. However L-dopa therapy has its own limitations and side effects that necessitate testing of regenerative medicine strategies in this disease. The regeneration of damaged or dying dopaminergic neurons with surgical implantation of adrenal medullary, fetal mesencephalic, and cultured human mesencephalic tissue grafts has been reported with encouraging outcomes. RPE cells may prove to be specifically useful for PD treatment as they can restore the production of dopamine. Some previous trials have reported the putamental implantation of human RPE cells in PD patients. However, Farag et al have reported for the first time, autopsy analysis of a PD patient's brain after RPE cell implantation.

Study Design

This study is a post-implantation autopsy analysis of a PD patient's brain with an idea to track and investigate the fate of implanted RPE cells. The subject in this study was a 68-year old man with 18 year long history of PD symptoms. The subject underwent bilateral putamental implantation of 325,000 RPE cells though stereotactic injections distributed over 5 tracts in each putamen. The subject died six months after implantation procedure due to a fall that lead to pulmonary empyema. The brain was removed and fixed in 10% neutral buffered formalin. The brain appeared to be normal upon gross examination and microscopic examination showed normal cortical neuronal laminar architecture. Coronal sections of left hemisphere were taken at intervals of 1 cm for histologic examination. Pathological analysis of the brain was performed to confirm the Parkinson disease (PD) neuropathology. Hematoxylin-eosin (H-E) stained sections of substantia nigra (SN) showed severe loss of pigmented neurons and Lewy bodies in Locus ceruleus (LC). a-synuclein reactive neurons were also observed in frontal cortex to further confirm the PD pathology. All such pathological findings are expected in such a case of prolonged PD.

In order to track and count the implanted RPE cells, tissue blocks from the coronal sections of brain were screened by serial sectioning to trace all the five implantation tracts by a detailed microscopic examination. A total of 118 cells were counted by manual method in all the Η-E stained sections examined, with a very low survival of 0.036%. The number of surviving RPE cells was found to be highly variable in different tracts and even between different sections in the same tract, in different regions of the brain. This is consistent with previous reports where up to six-fold variability was found in cell survival with respect to variables such as graft donors and target region of implant (e.g. striatum vs. midbrain).¹,² A 100-fold variability in cell survival between different tracts has been reported within the same subject and the same hemisphere whereas some other studies reported absence of survival to survival of 100,000 cells between different hemispheres of same subject. ², ³CD68 and glial fibrillary acidic protein immunostaining revealed inflammatory macrophage/microglial and astroglial activity along the implantation tracts. The adaptive cellular immune response as a result of implantation was demonstrated by immunostaining for B- and T-cell markers CD4, CD8, and CD19. The inflammatory response in implantation tracts was found to be predominantly macrophage mediated although there were a few CD8-positive T-cells. Perl's iron stain on parenchyma around lesion sites further confirmed the presence of iron in macrophages. The inflammatory response observed at the site of surviving RPE cells and the surrounding tissue appears to be the major factor responsible for the very low survival of RPE cells in this subject. Immunosuppression has been reported to be associated with little or no inflammation in subjects who received fetal mesencephalic grafts.¹,² It should be noted that the subject didn't receive any immunosuppressant which highlights the importance of these agents and inflammation management in implantation cases such that there is increase in the survival of donor cells.

Implications

Autopsy analysis of subjects after cell implantation is required to investigate the fate of implanted cells in validating such treatment methods. Such autopsy studies can reveal the causes of poor survival of implanted cells like inflammatory response to the donor cells as reported by Farag et al in this study and help in formulating protocols to raise the survival rate of donor cells.

doi:10.5214/ans.0972.7531.2009.160407

References

1 Olanow CW, Goetz CG, Kordower JH, et al. A double-blind controlled trial of bilateral fetal nigral transplantation in Parkinson's disease. Ann Neurol 2003;54:403-414.

2 Méndez I, Sanchez-Pernaute R, Cooper  et al. Cell type analysis of functional fetal dopamine cell suspension transplants in the striatum and substantia nigra of patients with Parkinson's disease. Brain 2005;128:1498-1510.

3 Kordower JH, Rosenstein JM, Collier TJ, et al. functional fetal nigral grafts in a patient with Parkinson's disease: chemoanatomic, ultrastructural and metabolic studies. J Comp Neurol 1996;370: 203-230.

4 Sharma NK, Prabhakar S, Anand A. Age related macular degeneration advances and trends. Annals of Neurosciences 2009;16(2):62-71.

5 Chaturvedi RK, Shukla S, Seth K et al Glial cell line derived neurotrophic factor (gdnf) increases the survival and function of hibernated fetal dopaminergic cells transplanted in rat model of parkinson's disease. Annals of Neurosciences 2006; 13(3)56-64.