[en] This issue is the collection of the papers presented at title meeting. The report contains 11 of the presented papers and 7 of them are indexed individually. (J.P.N.)

[en] Functional MRI has been world-widely developed. The potential of the imaging method is shown here. In the former part, delayed gadolinium enhanced MRI of cartilage is presented. In the latter part, up-date MRI techniques are explained as potential tools for Regenerative Medicine. (author)

[en] This paper summarizes PET/SPECT probes for the in vivo imaging of cell behavior such as cell growth, differentiation, migration, adhesion, angiogenesis, and apoptosis. These probes may be indispensable for the fundamental research of regenerative medicine. (author)

[en] The availability of the human genome sequence will lead to the discovery of many novel genes that are expressed in a disease-specific pattern. The use of antisense radiopharmaceuticals may be a way to image in vivo a gene of unknown function. However, the in vivo imaging of gene expression with antisense radiopharmaceuticals have been limited by several problems. In this presentation, recent attempts to overcome problems are discussed, and some promising examples are shown. In addition, the original approach being taken by the author's group is briefly demonstrated. Finally, this presentation emphasizes that in vivo imaging of gene expression will be possible by the use of antisense radiooligonucleotides in combination with advanced DDS technology. (author)

[en] Neural transplantation is expected as an eradicative treatment of intractable central neural disease. In addition to behavioral observations, the recent development of the in vivo imaging technique also enabled to assess functions of neural graft in living subjects. Then we performed the PET scans using the unilateral 6-OHDA-lesioned rats in order to assess the pre- and post-synaptic functions in the striatum after transplantation of fetal dopaminergic neurons. As a result of PET scan, the images of [11C]PE2I, tracer of dopamine transporter, showed increased accumulation in the region which corresponded to the transplanted site after the graft. Because dopamine transporter exists on the cytoplasma membrane of axonal terminal, the accumulation of [11C]PE2I was regarded as a market of survival and maturation of transplanted cells. Also the images of [11C]raclopride, tracer of dopamine D2 receptor, revealed that up-regulation of D2 receptors normalized 4 weeks after transplantation. [11C]Raclopride was considered a marker of change of secondary dopaminergic environment. We believed that assessments with PET bring us much information, and it will increasingly contribute to a development of the regenerative medicine. (author)

[en] Gene imaging with radio-labeled antisense deoxyribonucleic acid (DNA) or peptide nucleic acid (PNA) is useful for detection of the expression of therapeutic gene in gene therapy in vivo. A delivery carrier is requisite for the imaging with antisense to transport the antisense to cell inside, since in general antisense does not across biological membrane. In the case of brain, there is another obstruction, the blood brain barrier (BBB), have to overcome. In the present study, surface-modified liposome and conjugate were prepared as tool to delivery antisense through the BBB. Poly-arginine peptides were bonded to the surface of conventional liposome. Although a small amount, this enabled the conventional liposome to enter the brain across the BBB after i.v. administration, while the conventional liposome is unable to do it in itself. In addition, antisense PNA was capacitated of entering the cultured hepatocytes in the presence of asialofetuin conjugated with oligonucleotides, and released in cytoplasm in vitro. This is very ideal for function of antisense since the binding of antisense to target may be weakened if without the release from delivery carrier. The brain-specific molecule as pilot is very import for targeting of delivery system. Our co-investigators found that microglia can migrate into brain across BBB from blood, while the migration toward other tissue was exiguous. The isolated plasma membrane from microglia could enter the brain similar to microglia, suggesting the brain-specific migration due to certain unknown molecule(s) on the surface of microglia. Identification of them will help us develop brain-specific delivery system. (author)

[en] Many animal models have been for studying neutrodegenerative diseases in humans. Among them, Parkinson's disease (PD) model in primates treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is expected to be valid and useful in the field of regenerative medicine. MPTP-treated monkeys demonstrate parkinsonian syndrome, such as tremor, dyskinesia, rigidity, immobility, caused by the degeneration of dopamine neurons at the nigrostriatal pathway. In this model, investigation of cognitive impairment that is one of the important aspects of PD could be possible. We evaluated the degeneration process of nigrostriatal dopamine neurons with positron emission tomography (PET) using unanesthetized MPTP-treated two cynomolgus monkeys (Macaca fascicularis). The tracers used were [11C]PE2I, [11C]DOPA, [11C]raclopride for monitoring dopamine transporter (DAT) densities, dopamine (DA) turnover, dopamine D2-receptor (D2R) densities, respectively. The gross behavioral observation was also performed referring to the criteria of the PD symptoms. The motor dysfunction was not clearly observed up to the cumulative doses of 3 mg/kg MPTP. This period was called 'asymptomatic period'. As a result of PET scans in the asymptomatic period, DAT densities and DA turnover had already decreased greatly, but D2R densities had not changed clearly. These findings suggest that PET imaging can delineate the dopaminergic dysfunction in vivo even in the asymptomatic period. In human study of PD, it is reported that parkinsonism is shown after great loss of dopaminergic neutrons as well as pre-synaptic dysfunction. MPTP-treated monkeys demonstrate the parkinsonian syndrome with the similar mechanism as human PD. It can be expected that PET study with MPTP-monkeys would provide important clues relevant to the underlying cause of PD and be useful for preclinical study of regenerative medicine in this disease. (author)

[en] For functional assessment of gene therapy in experimental animals, in vivo assessment of transferred genes will provide a major advance over an in vitro analysis which must be done post-hoc. In the current study we have conducted positron emission tomography (PET) analysis in 5-, 13-, and 24-month-old Fischer 344 rats that had hemilateral gene transfer of D₂ receptors mediated by adenoviral vectors (AdCMV.DopD₂R) in the striatum with contralateral striatal injection of control vectors (AdCMV.LacZ) to provide a quantitative evaluation of D₂R overexpression. The significant increase of D₂R binding of three D₂R radioligand, [¹¹C]raclopride, [¹¹C]nemonapride and [¹¹C]N-methylspiperone, was found in the AdCMVDopD₂R-injected rat striatum 2 or 3 days after vector injection. The binding potential of [¹¹C]raclopride was significantly higher in the AdCMV.DopD₂R-injected striatum than the control side in each age group at a similar degree, suggesting no aging effect on the overexpression of D₂ receptors. The binding potential in the AdCMV.DopD₂R-injected striatum of 24-month-old rats was similar to that in the control side of 5-month-old rats, demonstrating that the adenoviral vector-mediated gene transfer of D₂ receptors compensated the decreased density of striatal D₂ receptors in the 24-month-old rats up to the level in the control striatum of 5-month-old rats. A group of rats underwent follow-up assessment by positron emission tomography. The overexpression of D₂ receptors decreased with time in all three groups, however, the decrease rate of the D₂ receptors expression was significantly smaller in the 24 month-old group than in the 6 month-old-group. (author)