Stem cells: their source, potency and use in regenerative therapies with focus on adipose-derived stem cells - a review.

Stem cells can be defined as units of biological organization that are responsible for the development and the regeneration of organ and tissue systems. They are able to renew their populations and to differentiate into multiple cell lineages. Therefore, these cells have great potential in advanced tissue engineering and cell therapies. When seeded on synthetic or nature-derived scaffolds in vitro, stem cells can be differentiated towards the desired phenotype by an appropriate composition, by an appropriate architecture, and by appropriate physicochemical and mechanical properties of the scaffolds, particularly if the scaffold properties are combined with a suitable composition of cell culture media, and with suitable mechanical, electrical or magnetic stimulation. For cell therapy, stem cells can be injected directly into damaged tissues and organs in vivo. Since the regenerative effect of stem cells is based mainly on the autocrine production of growth factors, immunomodulators and other bioactive molecules stored in extracellular vesicles, these structures can be isolated and used instead of cells for a novel therapeutic approach called "stem cell-based cell-free therapy". There are four main sources of stem cells, i.e. embryonic tissues, fetal tissues, adult tissues and differentiated somatic cells after they have been genetically reprogrammed, which are referred to as induced pluripotent stem cells (iPSCs). Although adult stem cells have lower potency than the other three stem cell types, i.e. they are capable of differentiating into only a limited quantity of specific cell types, these cells are able to overcome the ethical and legal issues accompanying the application of embryonic and fetal stem cells and the mutational effects associated with iPSCs. Moreover, adult stem cells can be used in autogenous form. These cells are present in practically all tissues in the organism. However, adipose tissue seems to be the most advantageous tissue from which to isolate them, because of its abundancy, its subcutaneous location, and the need for less invasive techniques. Adipose tissue-derived stem cells (ASCs) are therefore considered highly promising in present-day regenerative medicine.

Adding 11C-acetate to 18F-FDG at PET Examination Has an Incremental Value in the Diagnosis of Hepatocellular Carcinoma.

OBJECTIVE: The sensitivity of FDG at PET examination of Hepatocellular Carcinoma (HCC) is restricted. In a few studies, all done in Oriental patients, PET-examination with (11)C-acetate has shown a higher accuracy than with FDG. In the current study, the uptake of (11)C-acetate has been compared with the uptake of FDG in the primary HCC in a cohort of Occidental patients. MATERIAL AND METHODS: 44 patients underwent PET-examination with both tracers with a mean of 9 days between the examinations. 26 patients had a microscopical diagnosis and 18 were diagnosed with multimodal radiological methods. At least one relevant radiological examination was available for comparison. RESULTS: At visual evaluation, 13 of the HCC's were positive at PET-examination using FDG and 34 were positive using (11)C-acetate (p<0.001). Median tumor SUVmean of (11)C-acetate was 4.7 and of FDG was 1.9 (p<0.001). There was also a higher uptake of (11)C-acetate by the surrounding liver tissue than of FDG. Median liver SUVmean of [u]11[/u]C-acetate was 3.2 and of FDG it was 1.7 (p<0.001). This corresponded to a median tumour/liver tissue ratio for (11)C-acetate of 1.4 and for FDG of 1.0 (p<0.05). Previous reports of a negative correlation between the uptake of the tracers were weakly supported. In 4 large tumors some portions being hot using one of the tracers were cold using the other tracer and vice versa. CONCLUSION: Adding registration with (11)C-acetate to registration with FDG at PET-examination has an incremental value in the diagnosis of HCC. A higher tumor uptake of (11)C-acetate cannot be taken full advantage of because of a higher uptake also by the surrounding liver tissue. CONFLICT OF INTEREST: None declared.