Koichi Oishi

Quantum dots labeling using octa-arginine peptides for imaging of adipose tissue-derived stem cells.

Quantum dots (QDs) have been used to study the effects of fluorescent probes for biomolecules and cell imaging. Adipose tissue-derived stem cells, which carry a relatively lower donor site morbidity, while yielding a large number of stem cells at harvest, were transduced with QDs using the octa-arginine peptide (R8) cell-penetrating peptide (CPP). The concentration ratio of QDs:R8 of 1 x 10(4) was optimal for delivery into ASCs. No cytotoxicity was observed in ASCs transduced with less than 16 nM of QDs655. In addition, >80% of the cells could be labeled within 1 h and the fluorescent intensity was maintained at least for 2 weeks. The ASCs transduced with QDs using R8 could be differentiated into both adipogenic and osteogenic cells, thus suggesting that the cells maintained their stem cell potency. The ASCs labeled with QDs using R8 were further transplanted subcutaneously into the backs of mice or into mice through the tail vein. The labeled ASCs could be imaged with good contrast using the Maestro in vivo imaging system. These data suggested that QD labeling using R8 could be utilized for the imaging of ASCs.

Cell transplantation of adipose tissue-derived stem cells in combination with heparin attenuated acute liver failure in mice.

The effect of adipose tissue-derived stem cells (ASCs) in combination with heparin transplantation on acute liver failure mice with carbon tetrachloride (CCl4) injection was investigated. CCl4 is a well-known hepatotoxin and induces hepatic necrosis. Heparin did not affect the viability of ASCs for at least 24 h. The injection of heparin into the caudal tail vein decreased slightly the activities of the alanine aminotransferase (ALT), asparate aminotransferase (AST), and lactate dehydrogenase (LDH) in plasma. In the transplantation of ASCs (1 × 106 cells) group, there was a trend toward decreased activities of all markers. However, four out of six mice died of the lung infarction. In the transplantation of ASCs in combination with heparin group, there was also a trend toward decreased activities of all markers. In addition, all mice survived for at least the duration of the study period. In conclusion, the transplantation of ASCs in combination with heparin was thus found to effectively treat acute liver failure.

Quantum dots for labeling adipose tissue-derived stem cells.

Adipose tissue-derived stem cells (ASCs) have a self-renewing ability and can be induced to differentiate into various types of mesenchymal tissue. Because of their potential for clinical application, it has become desirable to label the cells for tracing transplanted cells and for in vivo imaging. Quantum dots (QDs) are novel inorganic probes that consist of CdSe/ZnS-core/shell semiconductor nanocrystals and have recently been explored as fluorescent probes for stem cell labeling. In this study, negatively charged QDs655 were applied for ASCs labeling, with the cationic liposome, Lipofectamine. The cytotoxicity of QDs655-Lipofectamine was assessed for ASCs. Although some cytotoxicity was observed in ASCs transfected with more than 2.0 nM of QDs655, none was observed with less than 0.8 nM. To evaluate the time dependency, the fluorescent intensity with QDs655 was observed until 24 h after transfection. The fluorescent intensity gradually increased until 2 h at the concentrations of 0.2 and 0.4 nM, while the intensity increased until 4 h at 0.8 nM. The ASCs were differentiated into both adipogenic and osteogenic cells with red fluorescence after transfection with QDs655, thus suggesting that the cells retain their potential for differentiation even after transfected with QDs655. These data suggest that QDs could be utilized for the labeling of ASCs.

Establishment of mouse pancreatic stem cell line.

β-Cell replacement therapy via islet transplantation is a promising possibility for the optimal treatment of type 1 diabetes. However, such an approach is severely limited by the shortage of donor organs. Pancreatic stem/progenitor cells could become a useful target for β-cell replacement therapy in diabetic patients because the cells are abundantly available in the pancreas of these patients and in donor organs. In this study, we established a mouse pancreatic stem cell line without genetic manipulation. The duct-rich population after islet isolation was inoculated into 96-well plates in limiting dilution. From over 200 clones, 15 clones were able to be cultured for over 3 months. The HN#13 cells, which had the highest expression of insulin mRNA after induction, expressed PDX-1 transcription factor, glucagon-like peptide-1 (GLP-1) receptor, and cytokeratin-19 (duct-like cells). These cells continue to divide actively beyond the population doubling level (PDL) of 300. Exendin-4 treatment and transduction of PDX-1 and NeuroD proteins by protein transduction technology in HN#13 cells induced insulin and pancreas-related gene expression. This cell line could be useful for analyzing pancreatic stem cell differentiation. Moreover, the isolation technique might be useful for identification and isolation of human pancreatic stem/progenitor cells.

Cryopreservation of human adipose tissue-derived stem/progenitor cells using the silk protein sericin.

Adipose tissue-derived stem/progenitor cells (ASCs) have attracted attention as a cell source that replaces marrow stromal cells (MSCs); ASCs may thus have applications in both regenerative medicine and cell transplantation. These medical treatments, however, require a high-quality supply of human ASCs. Therefore, the cryopreservation methods have been improved by changing a component of a cryopreservation medium. Sericin, a protein hydrolysate (with an average molecular weight of 30 kDa) is very rich in serine. The viability and the adipogenic/osteogenic potential of human ASCs were tested after freezing in a cryopreservation medium containing sericin. After thawing, the viability of the human ASCs frozen in the cryopreservation medium was found to be more than 95%. The proliferation rate of human ASCs frozen in CELLBANKER 2, and DMEM/Hams F-12 medium (serum free) + 10% DMSO, 0.1 mol/L maltose, and 1% sericin was higher than that of the cells frozen in the maintenance medium + 10% DMSO. The adipogenic/osteogenic differentiation capabilities of frozen human ASCs were examined by Oil Red O staining/Von Kossas method. The human ASCs were frozen using CELLBANKER 2, and DMEM/Hams F-12 medium (serum free) + 10% DMSO, 0.1 mol/L maltose, and 1% sericin were positive. In conclusion, the cryopreservation medium containing sericin is therefore considered to have a beneficial effect on freezing human ASCs. This serum-free cryopreservation medium should be widely used in regenerative medicine, cell transplantation, and biological research.

Cryopreservation of Mouse Adipose Tissue-Derived Stem/Progenitor Cells

Adipose tissue-derived stem/progenitor cells (ASCs) have been reported to differentiate not only into mesodermal cells such as osteoblasts, chondorocytes, and adipocytes, but also to endodermal cells such as hepatocytes and insulin-expressing cells. These stem/progenitor cells are expected to be used for variety of regenerative therapies. This study demonstrates the viability and the adipo/osteogenic potential of cryopreserved ASCs using seven cryopreservation solutions, including 10% DMSO, Cell Freezing Medium-DMSO, Cell Freezing Medium-Glycerol, Cell Banker 1, Cell Banker 1+, Cell Banker 2, and CP-1. ASCs were obtained from mouse subcutaneous adipose tissue. The viability of the cryopreserved ASCs was over 90% with Cell Banker 2 preservation, approximately 90% with Cell Banker 1, Cell Banker 1+, or CP-1 preservation, and less than 80% for 10% DMSO, Cell Freezing Medium-DMSO, or Cell Freezing Medium-Glycerol preservation. No difference in the adipo/osteogenic potential was found between cells with or without cryopreservation in Cell Banker 2. These data suggests that Cell Banker 2 is the most effective cryopreservation solution for ASCs and that cryopreserved as well as noncryopreserved ASCs could be applied for regenerative medicine.

Differential ability of somatic stem cells.

Somatic stem cells can be isolated from a variety of sources. Although some studies have suggested that somatic stem cells may represent a cell population that is very similar to embryonic stem (ES) cells, it remains unclear whether somatic stem cells retain the potential to differentiate into any cell type derived from the three germ layers. In this study, we investigated the transdifferentiation potential of somatic stem cells using adipose tissue-derived stem/progenitor cells (ASCs; mesodermal stem cells) and pancreatic stem cells (endodermal stem cells). Previous reports from other groups describe the protocol that has been used to differentiate ASCs or mesenchymal stem cells (MSCs) in bone marrow into insulin-producing cells. Induction 1: ASCs were cultured for 3 days in ultra-low attachment plates under serum-free conditions. Induction 2: ASCs were cultured for 24 h with L-DMEM, and reinduced with serum-free H-DMEM for another 10 h. Unlike previous reports, we did not get ASCs to express any pancreas-specific genes, including insulin-1 or insulin-2. Pancreatic stem cells were induced to differentiate into adipo/osteogenic by the following protocols. Induction protocol 1: ACSs were cultured for 7 days with medium containing indometacin, dexamethasone, hydrocortisone, and insulin for adipogenic differentiation. Induction protocol 2: The cells were cultured for 7 days with medium containing dexamethasone, ascorbate-2-phosphate, and β-glycerophosphate for osteogenic differentiation. Although these approaches have been widely used for adipo/osteogenic differentiation from MSCs, adipo/osteogenic differentiation from pancreatic stem cells was not observed. These data suggest that it is not easy for somatic stem cells to transdifferentiate into other germ cell types, at least, under these conditions.

Recombinant sendai virus-mediated gene transfer to adipose tissue-derived stem cells (ASCs).

Adipose tissue-derived stem cells (ASCs) are expected to have clinical applications as well as other stem cells, because ASCs can be obtained safely from adult donors and used in autologous therapies without concern about rejection and the need for immunosuppression. However, the use of gene transfer with Sendai virus (SeV) vectors, which can efficiently introduce foreign genes without toxicity into several cells, with ASCs has not yet been investigated. This study documents on the use of SeV vectors for gene transfer to ASCs. The dose-dependent GFP expression of ASCs transfected with SeV vectors after 48 h of culture at 37°C was first evaluated. Next, the cellular toxicity of ASCs transfected with SeV vectors was verified. In addition, SeV vectors were compared with adenovirus (AdV) vectors. Finally, the time-dependent GFP expression of ASCs transfected with SeV vectors was evaluated. The results showed that transfection of ASCs with SeV vectors results in more efficient expression of transgene (GFP expression) in the ASCs than with AdV vectors after 48 h of culture at 37°C. Moreover, while the transfection of ASCs with AdV vectors at high MOIs was cytotoxic (a lot of transfected cells died) that of ASCs with SeV vectors at high MOIs was not necessarily cytotoxic. In addition, the preservation of multilineage ASCs transfected with SeV was observed. In conclusion, this is the first report describing the successful use of SeV-mediated gene transfer in ASCs, and the results indicate that SeV may thus provide advantages with respect to safety issues in gene therapy.

In Vivo Imaging of Transplanted Islets Labeled with a Novel Cationic Nanoparticle

To monitor pancreatic islet transplantation efficiency, reliable noninvasive imaging methods, such as magnetic resonance imaging (MRI) are needed. Although an efficient uptake of MRI contrast agent is required for islet cell labeling, commercially-available magnetic nanoparticles are not efficiently transduced into cells. We herein report the in vivo detection of transplanted islets labeled with a novel cationic nanoparticle that allowed for noninvasive monitoring of islet grafts in diabetic mice in real time. The positively-charged nanoparticles were transduced into a β-cell line, MIN6 cells, and into isolated islets for 1 hr. MRI showed a marked decrease in the signal intensity on T1- and T2-weighted images at the implantation site of the labeled MIN 6 cells or islets in the left kidneys of mice. These data suggest that the novel positively-charged nanoparticle could be useful to detect and monitor islet engraftment, which would greatly aid in the clinical management of islet transplant patients.

Transduction of Cell-Penetrating Peptides into Induced Pluripotent Stem Cells:

Induced pluripotent stem (iPS) cells have recently been generated by Yamanakas group, and then followed by others. iPS cells are expected to have clinical applications including an important role in regenerative medicine. This study focused on the cell-penetrating peptides (CPPs) for differentiation or functional application of iPS cells, because several transduction domains can deliver a large size-independent variety of molecules into cells. Two CPPs, Texas Red-R8 and Rhodamine-TAT, were generated as representative CPPs and these CPPs were tested to determine their ability to penetrate the membrane of iPS cells. Both CPPs were transduced in iPS cells through macropinocytosis classified in endocytosis within 2 h in a manner consistent with many other cells, and no cytotoxicity and influence on their undifferentiated state was observed. In conclusion, CPPs can be utilized for their differentiation or functional application in iPS cells.