The effect of magnetic field during freezing and thawing of rat bone marrow-derived mesenchymal stem cells.

Previous studies showed that a programmed freezer with magnetic field can maintain a high survival rate of mesenchymal stem cells (MSCs). The purpose of this study was to evaluate the influences of magnetic field during freezing and thawing on the survival of MSCs isolated from rat bone marrow. The cells were frozen by a normal programmed freezer or a programmed freezer with magnetic field (CAS-LAB1) and cryopreserved for 7 days at -150 °C. Then, the cells were thawed in the presence or absence of magnetic field. Immediately after thawing, the number of surviving or viable cells was counted. The cell proliferation was examined after 1-week culture. Cryopreserved MSCs which were frozen by a normal freezer or a CAS freezer were transplanted into bone defects artificially made in calvaria of 4-week-old rats. Non-cryopreserved MSCs were used as a control. The rats were sacrificed at 8, 16, or 24 weeks after transplantation and the bone regeneration area was measured. Proliferation rates of MSCs after 1 week were significantly higher in the CAS-freezing-thawing group than in the CAS-freezing group. The extent of new bone formation in the CAS-freezing-thawing group tended to be larger than in CAS-freezing group 24 weeks after transplantation. These results suggest that a magnetic field enhances cell survival during thawing as well as freezing.

Cranial suture-like gap and bone regeneration after transplantation of cryopreserved MSCs by use of a programmed freezer with magnetic field in rats.

Mesenchymal stem cells (MSCs) can be used for regeneration of various organs and tissues. A previous study revealed that cryopreserved MSCs, which were frozen by a programmed freezer with a magnetic field (Cells Alive System: CAS) and cryopreserved for 7 days in a -150°C deep freezer, can maintain high survival and proliferation rates while retaining both adipogenic and osteogenic differentiation abilities. The purpose of this study was to examine MSC viability and tissue regenerative ability after long-term cryopreservation using a CAS freezer. MSCs were isolated from rat femora bone marrow and cryopreserved in a -150°C deep freezer (CAS group) or directly cryopreserved in a deep freezer (Direct group). After 3 years, the cells were thawed and the number of viable cells was counted. Cell proliferation was also examined after 14 days in culture. For histological examination, forty 4-week-old Fischer 344 male rats received bone and sagittal suture defects with a diameter of 6.0mm, and MSCs (CAS or Direct group) cryopreserved for 1 year were grafted with membranes. Non-cryopreserved MSCs (Control group) were transplanted to an additional twenty rats. The rats were sacrificed at 4, 8, 16, and 24 weeks after surgery. The parietal bones, including the sagittal suture, were observed under a light microscope and the extent of bone regeneration was measured. Our results indicate that MSCs survival and proliferation rates were significantly higher in the CAS group than in the Direct group. In the Control and CAS groups, a large amount of new bone formation and a suture-like gap was identified 24 weeks after transplantation, whereas only a small amount of new bone formation was observed in the Direct group. These results suggest that the CAS freezer is amenable to long-term cryopreservation of MSCs, which can be applied to the regeneration of various tissues, including bone tissue with suture-like gap formation.

Equivalent efficacy of mitomycin C plus doxorubicin instillation to bacillus Calmette-Guerin therapy for carcinoma in situ of the bladder.

BACKGROUND: To elucidate the most efficient topical therapy for carcinoma in situ of the bladder, the efficacy of intravesical mitomycin C plus doxorubicin therapy was compared with bacillus Calmette-Guerin (BCG) therapy. The clinical behavior of the tumor was analysed according to the histological grade. METHODS: Forty-two patients with carcinoma in situ of the bladder were randomized to intravesical BCG (21 patients) or mitomycin C plus doxorubicin sequential therapy (21 patients) as first line treatment. The non-responders underwent the subsequent instillation of the other intravesical therapy alternately. Of the patients, 27 had grade 2 and 15 had grade 3 cancer. RESULTS: Both topical therapies were equally effective with initial response rates of 86% (18/21) for BCG and 81% (17/21) for mitomycin C plus doxorubicin, irrespective of the tumor grade. Of seven initial non-responders, five patients achieved a complete response by subsequent instillation, resulting in a total response rate of 95%. After a mean follow-up of 47 months, five patients (12%) developed disease progression. The progression rates were not different between the topical therapies, but were significantly higher in grade 3 than in grade 2 cases. CONCLUSION: It appears likely that mitomycin C plus doxorubicin instillation has an equivalent efficacy to BCG as the initial therapy of carcinoma in situ and the combination of them would be the most efficient treatment for the disease. Moreover, histological grading would be clinically useful in defining the tumor characteristics and behavior of carcinoma in situ of the bladder.