Among autologous somatic stem cells, bone marrow-derived mesenchymal stem cells (BMSCs) are the most widely used worldwide to repair not only mesenchymal tissues (bone, cartilage) but also many other kinds of tissues, including heart, skin, and liver. Autologous BMSCs are thought to be safe because of the absence of immunological reaction and disease transmission. However, it is possible that they will form tumours during long-term follow-up. In 1988, we transplanted autologous BMSCs to repair articular cartilage, which was the first such trial ever reported. Subsequently we performed this procedure in about 40 patients. Demonstration that neither partial infections nor tumours appeared in these patients provided strong evidence for the safety of autologous BMSC transplantation. Thus, in this study we checked these patients for tumour development and infections. Between January 1998 and November 2008, 41 patients received 45 transplantations. We checked their records until their last visit. We telephoned or mailed the patients who had not visited the clinics recently to establish whether there were any abnormalities in the operated joints. Neither tumours nor infections were observed between 5 and 137 (mean 75) months of follow-up. Autologous BMSC transplantation is a safe procedure and will be widely used around the world.

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Background. The current study was undertaken to investigate whether or not tumor cells are dislodged into the portal venous stream during hepatic resection for hepatocellular carcinomas. Methods. A catheter was placed using echo guidance into the portal branch through the mesenteric vein in 31 patients. Cytologic examinations were done on multiple blood samples at various operative stages. Results. Tumor cells were recovered in 7 of 31 patients in whom the tumor sizes were more than 5 cm and portal invasions were found microscopically and/or macroscopically. By contrast, the remaining 24 tumors were less than 5 cm in size and showed negative portal invasions. Recovery of the tumor cells was found, not during the earlier operative stage of mobilization or rotation of the hepatic lobe, but during the later stages of hilar dissection or hepatic parenchymal dissection. Conclusions. The portal pedicles should be divided before hepatic dissection in segmentectomy and lobec‐tomy to lessen the chance of dissemination of intravasated tumor cells. Cancer 1992; 70:2263‐2267.

Oval cells that develop in the rat 2-acetylaminofluorene/ partial hepatectomy (AAF/PH) model express the c-kit receptor tyrosine kinase (KIT) and its ligand, stem cell factor (SCF). We investigated the role of the SCF/KIT system in the development of oval cells using Ws/Ws rats, whose c-kit kinase activity was severely impaired owing to a small deletion in the kinase domain. On days 7, 9, and 13 after PH in the AAF/PH model, the development Mature hepatocytes proliferate after partial hepatectomy (PH), resulting in regeneration of the liver. In contrast, if PH is performed under conditions in which the replication of mature hepatocytes is impaired, oval cells that are assumed to develop from hepatic stem cells located in the canal of Hering (biliary ductule) proliferate instead of mature hepatocytes and infiltrate into the surrounding parenchyma.

Introduction To investigate the efficacy of the transplantation of autologous bone marrow-derived mesenchymal stem cells (BMSCs) under arthroscopy with microfracture (MFX) compared with microfracture alone. Methods Eleven patients with a symptomatic articular cartilage defect of the knee were included in the study. They were randomized to receive BMSCs with MFX (cell-T group, n=7) or MFX alone (control group, n=4). Clinical results were evaluated using International Knee Documentation committee (IKDC) knee evaluation questionnaires and the Knee Injury and Osteoarthritis Outcome Score (KOOS) before and 48 weeks after surgery. Quantitative and qualitative assessments of repair tissue were carried out at 48 weeks by T2 mapping of magnetic resonance images (MRIs) and the magnetic resonance observation of cartilage repair tissue (MOCART) scoring system with follow-up MRI. Results No significant differences between preoperative and postoperative IKDC and KOOS were observed in the cell-T or control group. However, forty-eight weeks after surgery, the cell-T group showed a trend for a greater KOOS QOL score compared with the control group (79.4 vs. 39.1, respectively; P=0.07). The T2 value did not differ significantly between the two groups, but the mean MOCART score was significantly higher in the cell-T group than in the control group (P=0.02). Conclusions Compared with MFX alone, BMSC transplantation with MFX resulted in better postoperative healing of the cartilage and subchondral bone as determined by the MOCART score. Clinically, BMSC transplantation with MFX gave a higher KOOS QOL score after 48 weeks.