Human mesenchymal stem cells (MSCs) have been isolated from bone marrow and other adult tissues and are potentially useful for tissue engineering. Adipose tissue has several clear advantages as a starting material for harvesting stem cells, as it is abundant and relatively easy to procure. However, existing methods to expand adipose-derived MSCs are less than optimal. Here we describe a new cell culture method that accelerates greatly the growth rate and prolongs the lifespan of adipose MSCs. This was accomplished by using a growth medium with low calcium and supplemented with N-acetyl-L-cysteine and L-ascorbic acid-2-phosphate. Cells produced early in these cultures displayed characteristics similar to those previously reported for multipotential stem cells, including a high frequency of anchorage- independent growth in soft agar, lack of gap junctional intercellular communication in a cell type with serpiginous morphology, and the expression of Oct-4. Furthermore, these cells could readily be induced to differentiate into adipocytes, osteoblasts, and chondrocytes. Thus, modification of growth medium by reduction of calcium and addition of antioxidants greatly enhanced the growth rate and extended the lifespan of adipose-derived multipotential human MSCs.

Achilles tendon problems are commonly encountered in sports medicine and low-level laser therapy (LLLT) is widely used in rehabilitative applications to decrease pain, reduce inflammatory processes, and promote tissue healing. This study examined the effects on the proliferation of porcine Achilles tendon fibroblasts and gene expression, using different doses of low-level laser irradiation (LLLI). Four groups of identically cultured fibroblasts were exposed to LLLI and harvested after 24 h. The control group (Group 1) was subjected to no LLLI. Other groups received 1 J/cm 2 (Group 2), 2 J/cm 2 (Group 3), and 3 J/cm 2 (Group 4), respectively. Cell proliferation and mRNA expressions of type I collagen and decorin were then measured. When compared to the control group, the cell proliferation of irradiated Achilles tendon fibroblasts in the other three groups increased significantly by 13% AE 0.8% (Group 2), 30% AE 0.4% (Group 3), and 12% AE 0.6% (Group 4) respectively. But progressively higher laser intensity did not achieve a correspondingly higher cell proliferation effect in Achilles tendon fibroblasts. The mRNA expressions of decorin and type I collagen in fibroblasts with LLLI were significantly higher (p < 0.05). Therefore, suitable dosages of LLLI may result in more effective tissue healing by promoting type I collagen and decorin synthesis. However, these positive effects of LLLI on the repair of the Achilles tendon in humans should be further investigated in clinic. ß

The new cell culture method can be used to develop gastric epithelial cell clones with sustained growth from endoscopic biopsy. The gastric cell clone showed several stem and/or progenitor cell phenotypes (i.e. the ability of AIG, high differentiation capacity, high susceptibility to spontaneous immortalization and the expression of Oct-4). The telomerase expression in these gastric stem and/or progenitor cells can be upregulated by exposure to H. pylori culture products and MNNG, an important step in neoplastic transformation. These results show that putative human gastric stem and/or progenitor cell clones can be developed by our method and these cells could be useful for studying the mechanisms of human gastric carcinogenesis including the mechanism of action of H. pylori, as well as the regulation of the proliferation and differentiation of human gastric mucosa.

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