Human mesenchymal stem cells may be involved in keloid pathogenesis.

BACKGROUND: The pathogenesis of keloid is poorly understood. Although vigorous investigations have attempted to elucidate the mechanisms or causative factors of keloid, there are little data on why keloids are very intractable and recur easily in each patient. METHODS: In an attempt to analyze the possible interaction between human mesenchymal stem cells and keloid-derived fibroblasts, the dual-chamber cell-migration assay, cell proliferation, ultrastructural morphology, and Western blot analysis were used to investigate the production of the extracellular matrices of the coculture. RESULTS: Cell proliferation was not significantly different between keloid-derived fibroblasts and normal dermal fibroblasts during a 4-day observation period. There was a significant cell migration of human mesenchymal stem cells when keloid-derived fibroblasts were placed in the bottom chamber, compared to when normal dermal fibroblasts were placed in the same way in 8-microm diameter pore membranes (190.6 +/- 51.45 and 32.0 +/- 6.20 cells/field, respectively, P < 0.01). With 3-microm diameter pores, the human mesenchymal stem cells migrated in the pores only when the keloid-derived fibroblasts were placed in the bottom chambers (6.4 +/- 3.84 cells/field). Monolayer coculture of human mesenchymal stem cells and keloid-derived fibroblasts demonstrated further functional differentiation, such as collagen secretion and abundant rough endoplasmic reticulum. Western blot analysis of the cells in the modified dual-chamber culture demonstrated most significantly abundant fibronectin expression when the human mesenchymal stem cells contained keloid fibroblasts. CONCLUSION: The results of this study may indicate that human mesenchymal stem cells participate and recruit in keloid pathogenesis by differentiating themselves toward keloid recalcitrant formation and progression.

Attenuation of cysteinyl leukotrienes induces human mesenchymal stem cell differentiation.

Although there are numerous investigations describing bone marrow cells or bone-marrow derived cells at the site of such injuries as bone fractures, infarction and subsequent ischemic reperfusion injury, or cutaneous wounds, little is know about the factors that affect the cells in those clinical situations. Cysteinyl leukotrienes have been extensively investigated in airway diseases that may eventually lead to lung fibrosis; while the engraftment of mesenchymal stem cells have been shown to reverse bleomycin-induced lung fibrosis in vivo. Therefore, we elucidated the involvement of cysteinyl leukotrienes in human mesenchymal stem cell proliferation and differentiation. Human mesenchymal stem cells express the cysteinyl leukotriene type 1 receptor. Various doses of pranlukast, which is a specific cysteinyl leukotriene type 1 receptor antagonist, failed to affect the proliferation of cells; however, 10(-6) M of pranlukast significantly induced cellular cytoplasmic differentiation by showing microvilli sprouting and the emersion of rough endoplasmic reticulum within a 16-hour(s) incubation. Additionally, pranlukast-induced fibronectin protein production by human mesenchymal stem cells. Therefore, attenuation of the cysteinyl leukotriene pathway contributes to human mesenchymal stem cell differentiation and may contribute to modulation of the local injury site.

Early cellular changes of human mesenchymal stem cells and their interaction with other cells.

Cell-to-cell interactions between human mesenchymal stem cells and potential adjacent cells such as endothelial cells, dermal fibroblasts, and epidermal keratinocytes was investigated. A modified dual Boyden chamber assay using 8-microm pores revealed a more powerful chemotactic cell migration of human mesenchymal stem cells toward human epidermal keratinocytes than other cells, such as umbilical artery endothelial cells and dermal fibroblasts, during 16 hours of incubation (336.2+/-52.33, 36.0+/-11.20, and 62.7+/-18.16, cells/field, respectively, p<0.01; comparison between endothelial cells and keratinocytes, and fibroblasts and keratinocytes). Scanning electron microscopy showed human mesenchymal stem cell migration through the pores, with endothelial cells, fibroblasts, or keratinocytes in the lower chambers. Mesenchymal stem cell ultrastructural changes occurred, including a larger euchromatin nucleus, when the cells were placed in medium containing 10 percent fetal bovine serum, whereas basic fibroblast growth factor maintained the immature cell morphology for 4 days. Monolayer coculture also showed human mesenchymal stem cell changes in ultrastructural morphology in the vicinity of the epidermal keratinocytes. These data suggest that human mesenchymal stem cells may interact with human epidermal keratinocytes to accelerate wound healing and coverage.