Identification of label-retaining cells in human gastric cancer xenograft in nude mice

Objective:This study has investigated the existence of label-retaining cell and its distribution in gastric cancer,in the hope that this information will assist investigations on gastric cancer stem cells.Methods:The gastric carcinoma cell line BGC-823 was labeled with BrdU in vitro and then engrafted into the right axilla of nude mice,which developed tumors.Label-retaining cells were quantified by immunohistochemical methods.Results:BrdU positive cells constituted about 96%of the cells in xenograft tumors after 10 days.Subsequently,BrdU positive cells gradually decreased,at the 80th day,labelretaining cells steadily occupied about 0.5%.This set of population cell localized in the margin of cancer nests,which had no difference in cellular morpha.Conclusion:The study demonstrates the presence of label-retaining cells in human gastric cancer xenografts in nude mice and the label-retaining cells may be related with cancer stem cells,which are most likely the cause for spread,metastasis and recurrence.

New insight into dental epithelial stem cells:Identification,regulation,and function in tooth homeostasis and repair

Tooth enamel,a highly mineralized tissue covering the outermost area of teeth,is always damaged by dental caries or trauma.Tooth enamel rarely repairs or renews itself,due to the loss of ameloblasts and dental epithelial stem cells(DESCs)once the tooth erupts.Unlike human teeth,mouse incisors grow continuously due to the presence of DESCs that generate enamel-producing ameloblasts and other supporting dental epithelial lineages.The ready accessibility of mouse DESCs and wide availability of related transgenic mouse lines make mouse incisors an excellent model to examine the identity and heterogeneity of dental epithelial stem/progenitor cells;explore the regulatory mechanisms underlying enamel formation;and help answer the open question regarding the therapeutic development of enamel engineering.In the present review,we update the current understanding about the identification of DESCs in mouse incisors and summarize the regulatory mechanisms of enamel formation driven by DESCs.The roles of DESCs during homeostasis and repair are also discussed,which should improve our knowledge regarding enamel tissue engineering.

Injury-associated reacquiring of intestinal stem cell function

Epithelial layer of the intestine relies upon stem cells for maintaining homeostasis and regeneration.Two types of stem cells are currently defined in intestinal crypts:the cycling crypt base columnar cells and quiescent cells.Though several candidate markers and regulators of rapidly cycling and quiescent stem cells have been identified so far,the exact nature of quiescent cells is still questionable since investigations mainly focused on candidate markers rather than the label-retaining population itself.Recent results,however,have streng-thened the argument for functional plasticity.Using a lineage tracing strategy label-retaining cells(LRCs)of the intestinal epithelium were marked,then followed by a pulse-chase analysis it was found that during homeostasis,LRCs were Lgr5-positive and were destined to become Paneth and neuroendocrine cells.Nevertheless,it was demonstrated that LRCs are capable of clonogenic growth by recall to the self-renewing pool of stem cells in case of epithelial injury.These new findings highlight on the hierarchical and spatial organization of intestinal epithelial homeostasis and the important plasticity of progenitors during tissue regeneration,moreover,provide a motivation for studying their role in disorders like colorectal cancer.