Stem cell research provides promising strategies in improving healthcare for human beings. As a noninvasively obtained and easy-to-culture cell resource with relatively low expense, urine-derived stem cells have special advantages. They have been extensively studied on its proliferation ability and differentiation potential and were being reprogrammed to model diseases during the last decade. In this review, we intend to summarize the latest progress on the research of urine-derived stem cells for its broad application mainly in regenerative medicine and disease modeling, as well as in what is challenging currently. This minireview will highlight the potential application of urine-derived stem cells and provides possible direction of further research in the future.

High-quality biosamples are valuable resources for biomedical research. However, some tissues are stored without being sectioned into small aliquots and have to undergo repeated freeze–thaw cycles throughout prolonged experimentation. Little is known regarding the effects of repeated freeze–thaw cycles on the quality of biomolecules in tissues. The aim of this study was to evaluate the impact of repeated freeze–thaw (at room temperature or on ice) cycles on biomolecules and gene expression in four different types of tissues. Each fresh tissue was sectioned into seven aliquots and snap-frozen before undergoing repeated freeze–thaw cycles at room temperature or on ice. Biomolecules were extracted and analyzed. Both relative and absolute quantification were used to detect the changes in gene expression. The results indicated that the impact of repeated freeze–thaw cycles on RNA integrity varied by tissue type. Gene expression, including the housekeeping gene, was affected in RNA-degraded samples according to absolute quantification rather than relative quantification. Furthermore, our results suggest that thawing on ice could protect RNA integrity compared with thawing at room temperature. No obvious degradation of protein or DNA was observed with repeated freeze–thaw cycles either at room temperature or on ice. This research provides ample evidence for the necessity of sectioning fresh tissues into small aliquots before snap-freezing, thus avoiding degradation of RNA and alteration of gene expression resulting from repeated freeze–thaw cycles. For frozen tissue samples that were already in storage and had to be used repeatedly during their lifecycle, thawing on ice or sectioned at ultralow temperature is recommended.

A major concern in biomedical research is the quality of biological samples. RNA later is a stabilizer, which was originally developed for RNA preservation in fresh tissues and is important for collection and transportation. However, this reagent lacks a comprehensive and systematic evaluation of its preservative effect on different mammalian tissues under consistent experimental conditions. In this study, we collected liver, kidney, testis, brain, and colon tissues from mice and divided the samples into the following respective groups: fresh, RNA later preserved, and liquid nitrogen snap frozen. Biomolecules (RNA, DNA, and protein) were extracted from each tissue in each group, and samples were formalin fixed and paraffin embedded for quality assessment. Our results revealed that high-quality (yield, purity, and integrity) nucleic acids could be extracted from all samples. Gene expression determined by quantitative real-time polymerase chain reaction exhibited no major difference among the three groups. Notably, we observed significant protein degradation in brain tissue preserved by RNA later compared with fresh and snap-frozen tissue. Protein expression of the other four tissues was similar among the three groups. Hematoxylin and eosin staining of all tissue types indicated no apparent difference among the three groups. We concluded that high-quality nucleic acids can be obtained and tissue morphology conserved when tissues are preserved with RNA later . However, there are tissue-specific differences in protein preservation when using RNA later , which should be evaluated before extensive storage.

Stem cell-based therapy may be the most promising method to cure skeletal muscle degenerative diseases such as Duchenne muscular dystrophy (DMD) and trauma in the future. Human amniotic fluid is enriched with early-stage stem cells from developing fetuses and these cells have cardiomyogenic potential both in vitro and in vivo. In the present study, we investigated the characteristics of human amniotic fluid-derived AF-type stem (HAF-AFS) cells by flow cytometry, immunofluorescence staining, reverse-transcription polymerase chain reaction, and osteogenic and adipogenic differentiation analysis. After confirming the stemness of HAF-AFS cells, we tested whether HAF-AFS cells could differentiate into skeletal myogenic cells in vitro and incorporate into regenerating skeletal muscle in vivo. By temporary exposure to the DNA demethylation agent 5-aza-2'-deoxycytidine (5-Aza dC) or co-cultured with C2C12 myoblasts, HAF-AFS cells differentiated into skeletal myogenic cells, expressing skeletal myogenic cell-specific markers such as Desmin, Troponin I (Tn I) and α-Actinin. Four weeks after transplantation into cardiotoxin-injured and X-ray-irradiated tibialis anterior (TA) muscles of NOD/SCID mice, HAF-AFS cells survived, differentiated into myogenic precursor cells and fused with host myofibres. The findings that HAF-AFS cells differentiate into myogenic cells in vitro and incorporate in skeletal muscle regeneration in vivo hold the promise of HAF-AFS cell-based therapy for skeletal muscle degenerative diseases. Copyright © 2012 John Wiley & Sons, Ltd.