Zebrafish is an important model organism in biological research. One of the least explored tissues of zebrafish is blood, because the existing methods for isolating blood from this organism are tedious and irreproducible. The small volume of blood collected by these methods also prohibits many biochemical and cytological analyses. This technical obstacle limits the utilization of zebrafish in many applications, particularly in hematological research and plasma biomarker discovery. To overcome this limitation, we have established a novel method of extracting blood from zebrafish, based on the use of low centrifugal force to collect blood from a wound. This method consistently recovers more blood than traditional methods. Gel electrophoresis and flow cytometry showed that composition of blood harvested by this method is indistinguishable from traditional methods. The increase in yield enables us to perform biochemical experiments on zebrafish blood. In particular, we have demonstrated that quantitative proteomics can be performed on plasma collected from single zebrafish. Here, we have compared, by using shotgun proteomic analysis, the plasma proteomes of adult male and female zebrafish. Twenty-seven gender-dependent plasma proteins are identified and their biochemical importance discussed. Taken together, this novel technique enables analyses that were previously difficult to perform on zebrafish blood.

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Exploring the parallels between wound healing and epithelial cancers, Sundaram et al. elucidate the mechanism by which cancer cells hijack the wound healing switch to enhance invasion and metastasis in head and neck squamous cell carcinoma.

Background-Differentiation of pluripotent human embryonic stem cells (hESCs) to the cardiac lineage represents a potentially unlimited source of ventricular cardiomyocytes (VCMs), but hESC-VCMs are developmentally immature. Previous attempts to profile hESC-VCMs primarily relied on transcriptomic approaches, but the global proteome has not been examined. Furthermore, most hESC-CM studies focus on pathways important for cardiac differentiation, rather than regulatory mechanisms for CM maturation. We hypothesized that gene products and pathways crucial for maturation can be identified by comparing the proteomes of hESCs, hESC-derived VCMs, human fetal and human adult ventricular and atrial CMs. Methods and Results-Using two-dimensional-differential-in-gel electrophoresis, 121 differentially expressed (>1.5-fold; P<0.05) proteins were detected. The data set implicated a role of the peroxisome proliferator-activated receptor α signaling in cardiac maturation. Consistently, WY-14643, a peroxisome proliferator-activated receptor α agonist, increased fatty oxidative enzyme level, hyperpolarized mitochondrial membrane potential and induced a more organized morphology. Along this line, treatment with the thyroid hormone triiodothyronine increased the dynamic tension developed in engineered human ventricular cardiac microtissue by 3-fold, signifying their maturation. Conclusions-We conclude that the peroxisome proliferator-activated receptor α and thyroid hormone pathways modulate the metabolism and maturation of hESC-VCMs and their engineered tissue constructs. These results may lead to mechanism-based methods for deriving mature chamber-specific CMs.