Percutaneous radiofrequency (RF) ablation is feasible for the treatment of unresectable hepatocellular carcinoma, and experience at the authors' institution during 5 years indicates that percutaneous RF ablation can be performed safely in most cases. However, early or late complications related to mechanical or thermal damage may be observed at follow-up examination. Complications may be classified in three groups: vascular (eg, portal vein thrombosis, hepatic vein thrombosis with partial hepatic congestion, hepatic infarction, and subcapsular hematoma), biliary (eg, bile duct stenosis and biloma, abscess, and hemobilia), and extrahepatic (eg, injury to the gastrointestinal tract, injury to the gallbladder, pneumothorax and hemothorax, and tumor seeding). Most complications can be managed with conservative treatment, percutaneous or endoscopic drainage, or surgical repair. Because an early and accurate diagnosis is necessary for proper management, radiologists should be familiar with the imaging features of each type of complication.

The evolution of the echinoderm larval skeleton was examined from the aspect of interactions between skeletogenic mesenchyme cells and surrounding epithelium. We focused on vascular endothelial growth factor (VEGF) signaling, which was reported to be essential for skeletogenesis in sea urchin larvae. Here, we examined the expression patterns of vegf and vegfr in starfish and brittle stars. During starfish embryogenesis, no expression of either vegfr or vegf was detected, which contrast with previous reports on the expression of starfish homologs of sea urchin skeletogenic genes, including Ets, Tbr, and Dri. In later stages, when adult skeletogenesis commenced, vegfr and vegf expression were upregulated in skeletogenic cells and in the adjacent epidermis, respectively. These expression patterns suggest that heterochronic activation of VEGF signaling is one of the key molecular evolutionary steps in the evolution of the larval skeleton. The absence of vegf or vegfr expression during early embryogenesis in starfish suggests that the evolution of the larval skeleton requires distinct evolutionary changes, both in mesoderm cells (activation of vegfr expression) and in epidermal cells (activation of vegf expression). In brittle stars, which have well-organized skeletons like the sea urchin, vegfr and vegf were expressed in the skeletogenic mesenchyme and the overlying epidermis, respectively, in the same manner as in sea urchins. Therefore, the distinct activation of vegfr and vegf may have occurred in two lineages, sea urchins and brittle stars.

BackgroundBone-eating worms of the genus Osedax (Annelida, Siboglinidae) have adapted to whale fall environments by acquiring a novel characteristic called the root, which branches and penetrates into sunken bones. The worms lack a digestive tract and mouth opening, and it has been suggested that Osedax degrade vertebrate bones and uptake nutrients through acidification and secretion of enzymes from the root. Symbiotic bacteria in the root tissue may have a crucial role in the metabolism of Osedax. However, the molecular mechanisms and cells responsible for bone digestion and nutrient uptake are still unclear, and information on the metabolic interaction between Osedax and symbiotic bacteria is limited.ResultsWe compared transcriptomes from three different RNA samples from the following tissues: trunk + palps, root + ovisac, and larva + male. A Pfam domain enrichment analysis revealed that protease- and transporter-related genes were enriched in the root + ovisac specific genes compared with the total transcriptome. Through targeted gene annotation we found gene family expansions resulting in a remarkably large number of matrix metalloproteinase (mmp) genes in the Osedax compared with other invertebrates. Twelve of these Osedax mmp genes were expressed in the root epidermal cells. Genes encoding various types of transporters, including amino acid, oligopeptide, bicarbonate, and sulfate/carboxylate transporters, were also expressed in root epidermal cells. In addition, amino acid and other metabolite transporter genes were expressed in bacteriocytes. These protease and transporter genes were first expressed in root tissues at the juvenile stage, when the root starts to develop.ConclusionsThe expression of various proteinase and transporter genes in the root epidermis supports the theory that the root epidermal cells are responsible for bone digestion and subsequent nutrient uptake. Expression of transporter genes in the host bacteriocytes suggests the presence of metabolic interaction between Osedax and symbiotic bacteria.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0844-4) contains supplementary material, which is available to authorized users.

Convergent evolution of echinoderm pluteus larva was examined from the standpoint of functional evolution of a transcription factor Ets1/2. In sea urchins, Ets1/2 plays a central role in the differentiation of larval skeletogenic mesenchyme cells. In addition, Ets1/2 is suggested to be involved in adult skeletogenesis. Conversely, in starfish, although no skeletogenic cells differentiate during larval development, Ets1/2 is also expressed in the larval mesoderm. Here, we confirmed that the starfish Ets1/2 is indispensable for the differentiation of the larval mesoderm. This result led us to assume that, in the common ancestors of echinoderms, Ets1/2 activates the transcription of distinct gene sets, one for the differentiation of the larval mesoderm and the other for the development of the adult skeleton. Thus, the acquisition of the larval skeleton involved target switching of Ets1/2. Specifically, in the sea urchin lineage, Ets1/2 activated a downstream target gene set for skeletogenesis during larval development in addition to a mesoderm target set. We examined whether this heterochronic activation of the skeletogenic target set was achieved by the molecular evolution of the Ets1/2 transcription factor itself. We tested whether starfish Ets1/2 induced skeletogenesis when injected into sea urchin eggs. We found that, in addition to ectopic induction of mesenchyme cells, starfish Ets1/2 can activate some parts of the skeletogenic pathway in these mesenchyme cells. Thus, we suggest that the nature of the transcription factor Ets1/2 did not change, but rather that some unidentified co-factor(s) for Ets1/2 may distinguish between targets for the larval mesoderm and for skeletogenesis. Identification of the co-factor(s) will be key to understanding the molecular evolution underlying the evolution of the pluteus larvae.

Over the course of evolution, the acquisition of novel structures has ultimately led to wide variation in morphology among extant multicellular organisms. Thus, the origins of genetic systems for new morphological structures are a subject of great interest in evolutionary biology. The larval skeleton is a novel structure acquired in some echinoderm lineages via the activation of the adult skeletogenic machinery. Previously, VEGF signaling was suggested to have played an important role in the acquisition of the larval skeleton. In the present study, we compared expression patterns of Alx genes among echinoderm classes to further explore the factors involved in the acquisition of a larval skeleton. We found that the alx1 gene, originally described as crucial for sea urchin skeletogenesis, may have also played an essential role in the evolution of the larval skeleton. Unlike those echinoderms that have a larval skeleton, we found that alx1 of starfish was barely expressed in early larvae that have no skeleton. When alx1 overexpression was induced via injection of alx1 mRNA into starfish eggs, the expression patterns of certain genes, including those possibly involved in skeletogenesis, were altered. This suggested that a portion of the skeletogenic program was induced solely by alx1. However, we observed no obvious external phenotype or skeleton. We concluded that alx1 was necessary but not sufficient for the acquisition of the larval skeleton, which, in fact, requires several genetic events. Based on these results, we discuss how the larval expression of alx1 contributed to the acquisition of the larval skeleton in the putative ancestral lineage of echinoderms.