ABSTRACT
Objective To investigate the origin of α-SMA positive cells in the outflow tract ridge of the embyonic mouse heart and to explore the ultrastructure change of the mesenchymal cells during the ridges fusion. Methods Sections of embryonic day 10(E10d) to E14d mouse embryonic hearts were stained by immunohistochemistry assay with monoclonal antibodies against α-smooth muscle actin (α-SMA), α-sarcomeric actin(α-SCA) and in situ hybridization method with PlexinA2 probe. The outflow tract ridges fusion was observed by transmission electron microscopy at E12.5d. Results From E10d to E11d, PlexinA2 positive cells were seen in the neural tube with mesenchymes around it, the aortic sac and aortic arch. These cells also migrated into the outflow tract ridge along the aortic sac wall and part of them expressed α-SMA. At E12d, PlexinA2 was expressed in the spinal ganglia, the pharyngeal mesenchyme, the aorto-pulmonary septum and the ascending aorta and pulmonary trunk. The septum showed α-SMA strongly positive. But only a few of α-SMA positive cells were observed in the ascending aorta and pulmonary trunk. At E12.5d, two clusters of condensed mesenchymal cells in the outflow tract ridges formed and began to express PlexinA2 weakly and α-SMA strongly. When the ridges began to fuse, the endothelial cells formed a cellular seam, which rapidly broke into pieces and disappeared and were replaced by the sparsed mesenchymal cells containing a few of microfilaments. Two clusters of condensed mesenchymal cells gradully moved to merge. It was noted that some mesenchymal cells contained plenty of microfilament bundles, mitochondria and focal contacts between them. Some mesenchymal cells only had a few of microfilaments and plasma membrane fusion was seen between them. Conclusionα-SMA positive cells in the outflow tract cushion may be derived from cardiac neural crest. The endothelial cells might participate in the fusion of the outflow tract ridges by endothelial-mesenchymal transformation. Mesenchymal cells of the condensed cell mass contain plenty of microfilament bundles and focal contacts or membrane fusion, which contribute to the ridges fusion.
ABSTRACT
Objective To investigate the expression and distribution of Diacylglycerol Kinase α (DGKα) mRNA in human hepatocellular carcinoma (HCC),and to explore the function of DGKα in the metastasis of hepatocellular carcinoma.Methods Tissues from 30 cases of HCC and 5 normal liver tissues were collected immediately after surgical resection.Semi-quantitative RT-PCR and in situ hybridization were used to detect the expression levels and distribution of DGKα mRNA,respectively.Results Semi-quantitative RT-PCR showed that the expression level of DGKα mRNA in HCC (0.798±0.317) and normal tissues (0.908±0.425) was significantly higher than those in carcinoma adjacent tissue with cirrhosis (0.205±0.102,P<0.05).In situ hybridization demonstrated that the number of DGKα mRNA positive hepatocytes in HCC [(57.6±6.3)/mm2] and normal tissues [69.8±8.7)/mm2] was significantly higher than those in carcinoma adjacent tissue with cirrhosis [(26.3±4.9)/mm2,P<0.05]; DGKα mRNA was expressed in the cytoplasm of hepatocytes in HCC and carcinoma adjacent tissue with cirrhosis,and in the nuclear of hepatocytes in normal tissues.Conclusion The present study suggests that DGKa may play important roles in carcinogenesis and progressing of HCC.
ABSTRACT
Objective To investigate the early development of the sinus venosus and the cardiac conduction system (CCS) of human embryonic hearts. Methods Serial transverse sections of 29 human embryonic hearts from Carnegie stage 10 to Carnegie stage 16 (C10-C16) were stained immunohistochemically with antibodies against α-smooth muscle actin(α-SMA),α-sarcomeric actin(α-SCA) and desmin ( DES ). Results During C12 and C13, the sinus venosus formed by confluence of systematic veins at the caudal end of the pericardial cavity could be recognized in the mesenchyme of primitive transverse septum. The mesenchymal cells of the sinus venosus gradually differentiated into α-SCA positive cardiocyocytes. At C14, the sinus venosus was within the pericardial cavity due to expansion of the pericardial cavity and incorporated into the right atrium. Differentiation of DES positive conductive cardiomyocyte was initiated in the right wall of atrio-ventricular canal of C10 embryonic heart and with the development, extended towards the myocardium of the interventricular sulcus to form His bundle, left and right bundle branches as well as the ventricular trabecular myocardium. In the atium, the strong expression of DES was first detected in the dorsal wall of C11 atrium. At C13, unique myocardial band showing α-SCA, α-SMA and DES expression in the left dorsal wall of the sinus venosus were found to be continuous with the basal wall of left atium and the dorsal wall of the atrio-ventricular canal, this band might be related to the development of conduction system from sinoatrial node to atrio-ventricular canal. During C14 to C16, primary conduction pathway of atria with strong DES expression was formed that extended from sinoatrial node along venous valves, DES positive myocardium in the dorsal and ventral walls of the atria to the right atrio-ventricular canal, respectively. Conclusions The mesenchyme of the primitive transverse septum is the heart forming field of human embryos responsible for formation of sinus venosus myocardium, cardiomyocytes are differentiated from mesenchymal cells in the primitive transverse septum and progressively added to the venous pole of the heart tube to form myocardial sinus venosus. The differentiation of CCS of the early human embryo initiates in the atrio-ventricular canal and develops gradually towards the arterial and venous poles of the heart tube. By C16, DES positive embryonic CCS can be clearly recognized morphologically.
ABSTRACT
Objective To investigate the spatiotemporal expression patterns and the relationship of α-sarcomeric actin(α-SCA) ,α-smooth muscle actin(α-SMA) and intermediate filament protein desmin with the maturation of the prenatal and the neonatal mouse hearts. Methods Serial sections of the embryo mouse and the neonatal mouse hearts were immunostained with antibodies against α-SCA, α-SMA and desmin. Results Ventricle and outflow tract of embryonic day(ED) 9 heart showed stronger expression of α-SCA and α-SMA, but desmin expression was lower. In the atrium, the expressions of α-SCA and α-SMA were restricted to the dorsal and ventral walls. In the sinus venosus, only a few weakly stained α-SCA positive cells were detected. No desmin expression was found in the atrium and sinus venosus. The expressions of α-SCA, α-SMA and desmin were increased to their highest level at ED 12. The higher expression of α-SCA remained to the postnatal stages. After ED 12, the expressions of α-SMA and desmin gradually decreased in different parts of the heart, but their expressions in the right ventricle persisted longer. After birth,desmin expression was mainly concentrated in the Z lines of I bands and intercalated disks. Conclusion The presence of spatiotemporal differences in the expression of α-SMA and desmin reveals regional differences in cardiomyocyte maturation in various parts of the embryonic mouse heart. The right ventricle shows a relatively slow pace of maturation. The α-SMA may contribute to a peristaltoid contraction pattern of the embryonic myocardium with a slow shortening speed, and a relatively higher level of desmin is required for the maturation of the sarcomere.