Endothelin-induced differentiation of Nkx2.5⁺ cardiac progenitor cells into pacemaking cells.

The mechanisms governing the development of cardiac pacemaking and conduction system are not well understood. In order to provide evidence for the derivation of pacemaking cells and the signal that induce and maintain the cells in the developing heart, Nkx2.5(+) cardiac progenitor cells (CPCs) were isolated from embryonic heart tubes of rats. Endothelin-1 was subsequently added to the CPCs to induce differentiation of them towards cardiac pacemaking cells. After the treatment, Nkx2.5(+) CPCs displayed spontaneous beating and spontaneously electrical activity as what we have previously described. Furthermore, RT-PCR and immunofluorescence staining demonstrated that Tbx3 expression was increased and Nkx2.5 expression was decreased in the induced cells 4 days after ET-1 treatment. And the significantly increased expression of Hcn4 and connexin-45 were detected in the induced cells 10 days after the treatment. In addition, Nkx2.5(+) CPCs were transfected with pGCsi-Tbx3 4 days after ET-1 treatment in an attempt to determine the transcription regulatory factor governing the differentiation of the cells into cardiac pacemaking cells. The results showed that silencing of Tbx3 decreased the pacemaking activity and led to down-regulation of pacemaker genes in the induced cells. These results confirmed that Nkx2.5(+) CPCs differentiated into cardiac pacemaking cells after being treated with ET-1 and suggested that an ET-1-Tbx3 molecular pathway govern/mediate this process. In conclusion, our study support the notion that pacemaking cells originate from Nkx2.5(+) CPCs present in embryonic heart tubes and endothelin-1 might be involved in diversification of cardiomyogenic progenitors toward the cells.

Quantitative anatomical study of male pelvic autonomic plexus and its clinical potential in rectal resection.

The pelvic autonomic nerves innervate the pelvic viscera, and carry a high risk of damage during surgery. This high risk has been ascribed to the complex interrelationship of pelvic paravisceral structures and the difficulty in identifying particular structures, despite the fact that the anatomic characteristics of the pelvic autonomic plexus have been well documented. We dissected ten male embalmed adult cadavers with particular attention to the quantitative parameters of the pelvic plexus and its subsidiary plexus. The right inferior hypogastric plexus and its rectal branch were found to be significantly longer and wider than the left one, while the transverse diameter of the vesical and prostatic branches of the left side was significantly larger the right. The inferior mesenteric plexus gave off fibers directly to form the pelvic plexus in four of 20 hemipelves (20%). In the side-by-side comparison, the distance to midpoint of the sacral promontory of the left rectal plexus was significantly longer than that of the right, whereas the maximum length (the length of the longest nerve fiber from origin to corresponding organ) of the left vesical plexus was significantly shorter than that of the right. Additionally, the craniocaudal and dorsoventral diameters of the right pelvic autonomic plexus were significantly shorter those of the left. The quantitative parameters relating to the pelvic autonomic plexuses not only can enhance our understanding of its anatomy and function, but can also be used as references for surgical procedures and robot-assisted surgery.

Isolation, culture and characterization of cardiac progenitor cells derived from human embryonic heart tubes.

A variety of studies have reported on the isolation and expansion of cardiac stem cells from adult hearts. However, there is little information concerning cardiac stem/progenitor cells derived from embryonic hearts/heart tubes. To provide more evidence for embryonic heart-derived stem/progenitor cells, Nkx2.5+ human cardiac progenitorcells (hCPCs) were isolated and cloned from human heart tubes. The cells stained positive for Nkx2.5 and Oct-4, and negative for alpha-smooth muscle actin (alpha-SMA), cytokeratin, factor-VIII, alpha-sarcomeric actin and c-Kit. GATA-4 expression of Nkx2.5+ hCPCs was higher than that of embryonic limb bud mesenchymal cells of the control group (p < 0.05). These cells were passaged continuously for >3 months (23 passages) and proliferated actively in vitro. After being treated with 5-azacytidine, Nkx2.5+ hCPCs underwent cardiomyogenic differentiation. Ultrastructural observation confirmed that the longitudinal section of these cardiomyogenic differentiation cells clearly revealed typical sarcomeres and intercalated discs. alpha-MHC, alpha-sarcomeric actin and GATA-4 levels were increased in Nkx2.5+ hCPCs treated with 5-azacytidine compared to untreated cells. Nkx2.5+ hCPCs exhibited positive staining and had a higher expression for alpha-SMA when cocultured with canine vascular endothelial cells. After Nkx2.5+ hCPCs were treated with endothelin-1, all cells displayed spontaneous electrical activity and spontaneous beating. Connexin-40 and -45 were stained positive in the treated cells. In conclusion, Nkx2.5+ hCPCs derived from heart tubes have been isolated and cloned in vitro. These cells are capable of long-term self-renewal and possess a potential to differentiate into cardiac muscle-like cells, cardiac pacemaking cells and smooth muscle-like cells. They could have a significant impact on cardiac regeneration medicine and developmental biology.

[The anatomic study of chyle leakage due to operation on abdominal region].

OBJECTIVE: To provide morphological basis for chyle leakage due to operation on upper abdomen or retroperitoneum region. METHODS: The original part of thoracic duct, cisterna chyle, intestinal trunk, left and right lumbar trunks were examined in 32 adult cadavers. RESULTS: (1) The occurrence rate of cisterna chili was 22% (7 cases), among which 4 cases were oval, 3 cases were triangle. The cisterna chyle was (24 +/- 6) mm in length; the width of middle part was (4.1 +/- 0.9) mm. It was located to the right of midline at the level between the twelfth thoracic vertebral body and the second lumbar vertebral body anteriorly. (2) The original part of thoracic duct was (2.8 +/- 0.7) mm in diameter. The confluence form of thoracic duct included: left lumbar trunk and intestinal trunk united to form the common trunk first, right lumbar trunk then joined the common trunk (9 cases, 36%); right lumbar trunk and intestinal trunk united to form the common trunk first, left lumbar trunk then joined the common trunk (8 cases, 32%); left and right lumbar trunk united to form the common trunk first, intestinal trunk then joined the common trunk (4 cases, 16%); left, right lumbar trunk and intestinal trunk joined together (3 cases, 12%). (3) The intestinal trunk was (36 +/- 15) mm in length. It ascended on the left of descending aorta, superior to the left renal artery, crossed the second lumbar vertebra anteriorly, and joined left or right lumbar trunk to form common trunk, which extended to the cisterna chili or thoracic duct to the right of lumbar vertebra. (4) The lengths of left and right lumbar trunks were (107 +/- 24) mm and (111 +/- 18) mm, the external diameters of origins were (1.7 +/- 0.4) mm and (1.9 +/- 0.4) mm, and the external diameters of terminations were (2.2 +/- 0.6) mm and (2.2 +/- 0.5) mm, respectively. CONCLUSION: The larger lymph tubes should be protected emphatically in the relevant region when dissecting the root of celiac and superior mesenteric artery and the termination of inferior mesenteric vein during abdominal operation.

[The role of transforming growth factor beta superfamily in male germ cell development].

Transforming growth factor beta (TGF beta) superfamily can regulate the development of primordial germ cell (PGC) and gonocyte. TGF beta, bone morphogenetic protein (BMP), activin, inhibin, and anti-Müllerian hormone (AMH), all of which belong to the TGF beta superfamily, can play important roles in male germ cell development. Their downstream signaling molecules, Smads proteins are involved in the signal transduction pathway. In addition, TGF beta and AMH contribute to the apoptosis during development. Understanding this effect will help to elucidate the molecular mechanism of the early development of male reproductive system and the pathogenesis of testicular cancer.