Connexin 43 expression in the human atrioventricular junction delineates two pathways, with the leftward extension and compact node having significantly lower Cx43 than the interatrial septum (P<0.05).
Observational (n=4)
The differential expression of connexin 43 in the human atrioventricular junction delineates two discrete pathways, which may provide unique conduction properties contributing to AVJ arrhythmias.
p-value: p=<0.05
Gap junction expression has been studied in the atrioventricular junction (AVJ) of many species, however, their distribution in the human AVJ is unknown. The AVJ expression of the gap junction protein connexin 43 (Cx43) is species dependent; therefore we investigated its distribution in the human AVJ. Using Masson trichrome histology, we reconstructed the AVJ of three normal human hearts and one with dilated cardiomyopathy in three dimensions. Cx43 was immunolabeled with vimentin and alpha-actinin to determine the cellular origin of Cx43 and was quantified in the following structures: interatrial septum (IAS), His bundle, compact node (CN), lower nodal bundle (LNB), leftward and rightward nodal extensions (LE and RE), and inferior, endocardial, and left-sided transitional cells. Histology revealed two nodal extensions in three of four hearts. Cx43 was found in the myocytes, but not fibroblasts, of the AVJ. LE and CN Cx43 was lower than the IAS (P < 0.05) and the RE, LNB, and His all expressed Cx43 similarly, with approximately half of IAS expression (RE: 44 +/- 36%; LNB: 50 +/- 26%; His: 48 +/- 12%, P = NS compared with IAS). Cx43 levels in transitional cells were similar to the IAS (P = not significant). Cx43 was found in myocytes of the human AVJ, and its expression pattern delineates two separate continuous structures: one consists of the LE and CN with little Cx43, and the other consists of the His, LNB, and RE expressing approximately half the Cx43 of the IAS. The differential Cx43 expression may provide each structure with unique conduction properties, contributing to arrhythmias arising from the AVJ.
Hucker et al. (2007) conducted an observational in Normal and dilated cardiomyopathy (n=4). Connexin 43 expression vs. Interatrial septum (IAS) was evaluated on Connexin 43 expression levels in atrioventricular junction structures (p=<0.05). Connexin 43 expression in the human atrioventricular junction delineates two pathways, with the leftward extension and compact node having significantly lower Cx43 than the interatrial septum (P<0.05).