MOLECULAR STUDIES OF HUMAN CONNEXIN-43 (CX43) EXPRESSION IN ISOLATED CORPORAL TISSUE STRIPS AND CULTURED CORPORAL SMOOTH-MUSCLE CELLS

Intercellular communication plays an important role in erectile functi on. The goal of this study, therefore, was two-fold. Firstly, to deter mine if cultured corporal smooth muscle cells provide a valid model sy stem for evaluating the role of junctional communication to erectile p hysiology, and secondly, to explore the possibility that there may be age-related alterations in Cx43 mRNA expression. Human corpus cavernos um tissue was obtained from 31 patients with a mean age of 58 (range 2 7-89), while cell cultures were developed from 21 distinct patients wi th a mean age of 57 (range 26-59). Northern blots revealed that mRNA f or Cx43 was expressed at detectable levels in all samples examined. It migrated as a transcript with an apparent size of 3.1 Kb. Western blo ts revealed the presence of multiple bands of Cx43 protein in both tis sues and cells. However, Cx43 protein in tissue predominantly migrated as a 45 kDa band, while the Cx43 from cultured cells predominantly mi grated as 41 kDa band. Cx43 mRNA expression was similarly heterogeneou s in both frozen tissues and cultured cells. An similar to 3-5-fold in crease in Cx43 mRNA levels was observed in cultured cells relative to frozen tissue, but the expression of Cx43 mRNA was not further altered upon passaging (p1-5). When Cx43 mRNA levels were normalized, and exp ressed as a ratio of the Cx43/beta-tubulin mRNA, there was a significa nt negative correlation between patient age and Cx43 levels on frozen tissues, but not on cultured cells. We conclude that: (1) There is sim ilar heterogeneity/variability in Cx43 mRNA levels in frozen tissues a nd cultured cells derived from human corpus cavernosum (2) That the ex pression of Cx43 mRNA in cultured cells is sufficiently stable, and si milar to, expression levels in tissue as to provide a valid and physio logically relevant model system for further studying the role(s) of Cx 43 in the regulation of penile erection. (3) There is a statistically significant, albeit modest, negative correlation between the Cx43/beta -tubulin ratio and patient age in frozen corporal tissue strips, but n ot on cultured corporal smooth muscle cells. Such observations provide further evidence for the plasticity of intercellular communication in the erectile process. Moreover, the similarities in the apparent regu lation of Cx43 mRNA levels and that of the putative 'housekeeping' gen e beta-tubulin, may suggest. that Cx43 is constitutively synthesized i n this tissue.