Expression in the placenta of neuronal markers for perinatal brain damage

Determination of S-100 a and b and neuron-specific enolase (NSE) in (cord) blood and amniotic fluid has been used to assess neonatal neuronal damage after compromising conditions. However, these proteins are not only found in nervous tissue, and their expression in placenta and umbilical cord has never been investigated. In this study, S-100 (a and b) and NSE expression in human cord and placental tissue was studied by immunohistochemical analysis. Similar analysis was performed using two other brain-specific markers: glial fibrillary acidic protein and growth-associated protein B-50 (also known as GAP-43 or neuromodulin). Tissue was derived after elective cesarean section in seven women of different gestational ages after uncomplicated or complicated pregnancy. S-100 a and b and NSE immunoreactivity was found in several cell types and structures in the umbilical cord as well as in the placenta of all seven cases. Glial fibrillary acidic protein and B-50 showed no immunoreactivity. These data are of importance for interpreting findings of studies in which S-100 or NSE levels in cord blood or amniotic fluid have been related to neuronal damage in the neonate. The increased levels found may just as well be caused by leakage from placenta or umbilical cord as be caused by brain damage. We conclude that S-100 a and b and NSE are not suitable markers for neonatal brain damage. Brain-restricted proteins such as glial fibrillary acidic protein and B-50 seem more promising.