Cellular reactions of the choroid plexus induced by peripheral nerve injury.

The choroid plexus (CP) of brain ventricles forms the blood-cerebrospinal fluid (blood-CSF) barrier that is involved in many diseases affecting the central nervous system (CNS). We used ED1 and ED2 immunostaining to investigate epiplexus cell changes in rat CP after chronic constriction injury (CCI). In contrast to naïve CP, the CP of sham-operated rats showed an increase in the number of ED1+ cells of a similar magnitude during all periods of survival up to 3 weeks, while the number of ED2+ increased only at 3 days from operation. In comparison to naïve and sham-operated animals, the number of ED1+ and ED2+ cells in the epiplexus position increased with the duration of nerve compression. We detected no or negligible cell proliferation in the CP after sham- or CCI-operation. This suggests that increased number of ED1+ and ED2+ cells in the epiplexus position of the CP is derived from peripheral monocytes passing through altered blood-CSF barrier. The changes in epiplexus cells indicate that the CP reacts to tissue injury after the surgical approach itself and that the response to peripheral nerve lesion is greater. This suggests a role for an altered blood-CSF barrier allowing for propagation of signal molecules from damaged tissue and nerve to the CNS.