Nerve Growth Factor ( NGF ) and Its Receptors TrkA and p75NTR Are Expressed in Human Periapical Cysts. An Immunohistochemical Study

Periapical cysts present with an epithelium deriving from the epithelial rests of Malassez, which express growth factors. The aim was to evaluate the expression of nerve growth factor (NGF) and its receptors, TrkA and p75NTR in periapical cysts. Immunohistochemistry was carried out in 47 paraffin-embedded periapical cysts. Staining score was based on intensity and extent of immunoexpression. NGF was predominantly expressed in the cystic epithelium, nerve fibres, lymphocytes and endothelial cells; TrkA was mainly localized to the epithelial basement membrane zone and further expressed in nerve fibres, whereas p75NTR expression was limited and mutually opposed to that of TrkA. These findings suggest a potential role for NGF-mediated signalling pathways in the pathogenesis and biological behaviour of periapical cysts. Further studies are required to validate these observations and to provide additional insights into the role of NGF, TrkA, and p75NTR in the development, maintenance, and possible healing of periapical cysts.