Immunohistochemical analysis of human neuronectin expression in normal, reactive, and neoplastic tissues.

Neuronectin (NEC1) is a human extracellular matrix protein of central nervous system (CNS) parenchyma found throughout the white matter of rostral brain segments (telencephalon, diencephalon, some areas of mesencephalon), but not in rostral CNS gray matter, most areas of mesencephalon, pons, cerebellum, medulla, spinal cord, or peripheral nerves. The present immunohistochemical study, using two monoclonal antibodies to distinct epitopes on the NEC1 molecule, examined NEC1 expression in normal non-neural tissues, malignant tumors of diverse histological types, non-malignant skin lesions, and dermal incision wounds. We show that (a) NEC1 is expressed in normal fetal precartilage blastemas and fetal and adult vascular and visceral smooth muscle, but not in most loose connective tissues and skeletal or cardiac muscle; (b) NEC1 is found along epithelial-mesenchymal junctions, with marked differences in prevalence and histological patterns in different organs; and (c) mesenchymal activation associated with wound healing, actinic keratosis, psoriasis, and neoplasia leads to strong induction of NEC1 expression. Parallel studies with cultured human cells suggest that region-specific NEC1 expression in normal developing tissues and localized induction in wound healing and disparate diseases is under the control of extrinsic signals provided by regulatory polypeptides.