Aquaporin-4 expression is increased in oedematous human brain tumours
- 1Department of Anatomy and Developmental Biology, St George's Hospital Medical School, London SW17 0RE, UK
- 2Department of Infectious Diseases
- 3Department of Neurosurgery, Atkinson Morley's Hospital, London SW20 0NE, UK
- Correspondence to: Dr D C Davies, Department of Anatomy and Developmental Biology, Cranmer Terrace, Tooting, St George's Hospital Medical School, London SW17 0RE, UK; daviesdc{at}sghms.ac.uk
- Received 26 January 2001
- Accepted 23 July 2001
- Revised 23 July 2001
Abstract
Aquaporin-4 (AQP4) is a highly conserved water channel protein. In rats, AQP4 is expressed in astrocyte foot processes and is important in brain water homeostasis. AQP4 expression has not been investigated in non-neoplastic human brain or oedematous brain tumours, where water homeostasis is disrupted. Therefore, immunohistochemistry was used to study AQP4 expression in non-neoplastic and neoplastic human brain and blood-brain barrier permeability was assessed using contrast enhanced computed tomograms. AQP4 was present around microvessels in five specimens of non-neoplastic brain and five low grade (Daumas-Duport I or II) astrocytomas. AQP4 was massively upregulated in four and absent in one high grade (Daumas-Duport III or IV) astrocytoma. Massive upregulation of AQP4 was also found in reactive astrocytes in five metastatic adenocarcinomas. There was significant (p<0.0001) correlation between blood-brain barrier opening and upregulated AQP4 expression. Increased AQP4 expression in high grade astrocytomas and adenocarcinomas may facilitate the flow of oedema fluid.
- AQP4, Aquaporin-4; AQPs, aquaporins; LGA, grades I-II
- low grade astrocytoma, HGA, grades III-IV
- high grade astrocytoma; GFAP, glial fibrillary acidic protein
