Vascular endothelial growth factor (VEGF) gene gives rise to several distinct isoforms of VEGF, which differ in their expression patterns as well as their biochemical and biological properties. We examined the expression levels of VEGF isoforms and their receptors in the medial and lateral meniscus of rabbits under normal physiologic conditions as well their expression levels after 8 and 24 h of systemic normobaric hypoxia (13%). VEGF(121) is the most abundant VEGF isoform in the medial and lateral meniscus, followed by VEGF(165), VEGF(189), and VEGF(183). While the soluble VEGF(121) and VEGF165 are only upregulated at 8 h of hypoxia, the membrane-bound VEGF(183) and VEGF(189) are further increased at 24 h. VEGFR-2 is expressed at a much higher level than VEGFR-1 under normal conditions, and both receptors are upregulated under hypoxia. Differential expression levels under normoxia as well as a differential response to hypoxia may indicate different functions of VEGF isoforms in the meniscus. (C) 2004 Elsevier Inc. All rights reserved.