INTRODUCTION The development of the male reproductive tract is dependent upon androgens and mesenchymal-epithelial interactions. Androgens masculinise the reproductive tract during the latter third of gestation, and are required for the formation of the male sex accessory organs

The development of the male reproductive tract is dependent upon androgens and mesenchymal-epithelial interactions. Androgens masculinise the reproductive tract during the latter third of gestation, and are required for the formation of the male sex accessory organs including the prostate and seminal vesicle (Cunha et al., 1987). Studies using tissue recombination have shown that androgen receptor action in mesenchymal cells is essential for prostatic induction, and that mesenchymal androgen receptors are both necessary and sufficient for prostatic ductal development (Cunha and Chung, 1981). This has led to the hypothesis that paracrine factors, which are produced by the mesenchyme and regulated by androgens, control the development of the male reproductive tract. Genes that are known to be regulated by androgens are generally secretory proteins or other molecules involved in the differentiated function of prostate epithelial cells. The identity of androgen-regulated mesenchymal paracrine acting factors involved in the development of the male reproductive organs is unknown. While several growth factors are known to be expressed in the prostate only two are thought to function as mesenchymal paracrine acting factors; these are Keratinocyte growth factor (KGF, FGF7) and Hepatocyte growth factor (HGF; Story, 1995). KGF and HGF are not restricted to the prostate (or hormone target organs) and are unlikely to act as mediators of androgen action, although both play important roles in growth regulation throughout organs of the body. It remains to be seen if prostate-specific growth factors exist; it is possible that some growth factors may show partial 3693 Development 126, 3693-3701 (1999) Printed in Great Britain © The Company of Biologists Limited 1999 DEV4159