EMBRYONIC CHICK MUSCLE PRODUCES AN FGF-LIKE ACTIVITY

Normal and pathological formation of blood vessels is of considerable interest both in terms of basic scientific processes and clinical appl ications. Angiogenic events in the adult are likely to represent persi stence of developmental mechanisms, and embryos are therefore a suitab le experimental model for these processes. Among embryonic tissues, mu scle is particularly appropriate for investigation, since it is highly vascularised from early stages. There are a number of competing expla nations of how this process is controlled. Bioassays offer advantages over conventional molecular localisation techniques, in that they reve al the presence of active processed forms of the molecules under study , rather than non-processed forms, or non-translated messages. Using t hese techniques, we report here that embryonic chick muscle, taken fro m the stages at which blood vessels are forming, produces an angiogeni c activity on the chick chorioallantoic membrane (CAM), and transforms NR6 cells in soft agar. Basic fibroblast growth factor (bFGF) is show n to be angiogenic on the CAM in the same way, and also transforms NR6 cells (NR6 cells lack functional epidermal growth factor/transforming growth factor-a receptors, and are believed to respond only to bFGF i n this way). Anti-bFGF removes the transforming activity of the embryo nic muscle. We conclude that this represents evidence that embryonic c hick muscle is producing an FGF-like molecule which is capable of acti ng as an angiogenic agent at the appropriate times in development.