EXPERIMENTAL-EVIDENCE FOR FGF-1 CONTROL OF BLASTEMA CELL-PROLIFERATION DURING LIMB REGENERATION OF THE AMPHIBIAN-PLEURODELES WALTL

During regeneration, blastema cell proliferation depends on several di fferent factors which are, as yet, not fully understood. Previous stud ies showing the presence of FGF-1 and FGF receptors in the limb blaste ma make FGF-1 a potentially important molecule for limb regeneration b ut they do not demonstrate that this factor is active during the proce ss. In the present study, we have first of all confirmed the presence of FGF-1 in limb blastemas of the amphibian Pleurodeles waltl using im munochemistry. Second, we provide evidence in vivo that FGF-1 controls blastema cell proliferation by using different reagents which interfe re with FGF activity. Sulfated polysaccharides which bind FGFs, such a s heparin, iota-carrageenan and pentosan polysulfate, are able to decr ease both H-3-thymidine incorporation and the mitotic index in regener ation blastemas. In addition, suramin which inhibits the binding of gr owth factors to their receptors, induces the same effect. The presence of receptors in blastema cells is also demonstrated by using the FGF- saporin complex which is known to bind to FGF receptors and to kilt ce lls bearing these receptors. This complex decreases the mitotic index in mesenchyme, while saporin alone did not influence cell proliferatio n. Finally, results obtained using a neutralizing monoclonal antibody against FGF-1 which was able to specifically reduce blastema cell prol iferation, suggests that FGF-1 prays an important function in limb reg eneration.