Lauri Saxén and developmental biology in Helsinki


In 1955, Lauri Saxén (1927-2005) and his mentor, Sulo Toivonen, developed their “double gradient theory” for explaining the polarity of primary embryonic induction. Toivonen had already pioneered research on the biochemical nature of the amphibian organizer, and he had shown that different tissues produce different substances that could create either head or tail regions in the embryo. In 1968, Saxén and Toivonen wrote a paper in Science that formed the basis of contemporary hypotheses of Wnt and Bmp gradients for anterior-posterior and dorsal-ventral polarity. Viktor Hamburger (1988) noted that this collaboration between Saxén and Toivonen “left its mark on experimental embryology to this day."

Later on Saxén continued his research on embryonic induction but used the mouse kidney as a model system for asking questions about how reciprocal tissue interactions form an organ. He expanded the use of organ culture techniques including the so called transfilter technique where the interacting tissues of developing organs were cultured on opposite sides of a thin filter. In so doing, he trained numerous research physicians and biologists. Later on, Irma Thesleff imported his techniques to her own dental research.

Saxén invested a lot of his time in science education in Finland. He emphasized the importance of the questions in research, every question was not worthy of research and the science must be done for moral ends.  Saxén thought that many ethical problems in laboratories could be avoided by good research education. His laboratory frequently held discussions about moral and ethical problems in science, and he took his students to international meetings to learn the scientific interactions and culture.

Saxén kept his joy for science into his retirement days and stayed active in scientific discussions. His creative imagination did not just influence the research community – one of Saxén’s main aims was to improve the connections between scientists and society, and his success is borne out in the Finnish Science Center Heureka, an organization he helped to found, and first Finnish scientific magazine for the general public, Tiede.

Irma Thesleff, Lauri Saxén, Scott Gilbert and Jukka Jernvall

Lobodon teeth