introduction of madame emilienne wolff and professor etienne wolff

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  • IN VITRO Volume 15, No. 1, 1979 All rights reserved 9



    Institute/or Medical Research, Camden, New Jersey 08103

    It is indeed a great pleasure and a privilege for me to welcome today Madame Emilienne Wolff and Monsieur le Professeur Etienne Wolff, who so kindly agreed to cross the Atlantic to join us in this symposium organized in their honor. As you all know, Madame and Monsieur Wolff have been nominated Honorary Members of our As- sociation not only in recognition of their innumer- able contributions to the field of tissue culture, but more particularly for their pioneering studies in cancer research and on the mechanisms of dif- ferentiation. Such a distinction could not be con- ferred to more deserving scientists.

    Both of them are universally known, and their work is very familiar to all members of the H. B. Fell Division. Madame Wolff has a Doctor of Sciences degree, is a laureate from the French Na- tional Academy of Sciences and a Director of the Centre National de la Recherche Scientifique. For many years she dedicated herself, side by side with her husband, to the study of avian and mam- malian sexual differentiation. Professor Etienne Wolff occupies the Chair of Experimental Embry- ology at the Coll6ge de France, one of the most prestigious institutions of higher learning in Eur- ope; he is a Director of the Centre National de la Recherche Scientifique, a member of the Aca- demy of Sciences and of many other foreign aca- demies. As a philosopher and a writer, his literary successes won him a seat in the famed Acad6mie Fran~aise.

    Little did I know when I first met him in 1949 that one day I would be assigned the pleasant task of introducing him on such a happy occasion. I was then a young research fellow at the Institute for Cancer Research in Philadelphia, and Dr. Wolff was already an internationally known fig- ure in the field of teratology. At that time the dis- tance between a newly appointed assistant and a faculty professor was forbidding, and only the

    1Presented in the formal symposium on Sexual Differ- entiation in Vitro and in Vivo at the 29th Annual Meet- ing of the Tissue Culture Association, Denver, Col- orado, June 4-8, 1978.

    warm informal atmosphere of the United States could bring us together.

    Dr. Wolff came to our laboratory in Fox Chase in quest of information concerning ~he prepara- tion of a synthetic medium for tissue culture. I was immediately conquered by his simplicity, his kindness and the clarity of his approach to the most complex scientific problems. He is the first person who pointed out to me that "tissue cul- ture" was a misnomer because when a fragment of embryonic heart is explanted in a plasma coagulum, the uncontrolled proliferation of the fihrohlasts destroys the organization of the frag- ment to the profit of one cell type which has little to do with the original tissue or its function. Therefore one of the first objectives Dr. Wolff pursued was to find a nonnutritive substrate that would replace the classical plasma clot: a support of constant physical properties that would limit cell migration and simultaneously offer the possi- bility of testing well defined nutrients. He found his answer in agar. When explants are placed on top of an agar-gel, a thin epithelial membrane de- velops around the fragment, thereby limiting cell migration and healing surgical wounds. Such a contained organoid can retain normal physiologi- cal activity for days or weeks if the gel is supple- mented with serum, specific tissue extracts or, as demonstrated by Dr. Wolff, with a carefully bal- anced combination of salts, amino acids and vitamins.

    This is the fundamental tool which was forged in the early 1950's to investigate, in the laborator- ies of the Woiffs at the Coll6ge de France, the mysteries of differentiation. Thousands of ques- tions had to he answered, such as: Do explants ac- quire full function at the time of their mature de- velopment? Do they produce their specific secre- tions in culture as they do in the intact organism? Can morphogenesis be influenced by nutritional factors? Why does the normal process of morpho- genesis sometimes result in atrophy and regres- sion rather than in differentiation and growth? All these questions and hundreds of others have



    been prime objectives for a multitude of research- ers who over the past 20 years converged from all parts of the world to the Laboratory for Experi- mental Embryology. This huge coordinated re- search, acutely aimed at a deeper knowledge of life, functioned very much like a symphonic orchestra in which Professor Wolff was the maestro and Madame Wolff, the concertmaster.

    Among the breakthroughs that brought fame to the laboratory, one had its origin in organ associa- tions. Parabiosis, or association between organs in culture, rapidly established the fact that no in- compatibility really existed between embryonic cells from different species. However, although associated embryonic tissues were tolerant of one another, associations of adult organs were not. At this point the question arose whether cancer cells, which in many ways behave like embryonic tis- sues, could associate with chick embryonic or- gans. The answer was yes. When human tumor cells are associated with chicken mesonephros for instance, they rapidly invade the connective tissue surrounding the urinary tubules which are ulti- mately replaced. It has been one of the ac- complishments of Professor and Madame Wolff to demonstrate that freshly explanted human tu- mors can invade embryonic avian kidneys, thus giving cancer research another powerful tool to investigate the invasive and destructive properties of cancer cells.

    In the field of sexual differentiation, which is the primary concern of this symposium, the con- tributions of Madame and Monsieur Wolff are particularly impressive. One knows that in verte- brates, the genital organs, or gonads, go through a phase of bipotentiality when they can differentiate equally well toward one sex or the other. One of the early questions to which Professor and Madame Wolff addressed themselves was: What would happen to undifferentiated gonads ex- planted at about the 8th day of incubation in an organ-culture system deprived of hormones and removed from the complex influences of the or- ganism?

    Working with gonads from duck embryos, Pro- fessor and Madame Wolff observed that some gonads progressed toward well characterized ovaries, while others developed into testes. How- ever, if the left gonads from two embryos were as- sociated in parabiosis, while the right ones were explanted independently in another culture dish to determine their genetic sex, it was seen that whenever a female gonad happened to be associ- ated with a male one, the latter differentiated into

    a structure very similar to an ovary. The same re- suits were obtained if the male gonad was ex- planted by itself on a medium containing estra- diol, thus demonstrating a direct feminizing effect of the female hormone.

    In another cycle of experiments, Madame Wolff showed that unlike the gonads, the vocal or- gan of birds, the syrinx, always gave rise to a male structure when explanted on a medium without hormones. In this case the male form appeared to result from spontaneous asexual differentiation. However, departure from the male morphology could be induced in the syrinx by addition of fe- male hormones to the medium.

    Another example of what can happen following asexual differentiation is the development of the genital canal, or Mullerian ducts, in the chick em- bryo. The genital canal usually develops identi- cally in both sexes until the 10th day of incubation after which the Mullerian ducts regress in the male, while in the female, the left duct develops into a functional oviduct. If Mullerian ducts are explanted in organ culture before sexual differ- entiation has occurred, they all develop into fe- male ducts whatever the genetic sex; however, if they are explanted after sexual differentiation of the gonads, the male ducts regress while the fe- male ducts develop. Since addition of testosterone to the culture medium induces regression of the fe- male ducts, it is apparent that regression of the ducts is controlled by the male hormone. You will hear shortly, from Dr. Wolff, the results of more recent investigations on this subject.

    These are only very sketchy descriptions of fundamental experiments still used as models in experimental embryology. The variety of topics that Dr. Wolff and Madame Wolff have investi- gated with these techniques is so vast that it would be presumptuous even to attempt to summarize them all. Taking at random one of the annual re- ports on the activities of the laboratory, one can find no less than six areas of research equally investigated in depth. These include: experi- mental cancer research; organogenesis and terato- genesis; radiobiology; sexual development; chemical and molecular embryology; and physiol- ogy of the embryo. A new topic recently added is research on insect development. At a time when recombinant DNA and "cloning" occupy the front pages of daily papers, reflecting public con- cern and fear of biological research, it is comfort- ing to span the works of Dr. and Madame Wolff who dedicated a lifetime of efforts to teratology. "Teratology," according to Webster, "is that


    branch of science that deals with the production, the development, the anatomy and the classifica- tion of monsters." Despite this ominous defini- tion, I do not believe that Professor or Madame Wolff ever experienced pressure from public opin- ion or restraint in their academic freedom. If nothing else, they might be hailed