Charles Philippe Leblond

Charles Philippe Leblond (February 5, 1910 – April 10, 2007) was a pioneer of cell biology and stem cell research and a Canadian former professor of anatomy.

Leblond is notable for developing autoradiography and his work showing how cells continuously renew themselves, regardless of age.

CP Leblond was born in Lille, France, in 1910, the son of a building contractor who died when Leblond was only 10 years old, leaving his mother to raise four boys on her own.

A brilliant student, Leblond debated becoming a film producer, an architect or a scientist.

In the end, he decided on science, and enrolled in Medicine at the University of Paris.

He was fascinated by his first course in histology and decided to pursue this field as a career.

Leblond obtained his M.D. degree from the University of Paris in 1934.

His doctoral thesis described the histochemical localizion of ascorbic acid, which he found to predominate in steroid-secreting cells.

This study led him, with a Rockefeller postdoctoral fellowship in hand, to the endocrinology-orientated Department of Anatomy at Yale University in 1935, where he carried out studies on factors influencing maternal behavior.

It was here that he met his wife Gertrude Sternschuss, to whom he was married for 64 years.

Leblond had 4 children for which he chose names starting with the letter "P": Philippe, Paul, Pierre and (Marie)-Pascale.

He also had 7 grandchildren.

In 1937, Leblond joined the Laboratoire de Synthese Atomique in Paris which was involved in preparing radioactive isotopes for use in investigating the fate of various molecules in biological processes.

Under the guidance of Antoine Lacassagne, Leblond injected radioiodine-128, into a rat and found that the label promptly accumulated in the thyroid gland, presumably incorporated into the thyroid hormone precursor thyroglobulin.

To localize this label more precisely within the thyroid tissue, Leblond attempted to use the novel technique of autoradiography.

Unfortunately, Leblond's first attempt to use autoradiography failed, the reason being that the radioiodine-128 isotope, with its extremely short half-life (25 minutes), disintegrated so quickly that too little radioactivity remained to be detected by the photographic emulsion.

In 1941, Leblond moved to McGill University as a lecturer in histology, and quickly rose to assistant (1943), associate (1946), and then full professor of anatomy (1948).

In 1946, Leblond found that, when he poured liquid photographic emulsion on a histological section containing a radio element, the emulsion was eventually activated by the radio-element; and if thereafter routine photographic development and fixation were applied to the emulsion-covered section, black silver grains appeared in the emulsion wherever it overlay sites containing a radio-element.

This liquid emulsion approach has been used to develop a new High Resolution Autoradiography procedure characterized by close contact between emulsion and section.

Such close contact makes it possible to localize the radio-elements in the section at high resolution, so that radio-elements can be localized at high magnification in the light microscope.

This procedure has been utilized to examine some of the dynamic features of body components, with the main findings as follows:

His results threw doubt on the validity of three traditional concepts dear to biologists in the earlier part of the twentieth century: "stability" of the cell, in which the cell and its components are unchanging, permanent structures; "specificity" of cell function, in which each cell type has a distinct, unique function; and "activity-rest alternation" of cell function, in which each period of cellular activity is followed by a period during which the activity ceases.

He has proposed replacing cell "specificity" by "multipotentiality", "activity-rest alternation" by "continuity" and "stability" of cell components by "renewal".

These various results have provided the foundation not only for modern stem cell research, but also for modern cell biology.

"In 1946, after returning to Montreal from service with the Free French Forces, it was clear to me that the crude technique previously used for radioautography had to be improved".

In collaboration with Leonard Bélanger, Leblond worked on increasing the resolution of the autoradiographic technique.

They were advised by physicist Pierre Demers to melt the emulsion from Eastman Kodak lantern slides, paint it directly on the sections, and then develop the emulsion while it was still attached to the histologic sections.

This resulted in a tenfold improvement in resolution.

Subsequently, Leblond and his colleagues developed a technique in which the histologic slides were dipped directly into liquid emulsion.

The use of thinner sections and emulsion coats led to further advances in resolution, and the introduction of tritium was a technical milestone.

High Resolution Autoradiography procedure continues to be used today by molecular biologists to detect RNA molecules in situ, and to study the localization of genes and DNA sequences.

Leblond used autoradiography to introduce radioactive precursors of DNA and then examine the renewal and fate of cells of several basic tissue types.

He demonstrated for the first time that most cells and tissues in the adult body undergo continued renewal.

Using mathematical models and modern methods of quantitation, Leblond and his colleagues estimated with remarkable accuracy the turnover and mitotic rates of numerous cell types.

He served as the chair of the Department of Anatomy from 1957–1974.

At McGill, Leblond used the newly-available radioiodine-131 with a half-life of 8 days, to repeat his autoradiographic experiment on thyroid tissue.

With this method, the resolving power was less than 100 µm, but nonetheless he was able to localize the radioactivity to specific thyroid [follicles].

Leblond's early career at McGill was interrupted by World War II, during which he served in the Free French Forces.

He was dispatched first to Rio de Janeiro, then to London, where he conducted medical exams of would-be soldiers.

As Nobel laureate George Palade noted on the occasion of the 1992 Prix Marie-Victorin to Leblond, Charles Leblond's discoveries are so fundamental that they are taught in schools and colleges throughout the world.