[Dr Jean Languillon (1912-2003), a major unrecognized leprologist]. / Le Dr Jean Languillon (1912-2003), un léprologue majeur trop méconnu.

Languillon's contribution to the control of leprosy cannot be reduced to the manual of leprology which remains the reference for anyone working on this disease in sub-Saharan Africa. This would mean forgetting his works that established the immunological origin of leprosy and its cutaneous, adverse and neurological complications.Another major aspect, the importance of his contribution to the treatment of the disease, in particular through the development of polychimiotherapy (PCT), which has made Institut Marchoux in Bamako one of the five WHO's collaborating centers in the field of clinical research in leprosy.Languillon was also involved in a holistic approach of the disease by creating the first leprosy surgery unit and implementing physiotherapy, orthopedic care with appropriate equipment, and social rehabilitation… without forgetting preventive aspects of complications through the necessary regular administration of treatments, and control of patients spread over wide territories, by creating a corps of leprosy nurse monitors and leprosy specialists. These will provide essential support to the doctor most often in charge of a huge sector where the need of assistance was obvious.Languillon ended his African career by creating the ILAD, Institute of Applied Leprology in Dakar, which offers the full range of care, as he always advocated.Finally, he did not resist the call of Order of Malta which offered him to share his expertise in the different countries where the Order was involved.

Mouse differentiating spermatogonia can generate germinal stem cells in vivo.

In adults, stem cells are responsible for the maintenance of many actively renewing tissues, such as haematopoietic, skin, gut and germinal tissues. These stem cells can self-renew or be committed to becoming progenitors. Stem-cell commitment is thought to be irreversible but in male and female Drosophila melanogaster, it was shown recently that differentiating germ cells can revert to functional stem cells that can restore germinal lineage. Whether progenitors are also able to generate stem cells in mammals remains unknown. Here we show that purified mouse spermatogonial progenitors committed to differentiation can generate functional germinal stem cells that can repopulate germ-cell-depleted testes when transplanted into adult mice. We found that GDNF, a key regulator of the stem-cell niche, and FGF2 are able to reprogram in vitro spermatogonial progenitors for reverse differentiation. This study supports the emerging concept that the stem-cell identity is not restricted in adults to a definite pool of cells that self-renew, but that stemness could be acquired by differentiating progenitors after tissue injury and throughout life.

'Side Population' cells in adult mouse testis express Bcrp1 gene and are enriched in spermatogonia and germinal stem cells.

Stem cells in various somatic tissues (bone marrow, skeletal muscle) can be identified by the 'Side Population' marker based on Hoechst 33342 efflux. We show that mouse testicular cells also display a 'Side Population' that express Bcrp1 mRNA, the ABC transporter responsible for Hoechst efflux in hematopoietic cells. Inhibition of Hoechst efflux by specific BCRP1 inhibitor Ko143 show that germinal 'Side Population' phenotype is dependent on BCRP1 activity. Analysis of two well-defined models of altered spermatogenesis (W/Wv mutants and cryptorchid male mice) and RNA expression studies of differentiation markers demonstrate that germinal 'Side Population' contains spermatogonial cells. In addition, alpha 6-integrin and Stra8 germinal stem cell markers, are expressed in the 'Side Population'. In vivo repopulation assay clearly establishes that testis 'Side Population' in adult mice is highly enriched in male germ stem cells.