Human Skin as an Ex Vivo Model for Maintaining Mycobacterium leprae and Leprosy Studies.

The in vitro cultivation of M. leprae has not been possible since it was described as causing leprosy, and the limitation of animal models for clinical aspects makes studies on leprosy and bacteria-human host interaction a challenge. Our aim was to standardize the ex vivo skin model (hOSEC) to maintenance and study of M. leprae as an alternative animal model. Bacillary suspensions were inoculated into human skin explants and sustained in DMEM medium for 60 days. Explants were evaluated by RT-PCR-16SrRNA and cytokine gene expression. The viability and infectivity of bacilli recovered from explants (D28 and D60) were evaluated using the Shepard's model. All explants were RT-PCR-16SrRNA positive. The viability and infectivity of recovered bacilli from explants, analyzed after 5 months of inoculation in mice, showed an average positivity of 31%, with the highest positivity in the D28 groups (80%). Furthermore, our work showed different patterns in cytokine gene expression (TGF-ß, IL-10, IL-8, and TNF-α) in the presence of alive or dead bacilli. Although changes can be made to improve future experiments, our results have demonstrated that it is possible to use the hOSEC to maintain M. leprae for 60 days, interacting with the host system, an important step in the development of experimental models for studies on the biology of the bacillus, its interactions, and drug susceptibility.

Myelination key factor krox-20 is downregulated in Schwann cells and murine sciatic nerves infected by Mycobacterium leprae.

Schwann cells (SCs) critically maintain the plasticity of the peripheral nervous system. Peripheral nerve injuries and infections stimulate SCs in order to retrieve homeostasis in neural tissues. Previous studies indicate that Mycobacterium leprae (ML) regulates the expression of key factors related to SC identity, suggesting that alterations in cell phenotype may be involved in the pathogenesis of neural damage in leprosy. To better understand whether ML restricts the plasticity of peripheral nerves, the present study sought to determine the expression of Krox-20, Sox-10, c-Jun and p75NTR in SC culture and mice sciatic nerves, both infected by ML Thai-53 strain. Primary SC cultures were stimulated with two different multiplicities of infection (MOI 100:1; MOI 50:1) and assessed after 7 and 14 days. Sciatic nerves of nude mice (NU-Foxn1nu ) infected with ML were evaluated after 6 and 9 months. In vitro results demonstrate downregulation of Krox-20 and Sox-10 along with the increase in p75NTR-immunolabelled cells. Concurrently, sciatic nerves of infected mice showed a significant decrease in Krox-20 and increase in p75NTR. Our results corroborate previous findings on the interference of ML in the expression of factors involved in cell maturation, favouring the maintenance of a non-myelinating phenotype in SCs, with possible implications for the repair of adult peripheral nerves.