Resumo Este estudo teve como objetivo avaliar a eficácia das células-tronco mesenquimais (CTMs), isoladas ou associadas à dapsona (DAP), no tratamento de feridas dermonecróticas causadas pelo veneno de Loxosceles laeta. Vinte e cinco coelhos machos foram distribuídos em cinco grupos. O controle negativo recebeu água ultrapura (C-), enquanto todos os outros grupos foram injetados com 20 μg de veneno de L. laeta. Após 4 horas, cada grupo recebeu um dos seguintes tratamentos: PBS (C+), DAP, CTMs e DAP + CTMs. Os animais foram avaliados diariamente durante 12 dias, e feitos registros fotográficos para análise da ferida e no 12º dia, foram eutanasiados e, retiradas amostras de pele para análise histológica. Observou-se que a DAP apresentou o melhor percentual de contração da ferida no terceiro dia. Nos tratamentos com CTMs, observou-se uma contração negativa da ferida tanto para as CTMs isoladas, bem como a associação CTMs + DAP em relação ao PBS, possivelmente, pelo aumento da infamação inicial após a aplicação de células-tronco. Isso é devido ao fato de que as CTMs secretam um amplo espectro de moléculas bioativas como citocinas e fatores de crescimento que favorecem a regeneração. Histologicamente, observou-se que os animais de C+ apresentaram extensas áreas de necrose, úlceras, infiltrado neutrofílico, além de mineralização. Houve aumento de deposição de colágeno no tratamento CTMs + DAP, no entanto, a vascularização permaneceu inalterada. Este é o primeiro relato usando CTMs e CTMs + DAP como tratamento para loxoscelismo cutâneo e mais estudos são necessários para determinar seu uso como terapia alternativa para lesões demonecróticas causadas pela aranha Loxosceles.

Abstract This study aimed to evaluate the efficacy of mesenchymal stem cells (MSC), alone or associated with dapsone (DAP), in treating dermonecrotic wounds caused by Loxosceles laeta venom. Twenty-five male rabbits were distributed into five groups. Negative control received ultrapure water (C-), whilst all other groups were injected with 20 μg of L. laeta venom. After 4 hours, each group received one of the following treatments: PBS (C+), DAP, MSC, and DAP+MSC. Animals were evaluated daily and photographic records made for analysis of wound area. Twelve days after, animals were euthanized and skin samples removed for histological analysis. We observed that DAP showed the best percentage of wound contraction at day 3. In the treatments using MSCs, a negative value of wound contraction was observed for the isolated MSCs, as well as a lower contraction value for the association of the MSC + DAP when compared to PBS, probably, by the increase in initial infammation after the application of stem cells, due to the fact that MSCs secrete a broad spectrum of bioactive molecules such as cytokines and growth factors that favor regeneration. Histologically, it was observed that animals of C+ showed extensive areas of necrosis, ulcers, neutrophilic infiltrate, and mineralization. Collagen deposition showed increase in MSC+DAP treatment, however vascularization remained unchanged. This is the first report using MSC and MSC+DAP as a treatment for cutaneous loxoscelism and more studies are needed to determine its use as an alternative therapy for dermonecrotic lesions caused by Loxosceles spider.

The aim of this work was to evaluate the mesenchymal stem cells treatment of rats with myonecrosis caused by Rhinocerophis alternatus venom through acute phase proteins (APP) profile. The animals were distributed into three experimental groups (G1, G2 and G3). G1 and G2 were inoculated with 120 μg of R. alternatus venom diluted in 200 µL of ultra-pure water in gastrocnemic muscle, while G3 received 200 µL of ultra-pure water. Three days after, G1 was treated with 5 X 10(6) MSC diluted in PBS and G2 and G3 only with PBS. Each three days after the treatments (3rd, 6th, 9th, 12th 15th days), blood of five animals in each group was collected in order to evaluate the APP. A decrease (P<0.05) in α2-globulin fraction was observed in G1 on the 6th day. In G1 and G2, a raise (P<0.05) was observed in β globulin, a common occurrence in the late phases of inflammatory process, although no significant difference was observed between them. Concerning gamma globulins levels, on the 6th day after the treatments, in G1 and G2 groups, increase in the levels was observed. These data showed that the MSC treatment after bothropic envenomation in the rats caused alteration in APP.