Development and application of three-dimensional skin equivalents for the investigation of percutaneous worm invasion.

Investigation of percutaneous helminth infection is generally based on animal models or excised skin. As desirable replacement of animal experiments, tissue-engineered skin equivalents have recently been applied in microbial and viral in vitro infection models. In the present study, the applicability of tissue-engineered skin equivalents for the investigation of percutaneous helminth invasion was evaluated. Epidermal and a full-thickness skin equivalents that suit the requirements for helminth invasion studies were developed. Quantitative invasion assays were performed with the skin-invading larvae of the helminths Strongyloides ratti and Schistosoma mansoni. Both skin equivalents provided a physical barrier to larval invasion of the nematode S. ratti, while these larvae could invade and permeate a cell-free collagen scaffold and ex vivo epidermis. In contrast, the epidermal and full-thickness skin equivalents exhibited a human host-specific susceptibility to larvae of trematode S. mansoni, which could well penetrate. Invasion of S. mansoni in cell-free collagen scaffold was lowest for all experimental conditions. Thus, reconstructed epidermis and full-thickness skin equivalents confirmed a high degree of accordance to native tissue. Additionally, not only tailless schistosomula but also cercariae could permeate the skin equivalents, and thus, delayed tail loss hypothesis was supported. The present study indicates that the limitations in predictive infection test systems for human-pathogenic invading helminths can be overcome by tissue-engineered in vitro skin equivalents allowing a substitution of the human skin for analysis of the interaction between parasites and their hosts' tissues. This novel tissue-engineered technology accomplishes the endeavor to save animal lives.

[Malondialdehyde concentration in blood plasma of patients with liver diseases]. / Malondialdehyd-Konzentration im Blutplasma von Patienten mit Lebererkrankungen.

Malondialdehyde (MDA) level was determined spectrophotometrically with thiobarbituric acid method on 50 healthy persons and 160 patients with alcoholic and nonalcoholic liver diseases. Alcoholics without liver damage show normal plasma MDA values. Alcoholic fatty liver, alcoholic hepatitis and alcoholic liver cirrhosis cause an increase of MDA values. The highest concentrations of MDA were found on patients with acute virus hepatitis. Also noninfectional hepatitis and nonalcoholic liver cirrhosis showed an elevated MDA-Level. Liver damage and lipid peroxidation are considered as closely connected processes.