SAFETY AND PHARMACOKINETICS OF PRAZIQUANTEL IN EUROPEAN POND TURTLES (EMYS ORBICULARIS).

Spirorchiidosis, caused by blood flukes of the genus Spirorchis, is a disease of great concern for the critically endangered European pond turtle (EPT; Emys orbicularis) in Switzerland. The endogenous life cycle of the parasite often leads to systemic inflammatory reactions, thrombosis, and death. Praziquantel (PZQ) is the treatment of choice against adult Spirorchis spp. in green (Chelonia mydas) and in loggerhead (Caretta caretta) sea turtles and is therefore considered for the treatment of EPT. This study aimed to establish a safe, easily applicable PZQ treatment for EPT, based on pharmacokinetics and tolerability. Three application methods were tested in a total of 12 adult EPT. Each turtle received a total of 75 mg/kg PZQ (three doses of 25 mg/kg in 3-h intervals [q3h × 3]) via IM (n = 3 turtles), SC (n = 3 turtles), or PO (n = 6 turtles) administration. Blood was collected 3, 6, 24, and 48 h after the first administration to determine the plasma concentration of PZQ using high-performance liquid chromatography coupled to mass spectrometry. Maximum measured R-PZQ concentrations (Cmax) were reached after 6 h. The mean Cmax of the total PZQ (sum of R- and S-PZQ) in the PO-treated EPT group was 1,929 ng/ml. Significantly higher concentrations were measured after IM and SC injection (mean Cmax of total PZQ = 12,715 ng/ml and 10,114 ng/ml, respectively). Transient side effects were evident after IM administration (local swelling and lameness), whereas no adverse drug effects were observed after PO and SC administration. Based on these results and the ease of administration to EPT, SC injection of PZQ at 25 mg/kg q3h times 3 serves as promising treatment application for the future.

Full thickness 3D in vitro conjunctiva model enables goblet cell differentiation.

In vitro culture and generation of highly specialized goblet cells is still a major challenge in conjunctival 3D in vitro equivalents. A model comprising all physiological factors, including mucus-secreting goblet cells has the potential to act as a new platform for studies on conjunctival diseases. We isolated primary conjunctival epithelial cells and fibroblasts from human biopsies. 3D models were generated from either epithelial layers or a combination of those with a connective tissue equivalent. Epithelial models were investigated for marker expression and barrier function. Full-thickness models were analyzed for goblet cell morphology and marker expression via immunofluorescence and quantitative real-time PCR. Simple epithelial models cultured at the air-liquid interface showed stratified multi-layer epithelia with pathologic keratinization and without goblet cell formation. The combination with a connective tissue equivalent to generate a full-thickness model led to the formation of a non-keratinized stratified multi-layer epithelium and induced goblet cell differentiation. In our model, a high resemblance to natural conjunctiva was achieved by the combination of conjunctival epithelial cells with fibroblasts embedded in a collagen-hydrogel as connective tissue equivalent. In the future, our conjunctival in vitro equivalent enables the investigation of goblet cell differentiation, conjunctival pathologies as well as drug testing.

Human barrier models for the in vitro assessment of drug delivery.

In vitro test systems gain increasing importance in preclinical studies to increase the predictivity and reduce animal testing. Of special interest herein are barrier tissues that guard into the human body. These barriers are formed by highly specialized tissues such as the skin, the airways, and the intestine. However, to recapitulate these tissues, researchers are currently restricted by a lack of suitable supporting scaffolds. In this study, we present biological scaffolds based on decellularized porcine gut segments that offer a natural environment for cell growth and differentiation. Employing these scaffolds, human barrier models of the skin, the airways, and the intestine that mimic the natural histological architecture of the respective tissue are generated. These models show tissue specific barrier properties, such as the stratification of the skin, the mucociliary phenotype of the airways, and polarization of the intestinal epithelium. To investigate the transport characteristics of the intestinal test system, we incubated the tissue models with fluorescein (P app <1 × 106 cm/s), propranolol (P app >7 × 106 cm/s), and rhodamin123 (ratio 2.45). The here presented biological scaffolds facilitate the in vitro generation of human barrier models that might represent useful tools for drug delivery studies.