The increased antibiotics usage in biomedical and agricultural settings has been well documented. Antibiotics have now been shown to exert effects outside their purposive use, including effects on physiological and developmental processes. We explored the effect of various antibiotics on intestinal regeneration in the sea cucumber Holothuria glaberrima. For this, holothurians were eviscerated and left to regenerate for 10 days in seawater with different penicillin/streptomycin-based cocktails (100 µg/mL PS) including: 100 µg/mL kanamycin (KPS), 5 µg/mL vancomycin (VPS), and 4 µg/mL (E4PS) or 20 µg/mL (E20PS) erythromycin. Immunohistological and histochemical analyses were performed to analyze regenerative processes, including rudiment size, extracellular matrix (ECM) remodeling, cell proliferation, and muscle dedifferentiation. A reduction in muscle dedifferentiation was observed in all antibiotic-treated animals. ECM remodeling was decreased by VPS, E4PS, and E20PS treatments. In addition, organisms subjected to E20PS displayed a significant reduction in the size of their regenerating rudiments while VPS exposure altered cell proliferation. MTT assays were used to discard the possibility that the antibiotics directly affect holothurian metabolic activity while bacterial cultures were used to test antibiotic effects on holothurian enteric microbiota. Our results demonstrate a negative effect on intestinal regeneration and strongly suggest that these effects are due to alterations in the microbial community.

The microbiota, the set of microorganisms associated with a particular environment or host, has acquired a prominent role in the study of many physiological and developmental processes. Among these, is the relationship between the microbiota and regenerative processes in various organisms. Here we introduce the concept of the microbiota and its involvement in regeneration-related cellular events. We then review the role of the microbiota in regenerative models that extend from the repair of tissue layers to the regeneration of complete organs or animals. We highlight the role of the microbiota in the digestive tract, since it accounts for a significant percentage of an animal microbiota, and at the same time provides an outstanding system to study microbiota effects on regeneration. Lastly, while this review serves to highlight echinoderms, primarily holothuroids, as models for regeneration studies, it also provides multiple examples of microbiota-related interactions in other processes in different organisms.

Cystic fibrosis (CF) is a life‐threatening genetic disease caused by mutations in the CF transmembrane conductance regulator gene. It is the most common genetic disease among Caucasians. There is an urgent need to create more therapies for CF since current drugs are not effective in treating all the mutations that cause this disease. Furthermore, gene therapy is a potential treatment for CF airway disease. Because of this, various viral‐based gene transfer vectors have been evaluated for their efficiency in correcting the CF airway disease phenotype. This project aimed to compare side‐by‐side the differences in the transduction efficiency and targeting of specific cell types of adenovirus (Ad)‐based and adeno‐associated virus (AAV)‐based vectors in different models of the airway. Different serotypes of AAV, namely 1, 2, 5, 6, and Ad5‐based vectors, expressing green fluorescent protein (GFP), firefly luciferase (ffLuc) or ß‐galactosidase (LacZ) were assessed in in vitro and in vivo gene transfer studies. Madin‐Darby Canine Kidney (MDCK) cells were grown submerged on plastic, and human airway epithelial (HAE) cells were grown on transwells and fed only from the basolateral side to attempt to model the human conducting airways. The viral vectors expressing GFP were tested at doses of 102–103 genome copies (GC) for AAV or plaque‐forming unit (pfu) for Ad, and the level of transduction was assessed at different time points. The data demonstrates that in MDCK and HAE cells, the highest transduction was achieved by the Ad5 vector followed by the AAV2 vector, while AAV6 had the lowest transduction. Additionally, as examined in HAE cells, the age of the culture impacts transduction efficiency. In parallel, AAV vectors 1, 2, 5, 6 (at a dose of 8×1010 – 3×1011 GC) and Ad5 vector (at a dose of 1×1011 pfu) expressing ffLuc or LacZ were intranasally delivered to mice to assess the transduction efficiency in the epithelium of both the nose and lungs. AAV6 was the most efficient at transducing the cells of the nasal epithelium of mice and AAV5, at transducing lung cells. AAV2 did not transduce airway cells in mice. In conclusion, we confirmed that the viral vectors have different transduction profiles in different models of airway epithelium. More airway models should be studied to better understand which are more useful for preclinical assessments of CF gene therapeutics. Support or Funding Information This project was supported by the National Heart, Lung, and Blood Institute (R25‐HL084665‐14).