Publications

Abstract

Adipose-derived stromal/stem cells (ASC) are multipotent with abilities to differentiate into multiple lineages including connective tissue and neural cells. Despite unlimited opportunity and needs for human and veterinary regenerative medicine, applications of adipose-derived stromal/stem cells are at present very limited. Furthermore, the fundamental biological factors regulating stemness in ASC and their stable differentiation into other tissue cells are not fully understood. The objective of this review was to provide an update on the current knowledge of the nature and isolation, molecular and epigenetic determinants of the potency, and applications of adipose-derived stromal/stem cells, as well as challenges and future directions. The first quarter of the review focuses on the nature of ASC, namely their definition, origin, isolation and sorting methods and multilineage differentiation potential, often with a comparison to mesenchymal stem cells of bone marrow. Due to the indisputable role of epigenetic regulation on cell identities, epigenetic modifications (DNA methylation, chromatin remodeling and microRNAs) are described broadly in stem cells but with a focus on ASC. The final sections provide insights into the current and potential applications of ASC in human and veterinary regenerative medicine.

Abstract

Recent demands for the production of biofuels from lignocellulose led to an increased interest in engineered cellulases from Trichoderma reesei or other fungal sources. While the methods to generate such mutant cellulases on DNA level are straightforward, there is often a bottleneck in their production since a correct posttranslational processing of these enzymes is needed to obtain highly active enzymes. Their production and subsequent enzymatic analysis in the homologous host T. reesei is, however, often disturbed by the concomitant production of other endogenous cellulases. As a useful alternative, we tested the production of cellulases in T. reesei in a genetic background where cellulase formation has been impaired by deletion of the major cellulase transcriptional activator gene xyr1. Three cellulase genes (cel7a, cel7b, and cel12a) were expressed under the promoter regions of the two highly expressed genes tef1 (encoding translation elongation factor 1-alpha) or cdna1 (encoding the hypothetical protein Trire2:110879). When cultivated on d-glucose as carbon source, the Δxyr1 strain secreted all three cellulases into the medium. Related to the introduced gene copy number, the cdna1 promoter appeared to be superior to the tef1 promoter. No signs of proteolysis were detected, and the individual cellulases could be assayed over a background essentially free of other cellulases. Hence this system can be used as a vehicle for rapid and high-throughput testing of cellulase muteins in a homologous background.