A single day of TGF-β1 exposure activates chondrogenic and hypertrophic differentiation pathways in bone marrow-derived stromal cells

Virtually all bone marrow-derived stromal cell (BMSC) chondrogenic induction cultures include greater than 2 weeks exposure to transforming growth factor-β (TGF-β), but fail to generate cartilage-like tissue suitable for joint repair. Herein we used a micro-pellet model (5 × 103 BMSC each) to determine the duration of TGF-β1 exposure required to initiate differentiation machinery, and to characterize the role of intrinsic programming. We found that a single day of TGF-β1 exposure was sufficient to trigger BMSC chondrogenic differentiation and tissue formation, similar to 21 days of TGF-β1 exposure. Despite cessation of TGF-β1 exposure following 24 hours, intrinsic programming mediated further chondrogenic and hypertrophic BMSC differentiation. These important behaviors are obfuscated by diffusion gradients and heterogeneity in commonly used macro-pellet models (2 × 105 BMSC each). Use of more homogenous micro-pellet models will enable identification of the critical differentiation cues required, likely in the first 24-hours, to generate high quality cartilage-like tissue from BMSC.

Phytosociology and biodiversity patterns of annual wetland communities of Pyriatynskyi National Nature Park (Poltava Oblast, Ukraine)

The results of a comparative structural analysis of the annual wetland herb vegetation syntaxa (class Isoëto-Nano-Juncetea) of Pyriatynskyi National Nature Park (Poltava Oblast, Ukraine) are presented. The systematic, biomorphological, ecological and geographical structures of syntaxa were studied using cluster, discriminant and factor analysis. The principal conformity of the floristic similarity dendrogram and the previously developed classification scheme were analysed. It was revealed that the leading factor of coenosis development is the soil moisture, while most parameters of these ecotopes are constant. The critical differentiation of Nano-Cyperion and Eleocharition ovatae alliances and the legitimacy of the recognition of the Radiolion linoidis alliance and Polygono recti-Juncetum juzepczukii association as separate syntaxa of the main ranks are emphasized.

Mat1 Inhibits Peroxisome Proliferator-Activated Receptor γ-Mediated Adipocyte Differentiation

ABSTRACT Mammalian Cdk7, cyclin H, and Mat1 form the kinase submodule of transcription factor IIH (TFIIH) and have been considered ubiquitously expressed elements of the transcriptional machinery. Here we found that Mat1 and Cdk7 levels are undetectable in adipose tissues in vivo and downregulated during adipogenesis, where activation of peroxisome proliferator-activated receptor γ (PPARγ) acts as a critical differentiation switch. Using both Mat1 −/− mouse embryonic fibroblasts and Cdk7 knockdown approaches, we show that the Cdk7 complex is an inhibitor of adipogenesis and is required for inactivation of PPARγ through the phosphorylation of PPARγ-S112. The results demonstrate that the Cdk7 submodule of TFIIH acts as a physiological roadblock to adipogenesis by inhibiting PPARγ activity. The observation that components of TFIIH are absent from transcriptionally active adipose tissue prompts a reevaluation of the ubiquitous nature of basal transcription factors in mammalian tissues.