Shimane University

Mesenchymal stem cells (MSCs) form one of the types of adult stem cell which have the capacity to self-renew, and the multipotentiality for osteogenic, chondrogenic and adipogenic differentiation and immune modulation. Consequently, MSCs are an attractive cell source for regenerative medicine and therapy for inflammatory disease. However, biological criteria to ensure any particular MSCs are "stem cells" have not been clarified. Previously, we reported that MSCs isolated from a single CD90/CD271 double-positive cell in human bone marrow have high colony-forming capacity and tri-lineage differentiation potential in vitro. Such clonal MSCs are highly homogeneous and considered to be useful for the analysis of molecular function. In this study, we focused on Krüppel-like factor 4 (KLF4) which is highly expressed by our MSC subtype, and examined its role in vitro. The expression of KLF4 was significantly reduced within 24 h after the induction of adipogenic or osteogenic differentiation. Knockdown of KLF4 led to promotion of cellular proliferation and differentiation at an early stage. Furthermore, the expressions of TGFBR1, FZD6, FGFR2, THY1 and CXCL12 genes were upregulated in KLF4 knockdown MSCs. These results indicated that KLF4 regulates not only cellular proliferation but also the early stage of differentiation. Our findings suggest that KLF4 has an important role in maintaining the properties of MSCs and regulating differentiation via TGF-β, WNT and FGF signaling pathways.

Tire and road wear particles (TRWP) are the largest source of microplastics. These particles are generated through friction between tires and road surfaces during use, enter aquatic environments, and may affect aquatic organisms. In this study, TRWP in sediments from 11 different water bodies in Japan were analyzed using pyrolysis gas chromatography/mass spectrometry. TRWP were detected in 32 out of 36 samples, with concentrations up to 4260 µg/g dry weight. TRWP concentrations exceeded the estimated predicted no-effect concentration threshold at 30 out of 36 sites, indicating that potential ecological risks cannot be ruled out. A correlation was found between TRWP concentration and mud content, total organic carbon, or terrestrial organic carbon (terrOC) at sites where mud accumulates. The correlation between TRWP and terrOC was significant even at sites with a notable contribution of marine-derived mud. These findings suggest that TRWP are transported with terrestrial mud and organic matter in aquatic environments. Moreover, sedimentation patterns, as deduced from sediment properties such as mud content and elemental composition, may serve as indicators of TRWP distribution. This study contributes to transport modeling, environmental risk assessments, and development of future pollution control strategies for TRWP.

Hagfish and lampreys, which are both members of the class Agnatha, are widely considered to represent one of the most basal evolutionary lineages of vertebrates. Pituitary adenylate cyclase-activating polypeptide (PACAP) and growth hormone-releasing hormone (GHRH) are both members of the secretin/PACAP family. We searched the Ensembl database for putative PACAP and GHRH sequences in the inshore hagfish, Eptatretus burgeri. We identified three putative GHRH/PACAP precursors (hagfish-1/2/3) whose expression in various tissues, including the brain, was confirmed using RNA sequencing. The hagfish-1 precursor encodes both GHRH/PRP (PACAP-related peptide) and PACAP, whereas the hagfish-2 and -3 precursors encod only PACAP. Of the three putative hagfish PACAPs, PACAP-2, encoded by hagfish-2, showed relatively high identity (77.8%) and similarity (85.2%) with PACAP from other species. In contrast, hagfish GHRH/PRP encoded by hagfish-1 showed low identity (27.3%) and similarity (50.3%) with other GHRHs, and low identity (26.7%) and similarity (46.7%) with other PRPs. Phylogenetic analysis confirmed that the hagfish-2 sequence clustered within the same clade as lamprey PACAP. PACAP-like-immunoreactive (ir) cell bodies and dense punctate fibers have been detected in several brain regions, including the preoptic area, infundibular nucleus of the hypothalamus, midbrain tegmentum, and medulla oblongata. In the pituitary gland, PACAP-like-ir fibers were observed in the dorsal wall of the neurohypophysis. GHRH/PRP immunoreactivity was also observed in the medulla oblongata. The present study demonstrated that PACAP-like- and GHRH/PRP-like peptides are expressed in the brain of the inshore hagfish E. burgeri.