Smad1 stabilization and delocalization in response to the blockade of BMP activity

Reversely immortalized mouse salivary gland cells presented a promising metabolic and fibrotic response upon BMP9/Gdf2 stimulation

The submandibular gland (SMG) and the sublingual gland (SLG) are two of the three major salivary glands in mammals. In mice, they are adjacent to each other and open into the oral cavity, producing saliva to lubricate the mouth and aid in food digestion. Though salivary gland dysfunction accompanied with fibrosis and metabolic disturbance is common in clinic, in-depth mechanistic research is lacking. Currently, research on how to rescue salivary function is challenging, as it must resort to using terminally differentiated acinar cells or precursor acinar cells with unknown differentiation. In this study, we established reversely immortalized mouse primary SMG cells (iSMGCs) and SLG cells (iSLGCs) on the first postnatal day (P0). The iSMGCs and iSLGCs grew well, exhibited many salivary gland characteristics, and retained the metabolism-related genes derived from the original tissue as demonstrated using transcriptome sequencing (RNA-seq) analysis. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of these two cell lines, which overlapped with those of the SMG and SLG, were enriched in cysteine and methionine metabolism. Furthermore, we investigated the role of bone morphogenetic protein 9 (BMP9), also known as growth differentiation factor 2(Gdf2), on metabolic and fibrotic functions in the SMG and SLG. We demonstrated that iSMGCs and iSLGCs presented promising adipogenic and fibrotic responses upon BMP9/Gdf2 stimulation. Thus, our findings indicate that iSMGCs and iSLGCs faithfully reproduce characteristics of SMG and SLG cells and present a promising prospect for use in future study of salivary gland metabolism and fibrosis upon BMP9/Gdf2 stimulation.

Maclurin Promotes the Chondrogenic Differentiation of Bone Marrow Mesenchymal Stem Cells by Regulating miR-203a-3p/Smad1

Bone marrow mesenchymal stem cells (BMSCs) differentiate into chondrocytes under appropriate conditions, providing a method for the treatment of bone- and joint-related diseases. Previously, we found that mulberry (Morus nigra) promoted the chondrogenic differentiation of BMSCs. Although the mechanism of action and active ingredients remain unknown, several studies describe the involvement of micro-RNAs. We obtained BMSCs from the bone marrow of Sprague Dawley rats. Cell Counting Kit-8 assays showed that maclurin (25 μg/mL) treatment was not toxic to BMSCs, and compared with untreated controls, maclurin upregulated Sox9 and Col2a expression. Quantitative-PCR revealed that miR-203a-3p levels decreased significantly during chondrogenic differentiation of BMSCs promoted by maclurin. Compared with treatment with an miR-203a-3p inhibitor, miR-203a-3p mimic inhibited expression of Sox9 and Col2a as evidenced by immunofluorescence staining and Western blotting. Smad1 was identified as a key target gene of miR-203a-3p according to biological-prediction software, and miR-203a-3p negatively regulated its transcription and translation in the dual-luciferase reporter gene assay and Western blotting. Sox9 and Col2a expression was downregulated following transfection of short interfering Smad1 (siSmad1) plasmids into BMSCs. We elucidated how maclurin promotes the chondrogenic differentiation of BMSCs by regulating miR-203a-3p/Smad1, which provides a strategy for future exploration of osteoarthritis therapy through cell transplantation.