Poly ADP-ribosylation (PARylation) is a post-translational modification catalyzed by poly (ADP-ribose) polymerase (PARP) family proteins such as PARP1. Although PARylation regulates important biological phenomena such as DNA repair, chromatin regulation, and cell death, little is known about the relationship between osteoblast differentiation and the PARylation cycle involving PARP1 and the poly (ADP-ribose)-degrading enzyme poly (ADP-ribose) glycohydrolase (PARG). Here, we examined the effects of PARP inhibitor olaparib, an approved anti-cancer agent, and PARG inhibitor PDD00017273 on osteoblast differentiation. Olaparib decreased alkaline phosphatase (ALP) activity and suppressed mineralized nodule formation evaluated by Alizarin Red S staining in preosteoblastic MC3T3-E1 cells, while PDD00017273 promoted ALP activity and mineralization. Furthermore, PDD00017273 up-regulated the mRNA expression levels of osteocalcin and bone sialoprotein, as osteoblast differentiation markers, and osterix as transcription inducers for osteoblast differentiation, whereas olaparib down-regulated the expression of these genes. These findings suggest that PARG inhibition by PDD00017273 accelerates osteoblast differentiation in MC3T3-E1 cells. Thus, PARG inhibitor administration could provide therapeutic benefits for metabolic bone diseases such as osteoporosis.

The parathyroid gland plays an essential role in mineral and bone metabolism. A cultivation for physiological human parathyroid cells has yet to be established and the method by which parathyroid cells differentiate from pluripotent stem cells remains uncertain. Therefore, it has been hard to clarify the mechanisms underlying the onset of parathyroid disorders, such as hyperparathyroidism. Here, we developed a new method of parathyroid cell differentiation from human induced pluripotent stem (iPS) cells. The parathyroid cell differentiation occurred in accordance with embryologic development. The differentiated cells, which expressed parathyroid hormone, adopted a unique cell aggregation similar to the parathyroid gland. In addition, these differentiated cells were identified as calcium-sensing receptor (CaSR)/epithelial cell adhesion molecule (EpCAM) double-positive cells. Interestingly, stimulation with transforming growth factor-α (TGF-α), which is considered a causative molecule of parathyroid hyperplasia, increased the CaSR/EpCAM double-positive cells, but this effect was suppressed by erlotinib, which is an epidermal growth factor receptor (EGFR) inhibitor. These results suggest that TGF-α/EGFR signaling promotes parathyroid cell differentiation from iPS cells in a similar manner to parathyroid hyperplasia.

Background: Glycation, a non-enzymatic reaction between sugars and biomolecules, leads to the formation of advanced glycation end-products (AGEs), which are implicated in the progression of chronic diseases. Connarus ruber (Poepp.) Planch (C. ruber), a traditional medicinal plant used for diabetes, has shown anti-glycation activity. This study aimed to identify the active components in C. ruber extract and elucidate their anti-glycation mechanisms. Methods: Using NMR and LC-MS analyses, we identified epicatechin and procyanidin A2 as major polyphenolic constituents. Collagen glycation assays were performed to evaluate the inhibitory effects of these compounds on fructose- and glyceraldehyde (GA)-induced glycation. Additionally, their cytoprotective effects were assessed using GA-induced cytotoxicity assays in dental pulp stem cells (DPSCs). Results: Both epicatechin and procyanidin A2 inhibited fructose- and GA-induced glycation in a dose-dependent manner, showing greater efficacy than aminoguanidine. Furthermore, these compounds significantly alleviated GA-induced cytotoxicity in DPSCs. Conclusions: These findings suggest that epicatechin and procyanidin A2 are candidate contributors to the anti-glycation and cytoprotective effects of C. ruber. The results support the potential of C. ruber extract as a source of therapeutic agents for glycation-related diseases and for enhancing stem cell viability.

Several protocols have been reported for inducing parathyroid differentiation from human pluripotent stem cells in vitro. However, the efficiency of terminal differentiation into mature parathyroid cells remains limited. In this study, we performed comparative transcriptomic analyses of parathyroid lineage-induced human induced pluripotent stem (iPS) cells to clarify their developmental stage identity. Comparative analyses with adult parathyroid adenoma, used as a surrogate reference for mature parathyroid cells, and thymuses revealed that the differentiated cells exhibited gene expression patterns consistent with early-stage parathyroid and thymus development, including TBX1, which is required for fate determination of the parathyroid–thymic primordium. On the other hand, the expression of mature parathyroid marker genes, such as PTH, GCM2, and the calcium-sensing receptor (CaSR), remained markedly lower than that in parathyroid adenoma. Under the differentiation conditions and durations examined, application of modified differentiation protocols did not significantly enhance the expression of mature parathyroid markers, although pharyngeal pouch developmental gene expression was maintained. Our findings indicate that current in vitro differentiation systems effectively induce the parathyroid–thymic primordium stage, while a developmental bottleneck at the transition from the primordium toward parathyroid lineage commitment remains.