Parathyroid hormone (1-34) modulates odontoblast proliferation and apoptosis via PKA and PKC-dependent pathways

Glucocorticoids rapidly promote YAP phosphorylation via the cAMP-PKA pathway to repress mouse cardiomyocyte proliferative potential

Adult mammalian cardiomyocytes (CMs) lose their proliferative potential due to cell-cycle withdrawal and polyploidization and fail to mount a proliferative response to regenerate new CMs after cardiac injury. The decline in the proliferative potential of mammalian CMs occurs in the neonatal period when the endocrine system undergoes drastic changes for adaptation to extra-uterine life. There is an increase in circulating glucocorticoid (GC) levels shortly after birth in mammals, and thus, we sought to determine the roles and mechanisms of GCs in regulating CM proliferation. Here, we showed that GCs suppressed CM proliferation in vitro and in vivo, decreased the total number of CMs, and increased the cross-sectional area of CMs. However, the glucocorticoid receptor antagonist had no effect on CM proliferation. Agonists of adenylate cyclase and protein kinase A (PKA) inhibited CM proliferation, while PKA antagonists or knockdown of PKA alleviated the inhibitory effect of GCs on CM proliferation. GCs and the activation of the cyclic adenosine monophosphate (cAMP)/PKA signaling pathway facilitated yes-associated protein (YAP) phosphorylation in mouse CMs and promoted YAP protein translocation from the nucleus to the cytoplasm. Meanwhile, blocking the cAMP/PKA signaling pathway partially blocked the effect of GCs on YAP protein phosphorylation and YAP protein translocation. Thus, our findings suggest that GCs suppress mouse CM proliferation in vitro and in vivo, through a mechanism that involves targeting the cAMP-PKA-YAP signaling pathway.

Study of Dental Caries and PTH Gene

Parathyroid hormone (PTH) is essential for calcium and phosphate homeostasis in odontogenesis-related cells. Therefore, the present study aimed to investigate the association between single nucleotide polymorphisms in the gene encoding PTH, and dental caries in Brazilian children. Three hundred and fifty-three children (170 boys and 183 girls, age ranging from 8 to 11 years old) were included in this study. The International System for Detection and Assessment of Carious Lesions (ICDAS) was used for diagnosis of dental caries. Visible biofilm was also evaluated during the clinical examination. Genomic DNA was extracted from saliva for real-time PCR to evaluate the single nucleotide polymorphisms rs6256, rs307247 and rs694 in PTH gene. Dental caries was classified in ICDAS0 vs. ICDAS1−6 or ICDAS1−2 vs. ICDAS3−6. Chi-square test, binary logistic regression adjusted by biofilm and haplotype analyses were performed (p < 0.05). Biofilm was associated with dental caries (p < 0.05). There were no associations between dental caries and rs6256, rs307247, rs694 in none of the analyses performed (p > 0.05). In conclusion, the present study supports that the single nucleotide polymorphisms rs6256, rs307247, and rs694 in the PTH-encoding gene are not associated with dental caries in Brazilian children.

Intermittent Administration of Parathyroid Hormone 1-34 Enhances Osteogenesis of Human Mesenchymal Stem Cells by Regulating Protein Kinase Cδ

Human mesenchymal stem cells (hMSCs) can differentiate into osteoblasts and are regulated by chemical cues. The recombinant N-terminal (1–34 amino acids) fragment of the parathyroid hormone (PTH (1–34)) is identified to promote osteogenesis. The osteoanabolic effects of intermittent PTH (1–34) treatment are linked to a complex consisting of signaling pathways; additionally, protein kinase C (PKC) act as mediators of multifunctional signaling transduction pathways, but the role of PKC δ (PKCδ), a downstream target in regulating osteoblast differentiation during intermittent administration of PTH (1–34) is less studied and still remains elusive. The purpose of this study is to examine the role of PKCδ during intermittent and continuous PTH (1–34) administration using osteoblast-lineage-committed hMSCs. Relative gene expression of osteoblast-specific genes demonstrated significant upregulation of RUNX2, type I Collagen, ALP, and Osterix and increased alkaline phosphatase activity in the presence of PTH (1–34). Intermittent PTH (1–34) administration increased PKC activity at day 7 of osteogenic differentiation, whereas inhibition of PKC activity attenuated these effects. In addition, the specific isoform PKCδ was activated upon treatment. These findings demonstrate that intermittent PTH (1–34) treatment enhances the osteogenesis of hMSCs by upregulating osteoblast-specific genes via PKCδ activation.

Effects of Intermittent Administration of Parathyroid Hormone (1-34) on Bone Differentiation in Stromal Precursor Antigen-1 Positive Human Periodontal Ligament Stem Cells

Periodontitis is the most common cause of tooth loss and bone destruction in adults worldwide. Human periodontal ligament stem cells (hPDLSCs) may represent promising new therapeutic biomaterials for tissue engineering applications. Stromal precursor antigen-1 (STRO-1) has been shown to have roles in adherence, proliferation, and multipotency. Parathyroid hormone (PTH) has been shown to enhance proliferation in osteoblasts. Therefore, in this study, we aimed to compare the functions of STRO-1(+) and STRO-1(-) hPDLSCs and to investigate the effects of PTH on the osteogenic capacity of STRO-1(+) hPDLSCs in order to evaluate their potential applications in the treatment of periodontitis. Our data showed that STRO-1(+) hPDLSCs expressed higher levels of the PTH-1 receptor (PTH1R) than STRO-1(-) hPDLSCs. In addition, intermittent PTH treatment enhanced the expression of PTH1R and osteogenesis-related genes in STRO-1(+) hPDLSCs. PTH-treated cells also exhibited increased alkaline phosphatase activity and mineralization ability. Therefore, STRO-1(+) hPDLSCs represented a more promising cell resource for biomaterials and tissue engineering applications. Intermittent PTH treatment improved the capacity for STRO-1(+) hPDLSCs to repair damaged tissue and ameliorate the symptoms of periodontitis.