Inhibition of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) stimulates osteoblastogenesis by potentiating bone morphogenetic protein 2 (BMP2) responses

Histological and Immunohistochemical Evaluation of Rh-BMP2: Effect on Gingival Healing Acceleration and Proliferation of Human Epithelial Cells

This study aims to histologically and immunohistochemically evaluate the effect recombinant human bone morphogenetic protein (rh-BMP2) injected in gingival tissue has on the acceleration of the epithelial migration from the wound edges and epithelial cell proliferation after implant surgery.

MATERIAL AND METHODS

The study includes 20 patients who underwent bilateral implant surgeries in the premolar-molar region of the mandible, followed by guided bone regeneration. Each patient received an implant in both locations, but rh-BMP2 was only on the right side. At 9 days from the surgery, a gingival biopsy was performed 3 mm distally to the last implant. In total, 20 samples were collected from the left side (control group #1) and 20 from right (test group #1). This was repeated at a 4-month interval during healing abutment placements. Tissues were processed and stained with hematoxylin-eosin and then immunohistochemically for the expression of Ki-67 and further histological examination.

RESULT

Complete closure of the epithelium with new cell formation was observed in the 55% test group and 20% control group after 9 days. At 4 months, although 100% samples of all groups had complete epithelial closure, the test group showed that the epithelial cells were more organized and mature due to the increased number of blood vessels. The average number of new epithelial cells was 17.15 ± 7.545 and 16.12 ± 7.683 cells per mm in test group, respectively, at 9 days and 4 months and 10.99 ± 5.660 and 10.95 ± 5.768 in control groups.

CONCLUSION

Evident from histological observations, rh-BMP-2 can accelerate the closure of gingival wounds, the healing process of epithelial gingival tissue, and the formation of epithelial cells in patients undergoing dental implant treatment.

Zika virus alters osteogenic lineage progression of human mesenchymal stromal cells

Arboviruses target bone forming osteoblasts and perturb bone remodeling via paracrine factors. We previously reported that Zika virus (ZIKV) infection of early-stage human mesenchymal stromal cells (MSCs) inhibited the osteogenic lineage commitment of MSCs. To understand the physiological interplay between bone development and ZIKV pathogenesis, we employed a primary in vitro model to examine the biological responses of MSCs to ZIKV infection at different stages of osteogenesis. Precommitted MSCs were infected at the late stage of osteogenic stimulation (Day 7) with ZIKV (multiplicity of infection of 5). We observe that MSCs infected at the late stage of differentiation are highly susceptible to ZIKV infection similar to previous observations with early stage infected MSCs (Day 0). However, in contrast to ZIKV infection at the early stage of differentiation, infection at a later stage significantly elevates the key osteogenic markers and calcium content. Comparative RNA sequencing (RNA-seq) of early and late stage infected MSCs reveals that ZIKV infection alters the mRNA transcriptome during osteogenic induction of MSCs (1251 genes). ZIKV infection provokes a robust antiviral response at both stages of osteogenic differentiation as reflected by the upregulation of interferon responsive genes (n > 140). ZIKV infection enhances the expression of immune-related genes in early stage MSCs while increasing cell cycle genes in late stage MSCs. Remarkably, ZIKA infection in early stage MSCs also activates lipid metabolism-related pathways. In conclusion, ZIKV infection has differentiation stage-dependent effects on MSCs and this mechanistic understanding may permit the development of new therapeutic or preventative measures for bone-related effects of ZIKV infection.

Understanding the Impact of Obesity on Ageing in the Radiance of DNA Metabolism

Ageing is a multi-factorial phenomenon which is considered as a major risk factor for the development of neurodegeneration, osteoporosis, cardiovascular disease, dementia, cancer, and other chronic diseases. Phenotypically, ageing is related with a combination of molecular, cellular, and physiological levels like genomic and epi-genomic alterations, loss of proteostasis, deregulation of cellular and subcellular function and mitochondrial dysfunction. Though, no single molecular mechanism accounts for the functional decline of different organ systems in older humans but accumulation of DNA damage or mutations is a dominant theory which contributes largely to the development of ageing and age-related diseases. However, mechanistic, and hierarchical order of these features of ageing has not been clarified yet. Scientific community now focus on the effect of obesity on accelerated ageing process. Obesity is a complex chronic disease that affects multiple organs and tissues. It can not only lead to various health conditions such as diabetes, cancer, and cardiovascular disease but also can decrease life expectancy which shows similar phenotype of ageing. Higher loads of DNA damage were also observed in the genome of obese people. Thus, inability of DNA damage repair may contribute to both ageing and obesity apart from cancer predisposition. The present review emphasizes on the involvement of molecular phenomenon of DNA metabolism in development of obesity and how it accelerates ageing in mammals.

Lysine-Specific Demethylase 1 (LSD1) epigenetically controls osteoblast differentiation

Epigenetic mechanisms regulate osteogenic lineage differentiation of mesenchymal stromal cells. Histone methylation is controlled by multiple lysine demethylases and is an important step in controlling local chromatin structure and gene expression. Here, we show that the lysine-specific histone demethylase Kdm1A/Lsd1 is abundantly expressed in osteoblasts and that its suppression impairs osteoblast differentiation and bone nodule formation in vitro. Although Lsd1 knockdown did not affect global H3K4 methylation levels, genome-wide ChIP-Seq analysis revealed high levels of Lsd1 at gene promoters and its binding was associated with di- and tri-methylation of histone 3 at lysine 4 (H3K4me2 and H3K4me3). Lsd1 binding sites in osteoblastic cells were enriched for the Runx2 consensus motif suggesting a functional link between the two proteins. Importantly, inhibition of Lsd1 activity decreased osteoblast activity in vivo. In support, mesenchymal-targeted knockdown of Lsd1 led to decreased osteoblast activity and disrupted primary spongiosa ossification and reorganization in vivo. Together, our studies demonstrate that Lsd1 occupies Runx2-binding cites at H3K4me2 and H3K4me3 and its activity is required for proper bone formation.

Candidate kinases for adipogenesis and osteoblastogenesis from human bone marrow mesenchymal stem cells

Adipogenesis and osteoblastogenesis (adipo-osteoblastogenesis) are closely related processes involving with the phosphorylation of numerous cytoplasmic proteins and key transcription factors. Despite the recognition of the importance of protein phosphorylation in adipo-osteoblastocyte biology, relatively little is known about the specific kinases for adipo-osteoblastogenesis. Here, we constructed the comprehensive gene transcriptional landscapes of kinases at 3, 5, and 7 days during adipo-osteoblastogenesis from human bone marrow mesenchymal stem cells (hMSCs). We identified forty-four and eight significant DEGs (differentially expressed genes) separately for adipo-osteoblastogenesis. Five significant DEGs, namely CAMK2A, NEK10, PAK3, PRKG2, and PTK2B, were simultaneously shared by adipo-osteoblastogenic anecdotes. Using a lentivirus system, we confirmed that PTK2B (non-receptor protein tyrosine kinase 2 beta) simultaneously inhibited adipo-osteoblastogenesis through RNAi assays, and PRKG2 (protein kinase cGMP-dependent 2) facilitated adipogenesis and weakened osteoblastogenesis. The only certainty was that the identified candidate significant DEGs encoding kinases responsible for protein phosphorylation, especially PTK2B and PRKG2, were the potential molecular switches of cell fate determination for hMSCs. This study would provide novel study targets for hMSC differentiation and potential clues for the therapy of the adipo-osteoblastogenic balance-derived disorders.