Hypoxia-induced upregulation of angiogenic factors in immortalized human periodontal ligament fibroblasts

3D-Printed Titanium Trabecular Scaffolds with Sustained Release of Hypoxia-Induced Exosomes for Dual-Mimetic Bone Regeneration

Current Ti-6Al-4V bone implants lack trabecular structure and pro‑angiogenic cues, both essential for regeneration. Herein, a dual biomimetic strategy is devised that integrates a 3D-printed biomimetic trabecular porous Ti-6Al-4V scaffold (BTPS) with exosome-loaded PEGDA/GelMA hydrogel microspheres (PGHExo) designed for sustained release. BTPS is designed using Voronoi algorithms and imaging data, and replicates the geometry and mechanical properties of natural bone. Hypoxia-induced human umbilical vein endothelial cell (HUVEC) derived exosomes (HExo) are encapsulated in PGHExo microspheres via microfluidic technology, enabling controlled release of HExo, and anchored onto BTPS using polydopamine (pDA) modification (BTPS&pDA@PGHExo). BTPS exhibited an elastic modulus of ≈3.2 GPa and a permeability of 11.52 × 10-8 mm2, mimicking natural bone. In vitro assays demonstrated that BTPS&pDA@PGHExo significantly enhanced osteogenesis and angiogenesis. mRNA-Seq analysis suggested that BTPS&pDA@PGHExo regulates osteogenic and angiogenic gene expression through the activation of pathways including MAPK, mTOR, HIF-1, and VEGF. In vivo, BTPS&pDA@PGHExo improved bone volume, density, and neovascularization in a rabbit model. This dual biomimetic strategy offers a promising clinical solution, addressing the limitations of conventional Ti-6Al-4V scaffolds and providing an innovative approach for personalized bone defect repair.

Influence of Hypoxic Condition on Cytotoxicity, Cellular Migration, and Osteogenic Differentiation Potential of Aged Periodontal Ligament Cells

OBJECTIVE

 This study aimed to investigate and compare the influence of hypoxic conditions on cytotoxicity, cellular migration, and osteogenic differentiation of aged periodontal ligament (PDL) cells.

MATERIALS AND METHODS

 Isolated human PDL cells from aged and young subjects were cultured under hypoxic conditions, which were treated with hydrogen peroxide (H2O2) (0, 25, 50, 100, 200, and 500 µM). To assess cytotoxicity, lactate dehydrogenase release was determined by the optical density at 490 nm, and the percentage of cell death was calculated. An in vitro wound healing assay was performed over 24 to 48 hours for cellular migration determination. Osteogenic differentiation was determined by alizarin red staining and osteogenic gene expression, including the expression of runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), and osteopontin (OPN).

RESULTS

 There was a significant difference in the percentage of cell death with high hypoxic condition (200 and 500 µM) compared to low hypoxic conditions on both day 1 and 2. The highest cellular migration was depicted at 50 µM in both young and aged groups of the in vitro wound healing assay. Osteogenic gene expression of RUNX2 in the aged group was increased at 25 and 50 µM hypoxic condition at day 7, but the expression was gradually decreased after 14 days. On the contrary, the expression of ALP and OPN in the aged group was increased at day 14. Only OPN had been found to be statistically significantly different when compared with gene expression at day 7 and 14 (p < 0.05). The results showed no statistically significant differences when compared with the young and aged groups in all genes and all concentrations.

CONCLUSION

 The concentration of low hypoxic condition (25-50 µM) was proposed to promote cell viability, cellular migration, and osteogenic differentiation in aged PDL cells. We suggested that the potential of aged PDL cells for use in cell therapy for periodontal regeneration might possibly be similar to that of young PDL cells.

High-yield nanovesicles extruded from dental follicle stem cells promote the regeneration of periodontal tissues as an alternative of exosomes

AIM

To identify an optimized strategy for the large-scale production of nanovesicles (NVs) that preserve the biological properties of exosomes (EXOs) for use in periodontal regeneration.

MATERIALS AND METHODS

NVs from dental follicle stem cells (DFSCs) were prepared through extrusion, and EXOs from DFSCs were isolated. The yield of both extruded NVs (eNVs) and EXOs were quantified through protein concentration and particle number analyses. Their pro-migration, pro-proliferation and pro-osteogenesis capacities were compared subsequently in vitro. Additionally, proteomics analysis was conducted. To further evaluate the periodontal regeneration potential of eNVs and EXOs, they were incorporated into collagen sponges and transplanted into periodontal defects in rats. In vivo imaging and H&E staining were utilized to verify their biodistribution and safety. Micro-Computed Tomography analysis and histological staining were performed to examine the regeneration of periodontal tissues.

RESULTS

The yield of eNVs was nearly 40 times higher than that of EXOs. Interestingly, in vitro experiments indicated that the pro-migration and pro-proliferation abilities of eNVs were superior, and the pro-osteogenesis potential was comparable to EXOs. More importantly, eNVs exhibited periodontal regenerative potential similar to that of EXOs.

CONCLUSIONS

Extrusion has proven to be an efficient method for generating numerous eNVs with the potential to replace EXOs in periodontal regeneration.

The effect of smoking on clinical and biochemical early healing outcomes of coronally advanced flap with connective tissue graft: Prospective cohort study

BACKGROUND

This study aimed to determine the effects of smoking on early (≤3 months) clinical outcomes and relevant molecular biomarkers following root coverage surgery.

METHODS

Eighteen smokers and 18 nonsmokers, status biochemically verified, with RT1 gingival recession defects were recruited and completed study procedures. All patients received coronally advanced flap plus connective tissue graft. Baseline and 3 month recession depth (RD), recession width (RW), keratinized tissue width (KTW), clinical attachment level (CAL), and gingival phenotype (GP) were recorded. Root coverage (RC) percentage and complete root coverage (CRC) were calculated. Recipient (gingival crevicular fluid) and donor (wound fluid) site VEGF-A, HIF-1α, 8-OHdG, and ANG levels were determined.

RESULTS

There were no significant intergroup differences for any baseline or postoperative clinical parameters (P > 0.05), except for whole mouth gingival index (increased in nonsmokers at 3 months; P < 0.05). Compared to baseline, RD, RW, CAL, KTW, and GP significantly improved postoperatively, without significant intergroup differences. There were no significant intergroup differences for RC (smokers = 83%, nonsmokers = 91%, P = 0.069), CRC (smokers = 50%, nonsmokers = 72%, P = 0.177), and CAL gain (P = 0.193). The four biomarker levels significantly increased postoperatively (day 7; P ≤ 0.042) in both groups and returned to baseline (day 28) without significant intergroup differences (P > 0.05). Similarly, donor site parameters were not different between groups. Strong correlations, consistent over time, were found between biomarkers implicated in angiogenesis (VEGF-A, HIF-1α, and ANG).

CONCLUSIONS

The early (3 month) clinical and molecular changes after root coverage surgery utilizing a coronally advanced flap plus connective tissue graft are similar between smokers and nonsmokers.

HIF-1α and periodontitis: Novel insights linking host-environment interplay to periodontal phenotypes

Periodontitis, the sixth most prevalent epidemic disease globally, profoundly impacts oral aesthetics and masticatory functionality. Hypoxia-inducible factor-1α (HIF-1α), an oxygen-dependent transcriptional activator, has emerged as a pivotal regulator in periodontal tissue and alveolar bone metabolism, exerts critical functions in angiogenesis, erythropoiesis, energy metabolism, and cell fate determination. Numerous essential phenotypes regulated by HIF are intricately associated with bone metabolism in periodontal tissues. Extensive investigations have highlighted the central role of HIF and its downstream target genes and pathways in the coupling of angiogenesis and osteogenesis. Within this concise perspective, we comprehensively review the cellular phenotypic alterations and microenvironmental dynamics linking HIF to periodontitis. We analyze current research on the HIF pathway, elucidating its impact on bone repair and regeneration, while unraveling the involved cellular and molecular mechanisms. Furthermore, we briefly discuss the potential application of targeted interventions aimed at HIF in the field of bone tissue regeneration engineering. This review expands our biological understanding of the intricate relationship between the HIF gene and bone angiogenesis in periodontitis and offers valuable insights for the development of innovative therapies to expedite bone repair and regeneration.

Hypoxia Effects in Intervertebral Disc-Derived Stem Cells and Discus Secretomes: An in vitro Study

Background

This study aimed to investigate the effects of hypoxia and normoxia preconditioning in rabbit intervertebral disc-derived stem cells (IVDSCs) and discus-derived conditioned medium (DD-CM)/secretomes in vitro. Transforming growth factor (TGF)-β1, platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), and vascular endothelial growth factor (VEGF) have a role in the proliferation, development, differentiation, and migration of MSCs.

Materials and Methods

Intervertebral discs were isolated from rabbit and incubated in normoxia and hypoxia 1%, 3%, and 5% (hypoxia groups) condition. Cell counting was performed after 24 hours of manipulation, then analyzed using one-way ANOVA. TGF-β1, PDGF, FGF, and VEGF were measured using the ELISA.

Results

The highest number of cells was in the hypoxia 3% preconditioning compared to the normoxia, hypoxia 1%, and hypoxia 5% groups. Hypoxia 3% also had the highest increase in PDGF protein production compared to normoxia, with hypoxia 1% and 5%. Among hypoxia groups, the highest secretions of VEGF and FGF proteins were in the hypoxia 3% group. Based on TGF-β1 protein measurement, the hypoxia 1% group was the highest increase in this protein compared to other groups.

Conclusion

Oxygen level in hypoxia preconditioning has a role in the preparation of IVDSCs and secretome preparation in vitro. The highest cell numbers were found in the treatment group with 3% hypoxia, and 3% hypoxia was significantly related to support IVDSCs preparation. Preconditioning with 3% hypoxia had higher PDGF and VEGF levels than other hypoxia groups.

Enhanced Anti-Cancer Effects of Conditioned Medium from Hypoxic Human Adult Dermal Fibroblasts on Cervical Cancer Cells

Hypoxia regulates fibroblast function by changing intracellular signaling and secretion factors, that influence the states of nearby cells. In this work, we investigated how medium (CM) from human adult dermal fibroblasts (HDFs) cultured in normoxic and hypoxic conditions affected cervical cancer (HeLa) cells. The HeLa cells showed decreased cell viability, increased apoptosis, and cell cycle arrest in response to CM from hypoxic-cultured HDFs (H-CM) compared with CM from normoxic-cultured HDFs (N-CM). Among the proteins up-regulated (>2-fold) in H-CM compared with N-CM, lymphotoxin-beta receptor (LTBR) decreased the viability of HeLa cells. Among the intracellular proteins down-regulated (>2-fold) in HeLa cells treated with H-CM compared with N-CM, the most enriched biological process GO term and KEGG pathway were protein deubiquitination and hsa05166:HTLV-I infection, respectively. In the protein−protein interaction network of intracellular proteins with altered expression (>2-fold), 1 up-regulated (TNF) and 8 down-regulated (ESR1, MCL1, TBP, CD19, LCK, PCNA, CHEK1, and POLA1) hub proteins were defined. Among the down-regulated hub proteins, the most enriched biological process GO term and KEGG pathway were leading strand elongation and hsa05166:HTLV-I infection, respectively. This study reveals that H-CM had stronger anti-cancer effects on cervical cancer cells than N-CM and induced intracellular signaling patterns related to those enhanced anti-cancer effects.

Ligament/Tendon Culture under Hypoxic Conditions: A Systematic Review

The hypoxic environment is a substantial factor in maintenance, proliferation, and differentiation of the cell cultures. Low oxygen is known as a potent chondrogenesis stimulus in stem cells that is important for clinical application and engineering of functional cartilage. Hypoxia can potentially induce angiogenesis process by secretion of cytokines. This systematic review goal is to discover the effect of hypoxic condition on tendon/ ligament culture and the best oxygen level of hypoxia for in vitro and in vivo studies. We included 21 articles. A comprehensive review of this database confirms that the hypoxic condition is a substantial factor in the maintenance, proliferation, and differentiation of ligament/tendon cultures. Cell proliferation in the severe hypoxic (oxygen concentration of 1%) group at 24 h postcultivation was considered significant, but cell proliferation was markedly inhibited in the severe hypoxic group after 48 h.

Vascular Endothelial Growth Factor: A Translational View in Oral Non-Communicable Diseases

Vascular endothelial growth factors (VEGFs) are vital regulators of angiogenesis that are expressed in response to soluble mediators, such as cytokines and growth factors. Their physiologic functions include blood vessel formation, regulation of vascular permeability, stem cell and monocyte/macrophage recruitment and maintenance of bone homeostasis and repair. In addition, angiogenesis plays a pivotal role in chronic pathologic conditions, such as tumorigenesis, inflammatory immune diseases and bone loss. According to their prevalence, morbidity and mortality, inflammatory diseases affecting periodontal tissues and oral cancer are relevant non-communicable diseases. Whereas oral squamous cell carcinoma (OSCC) is considered one of the most common cancers worldwide, destructive inflammatory periodontal diseases, on the other hand, are amongst the most prevalent chronic inflammatory conditions affecting humans and also represent the main cause of tooth loss in adults. In the recent years, while knowledge regarding the role of VEGF signaling in common oral diseases is expanding, new potential translational applications emerge. In the present narrative review we aim to explore the role of VEGF signaling in oral cancer and destructive periodontal inflammatory diseases, with emphasis in its translational applications as potential biomarkers and therapeutic targets.

Gene expression and phosphorylation of ERK and AKT are regulated depending on mechanical force and cell confluence in murine cementoblasts

Cementoblasts, located on the tooth root surface covered with cementum, are considered to have tooth protecting abilities. They prevent tissue damage and secure teeth anchorage inside the periodontal ligament during mechanical stress. However, the involvement of cementoblasts in mechanical compression induced periodontal remodeling needs to be identified and better understood. Here, we investigated the effect of static compressive stimulation, simulating the compression side of orthodontic force and cell confluence on a murine cementoblast cell line (OC/CM). The influence of cell confluence in cementoblast cells was analyzed by MTS assay and immunostaining. Furthermore, mRNA and protein expression were investigated by real-time RT-PCR and western blotting at different confluence grades and after mechanical stimulation. We observed that cementoblast cell proliferation increases with increasing confluence grades, while cell viability decreases in parallel. Gene expression of remodeling markers is regulated by compressive force. In addition, cementoblast confluence plays a crucial role in this regulation. Confluent cementoblasts show a significantly higher basal expression of Bsp, Osterix, Alpl, Vegfa, Mmp9, Tlr2 and Tlr4 compared to sub-confluent cells. After compressive force of 48 h at 60% confluence, an upregulation of Bsp, Osterix, Alpl, Vegf and Mmp9 is observed. In contrast, at high confluence, all analyzed genes were downregulated through mechanical stress. We also proved a regulation of ERK, phospho-ERK and phospho-AKT dependent on compressive force. In summary, our findings provide evidence that cementoblast physiology and metabolism is highly regulated in a cell confluence-dependent manner and by mechanical stimulation.

Dimethyloxallyl glycine/nanosilicates-loaded osteogenic/angiogenic difunctional fibrous structure for functional periodontal tissue regeneration

The coupled process of osteogenesis-angiogenesis plays a crucial role in periodontal tissue regeneration. Although various cytokines or chemokines have been widely applied in periodontal in situ tissue engineering, most of them are macromolecular proteins with the drawbacks of short effective half-life, poor stability and high cost, which constrain their clinical translation. Our study aimed to develop a difunctional structure for periodontal tissue regeneration by incorporating an angiogenic small molecule, dimethyloxalylglycine (DMOG), and an osteoinductive inorganic nanomaterial, nanosilicate (nSi) into poly (lactic-co-glycolic acid) (PLGA) fibers by electrospinning. The physiochemical properties of DMOG/nSi-PLGA fibrous membranes were characterized. Thereafter, the effect of DMOG/nSi-PLGA membranes on periodontal tissue regeneration was evaluated by detecting osteogenic and angiogenic differentiation potential of periodontal ligament stem cells (PDLSCs) in vitro. Additionally, the fibrous membranes were transplanted into rat periodontal defects, and tissue regeneration was assessed with histological evaluation, micro-computed tomography (micro-CT), and immunohistochemical analysis. DMOG/nSi-PLGA membranes possessed preferable mechanical property and biocompatibility. PDLSCs seeded on the DMOG/nSi-PLGA membranes showed up-regulated expression of osteogenic and angiogenic markers, higher alkaline phosphatase (ALP) activity, and more tube formation in comparison with single application. Further, in vivo study showed that the DMOG/nSi-PLGA membranes promoted recruitment of CD90+/CD34− stromal cells, induced angiogenesis and osteogenesis, and regenerated cementum-ligament-bone complex in periodontal defects. Consequently, the combination of DMOG and nSi exerted admirable effects on periodontal tissue regeneration. DMOG/nSi-PLGA fibrous membranes could enhance and orchestrate osteogenesis-angiogenesis, and may have the potential to be translated as an effective scaffold in periodontal tissue engineering.

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Dual-load fibrous structure possessed preferable mechanical property and biocompatibility.

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Fibrous structure can orchestrate and enhance osteogenesis-angiogenesis coupling.

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Difunctional fibrous structure can recruit CD90+/CD34− stromal cells to periodontal defects.

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Difunctional fibrous structure obtained functional periodontal tissue regeneration.

Selection and validation of reference genes by RT-qPCR for murine cementoblasts in mechanical loading experiments simulating orthodontic forces in vitro

Different structures and cell types of the periodontium respond to orthodontic tooth movement (OTM) individually. Cementoblasts (OC/CM) located in the immediate vicinity of the fibroblasts on the cement have found way to the centre of actual research. Here, we identify and validate possible reference genes for OC/CM cells by RT-qPCR with and without static compressive loading. We investigated the suitability of 3 reference genes in an in vitro model of cementoblast cells using four different algorithms (Normfinder, geNorm, comparative delta-Ct method and BestKeeper) under different confluences and time. Comparable to our previous publications about reference genes in OTM in rats and human periodontal ligament fibroblasts (hPDLF), Rpl22 in murine OC/CM cells appears as the least regulated gene so that it represents the most appropriate reference gene. Furthermore, unlike to the expression of our recommended reference genes, the expression of additionally investigated target genes changes with confluence and under loading compression. Based on our findings for future RT-qPCR analyses in OC/CM cells, Rpl22 or the combination Rpl22/Tbp should be favored as reference gene. According to our results, although many publications propose the use of Gapdh, it does not seem to be the most suitable approach.