HIF-1α increases the osteogenic capacity of ADSCs by coupling angiogenesis and osteogenesis via the HIF-1α/VEGF/AKT/mTOR signaling pathway

Manipulating Mg/Ca ratios in MgO-CaO-SiO2 bioactive glass for achieving accelerated osteogenic differentiation of human adipose-derived stem cells

Cell-containing biomaterial is a promising material for treating nonunion or critical bone defect. Human adipose-derived stem cells (hADSCs) are suitable for bone repair due to their abundance in the abdomen, thighs, and buttocks. However, the low osteogenic capacities of hADSCs hinder their extended development for bone regeneration application. The present goal explores a novel MgO-CaO-SiO2 bioactive glass with suitable Mg/Ca ratios to enhance the osteogenic differentiation and bioactivity of hADSCs. The synthetic bioglass can be expressed as xMgO-(2-x)CaO-SiO2 (abbreviated as Mg(x)Ca(2-x)Si2, x = 0, 0.25, 0.5, 0.75, and 1). The expression levels of osteoblast-related genes (i.e., BMP2, RUNX2, DLX5, COL1A1, BGLAP2, and SPP1) were evaluated by reverse transcription-quantitative PCR (RT-PCR). The proteins involved in the p38/Akt/ERK signaling pathways were analyzed with Western blots. The results indicated that the extractions from the Mg(x)Ca(2-x)Si2 bioglass promoted hADSCs proliferation. Among the Mg(x)Ca(2-x)Si2 bioglass with different Mg/Ca ratios, the bioglass with a low Mg/Ca ratio (x = 0.25) presented greater osteogenic differentiation of hADSCs by promoting the p38 signaling pathway. Interestingly, the bioglass with low Mg/Ca ratio (x = 0.25) further presented on osteogenic potential with greater osteointegration in rat femoral defect model. This work provides the optimal Mg/Ca ratio in Mg(x)Ca(2-x)Si2 bioglass to promote the osteogenic induction of hADSCs and bone regeneration.

Dual-layer microneedles with NO/O2 releasing for diabetic wound healing via neurogenesis, angiogenesis, and immune modulation

Diabetic wounds present multiple functional impairments, including neurovascular dysregulation, oxidative imbalance, and immune dysfunction, making wound healing particularly challenging, while traditional therapeutical strategies fail to address these complex issues effectively. Herein, we propose a strategy utilizing dual-layer microneedles to deliver therapeutic gases by modulating neurovascular coupling and immune functions for diabetic wound treatment. The microneedle can respond to reactive oxygen species (ROS) in the diabetic microenvironment and subsequently generate oxygen (O2) and nitric oxide (NO). These gases comprehensively promote neuro-vascular regeneration, reduce oxidative stress levels, and attenuate inflammation. In vivo studies demonstrate that the microneedle can accelerate diabetic wound healing by modulating neurovascular regeneration and inflammatory processes. Transcriptomic analyses further validate the involvement of related advantageous signaling pathways. The potential mechanism involves the activation of the PI3K-AKT-mTOR pathway to facilitate autophagy, ultimately accelerating the healing process. Thus, our multifunctional dual-layer microneedles provide an effective strategy for treating diabetic wounds.

Strontium-based quaternary ammonium salt chitosan particles for ultrafast hemostasis of open fracture

The management of open bone defects poses a formidable challenge in clinical practice, primarily due to issues such as profuse bleeding, inflammation, bacterial infections, and compromised bone fracture healing. To tackle these complexities, we have devised a novel hemostatic powder, namely the compound strontium-based chitosan quaternary ammonium salt hemostatic powder (QCS@SrT-TA). This innovative powder leverages the self-assembly of tripolyphosphate and strontium ions, facilitated by a positively charged core cross-linker. Furthermore, its surface has been strategically modified with polyphenol and positively charged macromolecules, imparting unique properties. The mesoporous architecture of QCS@SrT-TA facilitates rapid moisture absorption, enhancing its efficacy. In preclinical studies using rat tail artery amputation and liver bleeding models, QCS@SrT-TA exhibited remarkable performance, significantly reducing both bleeding time and volume (62.39 ± 2.89 mg, 35.33 ± 4.16 s in tail amputation, 63.7 ± 5.19 mg, 62.33 ± 9.61 s in liver bleeding). Notably, the positively charged strontium ions and quaternary ammonium salts within the powder were effective in removing bacteria, minimizing the risk of infection. Beyond hemostasis, QCS@SrT-TA demonstrates additional therapeutic benefits. It polarizes M2 macrophage phenotypes and promotes angiogenesis within bone defect sites, accelerating bone healing processes. Ultimately, a substantially enhanced and notable functional recovery is achieved. In summary, the rapid hemostatic, potent antibacterial, anti-inflammatory, and angiogenesis-promoting characteristics of QCS@SrT-TA hold immense promise as a groundbreaking clinical treatment strategy for open bone defects.

Enhanced therapeutic effects of hypoxia-preconditioned mesenchymal stromal cell-derived extracellular vesicles in renal ischemic injury

BACKGROUND

Extracellular vesicles (EVs) secreted by mesenchymal stromal cells (MSCs) have been shown to provide significant protection against renal ischemia-reperfusion injury (IRI). Hypoxia has emerged as a promising strategy to enhance the tissue repair capabilities of MSCs. However, the specific effects of hypoxia on MSCs and MSC-EVs, as well as their therapeutic potential in renal IRI, remain unclear. In this study, we investigated the alterations occurring in MSCs and the production of MSC-EVs following hypoxia pre-treatment, and further explored the key intrinsic mechanisms underlying the therapeutic effects of hypoxic MSC-EVs in the treatment of renal IRI.

METHODS

Human umbilical cord MSCs were cultured under normoxic and hypoxic conditions. Proliferation and related pathways were measured, and RNA sequencing was used to detect changes in the transcriptional profile. MSC-EVs from both normoxic and hypoxic conditions were isolated and characterized. In vivo, the localization and therapeutic effects of MSC-EVs were assessed in a rat renal IRI model. Histological examinations were conducted to evaluate the structure, proliferation, and apoptosis of IRI kidney tissue respectively. Renal function was assessed by measuring serum creatinine and blood urea nitrogen levels. In vitro, the therapeutic potential of MSC-EVs were measured in renal tubular epithelial cells injured by antimycin A. Protein sequencing analysis of hypoxic MSC-EVs was performed, and the depletion of Glutathione S-Transferase Omega 1 (GSTO1) in hypoxic MSC-EVs was carried out to verify its key role in alleviating renal injury.

RESULTS

Hypoxia alters MSCs transcriptional profile, promotes their proliferation, and increases the production of EVs. Hypoxia-pretreated MSC-EVs demonstrated a superior ability to mitigate renal IRI, enhancing proliferation and reducing apoptosis of renal tubular epithelial cells both in vivo and in vitro. Protein profiling of the EVs revealed an accumulation of numerous anti-oxidative stress proteins, with GSTO1 being particularly prominent. Knockdown of GSTO1 significantly reduced the antioxidant and therapeutic effects on renal IRI of hypoxic MSC-EVs.

CONCLUSIONS

Hypoxia significantly promotes the generation of MSC-EVs and enhances their therapeutic effects on renal IRI. The antioxidant stress effect induced by GSTO1 is identified as one of the most critical underlying mechanisms. Our findings highlight that hypoxia-pretreated MSC-EVs represent a novel and promising therapeutic strategy for renal IRI.

Insulin for oral bone tissue engineering: a review on innovations in targeted insulin-loaded nanocarrier scaffold

The occurrence of oral bone tissue degeneration and bone defects by osteoporosis, tooth extraction, obesity, trauma, and periodontitis are major challenges for clinicians. Traditional bone regeneration methods often come with limitations such as donor site morbidity, limitation of special shape, inflammation, and resorption of the implanted bone. The treatment oriented with biomimetic bone materials has achieved significant attention recently. In the oral bone tissue engineering arena, insulin has gained considerable attention among all the known biomaterials for osteogenesis and angiogenesis. It also exhibits osteogenic and angiogenic properties by interacting with insulin receptors on osteoblasts. Insulin influences bone remodelling both directly and indirectly. It acts directly through the PI3K/Akt and MAPK signalling pathways and indirectly by modulating the RANK/RANKL/OPG pathway, which helps reduce bone resorption. The current review reports the role of insulin in bone remodelling and bone tissue regeneration in the oral cavity in the form of scaffolds and nanomaterials. Different insulin delivery systems, utilising nanomaterials and scaffolds functionalised with polymeric biomaterials have been explored for oral bone tissue regeneration. The review put forward a theoretical basis for future research in insulin delivery in the form of scaffolds and composite materials for oral bone tissue regeneration.

From oxidative stress to metabolic dysfunction: The role of TRPM2

Metabolic syndromes including atherosclerosis, diabetes, obesity, and hypertension are increasingly prevalent worldwide. The disorders are the primary attributes of oxidative stress and inflammation. The transient receptor potential M2 (TRPM2) channel is a pivotal mediator linking oxidative stress to metabolic dysfunction. TRPM2, a non-selective cation channel activated by reactive oxygen species (ROS) and adenosine diphosphate ribose (ADPR), regulates calcium influx, inflammation, and cell death across various tissues. This review explores the structural and activation mechanisms of TRPM2, emphasizing its significance in metabolic diseases. Elevated levels of TRPM2 play a vital role in the disease progression by influencing physiological and cellular processes such as endothelial dysfunction, immune cell activation, and mitochondrial impairment. In conditions such as atherosclerosis, ischemic stroke, diabetes, obesity, and hypertension; TRPM2 exacerbates oxidative damage, amplifies inflammatory responses, and disrupts metabolic homeostasis. Recent research highlights the potential of TRPM2 as a therapeutic target, developing specified inhibitors. This review underscores the multifaceted role of TRPM2 in metabolic disorders and its promise as a target for therapeutic interventions.

Bioinspired adhesive polydopamine-metal-organic framework functionalized 3D customized scaffolds with enhanced angiogenesis, immunomodulation, and osteogenesis for orbital bone reconstruction

Critical-sized orbital bone defects can lead to significant maxillofacial deformities and even eye movement disorders. The challenges associated with these defects, including their complicated structure, inadequate blood supply, and limited availability of progenitor cells that hinder successful repair. To overcome these issues, we developed a novel approach using computer numerical control (CNC) material reduction manufacturing technology to produce a customized polyetheretherketone (PEEK) scaffold that conforms to the specific shape of orbital bone defects. Deferoxamine (DFO) was in situ encapsulated into polydopamine-hybridized zeolitic imidazolate framework-8 (pZIF8-DFO) nanoparticles, which was subsequently adhered to the sulfonated PEEK (sPEEK) scaffold through polydopamine modification. This functionalization enhanced drug loading efficiency and imparted anti-inflammatory properties to the nanoparticle system. Our in vitro findings demonstrated that the sustained release of DFO from the sPEEK/pZIF8-DFO scaffolds extended over 14 days and significantly promoted angiogenesis and progenitor cell recruitment, as evidenced by increased expression of HIF-1α, VEGF, and SDF-1α expression in human umbilical vein endothelial cells (HUVECs). Moreover, sPEEK/pZIF8-DFO scaffolds exhibited superior immunomodulation and osteogenic differentiation capabilities on Raw 264.7 cells and rabbit bone marrow mesenchymal stem cells (rBMSCs), respectively. Most notably, our in vivo rabbit orbital bone defects revealed that sPEEK/pZIF8-DFO scaffolds resulted in a greater volume of new bone formation than on sPEEK and sPEEK/pZIF8 scaffolds, with partial bone connection to the sPEEK/pZIF8-DFO scaffolds. In summary, we develop a novel PEEK scaffold that combines enhanced angiogenesis, stem cell recruitment, immunomodulation, and osteogenic differentiation, showcasing its promising potential for orbital bone reconstruction.

Exosomes derived from umbilical cord mesenchymal stem cells promote healing of complex perianal fistulas in rats

BACKGROUND

Complex perianal fistulas, challenging to treat and prone to recurrence, often require surgical intervention that may cause fecal incontinence and lower quality of life due to large surgical wounds and potential sphincter damage. Human umbilical cord-derived MSCs (hUC-MSCs) and their exosomes (hUCMSCs-Exo) may promote wound healing.

METHODS

This study assessed the efficacy, mechanisms, and safety of these exosomes in treating complex perianal fistulas in SD rats. We established a rat model, divided rats with fistulas into the control and the exosome groups. We assessed treatment efficacy through ultrasound, clinical observations, and histopathological analysis. We also evaluated the activation of the HIF-1α/TGF-β/Smad signaling pathway via PCR and Western blot and assessed serological markers for HIF-1α and inflammatory indices through ELISA. We analyzed gut microbiota and the systemic metabolic environment via untargeted metabolomics.

RESULTS

The hUCMSCs-Exo effectively promoted healing of wound, regulated the immune balance enhanced collagen synthesis and angiogenesis in the perianal fistulas model of rats, and regulated the gut microbiota and metabolomic profiles. Results of PCR and Western blot analyses indicated that the exosomes activated HIF-1α/TGF-β/Smad signaling pathways. To the dosages tested, the 10ug/100ul concentration (medium dose) was found to be the most effective to the treatment of complex perianal fistulas.

CONCLUSIONS

The hUCMSCs-Exo significantly promoted the healing of wound in perianal fistulas of rats and demonstrated higher safety. The underlying mechanism facilitating the healing process was likely associated with the activation of the HIF-1α/TGF-β/Smad signaling pathway.

Everolimus in pituitary tumor: a review of preclinical and clinical evidence

Although pituitary tumors (PTs) are mostly benign, some PTs are characterized by low surgical resection rates, high recurrence rates, and poor response to conventional treatments and profoundly affect patients' quality of life. Everolimus (EVE) is the only FDA-approved mTOR inhibitor, which can be used for oral treatment. It effectively inhibits tumor cell proliferation and angiogenesis. It has been administered for various neuroendocrine tumors of the digestive tract, lungs, and pancreas. EVE not only suppresses the growth and proliferation of APT cells but also enhances their sensitivity to radiotherapy and chemotherapy. This review introduces the role of the PI3K/AKT/mTOR pathway in the development of APTs, comprehensively explores the current status of preclinical and clinical research of EVE in APTs, and discusses the blood-brain barrier permeability and safety of EVE.

The Physiological Functions and Therapeutic Potential of Hypoxia-Inducible Factor-1α in Vascular Calcification

HIF-1α plays a crucial regulatory role in vascular calcification (VC), primarily influencing the osteogenic differentiation of VSMCs through oxygen-sensing mechanisms. Under hypoxic conditions, the stability of HIF-1α increases, avoiding PHD and VHL protein-mediated degradation, which promotes its accumulation in cells and then activates gene expressions related to calcification. Additionally, HIF-1α modulates the metabolic state of VSMCs by regulating the pathways that govern the switch between glycolysis and oxidative phosphorylation, thereby further advancing the calcification process. The interaction between HIF-1α and other signaling pathways, such as nuclear factor-κB, Notch, and Wnt/β-catenin, creates a complex regulatory network that serves as a critical driving force in VC. Therefore, a deeper understanding of the role and regulatory mechanism of the HIF-1α signaling during the development and progression of VC is of great significance, as it is not only a key molecular marker for understanding the pathological mechanisms of VC but also represents a promising target for future anti-calcification therapies.

Comprehensive Overview of Interface Strategies in Implant Osseointegration

With the improvement of implant design and the expansion of application scenarios, orthopedic implants have become a common surgical option for treating fractures and end‐stage osteoarthritis. Their common goal is rapidly forming and long‐term stable osseointegration. However, this fixation effect is limited by implant surface characteristics and peri‐implant bone tissue activity. Therefore, this review summarizes the strategies of interface engineering (osteogenic peptides, growth factors, and metal ions) and treatment methods (porous nanotubes, hydrogel embedding, and other load‐release systems) through research on its biological mechanism, paving the way to achieve the adaptation of both and coordination between different strategies. With the transition of the osseointegration stage, interface engineering strategies have demonstrated varying therapeutic effects. Especially, the activity of osteoblasts runs almost through the entire process of osseointegration, and their physiological activities play a dominant role in bone formation. Furthermore, diseases impacting bone metabolism exacerbate the difficulty of achieving osseointegration. This review aims to assist future research on osseointegration engineering strategies to improve implant‐bone fixation, promote fracture healing, and enhance post‐implantation recovery.

The Expression of HIF-1α and VEGF in Radicular Cysts and Periapical Granulomas

OBJECTIVES

 This study aimed to evaluate the expression levels of hypoxia-inducible factor 1-α (HIF-1α) and vascular endothelial growth factor (VEGF) in radicular cysts and periapical granulomas, thereby contributing to the understanding of their potential significance in the differential diagnosis and treatment of these lesions.

MATERIALS AND METHODS

 In the present cross-sectional study, 51 samples of periapical lesions were included. Of them, 24 samples were radicular cysts, and 27 samples were periapical granulomas. Samples were immunohistochemically analyzed for HIF-1α and VEGF proteins expression. Chi-square tests and Spearman's rank correlation coefficient tests were used to detect differences and correlations among the parameters, respectively.

RESULTS

 In radicular cysts, HIF-1α expression was absent in 1 (4.2%), weak in 5 (20.8%), mild in 7 (29.2%), and strong in 11 (45.8%) cases, while VEGF expression was absent in 1 (4.2%), weak in 6 (25.0%), mild in 9 (37.5%), and strong in 8 (33.3%) of the cases; nevertheless, in periapical granulomas, HIF-1α expression was absent in 8 (29.6%), weak in 6 (22.2%), mild in 9 (33.3%), and strong in 4 (14.8%) of the cases, whereas VEGF expression was absent in 4 (14.8%), weak in 16 (59.3%), mild in 4 (14.8%), and strong in 3 (11.1%) of the cases. Chi-square test revealed a significant difference in the expression of HIF-1α and VEGF between radicular cysts and periapical granuloma (chi-square test = 8.906, p = 0.031; chi-square test = 10.401, p = 0.015, respectively). Spearman's correlation test showed a significant correlation between HIF-1α and VEGF in the total samples of both radicular cysts and periapical granulomas (rho = 0.385, p = 0.005).

CONCLUSION

 There is high expression of both HIF-1α and VEGF throughout the odontogenic epithelium and connective tissue of the radicular cyst and periapical granuloma. Both HIF-1α and VEGF are more highly expressed in radicular cysts than in periapical granulomas. These findings may aid in the diagnosis and management of suspected periapical lesions, suggesting that radicular cysts exhibit more advanced hypoxic conditions and associated pathways compared with periapical granulomas.

LncRNA H19 Promotes Angiogenesis in Mouse Pulmonary Artery Endothelial Cells by Regulating the HIF-1α/VEGF Signaling Pathway

Persistent pulmonary hypertension of the newborn (PPHN) is a syndrome of acute respiratory failure characterized by systemic hypoxemia and elevated pulmonary arterial pressure, which leads to pathological changes in pulmonary vascular remodeling and endothelial cell function. Long non-coding RNA (lncRNA) H19 has been shown to be involved in the regulation of arterial endothelial cell function, but its regulatory role in PPHN is not fully understood. In the present study, mouse pulmonary artery endothelial cells (MPAECs) were cultured in a hypoxic conditions. Subsequently, the regulatory function of lncRNA H19 on MPAECs was explored by constructing adenoviruses knocking down and overexpressing lncRNA H19. The results revealed that the hypoxic conditions could induce the proliferation and migration of MPAECs, as well as the high expression of lncRNA H19 in MPAECs. Knockdown of lncRNA H19 expression in MPAECs reversed hypoxic environment-induced functional changes in endothelial cells, whereas overexpression of lncRNA H19 further enhanced the proliferation and migration of MPAECs. In addition, lncRNA H19 upregulated the hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathway through sponge of miNA-20a-5p, which in turn promoted changes in endothelial cell function. LncRNA H19 may interfere with vascular remodeling in hypoxia-induced pulmonary hypertension by upregulating the expression of HIF-1α and VEGF in vascular endothelial cells.

Multifunctional layered microneedle patches enable transdermal angiogenesis and immunomodulation for scarless healing of thermal burn injuries

Thermal burn injuries induce substantial alterations in the immune compositions and anatomical structures in the skin, which are characterized by strong inflammatory responses and thick eschar formation on the wound surface. These traits challenge current treatment paradigms due to insufficient drug penetration into affected tissues and the unsatisfactory wound regeneration. Herein, we report a layered microneedle (MN) patch for addressing these challenges in burn injury healing. The MN patch features a core/shell structure with methacrylated gelatin (GelMA) encapsulated with human umbilical vein endothelial cell (HUVECs)-derived hypoxia-induced exosomes (EXO-H) as the bottom layer and sodium alginate (SA) containing naringin (Nar)-loaded CaCO3 nanoparticles (CaCO3@Nar) as the top layer. Upon administration onto thermal burn injury site, the MN patches enable transdermal drug delivery by perforating the eschar. The spontaneous degradation of CaCO3@Nar in the interstitial fluid triggers sustained Nar release to alleviate local inflammation and scavenge excessive reactive oxygen species (ROS). Meanwhile, EXO-H significantly promote the migration and proliferation of HUVECs and enhance their angiogenesis capacity to support scarless wound tissue regeneration. The MN patch in this work successfully promoted scarless healing of skin burn injuries on rat models, providing an approach for thermal burn treatment in the clinics.

Laponite modified methacryloyl gelatin hydrogel with controlled release of vascular endothelial growth factor a for bone regeneration

Reconstruction of bone defects has long been a major clinical challenge. Limited by the various shortcomings of conventional treatment like autologous bone grafting and inorganic substitutes, the development of novel bone repairing strategies is on top priority. Injectable biomimetic hydrogels that deliver stem cells and growth factors in a minimally invasive manner can effectively promote bone regeneration and thus represent a promising alternative. Therefore, in this study, we designed and constructed an injectable nanocomposite hydrogel co-loaded with Laponite (Lap) and vascular endothelial growth factor (VEGF) through a simplified and convenient scheme of physical co-mixing (G@Lap/VEGF). The introduced Lap not only optimized the injectability of GelMA by the electrostatic force between the nanoparticles, but also significantly delayed the release of VEGF-A. In addition, Lap promoted high expression of osteogenic biomarkers in mesenchymal stem cells (MSCs) and enhanced the matrix mineralization. Besides, VEGF-A exerted chemotactic effects recruiting endothelial progenitor cells (EPCs) and inducing neovascularization. Histological and micro-CT results demonstrated that the critical-sized calvarial bone defect lesions in the SD rats after treated with G@Lap/VEGF exhibited significant in vivo bone repairing. In conclusion, the injectable G@Lap/VEGF nanocomposite hydrogel constructed in our study is highly promising for clinical transformation and applications, providing a convenient and simplified scheme for clinical bone repairing, and contributing to the further development of the injectable biomimetic hydrogels.

Lactobacillus rhamnosus GG-derived extracellular vesicles promote wound healing via miR-21-5p-mediated re-epithelization and angiogenesis

Extracellular vesicles (EVs), especially those derived from stem cells, have emerged as a novel treatment for promoting wound healing in regenerative medicine. However, the clinical application of mammalian cells-derived EVs is hindered by their high cost and low yields. Inspired by the ability of EVs to mediate interkingdom communication, we explored the therapeutic potential of EVs released by the probiotic strain Lactobacillus rhamnosus GG (LGG) in skin wound healing and elucidated the underlying mechanism involved. Using full-thickness skin wound-healing mouse models, we found that LGG-EVs accelerated wound healing procedures, including increased re-epithelialization and promoted angiogenesis. Using in vitro experiments, we further demonstrated that LGG-EVs boosted the proliferation and migration capacities of both epithelial and endothelial cells, as well as promoted endothelial tube formation. miRNA profiling analysis revealed that miR-21-5p was highly enriched in LGG-EVs and LGG-EV treatment significantly increased miR-21-5p level in recipient cells. Mechanically, LGG-EVs induced regulatory effects via miR-21-5p mediated metabolic signaling rewiring. Our results suggest that EVs derived from LGG could serve as a promising candidate for accelerating wound healing and possibly for treating chronic and impaired healing conditions.

In-silico analysis predicts disruption of normal angiogenesis as a causative factor in osteoporosis pathogenesis

Angiogenesis-osteogenesis coupling is critical for proper functioning and maintaining the health of bones. Any disruption in this coupling, associated with aging and disease, might lead to loss of bone mass. Osteoporosis (OP) is a debilitating bone metabolic disorder that affects the microarchitecture of bones, gradually leading to fracture. Computational analysis revealed that normal angiogenesis is disrupted during the progression of OP, especially postmenopausal osteoporosis (PMOP). The genes associated with OP and PMOP were retrieved from the DisGeNET database. Hub gene analysis and molecular pathway enrichment were performed via the Cytoscape plugins STRING, MCODE, CytoHubba, ClueGO and the web-based tool Enrichr. Twenty-eight (28) hub genes were identified, eight of which were transcription factors (HIF1A, JUN, TP53, ESR1, MYC, PPARG, RUNX2 and SOX9). Analysis of SNPs associated with hub genes via the gnomAD, I-Mutant2.0, MUpro, ConSurf and COACH servers revealed the substitution F201L in IL6 as the most deleterious. The IL6 protein was modeled in the SWISS-MODEL server and the substitution was analyzed via the YASARA FoldX plugin. A positive ΔΔG (1.936) of the F201L mutant indicates that the mutated structure is less stable than the wild-type structure is. Thirteen hub genes, including IL6 and the enriched molecular pathways were found to be profoundly involved in angiogenesis/endothelial function and immune signaling. Mechanical loading of bones through weight-bearing exercises can activate osteoblasts via mechanotransduction leading to increased bone formation. The present study suggests proper mechanical loading of bone as a preventive strategy for PMOP, by which angiogenesis and the immune status of the bone can be maintained. This in silico analysis could be used to understand the molecular etiology of OP and to develop novel therapeutic approaches.

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.

Computed Tomography Imaging Guided Microenvironment-Responsive Ir@WO3-x Dual-Catalytic Nanoreactor for Selective Radiosensitization

Radiotherapy (RT) is often administered, either alone or in combination with other therapies, for most malignancies. However, the degree of tumor oxygenation, damage to adjacent healthy tissues, and inaccurate guidance remain issues that result in discontinuation or failure of RT. Here, a multifunctional therapeutic platform based on Ir@WO3-x is developed which simultaneously addresses these critical issues above for precision radiosensitization. Ir@WO3-x nanoreactors exhibit strong absorption of X-ray, acting as radiosensitizers. Moreover, ultrasmall Ir enzyme-mimic nanocrystals (NCs) are decorated onto the surface of the nanoreactor, where NCs have catalyst-like activity and are sensitive to H2O2 in the tumor microenvironment (TME) under near infrared-II (NIR-II) light stimulation. They efficiently catalyze the conversion of H2O2 to O2, thereby ameliorating hypoxia, inhibiting the expression of HIF-1α, and enhancing RT-induced DNA damage in cancerous tissue, further improving the efficiency of RT. Additionally, in response to high H2O2 levels in TME, the Ir@WO3-x nanoreactor also exerts peroxidase-like activity, boosting exogenous ROS, which increases oxidative damage and enhances ROS-dependent death signaling. Furthermore, Ir@WO3-x can serve as a high-quality computed tomography contrast agent due to its high X-ray attenuation coefficient and generation of pronounced tumor-tissue contrast. This report highlights the potential of advanced health materials to enhance precision therapeutic modalities.

Hydrogel microspheres for bone regeneration through regulation of the regenerative microenvironment

Bone defects are a prevalent category of skeletal tissue disorders in clinical practice, with a range of pathogenic factors and frequently suboptimal clinical treatment effects. In bone regeneration of bone defects, the bone regeneration microenvironment-composed of physiological, chemical, and physical components-is the core element that dynamically coordinates to promote bone regeneration. In recent years, medical biomaterials with bioactivity and functional tunability have been widely researched upon and applied in the fields of tissue replacement/regeneration, and remodelling of organ structure and function. The biomaterial treatment system based on the comprehensive regulation strategy of bone regeneration microenvironment is expected to solve the clinical problem of bone defect. Hydrogel microspheres (HMS) possess a highly specific surface area and porosity, an easily adjustable physical structure, and high encapsulation efficiency for drugs and stem cells. They can serve as highly efficient carriers for bioactive factors, gene agents, and stem cells, showing potential advantages in the comprehensive regulation of bone regeneration microenvironment to enhance bone regeneration. This review aims to clarify the components of the bone regeneration microenvironment, the application of HMS in bone regeneration, and the associated mechanisms. It also discusses various preparation materials and methods of HMS and their applications in bone tissue engineering. Furthermore, it elaborates on the relevant mechanisms by which HMS regulates the physiological, chemical, and physical microenvironment in bone regeneration to achieve bone regeneration. Finally, we discuss the future prospects of the HMS system application for comprehensive regulation of bone regeneration microenvironment, to provide novel perspectives for the research and application of HMS in the bone tissue engineering field.

Activating UCHL1 through the CRISPR activation system promotes cartilage differentiation mediated by HIF-1α/SOX9

Developing strategies to enhance cartilage differentiation in mesenchymal stem cells and preserve the extracellular matrix is crucial for successful cartilage tissue reconstruction. Hypoxia-inducible factor-1α (HIF-1α) plays a pivotal role in maintaining the extracellular matrix and chondrocyte phenotype, thus serving as a key regulator in chondral tissue engineering strategies. Recent studies have shown that Ubiquitin C-terminal hydrolase L1 (UCHL1) is involved in the deubiquitylation of HIF-1α. However, the regulatory role of UCHL1 in chondrogenic differentiation has not been investigated. In the present study, we initially validated the promotive effect of UCHL1 expression on chondrogenesis in adipose-derived stem cells (ADSCs). Subsequently, a hybrid baculovirus system was designed and employed to utilize three CRISPR activation (CRISPRa) systems, employing dead Cas9 (dCas9) from three distinct bacterial sources to target UCHL1. Then UCHL1 and HIF-1α inhibitor and siRNA targeting SRY-box transcription factor 9 (SOX9) were used to block UCHL1, HIF-1α and SOX9, respectively. Cartilage differentiation and chondrogenesis were measured by qRT-PCR, immunofluorescence and histological staining. We observed that the CRISPRa system derived from Staphylococcus aureus exhibited superior efficiency in activating UCHL1 compared to the commonly used the CRISPRa system derived from Streptococcus pyogenes. Furthermore, the duration of activation was extended by utilizing the Cre/loxP-based hybrid baculovirus. Moreover, our findings show that UCHL1 enhances SOX9 expression by regulating the stability and localization of HIF-1α, which promotes cartilage production in ADSCs. These findings suggest that activating UCHL1 using the CRISPRa system holds significant potential for applications in cartilage regeneration.

The impact and mechanism study of Sijunzi decoction and Rg1 on proliferation and differentiation of human umbilical cord mesenchymal stem cells: An experimental study

BACKGROUND

Previous researches have demonstrated that the traditional Chinese medicine could therapeutically treat inflammatory and hypoxic diseases by enhancing the functionality of mesenchymal stem cells. However, its mechanism was not yet clear. This research aimed to investigate the impact of the traditional Chinese medicine Sijunzi decoction and its herb monomer ginsenoside Rg1 on the proliferation and differentiation of human umbilical cord mesenchymal stem cells (hUC-MSCs) and explore the underlying mechanisms.

METHODS

Different concentrations of Sijunzi decoction and Rg1 were applied to differentiating induced hUC-MSCs. The CCK-8 test was utilized to evaluate cell proliferation activity and identify suitable drug concentrations. Alizarin Red staining was employed to detect the formation of calcium nodules, and Oil Red O staining was used to assess the formation of lipid droplets. PCR was utilized to examine gene expression related to osteogenic differentiation, adipogenic differentiation, and the HIF-1α signaling pathway in hUC-MSCs. Western blot analysis was conducted to evaluate protein expression in osteogenic differentiation and HIF-1α. ELISA was performed to measure HIF-1α signaling factors and inflammatory cytokine expression. Biochemical assays were used to assess changes in oxidative stress indicators.

RESULTS

The Sijunzi decoction and Rg1 both demonstrated a dose-dependent promotion of hUC-MSC proliferation. The Sijunzi decoction significantly increased the expression of genes and proteins relevant to osteogenesis, such as osterix, osteocalcin, RUNX2, and osteopontin, and activated the HIF-1α pathway in hUC-MSCs. (P < .05). Similar effects were observed at the gene level after treatment with Rg1. Simultaneously, Sijunzi decoction significantly reduced the secretion of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β, while increasing the secretion of the anti-inflammatory cytokine IL-10 during osteogenic differentiation (P < .05). Moreover, Sijunzi decoction lowered oxidative stress levels and enhanced the antioxidant capacity of hUC-MSCs during osteogenic differentiation (P < .05). However, the impact of Sijunzi decoction on hUC-MSCs toward adipogenic differentiation was not significant (P > .05).

CONCLUSION

Sijunzi decoction promotes the proliferation and osteogenic differentiation of hUC-MSCs, potentially through the activation of the HIF-1α signaling pathway and by modulating the microenvironment via reducing inflammation and oxidative stress levels. Rg1 might be involved in this process.

Hypoxia-inducible factor-1α can reverse the Adriamycin resistance of breast cancer adjuvant chemotherapy by upregulating transferrin receptor and activating ferroptosis

Breast cancer is a common malignant tumor in women. Ferroptosis, a programmed cell death pathway, is closely associated with breast cancer and its resistance. The transferrin receptor (TFRC) is a key factor in ferroptosis, playing a crucial role in intracellular iron accumulation and the occurrence of ferroptosis. This study investigates the influence and significance of TFRC and its upstream transcription factor hypoxia-inducible factor-1α (HIF1α) on the efficacy of neoadjuvant therapy in breast cancer. The differential gene obtained from clinical samples through genetic sequencing is TFRC. Bioinformatics analysis revealed that TFRC expression in breast cancer was significantly greater in breast cancer tissues than in normal tissues, but significantly downregulated in Adriamycin (ADR)-resistant tissues. Iron-responsive element-binding protein 2 (IREB2) interacts with TFRC and participates in ferroptosis. HIF1α, an upstream transcription factor, positively regulates TFRC. Experimental results indicated higher levels of ferroptosis markers in breast cancer tissue than in normal tissue. In the TAC neoadjuvant regimen-sensitive group, iron ion (Fe2+) and malondialdehyde (MDA) levels were greater than those in the resistant group (all p < .05). Expression levels of TFRC, IREB2, FTH1, and HIF1α were higher in breast cancer tissue compared to normal tissue. Additionally, the expression of the TFRC protein in the TAC neoadjuvant regimen-sensitive group was significantly higher than that in the resistant group (all p < .05), while the difference in the level of expression of IREB2 and FTH1 between the sensitive and resistant groups was not significant (p > .05). The dual-luciferase assay revealed that HIF1α acts as an upstream transcription factor of TFRC (p < .05). Overexpression of HIF1α in ADR-resistant breast cancer cells increased TFRC, Fe2+, and MDA content. After ADR treatment, the cell survival rate decreased significantly, and ferroptosis could be reversed by the combined application of Fer-1 (all p < .05). In conclusion, ferroptosis and chemotherapy resistance are correlated in breast cancer. TFRC is a key regulatory factor influenced by HIF1α and is associated with chemotherapy resistance. Upregulating HIF1α in resistant cells may reverse resistance by activating ferroptosis through TFRC overexpression.

Targeting HSP47 for cancer treatment

Heat shock protein 47 (HSP47) serves as an endoplasmic reticulum residing collagen-specific chaperone and plays an important role in collagen biosynthesis and structural assembly. HSP47 is encoded by the SERPINH1 gene, which is located on chromosome 11q13.5, one of the most frequently amplified regions in human cancers. The expression of HSP47 is regulated by multiple cellular factors, including cytokines, transcription factors, microRNAs, and circular RNAs. HSP47 is frequently upregulated in a variety of cancers and plays an important role in tumor progression. HSP47 promotes tumor stemness, angiogenesis, growth, epithelial-mesenchymal transition, and metastatic capacity. HSP47 also regulates the efficacy of tumor therapies, such as chemotherapy, radiotherapy, and immunotherapy. Inhibition of HSP47 expression has antitumor effects, suggesting that targeting HSP47 is a feasible strategy for cancer treatment. In this review, we highlight the function and expression of regulatory mechanisms of HSP47 in cancer progression and point out the potential development of therapeutic strategies in targeting HSP47 in the future.

Benserazide, a cystathionine beta-synthase (CBS) inhibitor, potentially enhances the anticancer effects of paclitaxel via inhibiting the S-sulfhydration of SIRT1 and the HIF1-α/VEGF pathway

Cancer targeted therapy is essential to minimize damage to normal cells and improve treatment outcomes. The elevated activity of Cystathionine beta-synthase (CBS), an enzyme responsible for producing endogenous hydrogen sulfide (H2S), plays a significant role in promoting tumor growth, invasiveness, and metastatic potential. Consequently, the selective inhibition of CBS could represent a promising therapeutic strategy for cancer. Currently, there is much interest in combining paclitaxel with other drugs for cancer treatment. This study aimed to investigate the efficacy of combining benserazide, a CBS inhibitor, with paclitaxel in treating tumors. Firstly, we demonstrated CBS is indeed involved in the progression of multiple cancers. Then it was observed that the total binding free energy between the protein and the small molecule is -98.241 kJ/mol. The release of H2S in the group treated with 100 μM benserazide was reduced by approximately 90% compared to the negative control, and the thermal denaturation curve of the complex protein shifted to the right, suggesting that benserazide binds to and blocks the CBS protein. Next, it was found that compared to paclitaxel monotherapy, the combination of benserazide with paclitaxel demonstrated stronger antitumor activity in KYSE450, A549, and HCT8 cells, accompanied by reduced cell viability, cell migration and invasion, as well as diminished angiogenic and lymphangiogenic capabilities. In vivo studies showed that the combined administration of benserazide and paclitaxel significantly reduced the volume and weight of axillary lymph nodes in comparison to the control group and single administration group. Further mechanistic studies revealed that the combination of benserazide and paclitaxel significantly suppressed the S-sulfhydration of SIRT1 protein, thereby inhibiting the expression of SIRT1 protein and activating SIRT1 downstream Notch1/Hes1 signaling pathway in KYSE450, A549, and HCT8 cells. Meanwhile, we observed that benserazide combined with paclitaxel induced a more significant downregulation of HIF-1α, VEGF-A, VEGF-C, and VEGF-D proteins expression levels in KYSE450, A549, and HCT8 cells compared to paclitaxel alone. These findings indicated that benserazide enhances the anticancer effects of paclitaxel via inhibiting the S-sulfhydration of SIRT1 and down-regulating HIF-1α/VEGF signaling pathway. This study suggests that benserazide may have potential as a chemosensitizer in cancer treatment.

The Effects of Hypoxia-Preconditioned Dental Stem Cell-Derived Secretome on Tissue Regeneration

Mesenchymal stroma cells derived from oral tissues are known as dental stem cells (DSCs). Owing to their unique therapeutic niche and clinical accessibility, DSCs serve as a promising treatment option for bone defects and oral tissue regeneration. DSCs exist in a hypoxic microenvironment in vivo, which is far lower than the current 20% oxygen concentration used in in vitro culture. It has been widely reported that the application of an oxygen concentration less than 5% in the culture of DSCs is beneficial for preserving stemness and promoting proliferation, migration, and paracrine activity. The paracrine function of DSCs involves the secretome, which includes conditioned media (CM) and soluble bioactive molecules, as well as extracellular vesicles extracted from CM. Hypoxia can play a role in immunomodulation and angiogenesis by altering the protein or nucleic acid components in the secretory group, which enhances the therapeutic potential of DSCs. This review summarizes the biological characteristics of DSCs, the influence of hypoxia on DSCs, the impact of hypoxia on the secretory group of DSCs, and the latest progress on the use of DSCs secretory group in tissue regeneration based on hypoxia pretreatment. We highlighted the multifunctional biological effect of hypoxia culture on tissue regeneration and provided a summary of the current mechanism of hypoxia in the pretreatment of DSCs.

Hypoxia preconditioning of adipose stem cell-derived exosomes loaded in gelatin methacryloyl (GelMA) promote type H angiogenesis and osteoporotic fracture repair

The challenges posed by delayed atrophic healing and nonunion stand as formidable obstacles in osteoporotic fracture treatment. The processes of type H angiogenesis and osteogenesis emerge as pivotal mechanisms during bone regeneration. Notably, the preconditioning of adipose-derived stem cell (ADSC) exosomes under hypoxic conditions has garnered attention for its potential to augment the secretion and functionality of these exosomes. In the present investigation, we embarked upon a comprehensive elucidation of the underlying mechanisms of hypo-ADSC-Exos within the milieu of osteoporotic bone regeneration. Our findings revealed that hypo-ADSC-Exos harboured a preeminent miRNA, namely, miR-21-5p, which emerged as the principal orchestrator of angiogenic effects. Through in vitro experiments, we demonstrated the capacity of hypo-ADSC-Exos to stimulate the proliferation, migration, and angiogenic potential of human umbilical vein endothelial cells (HUVECs) via the mediation of miR-21-5p. The inhibition of miR-21-5p effectively attenuated the proangiogenic effects mediated by hypo-ADSC-Exos. Mechanistically, our investigation revealed that exosomal miR-21-5p emanating from hypo-ADSCs exerts its regulatory influence by targeting sprouly1 (SPRY1) within HUVECs, thereby facilitating the activation of the PI3K/AKT signalling pathway. Notably, knockdown of SPRY1 in HUVECs was found to potentiate PI3K/AKT activation and, concomitantly, HUVEC proliferation, migration, and angiogenesis. The culminating stage of our study involved a compelling in vivo demonstration wherein GelMA loaded with hypo-ADSC-Exos was validated to substantially enhance local type H angiogenesis and concomitant bone regeneration. This enhancement was unequivocally attributed to the exosomal modulation of SPRY1. In summary, our investigation offers a pioneering perspective on the potential utility of hypo-ADSC-Exos as readily available for osteoporotic fracture treatment.

Effect of the Sr-Fe layered double hydroxide coating based on the microenvironment response on implant osseointegration in osteoporotic rats

Osteoporosis is a disease that manifests itself as an abnormality of bone metabolism and is characterized by low bone mass and destruction of the bone microstructure. Since bone resorption occurs more rapidly than new bone formation, osteoporosis leads to reduced orthopedic implant stability. From a microenvironmental point of view, the rationale for this outcome is that osteoclasts are overactive in the bone tissue of patients with osteoporosis, and the large amount of H+ they produce leads to local chronic acidosis, which promotes bone mineral loss. Therefore, we designed a weakly alkaline layered double hydroxide (LDH) coating to modulate the pathologically acidic microenvironment and the osteogenic-osteoclastic coupling by releasing Sr2+. We prepared Sr-Fe LDH coatings on pure titanium implants using a hydrothermal method in this study and characterized the material using SEM, AFM, XRD, XPS, EDS, ICP, pH acidimeter, etc. We found that the coatings had good nanomorphology and were able to efficiently neutralize H+ as well as steadily release Sr2+ for up to 21 days. In vitro, the coating not only significantly promoted the adhesion, proliferation, and differentiation of osteoblasts, but also inhibited the differentiation of osteoclasts at the same time. In addition, in animal experiments, the coating significantly improved the mechanical stability of the implant in osteoporotic rats, increasing Sr-Fe LDH@Ti maximal push-out force by 72.2% compared to Ti. At the same time, the coating was effective in reversing the osteoporotic state, resulting in a 58.5% increase in BV/TV (%), and a 12.4% increase in Tb. N (1 mm-1), a 31.6% increase in Tb. Th (μm), and a 30.9% increase in BA (%). Our results suggest that this Sr-Fe LDH nanocoating material with acid-neutralizing, as well as long-term Sr2+-releasing capabilities, is a novel and effective orthopedic implant coating material under osteoporotic conditions.

AFF4 regulates osteogenic potential of human periodontal ligament stem cells via mTOR-ULK1-autophagy axis

Scaffold protein AF4/FMR2 family member 4 (AFF4) has been found to play a role in osteogenic commitment of stem cells. However, function of AFF4 in human periodontal ligament stem cells (hPDLSCs) has not been studied yet. This present study aims to investigate the biological effect of AFF4 on osteogenic differentiation of hPDLSCs and potential mechanistic pathway. First, AFF4 expression profile was evaluated in conditions of periodontitis and osteogenic differentiation of hPDLSCs by immunohistochemical staining, western blot and qRT-PCR. Next, si-RNA mediated knockdown and lentiviral transduction mediated overexpression of AFF4 were adopted to explore impact of AFF4 on osteogenic capacity of hPDLSCs. Then, possible mechanistic pathway was identified. At last, pharmacological agonist of autophagy, rapamycin, was utilized to affirm the role of autophagy in AFF4-regulated osteogenesis of hPDLSCs. First, AFF4 expressions were significantly lower in inflamed periodontal tissues and lipopolysaccharides-treated hPDLSCs than controls, and were up-regulated during osteogenic differentiation of hPDLSCs. Next, osteogenic potential of hPDLSCs was impaired by AFF4 knockdown and potentiated by AFF4 overexpression. Moreover, AFF4 was found to positively regulate autophagic activity in hPDLSCs. At last, rapamycin treatment was shown to be able to partly restore AFF4 knockdown-suppressed osteogenic differentiation. Our study demonstrates that AFF4 regulates osteogenic potential of hPDLSCs via targeting autophagic activity. The involvement of AFF4 in periodontal homeostasis was identified for the first time.

LncRNA ADAMTS9-AS2 regulates periodontal ligament cell migration under mechanical compression via ADAMTS9/fibronectin

BACKGROUND

Periodontal ligament cells (PDLCs) are key mechanosensory cells involved in extracellular matrix (ECM) remodeling during orthodontic tooth movement (OTM). Mechanical force changes the ECM components, such as collagens and matrix metalloproteinases. However, the associations between the changes in ECM molecules and cellular dynamics during OTM remain largely uncharacterized.

OBJECTIVES

To investigate the influence of mechanical force on the morphology and migration of PDLCs and explore the interaction between ECM remodeling and cellular dynamics, including the detailed mechanisms involved.

METHODS

Human PDLCs (hPDLCs) were subjected to a static mechanical compression to mimic the compression state of OTM in vitro. A mouse OTM model was used to mimic the OTM procedure in vivo. The migration of hPDLCs was compared by wound healing and transwell migration assays. Moreover, expression levels of ADAM metallopeptidase with thrombospondin type 1 motif 9 (ADAMTS9) and fibronectin (FN) in hPDLCs were determined via western blotting, immunofluorescence staining, and enzyme-linked immunosorbent assays. Expression levels of ADAMTS9 and FN in mice were assessed via immunohistochemical staining. Additionally, the relative expression of long non-coding RNA (lncRNA) ADAMTS9-antisense RNA 2 (ADAMTS9-AS2) was assessed via quantitative real-time polymerase chain reaction. ADAMTS9-AS2 knockdown was performed to confirm its function in hPDLCs.

RESULTS

Mechanical compression induced changes in the morphology of hPDLCs. It also promoted migration and simultaneous upregulation of FN and downregulation of ADAMTS9, a fibronectinase. The mouse OTM model showed the same expression patterns of the two proteins on the compression side of the periodontium of the moved teeth. RNA sequencing revealed that lncRNA ADAMTS9-AS2 expression was significantly upregulated in hPDLCs under mechanical compression. After knocking down ADAMTS9-AS2, hPDLCs migration was significantly inhibited. ADAMTS9 expression was increased as FN expression decreased compared to that in the control group. Moreover, knockdown of ADAMTS9-AS2 reduced the effect of mechanical compression on hPDLCs migration and reversed the expression change of ADAMTS9 and FN. RNA immunoprecipitation revealed direct binding between ADAMTS9-AS2 and ADAMTS9 protein.

CONCLUSION

Our study suggests that mechanical compression induces the expression of ADAMTS9-AS2, which directly binds to ADAMTS9 and inhibits its function, leading to the promotion of downstream FN expression and ECM remodeling to facilitate hPDLCs migration and maintain the stability of the periodontium.