Morphometric Changes of Osteocyte Lacunar in Diabetic Pig Mandibular Cancellous Bone

A crosstalk between 'osteocyte lacunal-canalicular system' and metabolism

Considering the importance, bone physiology has long been studied to understand what systematic and cellular impact its cells and functions have. Exploring more questions is a substantially solid way to improve the understanding of bone physiological functions in/out sides. In adult bone, osteocytes (Ots) form about 95% of bone cells and live the longest lifespan inside their mineralized surroundings. Ots are the endocrine cells and originate from blood vessel's endothelial cells. In this work, we discussed the vital role of the "Ots". To determine the association between osteocytes' network with metabolic parameters in healthy mice, the experiments were performed on ten (10) adult C57BL6 male mice. Fasting blood and bone samples were collected weekly from mice for measurement of metabolic parameters and bone morphology. Scanning electron microscopy (SEM) revealed a 2D fine morphology of the bone which indicates a strong functional interconnection with bone nano/micro, and macro components of the organs. The long-branched canaliculi look like neurocytes in structure. The morphology and quantitative measurements of the osteocyte lacunal-canalicular system showed its wide spectrum spatial resolution of the positive and negative relationship within this system or metabolite parameters, confirming a strong cross connection between osteocyte lacunal-canalicular system and metabolism. We believe that the findings of this study can deliver a strategy about the potential roles of metabolic relation among osteocytes, insulin, and lipid in management of bone and metabolic diseases.

Utility and Limitations of TALLYHO/JngJ as a Model for Type 2 Diabetes-Induced Bone Disease

Type 2 diabetes mellitus (T2DM) increases risk of fractures due to bone microstructural and material deficits, though the mechanisms remain unclear. Preclinical models mimicking diabetic bone disease are required to further understand its pathogenesis. The TALLYHO/JngJ (TH) mouse is a polygenic model recapitulating adolescent-onset T2DM in humans. Due to incomplete penetrance of the phenotype ~25% of male TH mice never develop hyperglycemia, providing a strain-matched nondiabetic control. We performed a comprehensive characterization of the metabolic and skeletal phenotype of diabetic TH mice and compared them to either their nondiabetic TH controls or the recommended SWR/J controls to evaluate their suitability to study diabetic bone disease in humans. Compared to both controls, male TH mice with T2DM exhibited higher blood glucose levels, weight along with impaired glucose tolerance and insulin sensitivity. TH mice with/without T2DM displayed higher cortical bone parameters and lower trabecular bone parameters in the femurs and vertebrae compared to SWR/J. The mechanical properties remained unchanged for all three groups except for a low-energy failure in TH mice with T2DM only compared to SWR/J. Histomorphometry analyses only revealed higher number of osteoclasts and osteocytes for SWR/J compared to both groups of TH. Bone turnover markers procollagen type 1 N-terminal propeptide (P1NP) and tartrate-resistant acid phosphatase (TRAP) were low for both groups of TH mice compared to SWR/J. Silver nitrate staining of the femurs revealed low number of osteocyte lacunar and dendrites in TH mice with T2DM. Three-dimensional assessment showed reduced lacunar parameters in trabecular and cortical bone. Notably, osteocyte morphology changed in TH mice with T2DM compared to SWR/J. In summary, our study highlights the utility of the TH mouse to study T2DM, but not necessarily T2DM-induced bone disease, as there were no differences in bone strength and bone cell parameters between diabetic and non-diabetic TH mice. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Effects of 4-hexylresorcinol on facial skeletal development in growing rats: Considerations for diabetes

Objective

: To investigate the long-term effects of 4-hexylresorcinol (4HR) on facial skeletal growth in growing male rats, with a focus on diabetic animal models.

Methods

: Forty male rats were used. Of them, type 1 diabetes mellitus was induced in 20 animals by administering 40 mg/kg streptozotocin (STZ), and they were assigned to either the STZ or 4HR-injected group (STZ/4HR group). The remaining 20 healthy rats were divided into control and 4HR groups. We administered 4HR subcutaneously at a weekly dose of 10 mg/kg until the rats were euthanized. At 16 weeks of age, whole blood was collected, and micro-computed tomography of the skull and femur was performed.

Results

: All craniofacial linear measurements were smaller in the STZ group than in the control group. The mandibular molar width was significantly smaller in the 4HR group than in the control group (P = 0.031) but larger in the STZ/4HR group than in the STZ group (P = 0.011). Among the diabetic animals, the STZ/4HR group exhibited significantly greater cortical bone thickness, bone mineral density, and bone volume than the STZ group. Serum testosterone levels were also significantly higher in the STZ/4HR group than in the STZ group.

Conclusions

: 4HR administration may have divergent effects on mandibular growth and bone mass in healthy and diabetic rats. In the context of diabetes, 4HR appears to have beneficial effects, potentially through the modulation of mitochondrial respiration.

Controlling differentiation of stem cells via bioactive disordered cues

Ideal bone tissue engineering is to induce bone regeneration through the synergistic integration of biomaterial scaffolds, bone progenitor cells, and bone-forming factors. Biomimetic scaffolds imitate the native extracellular matrix (ECM) and are often utilized in vitro as analogues of the natural ECM to facilitate investigations of cell-ECM interactions and processes. In vivo, the cellular microenvironment has a crucial impact on regulating cell behavior and functions. A PET surface was activated and then functionalized with mimetic peptides to promote human mesenchymal stem cell (hMSC) adhesion and differentiation into an osteogenic lineage. Spray technology was used to randomly micropattern peptides (RGD and BMP-2 mimetic peptides) on the PET surface. The distribution of the peptides grafted on the surface, the roughness of the surfaces and the chemistry of the surfaces in each step of the treatment were ascertained by atomic force microscopy, fluorescence microscopy, time-of-flight secondary ion mass spectrometry, Toluidine Blue O assay, and X-ray photoelectron spectroscopy. Subsequently, cell lineage differentiation was evaluated by quantifying the expression of immunofluorescence markers: osteoblast markers (Runx-2, OPN) and osteocyte markers (E11, DMP1, and SOST). In this article, we hypothesized that a unique combination of bioactive micro/nanopatterns on a polymer surface improves the rate of morphology change and enhances hMSC differentiation. In DMEM, after 14 days, disordered micropatterned surfaces with RGD and BMP-2 led to a higher osteoblast marker expression than surfaces with a homogeneous dual peptide conjugation. Finally, hMSCs cultured in osteogenic differentiation medium (ODM) showed accelerated cell differentiation. In ODM, our results highlighted the expression of osteocyte markers when hMSCs were seeded on PET surfaces with random micropatterns.

In Vivo Evaluation of Collagen and Chitosan Scaffold, Associated or Not with Stem Cells, in Bone Repair

Natural polymers are increasingly being used in tissue engineering due to their ability to mimic the extracellular matrix and to act as a scaffold for cell growth, as well as their possible combination with other osteogenic factors, such as mesenchymal stem cells (MSCs) derived from dental pulp, in an attempt to enhance bone regeneration during the healing of a bone defect. Therefore, the aim of this study was to analyze the repair of mandibular defects filled with a new collagen/chitosan scaffold, seeded or not with MSCs derived from dental pulp. Twenty-eight rats were submitted to surgery for creation of a defect in the right mandibular ramus and divided into the following groups: G1 (control group; mandibular defect with clot); G2 (defect filled with dental pulp mesenchymal stem cells-DPSCs); G3 (defect filled with collagen/chitosan scaffold); and G4 (collagen/chitosan scaffold seeded with DPSCs). The analysis of the scaffold microstructure showed a homogenous material with an adequate percentage of porosity. Macroscopic and radiological examination of the defect area after 6 weeks post-surgery revealed the absence of complete repair, as well as absence of signs of infection, which could indicate rejection of the implants. Histomorphometric analysis of the mandibular defect area showed that bone formation occurred in a centripetal fashion, starting from the borders and progressing towards the center of the defect in all groups. Lower bone formation was observed in G1 when compared to the other groups and G2 exhibited greater osteoregenerative capacity, followed by G4 and G3. In conclusion, the scaffold used showed osteoconductivity, no foreign body reaction, malleability and ease of manipulation, but did not obtain promising results for association with DPSCs.

Resveratrol Alleviates Diabetic Periodontitis-Induced Alveolar Osteocyte Ferroptosis Possibly via Regulation of SLC7A11/GPX4

The mode and mechanism of diabetic periodontitis-induced alveolar-osteocyte death are still unclear. This study aimed to investigate the occurrence of ferroptosis in alveolar osteocytes during diabetic periodontitis and the therapeutic potential of resveratrol to alleviate osteocyte ferroptosis. Diabetic periodontitis was induced in C57/BL6-male mice and treated with or without resveratrol. Periodontitis pathogenicity was analyzed by micro-CT and histology, and alveolar-osteocyte ferroptosis was analyzed by immunohistochemistry. MLOY4 osteocytes were treated with P. gingivalis-derived lipopolysaccharide (LPS)+advanced glycosylated end products (AGEs) mimicking diabetic periodontitis condition in vitro, with or without resveratrol or ferrostatin-1 (ferroptosis inhibitor). Osteocyte ferroptosis and expression of inflammatory mediators were analyzed. Diabetic periodontitis aggravated periodontitis pathogenicity and inhibited the expression of GPX4 and SLC7A11 in alveolar osteocytes and resveratrol alleviated these effects. LPS+AGEs triggered osteocyte ferroptosis in vitro as indicated by the downregulated GPX4 and SLC7A11, upregulated malondialdehyde, disrupted mitochondrial morphology, and overexpressed pro-inflammatory mediators IL-1β, TNF-α, SOST, RANKL, and IL-6, and ferrostatin-1 or resveratrol treatment reversed these effects. LPS+AGEs upregulated pIKBα and pNF-κB p65 expression in osteocytes, and resveratrol or ferrostatin-1 reversed this effect. In conclusion, diabetic periodontitis triggers alveolar osteocyte ferroptosis possibly via disruption of the SLC7A11/GPX4 axis, and resveratrol has therapeutic potential to correct this biological event.