Comparison of contact radiographed and stained histological sections for osseointegration analysis of dental implants: an in vivo study

Naringin-induced M2 macrophage polarization facilitates osteogenesis of BMSCs and improves cranial bone defect healing in rat

Osteoimmunology has uncovered the critical role of the immune microenvironment in the bone healing process, with macrophages playing a central part in generating immune responses via chemokine production. Naringin, a flavanone glycoside extracted from various plants, has been shown to promote osteoblast differentiation, thereby enhancing bone formation and mitigating osteoporosis progression. Current research on the osteogenic mechanism primarily focuses on the direct impact of naringin on mesenchymal stem cells, while its indirect immunoregulatory effects remain elusive. In this study, we investigated the bone defect-enhancing effects of varying naringin concentrations in vivo using a cranial bone defect model in Sprague-Dawley rats. We assessed the osteoimmune modulation capacity of naringin by exposing lipopolysaccharide (LPS)-induced RAW 264.7 macrophages to different doses of naringin. To further elucidate the underlying osteogenic enhancement mechanism, Bone Marrow Stromal Cells (BMSCs) derived from mice were treated with conditioned media from naringin-treated macrophages. Our findings indicated that naringin promotes M2 phenotype polarization in macrophages, as evidenced by the downregulation of pro-inflammatory cytokines Inducible Nitric Oxide Synthase (iNOS), interleukin (IL)-1β, and Tumor Necrosis Factor (TNF)-α, and the upregulation of anti-inflammatory cytokine Transforming growth factor (TGF)-β. Transcriptome analysis revealed that differentially expressed genes were significantly enriched in osteoblast differentiation and anti-inflammatory response pathways in naringin-pretreated macrophages, with the cytokines signaling pathway being upregulated. The conditioned media from naringin-treated macrophages stimulated the expression of osteogenic-related genes Alkaline phosphatase (Alp), osteocalcin (Ocn), osteopontin (Opn), and Runt-related transcription factor (Runx) 2, as well as protein expression in BMSCs. In conclusion, naringin alleviates macrophage inflammation by promoting M2 phenotype polarization, which in turn enhances the osteogenic differentiation of BMSCs, contributing to its bone healing effects in vivo. These results suggest that naringin holds significant potential for improving bone defect healing through osteoimmune modulation.

Influence of Section Thickness on the Accuracy and Specificity of Histometric Parameters Using Confocal Laser Scanning Microscopy in a Canine Model of Experimental Peri-Implantitis-A Proof of Concept

OBJECTIVES

Tissue breakdown was assessed by confocal laser scanning microscopy (CLSM) using autofluorescence around implants with ligatures, on a dog hemimandible. Influence of section thickness on the accuracy of histometrical observations was also evaluated, in comparison with thin sections in light microscopy.

MATERIAL AND METHODS

Three months after tooth extraction, implants were placed. Two months after abutment placement, ligatures were placed with no plaque control. 11 months post-implantation, the animal was sacrificed. Undecalcified thin (30 µm) sections were cut, stained and evaluated by light microscopy to be used as a reference. Additional sections were performed, so that another pair of unstained thick sections resulted (250-300 µm). Tissue loss was assessed using histomorphometric parameters under CLSM and was compared to the light microscopy reference ones.

RESULTS

Morphometry confirmed tissue loss more pronounced on the "thick" and quick sections, when compared to the time-consuming and technique-sensitive "thin" ones.

CONCLUSIONS

Within the limits of the present study, the adequacy of histometrical observations under CLSM reveal commensurable information about soft-tissue-bone-implant details, when compared to traditional light microscopy histological protocols. The CLSM investigation may seem demanding, yet the richness of data acquired may justify this approach, provided seatbacks caused by improper manipulation of "thick" sections are avoided.

Correlation between two-dimensional micro-CT and histomorphometry for assessment of the implant osseointegration in rabbit tibia model

BACKGROUND

Histology is considered as a gold standard for analyzing bone architecture. However, histomorphometry is a destructive method and only offers the bone information of a limited location. Micro-computed tomography (μCT) is a non-destructive technology and provides a slice at any site. The aim of this study was to compare the correlation of the Bone-to-Implant Contact ratio (BIC) between 2D micro-CT (μCT) and histomorphometry and to investigate a method for assessing the osseointegration of the implant by 2D μCT.

METHODS

A total of 18 implants were divided into three groups (6 implants per group), and inserted into the rabbit tibia defects as follow: implant only (Implant group), implant with β-TCP/hydrogel (TCP group), implant with rhBMP-2 loaded β-TCP/hydrogel composite (BMP-2 group). After 4 weeks of implantation, the specimens were collected to take the micro-CT scan with an aluminum filter and performed H&E staining on the undecalcified sections. The 2D μCT slices were chosen at an angle of 0°, 45°, 90° and 135° with the representative histological section to measure BIC. And the correlations between BICs of 2D μCT and BICs of histology were evaluated.

RESULTS

In each group, BICs at the same sites measured by histomorphometry and corresponding 2D μCT presented the same trend and shown no significant difference between the two methods (P > 0.05). BICs of histological sections and BICs of corresponding 2D μCT slices presented a strong correlation in the implant group (γ = 0.74, P = 0.09), a moderate correlation in the TCP group (γ = 0.46, P = 0.35), a weak correlation in the BMP-2 group (γ = 0.30, P = 0.56). In the implant group, the relationship between BIC-Mean-μCTs and BICs-Histology has presented a significant linear correlation (γ = 0.84, P = 0.04).

CONCLUSIONS

Integrating bone information of several 2D μCT slices in different sites to measure BIC is a feasible method for assessing the implant osseointegration.