Bone regeneration in diabetic patients. A systematic review

Metformin's mechanism in reducing oxidative stress and promoting bone regeneration in T2DM rat BMMSCs: A focus on NRF2-GPX7 signaling pathway

OBJECTIVES

Metformin (MF) could improve the osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) and bone regeneration under diabetes mellitus (T2DM) environment, however, its specific mechanism has not been elucidated. The aim of this study was to investigate whether MF inhibited oxidative stress and promoted osteogenic differentiation of T2DM rats BMMSCs (Tr-BMMSCs) through NRF2-GPX7 pathway.

METHODS

BMMSCs were extracted from normal and diabetic rats. In vitro, the western blot analysis were first used to determine the effect of MF on the NRF2-GPX7 signaling pathway. Then, the levels of oxidative stress markers and ALP staining, alizarin red staining, immunofluorescence assay were performerd respectively to detect the role of NRF2-GPX7 pathway in the regulating effect of MF on the oxidative stress and osteogenic differentiation of Tr-BMMSCs. In vivo, the newly formed bone was evaluated by micro computed tomography, HE staining, Masson staining and immunohistochemistry through T2DM rat mandibular bone defect model.

RESULTS

In vitro assays revealed that MF significantly promoted the expression of NRF2, NQO1, HO-1 and GPX7. The NRF2 pathway inhibitor (ML385) significantly inhibited the antioxidant and osteogenic promotion effects of MF on Tr-BMMSCs, while GPX7 overexpression effectively reversed the inhibitory effect of ML385. In vivo experiments showed that ML385 completely inhibited the combined promoting effects of MF and Tr-BMMSCs on the mandibular defect regeneration in T2DM rats. However, when MF was used in combination with GPX7 overexpressed Tr-BMMSCs, both new bone mass and OCN expression were significantly increased, indicating that GPX7 overexpression effectively reversed the osteogenesis inhibition of ML385 on Tr-BMMSCs.

CONCLUSIONS

MF inhibits oxidative stress level and promots osteogenic differentiation of Tr-BMMSCs and the repair of mandible bone defects of T2DM rats through NRF2-GPX7 pathway.

Biologically-oriented alveolar ridge preservation to correct bone dehiscence at immediate implant placement

BACKGROUND

The purpose of the present case study is to describe the application of a modification of the Biologically-oriented Alveolar Ridge Preservation (BARP) principles in cases of peri-implant bone dehiscence (PIBD) due to a compromised alveolus at immediate implant placement (IIP).

METHODS

The technique is based on the stratification of three layers: a deep layer with a collagen sponge (CS) in the apical part of the alveolus (where the buccal bone plate was still present) to support the blood clot; a graft layer to correct the PIBD; and a superficial collagen layer to cover the graft thus providing space and enhancing clot/graft stability. Healing was obtained by primary closure.

RESULTS

At the re-entry procedure for implant uncovering, a complete PIBD correction with newly formed peri-implant bone up to the level of the polished collar was observed in both cases.

CONCLUSIONS

These observations suggest that BARP based on the combined use of CS and deproteinized bovine bone mineral may be regarded as a simplified treatment option to correct a PIBD at IIP.

KEY POINTS

Why treat a Peri-Implant Bone Dehiscence (PIBD)? PIBD should be treated to avoid biological and esthetic complications over time. What plays a key role in this case? The stability of both the graft and the cloth is essential for providing space for bone formation to correct the PIBD; the extraction socket supports angiogenic and osteogenic properties; Primary intention closure is crucial to prevent potential infection.

LIMITATION

the efficacy of the technique must be assessed.

PLAIN LANGUAGE SUMMARY

This case study described the potential to correct a post-extraction osseous defect associated with a substantial portion of a dental implant which resulted exposed and without bone support on its buccal aspect. The application of a novel bone augmentation technique, namely the biologically oriented Alveolar Ridge Preservation, has been described. This simplified procedure is based on the stratification of i) a deep collagen layer in the apical part of the socket to support the blood clot and spontaneous bone formation, ii) a graft of bone substitute to correct the missing bone, and iii) a superficial collagen layer to protect the graft and the wound. After 5 months, a complete correction of the osseous defect with newly formed bone up to the head of the implant was observed in both treated cases.

Anti-diabetic therapies on dental implant success in diabetes mellitus: a comprehensive review

Background and Objective

Dental implant therapy faces challenges in patients with Type 1 and Type 2 Diabetes Mellitus (T1DM and T2DM) due to adverse effects on bone metabolism and immune response. Despite advancements, diabetic patients face higher risks of peri-implantitis and compromised osseointegration. This review assesses the impact of anti-diabetic medications on implant outcomes, offering insights to bridge the gap between animal studies and clinical practice. By evaluating pharmacotherapeutic strategies in preclinical models, this review guides future research designs to improve implant success rates in diabetic individuals.

Method

A comprehensive literature review identified 21 animal studies examining the impact of anti-diabetic medications on dental and bone implants. These studies explored diabetes models, medication regimens, and designs to assess outcomes related to bone metabolism, osseointegration, and peri-implant tissue responses. The findings are systematically summarized, highlighting the scope, design, and procedures of each study. An example includes placing a dental implant in the molar region of a mouse, providing insight into preclinical approaches.

Results

Twenty-one animal studies, primarily using rodents, investigate various anti-diabetic medications on dental and bone implants. Interventions include insulin, aminoguanidine, voglibose, sitagliptin, exenatide, and metformin, analyzing outcomes like bone-implant contact (BIC), bone volume (BV), and counter-torque values in T1DM and T2DM models. The impacts of these medications on implant osseointegration under diabetic conditions are detailed, with their benefits and shortcomings assessed.

Discussion

The findings and challenges of existing animal studies on diabetes mellitus (DM) and implant osseointegration are presented. Despite T2DM prevalence, research primarily focuses on T1DM models due to easier experimental practicalities, limiting applicability. Inconsistent protocols in studies compromise reliability regarding anti-diabetic treatments' effectiveness on osseointegration. Standardized methodologies and long-term assessments of local drug delivery alongside systemic anti-DM treatments are crucial to manage DM-related complications in implant dentistry.

Conclusion

Insulin administration in short-term T1DM animal studies enhances implant osseointegration. However, the efficacy of non-insulin medications remains inconclusive. Rigorous experimental designs are needed to address inconsistencies and assess long-term impacts. Larger-sized (e.g., porcine) animal studies across various intraoral implant scenarios are required. Future research should focus on enhancing clinical applicability and improving implant stability in evolving conditions.

Healthy and diabetic primary human osteoblasts exhibit varying phenotypic profiles in high and low glucose environments on 3D-printed titanium surfaces

Background

The revolution of orthopedic implant manufacturing is being driven by 3D printing of titanium implants for large bony defects such as those caused by diabetic Charcot arthropathy. Unlike traditional subtractive manufacturing of orthopedic implants, 3D printing fuses titanium powder layer-by-layer, creating a unique surface roughness that could potentially enhance osseointegration. However, the metabolic impairments caused by diabetes, including negative alterations of bone metabolism, can lead to nonunion and decreased osseointegration with traditionally manufactured orthopedic implants. This study aimed to characterize the response of both healthy and diabetic primary human osteoblasts cultured on a medical-grade 3D-printed titanium surface under high and low glucose conditions.

Methods

Bone samples were obtained from six patients, three with Type 2 Diabetes Mellitus and three without. Primary osteoblasts were isolated and cultured on 3D-printed titanium discs in high (4.5 g/L D-glucose) and low glucose (1 g/L D-Glucose) media. Cellular morphology, matrix deposition, and mineralization were assessed using scanning electron microscopy and alizarin red staining. Alkaline phosphatase activity and L-lactate concentration was measured in vitro to assess functional osteoblastic activity and cellular metabolism. Osteogenic gene expression of BGLAP, COL1A1, and BMP7 was analyzed using reverse-transcription quantitative polymerase chain reaction.

Results

Diabetic osteoblasts were nonresponsive to variations in glucose levels compared to their healthy counterparts. Alkaline phosphatase activity, L-lactate production, mineral deposition, and osteogenic gene expression remained unchanged in diabetic osteoblasts under both glucose conditions. In contrast, healthy osteoblasts exhibited enhanced functional responsiveness in a high glucose environment and showed a significant increase in osteogenic gene expression of BGLAP, COL1A1, and BMP7 (p<.05).

Conclusion

Our findings suggest that diabetic osteoblasts exhibit impaired responsiveness to variations in glucose concentrations, emphasizing potential osteoblast dysfunction in diabetes. This could have implications for post-surgery glucose management strategies in patients with diabetes. Despite the potential benefits of 3D printing for orthopedic implants, particularly for diabetic Charcot collapse, our results call for further research to optimize these interventions for improved patient outcomes.

Diabetes Mellitus and Dental Implants: A Systematic Review and Meta-Analysis

The present review aimed to evaluate the impact of diabetes mellitus on dental implant failure rates and marginal bone loss (MBL). An electronic search was undertaken in three databases, plus a manual search of journals. Meta-analyses were performed as well as meta-regressions in order to verify how the odds ratio (OR) and MBL were associated with follow-up time. The review included 89 publications. Altogether, there were 5510 and 62,780 implants placed in diabetic and non-diabetic patients, respectively. Pairwise meta-analysis showed that implants in diabetic patients had a higher failure risk in comparison to non-diabetic patients (OR 1.777, p < 0.001). Implant failures were more likely to occur in type 1 diabetes patients than in type 2 (OR 4.477, p = 0.032). The difference in implant failure between the groups was statistically significant in the maxilla but not in the mandible. The MBL mean difference (MD) between the groups was 0.776 mm (p = 0.027), with an estimated increase of 0.032 mm in the MBL MD between groups for every additional month of follow-up (p < 0.001). There was an estimated decrease of 0.007 in OR for every additional month of follow-up (p = 0.048). In conclusion, implants in diabetic patients showed a 77.7% higher risk of failure than in non-diabetic patients.

Induction and rescue of skeletal fragility in a high-fat diet mouse model of type 2 diabetes: An in vivo and in vitro approach

Poor bone quality is associated with Type 2 Diabetes (T2D), with patients having a higher risk of fracture despite normal to high bone mineral density (BMD). Diabetes contributes to modifications of the mineral and organic matrix of bone. Hyperglycemia has been linked to the formation of advanced glycation end-products (AGEs) which increase the risk for skeletal fragility fractures. To this end, we investigated diabetes-induced skeletal fragility using a high-fat diet (HFD) mouse model and evaluated the efficacy of phenacyl thiazolium chloride (PTC) for in vitro removal of glycation products to rescue bone toughness. Ten-week-old C57BL/6 J male mice (n = 6/group) were fed a HFD or low-fat diet (LFD) for 22 weeks. Mice given a HFD developed T2D and increased body mass compared to LFD-fed mice. MicroCT results showed that diabetic mice had altered microarchitecture and increased mineralization as determined by volumetric BMD and increased mineral crystal size as determined by X-ray Diffraction (XRD). Diabetic mice demonstrated loss of initiation and maximum toughness, which represent estimates of the stress intensity factor at a notch tip using yield force and ultimate force, respectively. Diabetic mice also showed higher accumulation of AGEs measured by biochemical assay (total fAGEs) and confocal Raman spectroscopy (Pentosidine (PEN), Carboxymethyl-lysine (CML)). Regression analyses confirmed the association between increased glycoxidation (CML, PEN) and loss of fracture toughness. Within the diabetic group, CML was the most significant predictor of initiation toughness while PEN predicted maximum toughness as determined by stepwise linear regression (i.e., stepAIC). Contralateral femora from HFD group were harvested and treated with PTC in vitro. PTC-treated samples showed total fAGEs decreased by 41.2%. PTC treatment partially restored bone toughness as, compared to T2D controls, maximum toughness increased by 35%. Collectively, our results demonstrate that matrix modifications in diet-induced T2D, particularly AGEs, induce bone fragility and their removal from bone matrix partially rescues T2D associated bone fragility.

Should the Quality of Glycemic Control Guide Dental Implant Therapy in Patients with Diabetes? Focus on Implant Survival

INTRODUCTION

Optimal glycemic control is crucial to dental implant long-term functional and esthetic success. Despite HbA1c levels of 7% or lower used is as an indicator for good glycemic control, however, this level may not be attainable for all diabetic patients. Most dentists do not consider patients with poor glycemic control candidates for implant therapy due to higher implant failure, infection or other complications.

AIM

This review challenges the concept of one size fits all and aims to critically appraise the evidence for the success or failure rate of dental implants and peri-implant health outcomes in patients with less than optimal glycemic control.

DISCUSSION

Evidence suggests that estimating glycemic control from HbA1c measurement alone is misleading. Moreover, elevated preoperative HbA1c was not associated with increased mortality and morbidity after major surgical procedures. Literature for the survival or success of implants in diabetic patients is inconsistent due to a lack of standardized reporting of clinical data collection and outcomes. While a number of studies report that implant treatment in patients with well controlled diabetes has a similar success rate to healthy individuals, other studies suggest that the quality of glycemic control in diabetic patients does not make a difference in the implant failure rate or marginal bone loss. This discrepancy could indicate that risk factors other than hyperglycemia may contribute to the survival of implants in diabetic patients.

CONCLUSION

In the era of personalized medicine, the clinician should utilize individualized information and analyze all risk factors to provide the patient with evidence-based treatment options.

Morphological Characteristics and Correction of Long Tubular Bone Regeneration under Chronic Hyperglycemia Influence

Introduction

Unsatisfactory consequences of bone regeneration disorders in diabetes mellitus (DM) patients, their high prevalence, complication number, and difficulties in treatment require further study and deeper understanding of reparative osteogenesis mechanisms under chronic hyperglycemia and finding new effective and affordable approaches to their treatment. Therefore, the aim of our work was to study the histological, ultramicroscopic, and histomorphometric features of reparative osteogenesis in rats with chronic hyperglycemia (CH), as well as to investigate the possibility of platelet-rich plasma (PRP) use in a fracture area in order to correct the negative effects of CH on reparative osteogenesis processes. Study Object and Methods. The studies were performed on 70 white laboratory rats, mature males, which were divided into the following groups: control group, animals with posttraumatic tibial defect under conditions of CH exposure, rats with experimental CH that were administered with PRP into the bone defect, and animals for the assessment of glucose homeostasis and confirmation of simulated CH. Light microscopy was performed using an Olympus BH-2 microscope (Japan). Ultramicroscopic examination was performed using REM-102 scanning electron microscope. The statistical analysis was performed using SPSS-17 software package.

Results

The formation of new bone tissue in animals with CH did not occur after two weeks. Only on the 30th day of reparative osteogenesis the newly formed woven bone tissue was 61.54% of the total regenerated area. It was less than the reference value by 22.89% (P < 0.001). On the 14th day of reparative osteogenesis, the regenerated area in a group of animals with CH and PRP injection consisted of connective tissue by 68.94% (4.94% less than in animals with CH (P < 0.001)) and woven bone tissue by 31.06%, (13.51% less than in the control group (P < 0.001)). On the 30th day, the area of woven bone tissue in a regenerate of this group was less than that of the control group by 12.41% (P < 0.001).

Conclusion

Thus, chronic hyperglycemia contributes to inflammation delay within the bone defect site, which makes the process of reparative osteogenesis more prolonged. The results of chronic hyperglycemia effect on bone regeneration are also impairment of osteogenic cell proliferation and shift of their differentiation towards the fibrocartilage regenerate formation. The PRP corrects the negative impact of chronic hyperglycemia on reparative osteogenesis, promoting more rapid inflammatory infiltrate removal from the bone defect site and osteogenic beam formation and remodeling of woven bone into lamellar membranous bone tissue.