Depletion of macrophages deteriorates bisphosphonate-related osteonecrosis of the jaw-like lesions in mice

Crosstalk between macrophages and adjacent cells in AKI to CKD transition

Acute kidney injury (AKI), triggered by ischemia, sepsis, toxicity, or obstruction, is marked by a rapid impairment of renal function and could lead to the initiation and advancement of chronic kidney disease (CKD). The concept of AKI to CKD transition has gained much interest. Despite a series of studies highlighting the diverse roles of renal macrophages in the immune response following AKI, the intricate mechanisms of macrophage-driven cell-cell communication in AKI to CKD transition remains incompletely understood. In this review, we introduce the dynamic phenotype change of macrophages under the different stages of kidney injury. Importantly, we present novel perspectives on the extensive interaction of renal macrophages with adjacent cells, including tubular epithelial cells, vascular endothelial cells, fibroblasts, and other immune cells via soluble factors, extracellular vesicles, and direct contact, to facilitate the transition from AKI to CKD. Additionally, we summarize the potential therapeutic strategies based on the adverse macrophage-neighboring cell crosstalk.

Macrophage Depletion Reduces Bone Loss and Alters Inflammatory Responses: A Mouse Peri-Implantitis Model

AIM

To evaluate the impact of macrophage depletion on bone loss and inflammatory responses in a mouse model of peri-implantitis, assessing macrophage depletion potential as a therapeutic strategy.

MATERIALS AND METHODS

Using 6-week-old male C57BL/6 mice, peri-implantitis was induced by placing a silk ligature around osteointegrated dental implants. Mice were divided into three groups: Healthy control (Healthy group); peri-implantitis with liposomal phosphate-buffered saline (PBS group); and peri-implantitis with liposomal clodronate for macrophage depletion (CLOD group). Two weeks after ligature placement, micro-CT, histological and real-time PCR analyses were performed to assess bone density, leukocyte infiltration and cytokine levels.

RESULTS

The CLOD group showed a significantly higher bone-to-implant contact (74%) and bone volume relative to total volume (79%) compared to the PBS group (53% and 54%, respectively) and Healthy group (64% and 66%, respectively). Histological analysis revealed significantly reduced leukocyte and macrophage counts in the CLOD group. Additionally, TNF-α and IL-10 levels were significantly decreased in the CLOD group compared with the PBS group.

CONCLUSION

Macrophage depletion effectively reduces bone loss and inflammation in peri-implantitis. This study highlights targeting macrophages as a promising approach for managing peri-implantitis, although further research is needed to optimize therapeutic strategies.

Macrophage Polarization during MRONJ Development in Mice

Macrophages are important regulators of bone remodeling, and M1 polarization is observed in the setting of medication-related osteonecrosis of the jaws (MRONJ). Here, we characterize the phenotype of macrophages during early stages of MRONJ development in zoledronate (ZA)-treated mice with periodontal disease and explore the role of rosiglitazone, a drug that has been reported to lower the M1/M2 macrophage ratio, in MRONJ burden. Mice received ZA, and experimental periodontal disease (EPD) was induced around their second left maxillary molar. The mice were euthanized 1, 2, or 4 wk later. Micro-computed tomography and histologic and immunohistochemical analyses were carried out. In a separate experiment, mice were treated with ZA in the absence or presence of rosiglitazone, EPD was induced for 5 wk, and the MRONJ burden was assessed. An M1 predilection was noted in ZA versus vehicle (Veh) mice at 1, 2, or 4 wk after ligature placement. M1 cells were found to be positive for MMP-13, and their presence coincided with disruption of the surrounding collagen network in ZA mice. Rosiglitazone caused a reversal in the M1/M2 polarization in Veh and ZA mice. Rosiglitazone did not cause significant radiographic changes 5 wk after EPD in Veh or ZA animals. Importantly, percentage osteonecrosis and bone exposure were decreased in the rosiglitazone-treated versus nontreated ZA sites 5 wk after EPD. Our data point to an important role of M1 macrophage polarization with an overexpression of MMP-13 in the early phases of MRONJ development and provide insight into the use of interventional approaches promoting an M2 phenotype as a preventative means to alleviate MRONJ burden.