Diagnostic imaging modalities and surgical anatomy of the temporomandibular joint in rabbits

Inflammation-Stimulated MSC-Derived Small Extracellular Vesicle miR-27b-3p Regulates Macrophages by Targeting CSF-1 to Promote Temporomandibular Joint Condylar Regeneration

Small extracellular vesicles (sEVs) secreted by mesenchymal stem cells (MSCs) have been extensively studied in recent years. sEV contents change with the secreting cell state. When MSCs are exposed to an inflammatory environment, they release more functional growth factors, exosomes, and chemokines. Herein, MSCs are stimulated to alter sEV cargos and functions to regulate the inflammatory microenvironment and promote tissue regeneration. Sequencing of sEV miRNAs shows that certain RNAs conducive to cell function are upregulated. In this study, in vitro cell function experiments show that both inflammation-stimulated adipose-derived MSC (ADSC)-derived sEV (IAE) and normal ADSC-derived sEV (AE) promote cell proliferation; IAE also significantly improves cell migration. Regarding macrophage polarization regulation, IAE significantly promotes M2 macrophage differentiation. RNA-sequencing analysis indicates that high miR-27b-3p expression levels in IAE may regulate macrophages by targeting macrophage colony-stimulating factor-1 (CSF-1). In vivo, a rabbit temporomandibular joint (TMJ) condylar osteochondral defect model shows that both AE and IAE promote TMJ regeneration, with IAE having the most significant therapeutic effect. Therefore, the authors confirm that exposing MSCs to an inflammatory environment can feasibly enhance sEV functions and that modified sEVs achieve better therapeutic effects.

A rabbit model to investigate temporomandibular joint osteochondral regeneration

OBJECTIVE

The objective of this study was 2-fold: (1) to describe the rabbit temporomandibular joint (TMJ) anatomy and (2) to provide a detailed, step-by-step description of a minimally invasive approach to perform a standard osteochondral TMJ defect that can be used to investigate the regenerative potential of biomaterials.

STUDY DESIGN

This study was performed in 2 steps. In the first, a total of 8 rabbit carcasses (n = 16 joints) were used to study the normal TMJ anatomy and histology to develop a minimally invasive approach to access the articulating surface of the condyle to perform a standard osteochondral defect. In the second, the surgical procedure was performed in 10 live animals to evaluate the feasibility of the model and to evaluate the regenerative potential of a biodegradable light-cured hydrogel seeded with stem cells (results not shown).

RESULTS

The cartilage of the mandibular condyle showed 4 layers: fibrous, proliferative, hypertrophic, and a zone of calcified cartilage. Positive safranin O staining was observed in the cartilage. The mean duration of the procedure (from incision to last stitch) was 35.5 (±9.21) minutes. All animals survived the procedures without any major complications.

CONCLUSIONS

This animal model represents an easy and nonmorbid surgical approach to rabbit TMJ.

Repeated Live Imaging in the Temporomandibular Joint of an Anterior Crossbite Mouse Model Using a 7T Magnetic Resonance Device

BACKGROUND/AIM

Few studies have performed magnetic resonance (MR) imaging on live animals. The aim of this study was to perform 7T MR microimaging of the temporomandibular joint (TMJ) multiple times in the same living mice with malocclusion, and to compare between MR imaging and histopathological findings.

MATERIALS AND METHODS

Mice were examined by MR imaging at 3-4, 6 and 12 weeks following the attachment of a metal tube on the left mandibular incisor. Histopathological examination was done at 3, 6 and 12 weeks.

RESULTS

The detailed structure of the TMJ was evident from MR microimaging. The histopathological examination showed some changes in the cartilage, but no changes in the bone structure of these mice.

CONCLUSION

We successfully performed multiple 7T MR imaging in living mice. Even if the TMJ showed no obvious changes on MR images, minute changes may be present in the cartilage.