Abstract

Background: There are several reports of Synovial chondromatosis (SC) and loose bodies (LBs) analyzed with histological and immunohistochemical staining. However, the process of formation of LBs remains unclear. Furthermore, there are very few reports of electron microscopic analysis of the LBs of the human temporomandibular joint (TMJ). Recently, we reported findings of the LBs of the human TMJ with scanning electron microscopy (SEM). The LBs might develop in a multi-layer style, in which fibrous tissues were piled up loosely around the inside part. The proliferating activity of LBs grows from the inside to outside of SC in TMJ.

In this study, we investigated ultrastructural difference findings of inside and outside in human TMJ LBs with transmission electron microscopy (TEM).

Methods: Specimens were surgically removed from the TMJ of three female patients clinically staged in phase II. Small pieces of the specimens were soaked in a buffered mixture of 0.5% glutaraldehyde and 4% paraformaldehyde for one week. The specimens were observed with a TEM (JSM-5500, JEOL, Tokyo) at an accelerating voltage of 3 KV.

Results: Ultrastructurally, cartilagenous cells were located in the fibrillar matrix intermingled with collagen fibrils, and accompanied micropodia extending toward the myxoid matrix. The cartilaginous cells were rich in rough endoplasmic reticula and Golgi apparati. Glycogen particles and fat droplets were clustered in the cytoplasm. The matrix was occasionally associated with deposition of amorphous electron-dense material, probably deriving from secretory products or cellular debris of stromal fibroblastic cells. Near the surface of the LBs, fibroblast-like cells, rich in rough endoplasmic reticula and bundles of intermediate filaments, were laminated.

Conclusions: There are different morphological features inside and outside of the human TMJ LBs.

Keywords: Temporomandibular joint (TMJ), Synovial chondromatosis (SC), loose body (LB), Transmission electron microscope (TEM)