Electrical Stimulation of Masseter Muscles Maintains Condylar Cartilage in Long-term Organ Culture

Abstract

When condylar cartilage is maintained under non-functional organ culture conditions, its phenotypic expression is altered to a premature form with less expression of the type II collagen characteristic of mature chondroblasts. The aim of this study was to examine whether, by electrical stimulation of the major masticatory muscle, the masseter muscle, chondrogenic expression could be maintained under organ culture conditions in which the jaws with the craniomandibular joint were cultured in one block. Sixty BALB/c mice of both sexes were divided randomly into three groups of equal size. Two groups were decapitated at the age of 5 days. The cranial base and mandible were dissected out in one block, and the explant was placed on its cut surface on a culture dish. The masseter muscles of the explants in one group were stimulated with an electric pulsing device delivering an AC current of a frequency of 0.7 Hz and an amplitude of 5V with hourly active and silent periods. Five experimental and five control explants were fixed after culture periods of 1, 3, 7, and 14 days. The mice in the third group were used as in vivo controls. By electrical stimulation of the masseter muscle, the phenotypic characteristics of the condylar chondroblasts, such as the deposition of type II collagen and the thickness of the cartilage layers, closely resembled the situation in vivo, while the controls in a non-functional environment gradually lost their characteristic form.