DIRECT EVIDENCE OF EPITHELIAL-MESENCHYMAL INTERDEPENDENCE INSITU

  • 1 January 1980
    • journal article
    • research article
    • Vol. 130  (MAY) , 469-478
Abstract
In the basal odontogenic zone of the continuously growing mandibular incisor of the rat, the cytological evidence of the toxicity of 40 mg cyclophosphamide/kg, 24 h after a single i.p. injection, was confined to the proliferating mesenchyme. Localized loss of precursors of odontoblasts, cessation of basal odontogenesis and acellularity of the related part of the pulp ensued. The cells of the internal enamel epithelium bordering this region did not differentiate into ameloblasts and appeared atrophic. Upon recovery of the proliferating mesenchymal cell population, odontogenic tissues were reconstituted and odontogenesis was resumed basal to the zone of the cytotoxic injury. At the same time pulpal connective tissue generating irregular dentine advanced incisally from the reconstituted basal zone and filled the area of pulpal acellularity. This was attended by the differentiation of the peripheral stunted cells of the internal enamel epithelium into ameloblasts and resumption of locally arrested amelogenesis. The cytotoxic injury, apparently localized to the basal mesenchyme in the rat incisor, also arrests the differentiation of the associated cells of the odontogenic epithelium into ameloblasts. The development of the affected epithelial cells remains arrested as long as they are dissociated from the mesenchyme or the connective tissue matrix. The stunted epithelial cells in the same experimental organ develop to functional ameloblasts when an interface with the mesenchymal tissue is re-established. Epithelial-mesenchymal interdependence in situ was evidenced.