Immunolocalisation of collagens in the developing rat molar tooth

This study identifies different types of collagens during tooth development, maturation and ageing. Tissues from the rat first molar (from animals ranging in age from E14 to 104 wk postnatally) were immunostained using a panel of mono- and polyclonal antibodies against types I, II, III, IV, VI, IX and X collagen, fibronectin and laminin. During tooth development, types I and III collagens were expressed in the dental papilla at all stages but were also unexpectedly observed in the stellate reticulum of the enamel organ. Transient expression of type II collagen was also observed in the stellate reticulum during the late bell stage. Types IV and VI collagens, with laminin and fibronectin, were located within the basement membranes of the tooth germ. Collagen types I and III were observed within the developing follicle/periodontal ligament, type III predominating where collagen fibres were inserting into the alveolar bone and cementum. The pattern of types I and III collagen labelling within the periodontal ligament and the dental pulp did not change with age. Thus, some unusual collagen localisations were observed in the tooth germ, particularly within the stellate reticulum.