FIBROBLAST HETEROGENEITY IN THE PERIODONTIUM AND OTHER TISSUES

Fibroblasts are the major resident cells which inhabit the periodontal tissues. As such, they are crucial for maintaining the connective tis sues which support and anchor the tooth. Little is known of their orig ins, synthesis of regulatory cytokines and growth factors in health an d disease, and importance in soft tissue regeneration. An emerging con cept is that fibroblasts are not homogeneous, but instead consist of s ubsets of cells which can regulate bone marrow-derived cells such as T lymphocytes. Fibroblasts can be separated into subsets on the basis o f morphology, size and expression of intermediate filaments as well as collagen subtypes. Differential surface marker expression has also be en a key feature to distinguish fibroblast subsets from many tissues. Antigens such as Thy-1, class II MHC, and Clq are among those surface proteins which have been employed successfully to separate fibroblasts . Importantly, these fibroblast subsets are not only antigenically div erse, but also possess distinct functions. Thy 1(-) pulmonary fibrobla sts can display class II MHC antigens, synthesize IL-1 and can activat e T lymphocytes, whereas the Thy 1(+) subset is devoid of these functi ons. Recently, fibroblasts from the human orbit have also been shown t o be separable on the basis of Thy 1 surface marker expression. Fibrob lasts derived from human gingiva and periodontal ligament also appear to be composed of subsets with a heritable pattern of surface markers which will permit their separation into functional subpopulations. Thi s paper will review findings of fibroblast heterogeneity in periodonta l and other tissues. Evidence will be presented for the use of surface markers to delineate functional subsets. The ability to discriminate subsets of fibroblasts will aid in studies of periodontal disease path ogenesis and wound healing.