“…(Boyko et a., 1981 (Rose et al, 1987), proliferative capacity and glycosaminoglycan content (Mariotti and Cochran, 1990), chemotactic responses (Nishimura and Terranova, 1996), protein and collagen synthesis (Somerman et al, 1988), response to attachment factors (Somerman et al, 1989), and capacity for mineralized tissue formation (Arceo et al, 1991). Currently, it is unknown if these in vitro findings have clinical correlates in vivo, but it is tempting to speculate that periodontal ligament and gingival fibroblasts have constitutively different differentiation repertoires that critically determine the outcome of periodontal wound healing (i.e., regeneration or repair; see Aukhil et al, 1990). What are currently lacking from studies that contrast, for example, gingival and periodontal ligament fibroblasts are: (1) reproducible and comparable methods of primary cell culture; (2) large patient sample sizes; (3) clonal investigations; (4) microdissection methods for the isolation of specific, regional cell populations (see Irwin et al, 1994); (5) defined, clear-cut phenotypic markers that are stable and propagable over long-term culture (see, for example, Bordin et al, 1984); (6) specific identification of fibroblastic cells; and (7) in vivo functional assays that test unambiguously for differences between gingival and periodontal ligament fibroblasts.…”