Pachydermoperiostosis (primary hypertrophic osteoarthropathy): in vitro evidence for abnormal fibroblast proliferation.

Pachydermoperiostosis (PDP) is a disease characterized by the presence of pachydermia, periostosis and finger clubbing. Evidence that the skin and soft tissues are involved in the disease prompted the in vitro investigation of the behaviour of fibroblasts obtained from cutaneous biopsies of involved and apparently uninvolved PDP skin. PDP fibroblasts from affected skin demonstrated an abnormal proliferation, very rapid and tumultuous when compared to the growth of fibroblasts derived from apparently uninvolved skin and fibroblasts from the skin of healthy subjects. This characteristic was confirmed by the rate of thymidine incorporation, which was increased in PDP-affected fibroblasts (1152 dpm) compared to apparently non-PDP involved fibroblasts (273 dpm) and controls (262 dpm). Ultracentrifuged and non-centrifuged conditioned medium (CM) of fibroblasts affected or apparently not affected with PDP were used to evaluate the effect on the proliferation of healthy skin fibroblasts, compared to the effect of CM derived from healthy fibroblasts and from healthy fibroblasts incubated with 10% and 1% foetal calf serum. The CM of non-centrifuged PDP fibroblasts resulted in a statistically significant stimulation of fibroblast growth when compared to that expressed by ultracentrifuged PDP CM, healthy fibroblast CM and 10% stimulated CM. These data show that PDP fibroblasts maintain in vitro the capacity to proliferate at a higher rate than healthy fibroblasts and that in the CM residual cells and/or their debris may be present, inducing the abnormal growth of healthy fibroblasts. This evidence suggests that fibroblasts in PDP may play a role in the development of the disease.