RESUMO
During orthodontic tooth movement, mechanical forces acting on periodontal ligament (PDL) cells induce the synthesis of mediators which alter the growth, differentiation, and secretory functions of cells of the PDL. Since the cells of the PDL represent a heterogeneous population, we examined mechanically stress-induced cytokine profiles in three separate clones of human osteoblast-like PDL cells. Of the four pro-inflammatory cytokines investigated, only IL-6 and TGF-beta1 were up-regulated in response to mechanical stress. However, the expression of other pro-inflammatory cytokines such as IL-1 beta, TNF-alpha, or IL-8 was not observed. To understand the consequences of the increase in TGF-beta1 expression following mechanical stress, we examined the effect of TGF-beta1 on PDL cell phenotype and functions. TGF-beta1 was mitogenic to PDL cells at concentrations between 0.4 and 10 ng/mL. Furthermore, TGF-beta1 down-regulated the osteoblast-like phenotype of PDL cells, i.e., alkaline phosphatase activity, calcium phosphate nodule formation, expression of osteocalcin, and TGF-beta1, in a dose-dependent manner. Although initially TGF-beta1 induced expression of type I collagen mRNA, prolonged exposure to TGF-beta1 down-regulated the ability of PDL cells to express type I collagen mRNA. Our results further show that, within 4 hrs, exogenously applied TGF-beta1 down-regulated IL-6 expression in a dose-dependent manner, and this inhibition was sustained over a six-day period. In summary, the data suggest that mechanically stress-induced TGF-beta1 expression may be a physiological mechanism to induce mitogenesis in PDL cells while down-regulating its osteoblast-like features and simultaneously reducing the IL-6-induced bone resorption.
Assuntos
Homeostase/efeitos dos fármacos , Ligamento Periodontal/efeitos dos fármacos , Fator de Crescimento Transformador beta/farmacologia , Adolescente , Fosfatase Alcalina/análise , Fosfatase Alcalina/efeitos dos fármacos , Sequência de Bases , Linhagem Celular , Criança , Células Clonais/citologia , Células Clonais/efeitos dos fármacos , Células Clonais/enzimologia , Relação Dose-Resposta a Droga , Feminino , Homeostase/fisiologia , Humanos , Masculino , Dados de Sequência Molecular , Ligamento Periodontal/citologia , Ligamento Periodontal/enzimologia , Fenótipo , RNA Mensageiro/análise , RNA Mensageiro/efeitos dos fármacos , Estresse Mecânico , Fatores de TempoRESUMO
Eighty young athletes with weight training-related injuries were seen from August 1976 to August 1980. In 37 of the 80 athletes, it was difficult to pinpoint the cause of injury since the history revealed, in addition to weight training, either a program of running excessive mileage or participation in repetitive lap running in the gymnasium. The injuries of the remaining 43 athletes had a direct causal relationship to the weight training program. Twenty-nine developed lumbosacral pain. Seven of the 29 were hospitalized, and four required surgical treatment. Anterior iliac spine avulsion occurred in six cases, and laceration of the knee meniscus occurred as an initial injury in four athletes who required surgery. Four athletes developed a cervical sprain. Universal Gym (Cedar Rapids, IA), Leaper (Strength/Fitness Systems, Independence MO) Orthotron (Lumex Inc., Bay Shore, NY), and free weights were used either singly or in combination by these young athletes in weight training.