Rabbit cranial sutures in vitro: a new experimental model for studying the response of fibrous joints to mechanical stress.

An organ culture system has been developed whereby mechanical stress can be applied to cranial sutures under controlled experimental conditions. The application of a continuous tensile mechanical stress (30 g) to cranial sutures from newborn rabbits (1--2 days) was accompanied by a significant increase in the incorporation of 3H-leucine and 3H-proline into suture protein. The specific activities of 3H-hydroxyproline indicated that mechanical stress produced a two-fold increase in the incorporation of 3H-proline into collagen. However, the proportion of the total radioactivity recoverable in collagen (45.63 +/- 2.33% for nonstressed; 40.58 +/- 2.17% for stressed sutures) was not significantly different. These data suggest that the increase in collagen synthesis occurs as part of a general stimulation of protein synthesis, and do not support the view that mechanical stress is the principal mechanism regulating the turnover of collagen in fibrous joints. These initial studies demonstrate that an in vitro experimental model has considerable potential for investigating the morphological and metabolic response of fibrous joints to mechanical deformation.