RESUMEN
Musculoskeletal allografts are a valuable alternative to autograft tissue in orthopaedic surgeries. However, the effects of the allografts' storage history on the collagen and subsequent allograft scaffold properties are unknown. In this study, we hypothesized that freezing and refrigeration of allografts for 1 week would alter the biologic performance and mechanical properties of the allograft collagen. Allograft collagen was characterized by SDS-PAGE migration pattern, amino acid profile and measured denaturation. Scaffolds made from allograft collagen were evaluated for fibroblast proliferation, platelet activation and scaffold retraction. Collagen gelation kinetics (elastic and inelastic moduli and the viscous-elastic transition point) were also evaluated. Fibroblast proliferation, platelet activation and scaffold retraction results showed only minor, though statistically significant, differences between the storage groups. In addition, there were no significant differences in rheological properties or collagen biochemistry. In conclusion, this study suggests that freezing or refrigeration for 1 week does not appear to have any detrimental effect on the mechanical properties and biologic performance of the collagen within allografts.
Asunto(s)
Colágeno/química , Colágeno/metabolismo , Criopreservación , Andamios del Tejido , Trasplante Homólogo , Aminoácidos/análisis , Animales , Proliferación Celular , Células Cultivadas , Electroforesis en Gel de Poliacrilamida , Fibroblastos/citología , Humanos , Activación Plaquetaria , Desnaturalización Proteica , Ratas , ReologíaRESUMEN
Collagen-platelet composites have recently been successfully used as scaffolds to stimulate anterior cruciate ligament (ACL) wound healing in large animal models. These materials are typically kept on ice until use to prevent premature gelation; however, with surgical use, placement of a cold solution then requires up to an hour while the solution comes to body temperature (at which point gelation occurs). Bringing the solution to a higher temperature before injection would likely decrease this intra-operative wait; however, the effects of this on composite performance are not known. The hypothesis tested here was that increasing the temperature of the gel at the time of injection would significantly decrease the time to gelation, but would not significantly alter the mechanical properties of the composite or its ability to support functional tissue repair. Primary outcome measures included the maximum elastic modulus (stiffness) of the composite in vitro and the in vivo yield load of an ACL transection treated with an injected collagen-platelet composite. In vitro findings were that injection temperatures over 30 degrees C resulted in a faster visco-elastic transition; however, the warmed composites had a 50% decrease in their maximum elastic modulus. In vivo studies found that warming the gels prior to injection also resulted in a decrease in the yield load of the healing ACL at 14 weeks. These studies suggest that increasing injection temperature of collagen-platelet composites results in a decrease in performance of the composite in vitro and in the strength of the healing ligament in vivo and this technique should be used only with great caution.
Asunto(s)
Plaquetas/citología , Colágeno , Traumatismos de la Rodilla/cirugía , Temperatura , Ingeniería de Tejidos/métodos , Andamios del Tejido , Animales , Fenómenos Biomecánicos , Temperatura Corporal , Elasticidad , Femenino , Hidrogel de Polietilenoglicol-Dimetacrilato , Inyecciones , Traumatismos de la Rodilla/fisiopatología , Articulación de la Rodilla/citología , Articulación de la Rodilla/fisiología , Ratas , Reología , Sus scrofa , Cicatrización de HeridasRESUMEN
A perifusion chamber technique is described that permits continuous measurement of the in vitro release of salivary enzymes from slices of mouse salivary glands responding to various stimuli. Kinetics of amylase secretion differed from those of esterase, which suggests that the secretory processes differ for these two enzymes.