Glycosaminoglycans (GAGs) determination in healthy and damaged equine articular cartilage

The purpose of this study was to establish if there was any difference in the GAGs content between loaded and unloaded surfaces of the joint. Furthermore, the results were compared between macroscopically healthy and damaged joints. Cartilage samples were obtained from two different zones of the equine metacarpophalangeal joint (metacarpal condyles). Samples were collected from the loaded surface of macroscopically healthy joints (N1; n=10) and from macroscopically damaged cartilage (P1; n=10). Additionally, cartilage samples were collected from unloaded areas at the most dorso-proximal zone of the joint in macroscopically healthy joints (N2; n=10) and from the macroscopically pathological joints but without damaged cartilage on the site of sampling (P2; n=10). The GAGs were extracted from 100 mg of cartilage of each sample and quantified through the safranine - O method that measured the total anionic charges, and through the carbazole method that measured the uronic acid content. Both methods measured the GAGs content, showing no differences between intra-joint zones (1 and 2), but when the GAGs content was compared between healthy and pathological joints, both methods showed a significantly decreased GAGs content in the damaged joints (1 and 2). These results show that the whole articular cartilage could be affected in a chronic pathological process and is not only a local process occurring in the macroscopically damaged cartilage associated with the loaded area.El propósito de este estudio fue establecer la existencia de alguna diferencia en el contenido de GAG entre las superficies articulares que soportan y no soportan peso, comparando articulaciones metacarpofalángicas equinas macroscópicamente sanas y dañadas. Las muestras de cartílago se obtuvieron desde la superficie de apoyo de articulaciones macroscópicamente sanas (N1; n=10) y de aquellas macroscópicamente dañadas (P1; n=10). Adicionalmente, en una localización dorsoproximal se obtuvieron muestras de la superficie del cartílago sin apoyo, desde articulaciones sanas (N2; n=10) y dañadas (P2; n=10). Los GAG fueron extraídos desde 100 mg de cartílago de cada muestra y cuantificados mediante el método safranina-O que mide la carga aniónica total y por el método del carbazol que mide el contenido de ácido urónico. Ambos métodos fueron capaces de medir el contenido de GAG no encontrándose diferencias entre zonas intraarticulación (1 y 2). Al comparar el contenido de GAG entre articulaciones sanas y dañadas, ambos métodos evidenciaron una disminución significativa de GAG en las articulaciones dañadas (1 y 2). Estos resultados muestran que en un proceso patológico articular crónico se afecta el cartílago en su conjunto y no solo aquellas zonas que muestran lesiones macroscópicas al soportar mayor impacto mecánic