title: Of mice, men and elephants: the relation between articular cartilage thickness and body mass.
abstract: Mammalian articular cartilage serves diverse functions, including shock absorption, force transmission and enabling low-friction joint motion. These challenging requirements are met by the tissue's thickness combined with its highly specific extracellular matrix, consisting of a glycosaminoglycan-interspersed collagen fiber network that provides a unique combination of resilience and high compressive and shear resistance. It is unknown how this critical tissue deals with the challenges posed by increases in body mass. For this study, osteochondral cores were harvested post-mortem from the central sites of both medial and lateral femoral condyles of 58 different mammalian species ranging from 25 g (mouse) to 4000 kg (African elephant). Joint size and cartilage thickness were measured and biochemical composition (glycosaminoclycan, collagen and DNA content) and collagen cross-links densities were analyzed. Here, we show that cartilage thickness at the femoral condyle in the mammalian species investigated varies between 90 µm and 3000 µm and bears a negative allometric relationship to body mass, unlike the isometric scaling of the skeleton. Cellular density (as determined by DNA content) decreases with increasing body mass, but gross biochemical composition is remarkably constant. This however need not affect life-long performance of the tissue in heavier mammals, due to relatively constant static compressive stresses, the zonal organization of the tissue and additional compensation by joint congruence, posture and activity pattern of larger mammals. These findings provide insight in the scaling of articular cartilage thickness with body weight, as well as in cartilage biochemical composition and cellularity across mammalian species. They underscore the need for the use of appropriate in vivo models in translational research aiming at human applications.
authors: Department of Orthopaedics, University Medical Center Utrecht, Utrecht, The Netherlands. j.malda@umcutrecht.nl
authors: Jos
authors: J
authors: Malda
authors: Janny C
authors: JC
authors: de Grauw
authors: Kim E M
authors: KE
authors: Benders
authors: Marja J L
authors: MJ
authors: Kik
authors: Chris H A
authors: CH
authors: van de Lest
authors: Laura B
authors: LB
authors: Creemers
authors: Wouter J A
authors: WJ
authors: Dhert
authors: P René
authors: PR
authors: van Weeren
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015992:Body Mass Index; D049628:Body Size; D002358:Cartilage, Articular / Q000737:chemistry*; D003094:Collagen / Q000032:analysis*; D004247:DNA / Q000032:analysis*; D004606:Elephants; D005109:Extracellular Matrix / Q000737:chemistry*; D005269:Femur / Q000737:chemistry*; D006025:Glycosaminoglycans / Q000032:analysis*; D006801:Humans; D008297:Male; D051379:Mice; D033081:Shear Strength
chemical_list: D006025:Glycosaminoglycans; D003094:Collagen; D004247:DNA