Brama P A, Tekoppele J M, Bank R A, Barneveld A, van Weeren P R
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
Equine Vet J. 2000 May;32(3):217-21. doi: 10.2746/042516400776563626.
Biochemical heterogeneity of cartilage within a joint is well known in mature individuals. It has recently been reported that heterogeneity for proteoglycan content and chondrocyte metabolism in sheep develops postnatally under the influence of loading. No data exist on the collagen network in general or on the specific situation in the horse. The objective of this study was to investigate the alterations in equine articular cartilage biochemistry that occur from birth up to age one year, testing the hypothesis that the molecular composition of equine cartilage matrix is uniform at birth and biochemical heterogeneity is formed postnatally. Water content, DNA content, glycosaminoglycan content (GAG) and biochemical characteristics of the collagen network (collagen content, hydroxylysine content and hydroxylysylpyridinoline [HP] crosslinks) were measured in immature articular cartilage of neonatal (n = 16), 5-month-old foals (n = 16) and yearlings (n = 16) at 2 predefined differently loaded sites within the metacarpophalangeal joint. Statistical differences between sites were analysed by ANOVA (P<0.01), and age correlation was tested by Pearson's product moment correlation analysis (P<0.01). In neonatal cartilage no significant site differences were found for any of the measured biochemical parameters. This revealed that the horse has a biochemically uniform joint (i.e. the cartilage) at birth. In the 5-month-old foals and yearlings, significant site differences, comparable to those in the mature horse, were found for DNA, GAG, collagen content and hydroxylysine content. This indicates that functional adaptation of articular cartilage to weight bearing for these biochemical parameters takes place during the first months postpartum. Water content and HP crosslinks showed no difference between the 2 sites from neonatal horses, 5-month-old animals and yearlings. At both sites water, DNA and GAG decreased during maturation while collagen content, hydroxylysine content and HP crosslinks increased. We propose that a foal is born with a uniform biochemical composition of cartilage in which the functional adaptation to weight bearing takes place early in life. This adaptation results in biochemical and therefore biomechanical heterogeneity and is thought to be essential to resist the different loading conditions to which articular cartilage is subjected during later life. As collagen turnover is extremely low at mature age, an undisturbed functional adaptation of the collagen network of articular cartilage at a young age may be of significant importance for future strength and resistance to injury.
关节内软骨的生化异质性在成熟个体中是众所周知的。最近有报道称，绵羊蛋白聚糖含量和软骨细胞代谢的异质性在出生后受负荷影响而形成。目前尚无关于一般胶原网络或马的具体情况的数据。本研究的目的是调查出生至一岁的马关节软骨生物化学的变化，检验马软骨基质的分子组成在出生时是均匀的，生化异质性在出生后形成这一假设。在掌指关节内2个预先定义的不同负荷部位，测量新生马（n = 16）、5月龄马驹（n = 16）和一岁马（n = 16）未成熟关节软骨的含水量、DNA含量、糖胺聚糖含量（GAG）和胶原网络的生化特性（胶原含量、羟赖氨酸含量和羟赖氨酰吡啶啉[HP]交联）。通过方差分析（P<0.01）分析部位间的统计学差异，通过Pearson积矩相关分析（P<0.01）检验年龄相关性。在新生软骨中，任何测量的生化参数均未发现显著的部位差异。这表明马在出生时关节（即软骨）的生化组成是均匀的。在5月龄马驹和一岁马中，发现DNA、GAG、胶原含量和羟赖氨酸含量存在与成年马相当的显著部位差异。这表明在产后的头几个月，关节软骨对负重的功能适应在这些生化参数方面发生了。新生马、5月龄动物和一岁马的2个部位之间的含水量和HP交联没有差异。在两个部位，随着成熟，水、DNA和GAG减少，而胶原含量、羟赖氨酸含量和HP交联增加。我们认为，马驹出生时软骨的生化组成是均匀的，其中对负重的功能适应在生命早期发生。这种适应导致生化异质性，进而导致生物力学异质性，并且被认为对于抵抗关节软骨在后期生活中所承受的不同负荷条件至关重要。由于成熟时胶原周转极低，幼年时关节软骨胶原网络的无干扰功能适应对于未来的强度和抗损伤能力可能具有重要意义。
