Aging affects mechanical properties and lubricin/PRG4 gene expression in normal ligaments

• Published in: Journal of biomechanics 2015-09, Vol.48 (12), p.3306-3311
• Main Authors: Thornton, Gail M, Lemmex, Devin B, Ono, Yohei, Beach, Cara J, Reno, Carol R, Hart, David A, Lo, Ian K.Y
• Format: Article
• Language: English
• Subjects: Aging; Animals; Assessments; Collagen - metabolism; Collagens; Conflicts of interest; Failure; Female; Gene Expression; Glycoproteins - genetics; Glycoproteins - metabolism; Injuries; Knee; Ligament; Ligaments; Lubricin/PRG4; Matrix Metalloproteinase 1 - genetics; Matrix Metalloproteinase 1 - metabolism; Medial Collateral Ligament, Knee - metabolism; Medial Collateral Ligament, Knee - physiology; Modulus; Physical Medicine and Rehabilitation; Proteoglycans - genetics; Proteoglycans - metabolism; Rabbits; Receptors, Estrogen - genetics; Receptors, Estrogen - metabolism; Sports injuries; Strain; Tissue Inhibitor of Metalloproteinase-3 - genetics; Tissue Inhibitor of Metalloproteinase-3 - metabolism
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2015.06.005

Abstract Age-related changes in ligament properties may have clinical implications for injuries in the mature athlete. Previous preclinical models documented mechanical and biochemical changes in ligaments with aging. The purpose of this study was to investigate the effect of aging on ligament properties (mechanical, molecular, biochemical) by comparing medial collateral ligaments (MCLs) from 1-year-old and 3-year-old rabbits. The MCLs underwent mechanical ( n =7, 1-year-old; n =7, 3-year-old), molecular ( n =8, 1-year-old; n =6, 3-year-old), collagen and glycosaminoglycan (GAG) content ( n =8, 1-year-old; n =6, 3-year-old) and water content ( n =8, 1-year-old; n =5, 3-year-old) assessments. Mechanical assessments evaluated total creep strain, failure strain, ultimate tensile strength and modulus. Molecular assessments using RT-qPCR evaluated gene expression for collagens, proteoglycans, hormone receptors, and matrix metalloproteinases and their inhibitors. While total creep strain and ultimate tensile strength were not affected by aging, failure strain was increased and modulus was decreased comparing MCLs from 3-year-old rabbits to those from 1-year-old rabbits. The mRNA expression levels for lubricin/proteoglycan 4 (PRG4) and tissue inhibitor of metalloproteinase-3 increased with aging; whereas, the mRNA expression levels for estrogen receptor and matrix metalloproteinase-1 decreased with aging. Collagen and GAG content assays and water content assessments did not demonstrate any age-related changes. The increased failure strain and decreased modulus with aging may have implications for increased susceptibility to ligament damage/injury with aging. Lubricin/PRG4 gene expression was affected by aging and its speculated role in ligament function may be related to interfascicular lubrication, which in turn may lead to altered mechanical function with aging and increases in potential for injury.