Long-term cyclical in vivoloading increases cartilage proteoglycan content in a spatially specific manner: an infrared microspectroscopic imaging and polarized light microscopy study

Abstract

Understanding the changes in collagen and proteoglycan content of cartilage due to physical forces is necessary for progress in treating joint disorders, including those due to overuse. Physical forces in the chondrocyte environment can affect the cellular processes involved in the biosynthesis of extracellular matrix. In turn, the biomechanical properties of cartilage depend on its collagen and proteoglycan content. To understand changes due to physical forces, this study examined the effect of 80 cumulative hours of in vivo cyclical joint loading on the cartilage content of proteoglycan and collagen in the rabbit metacarpophalangeal joint. The forepaw digits of six anesthetized New Zealand White adult female rabbits were repetitively flexed at 1 Hz with an estimated joint contact pressure of 1 to 2 MPa. Joints were collected from loaded and contralateral control specimens, fixed, decalcified, embedded, and thin-sectioned. Sections were examined under polarized light microscopy to identify and measure superficial and mid zone thicknesses of cartilage. Fourier Transform Infrared microspectroscopy was used to measure proteoglycan and collagen contents in the superficial, mid, and deep zones. Loading led to an increase in proteoglycan in the cartilage of all six rabbits. Specifically, there was a 46% increase in the cartilage deep zone (p = 0.003). The collagen content did not change with loading. Joint loading did not change the superficial and mid zone mean thicknesses. We conclude that long-term (80 cumulative hours) cyclical in vivo joint loading stimulates proteoglycan synthesis. Furthermore, stimulation is localized to cartilage regions of high hydrostatic pressure. These data may be useful in developing interventions to prevent overuse injuries or in developing therapies to improve joint function.

Altered regional loading patterns on articular cartilage following meniscectomy are not fully restored by autograft meniscal transplantation

“…The effect of cyclic loading on collagen and proteoglycan content has also been tested in vivo using a rabbit model. 28 In that study, cyclical joint loading with moderate magnitude (1~2 MPa) stimulated the proteoglycan synthesis in deep zone of the articular cartilage. More recently, Ko et al 29 studied the effect of in vivo cyclic compression on joint degeneration.…”

Specificity of Fourier Transform Infrared (FTIR) Microspectroscopy to Estimate Depth-Wise Proteoglycan Content in Normal and Osteoarthritic Human Articular Cartilage

“…In several studies using FTIR microspectroscopy, the collagen and PG contents of cartilage tissue have been determined. 2 - 10 The most commonly used and simplest analysis technique is to directly calculate the areas under the absorbance spectrum. Specifically, areas under the Amide I peak (1585-1720 cm –1 ) and carbohydrate region (985-1140 cm –1 ) have been considered to estimate the collagen and PG contents, respectively.…”

Ontogenetic scaling of pelvic limb muscles, tendons and locomotor economy in the Ostrich (Struthio camelus)

“…Musculoskeletal tissues show considerable ability to respond and adapt to changes in the loading environment (Rubin and Lanyon, 1985;Reeves et al, 2003;Saadat et al, 2006), and adaptive musculoskeletal responses have been reported in previous ontogenetic scaling studies. Positive allometric scaling of long bones has been noted in a range of species during ontogeny (Carrier, 1983;Main and Biewener, 2007;Smith et al, 2010;Doube et al, 2011;Lamas et al, 2014) suggesting that bone stresses may, at least in part, be maintained via structural changes to the skeleton.…”