Distributions of types I, II and III collagen by region in the human supraspinatus tendon

Abstract

The mechanical properties of the human supraspinatus tendon (SST) are highly heterogeneous and may reflect an important adaptive response to its complex, multiaxial loading environment. However, these functional properties are associated with a location-dependent structure and composition that have not been fully elucidated. Therefore, the objective of this study was to determine the concentrations of types I, II and III collagen in 6 distinct regions of the SST and compare changes in collagen concentration across regions with local changes in mechanical properties. We hypothesized that type I collagen content would be high throughout the tendon, type II collagen would be restricted to regions of compressive loading and type III collagen content would be high in regions associated with damage. We further hypothesized that regions of high type III collagen content would correspond to regions with low tensile modulus and a low degree of collagen alignment. Although type III collagen content was not significantly higher regions that are frequently damaged, all other hypotheses were supported by our results. In particular, type II collagen content was highest near the insertion while type III collagen was inversely correlated with tendon modulus and collagen alignment. The measured increase in type II collagen under the coracoacromial arch provides evidence of adaptation to compressive loading in the SST. Moreover, the structure-function relationship between type III collagen content and tendon mechanics established in this study demonstrates a mechanism for altered mechanical properties in pathological tendons and provides a guideline for identifying therapeutic targets and pathology-specific biomarkers.

Multiscale strain analysis of tendon subjected to shear and compression demonstrates strain attenuation, fiber sliding, and reorganization

“…[1][2][3][4] As a result, specific locations of the human SST exhibit significantly different fiber alignment and tensile modulus during tensile loading, 5,6 as well as compositional differences (i.e., collagens, proteoglycans) by location. 3,7 Similarly, the bovine deep digital flexor tendon (DDFT) functions in a multiaxial physiological loading environment with forces that vary at different anatomical locations: the proximal region is mostly loaded in tension, while the distal region is also compressed against the navicular bone during normal joint function. [8][9][10][11][12][13] Our previous study, 14 which evaluated the DDFT as an easily accessible example of a complexly loaded tendon with tissue-level properties that vary by location, 8 demonstrated that the proximal and distal regions exhibited different elastic mechanical properties, yet similar viscoelastic properties, and inhomogeneous proteoglycan distribution and collagen organization.…”

Effects of Human Placenta Extract (Laennec) on Ligament Healing in a Rodent Model

“…35,36) An injured ligament may become physically weaker and stiffer during the healing process as rigidity increases and elasticity decreases. 37) The group treated with Laennec maintained physical characteristics that were similar to those of the normal ligament group at 1 and 4 weeks after treatment. Since our biomechanical test results show no significant differences in physical characteristics between normal and saline treatment group, more supporting experiments may be necessary.…”

Experimental evaluation of multiscale tendon mechanics

“…), lubricin, tenascin‐C, and collagen oligomeric matrix protein (COMP), which may contribute mechanically (Fig. ) . Interestingly, previous studies showed that fibrils formed by collagen types II and III, related with tendon healing, were smaller than these of collagen type I .…”

“…Interestingly, previous studies showed that fibrils formed by collagen types II and III, related with tendon healing, were smaller than these of collagen type I . Collagen type II content was higher near the insertion of human SST, which experiences more compressive loading compared to the midsubstance, and collagen type III content was inversely correlated with tendon tensile modulus and collagen alignment . Mutations of collagen type V causes joint hypermobility in classic Ehlers‐Danols syndrome, which motivates the evaluation of the contribution of collagen type V to tendon mechanics .…”