Adipocytes are present at human and murine myotendinous junctions

Jakobsen, Jens Rithamer; Jakobsen, Niels R.; Mackey, Abigail L.; Knudsen, Andreas B.; Hannibal, Jens; Koch, Manuel; Kjær, Michael; Krogsgaard, Michael

doi:10.1002/tsm2.212

Cited by 4 publications

(2 citation statements)

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“…Osteocrin is produced by skeletal muscle (51), is responsive to exercise (52), and overexpression of osteocrin has been reported to prevent muscle atrophy in cachexic mice (53). Furthermore, osteocrin has been linked to browning of adipose tissue (54), which is potentially related to our recent observations of adipocytes at the muscle-tendon interface in human hamstring tissue (55). Together these studies suggest a role for osteocrin specifically in the domain of skeletal muscle fibers close to the MTJ.…”

Section: Discussionmentioning

confidence: 63%

RNA sequencing and immunofluorescence of the myotendinous junction of mature horses and humans

Jakobsen

Schjerling

Svensson

et al. 2021

American Journal of Physiology-Cell Physiology

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The myotendinous junction (MTJ) is a specialised interface for transmitting high forces between muscle and tendon and yet the MTJ is a common site of strain injury with a high recurrence rate. The aim of this study was to identify previously unknown MTJ components in mature animals and humans. Samples were obtained from the superficial digital flexor (SDF) muscle-tendon interface of 20 horses and the tissue was separated through a sequential cryo-sectioning approach into muscle, MTJ (muscle tissue enriched in myofiber tips attached to the tendon), and tendon fractions. RT-PCR was performed for genes known to be expressed in the three tissue fractions and t-SNE plots were used to select the muscle, MTJ and tendon samples from 5 horses for RNA-sequencing. The expression of previously known and unknown genes identified through RNA-sequencing was studied by immunofluorescence on human hamstring MTJ tissue. The main finding was that RNA-sequencing identified expression of a panel of 61 genes enriched at the MTJ. 48 of these genes were novel for the MTJ, and 13 genes had been reported to be associated with the MTJ in earlier studies. The expression of known (COL22A1, NCAM, POSTN, NES, OSTN) and previously undescribed (MNS1 and LCT) MTJ genes was confirmed at the protein level by immunofluorescence on tissue sections of human MTJ. In conclusion, in muscle-tendon interface tissue enriched with myofiber tips, we identified expression of previously unknown MTJ genes representing diverse biological processes, which may be important in the maintenance of the specialized MTJ.

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Section: Discussionmentioning

confidence: 63%

RNA sequencing and immunofluorescence of the myotendinous junction of mature horses and humans

Jakobsen

Schjerling

Svensson

et al. 2021

American Journal of Physiology-Cell Physiology

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“…It has recently been demonstrated that adipocytes exist in high numbers in close relation to the MTJ in humans and mice (Figure 5; Jakobsen et al, 2020). Adipocytes in skeletal muscle is normally a sign of poor muscle function and insulin resistance (Vettor et al, 2009), but at the MTJ adipocytes are present in healthy humans and animals.…”

Section: Cell Turnovermentioning

confidence: 99%

The Myotendinous Junction—A Vulnerable Companion in Sports. A Narrative Review

Jakobsen

Krogsgaard

2021

Front. Physiol.

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The incidence of strain injuries continues to be high in many popular sports, especially hamstring strain injuries in football, despite a documented important effect of eccentric exercise to prevent strains. Studies investigating the anatomical properties of these injuries in humans are sparse. The majority of strains are seen at the interface between muscle fibers and tendon: the myotendinous junction (MTJ). It has a unique morphology with a highly folded muscle membrane filled with invaginations of collagen fibrils from the tendon, establishing an increased area of force transmission between muscle and tendon. There is a very high rate of remodeling of the muscle cells approaching the MTJ, but little is known about how the tissue adapts to exercise and which structural changes heavy eccentric exercise may introduce. This review summarizes the current knowledge about the anatomy, composition and adaptability of the MTJ, and discusses reasons why strain injuries can be prevented by eccentric exercise.

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