Expression of MyHC-15 and -2x in human muscle spindles : an immunohistochemical study

Smerdu, Vika (author)

To build on the existing data on the pattern of myosin heavy chain (MyHC) isoforms expression in the human muscle spindles, we aimed to verify whether the 'novel' MyHC-15, -2x and -2b isoforms are co-expressed with the other known isoforms in the human intrafusal fibres. Using a set of antibodies, we attempted to demonstrate nine isoforms (15, slow-tonic, 1, α, 2a, 2x, 2b, embryonic, neonatal) in different regions of intrafusal fibres in the biceps brachii and flexor digitorum profundus muscles. The reactivity of some antibodies with the extrafusal fibres was also tested in the masseter and laryngeal cricothyreoid muscles. In both upper limb muscles, the expression of slow-tonic isoform was a reliable marker for differentiating positive bag fibres from negative chain fibres. Generally, bag1 and bag2 fibres were distinguished in isoform 1 expression; the latter consistently expressed this isoform over their entire length. Although isoform 15 was not abundantly expressed in intrafusal fibres, its expression was pronounced in the extracapsular region of bag fibres. Using a 2x isoform-specific antibody, this isoform was demonstrated in the intracapsular regions of some intrafusal fibres, particularly chain fibres. To the best of our knowledge, this study is the first to demonstrate 15 and 2x isoforms in human intrafusal fibres. However, whether the labelling with an antibody specific for rat 2b isoform reflects the expression of this isoform in bag fibres and some extrafusal ones in the specialised cranial muscles requires further evaluation. The revealed pattern of isoform co-expression only partially agrees with the results of previous, more extensive studies. Nevertheless, it may be inferred that MyHC isoform expression in intrafusal fibres varies along their length, across different muscle spindles and muscles. Furthermore, the estimation of expression may also depend on the antibodies utilised, which may also react differently with intrafusal and extrafusal fibres.

• Language: English
• Keywords: immunohistochemistry, intrafusal fibre, muscle spindle, myosin heavy chain isoforms, MyHC, skleletal muscle
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: MF - Faculty of Medicine
• Publication status: Published
• Publication version: Version of Record
• Year: 2023
• Number of pages: Str. 826-841
• Numbering: Vol. 243, iss. 5
• PID: 20.500.12556/RUL-153152
• UDC: 611
• ISSN on article: 0021-8782
• DOI: 10.1111/joa.13923
• COBISS.SI-ID: 177913347
• Publication date in RUL: 19.12.2023

Record is a part of a journal

• Title: Journal of anatomy
• Shortened title: J. anat.
• Publisher: Wiley, Anatomical Society
• ISSN: 0021-8782
• COBISS.SI-ID: 1312266

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: imunohistokemija, intrafuzalna vlakna, mišično vreteno, izoforme težke verige miozina, skeletne mišice

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P3-0043
• Name: Molekularni mehanizmi razvoja in delovanja skeletne mišice