Histochemical and immunohistochemical profile of human and rat ocular medial rectus muscles

Abstract

Purpose To compare the organization of human and rat ocular medial recti muscles (MR). Methods The cryosections of human and rat MR were processed for myofibrillar ATPase (mATPase), succinate dehydrogenase and glycerol-3-phosphate dehydrogenase. To reveal myosin heavy chain (MyHC) isoforms, specific monoclonal antibodies against MyHC-1/β-slow, α-cardiac (-α), -2a, -2x, -2b, -extraocular (eom), -embryonic (-emb) and -neonatal (-neo) were applied. The MyHC gene expression was studied by in situ hybridization in human muscle. Results The muscle fibers were arranged in two distinct layers in both species. In the orbital layer most fibers were highly oxidative and expressed fast MyHC isoforms, whereas slow and oxidative fibers expressed MyHC-1 and -α, some of them also MyHC-2a, -2x, -eom, very rarely -emb, and -neo. In the global layer, slow fibers with very low oxidative and glycolytic activity and three types of fast fibers, glycolytic, oxidative and oxidative-glycolytic, could be distinguished. The slow medium-sized fibers with mATPase activity stable at pH 4.4 expressed mostly MyHC-1 and -α in rat, while in humans they coexpressed MyHC-1 with -2b, -2x, -eom, and -neo. In both species, the fast fibers showed variable mATPase activity after preincubation at pH 9.4, and co-expressed various combinations of MyHC-2b, -2x, -2a and -eom but not -emb and -neo. MyHC-2b expressing fibers were larger and glycolytic, while MyHC-2a expressing fibers were smaller and highly oxidative in both species. To our knowledge, the present study is the first that demonstrated the expression of MyHC-2b in any of human skeletal muscles. Though the expression of MyHC genes did not correlate with the immunohistochemical profile of fibers in human MR, the expression of MyHC-2b gene was undoubtedly confirmed. Conclusions Rat MR represent a good model that can be applied to study human MR in experiment or disease, however certain differences are to be expected due to specific oculomotor demands in humans.

Myosin Heavy Chain-2b Transcripts and Isoform Are Expressed in Human Laryngeal Muscles

“…Nevertheless, in this study we have confirmed that the range of MyHC gene expression is wider in the laryngeal muscles compared to the limb muscles and is similar to that found in the extraocular muscles [Wieczorek et al, 1985;Kjellgren et al, 2003;Stirn Kranjc et al, 2009].…”

“…However, contrary to these studies, we recently demonstrated the expression of both, i.e. MyHC-2b transcripts and MyHC-2b isoform, in extraocular muscles by in situ hybridization and immunohistochemistry, respectively Stirn Kranjc et al, 2009].…”

Myosin Heavy Chain Composition of the Human Genioglossus Muscle

“…To determine expression of unconventional MHC we reacted tissue with Ab 4A6 (Developmental Studies Hybridoma Bank, Iowa, DSHB), which in rabbits and likely baboons and humans is specific for MHCeom (Kjellgren et al, 2003; Lucas & Hoh, 1997; Sokoloff, Daugherty, & Li, 2010), Ab MYH6 (Sigma-Aldrich), which in humans is reported to be specific for MHCac (Stirn Kranjc, Smerdu & Erzen, 2009) and Ab S46 (DSHB), which reacts with putative MHCst in adult human muscle spindles and human extraocular muscles but does not cross-react with MHCac or MHCI in adult catarrhine primate muscle (Sokoloff, Yang, Li, & Burkholder, 2007b). …”

“…Here we tested the putative anti-MHCac Ab MYH6 (Stirn Kranjc et al, 2009) by IHC. Ab MYH6 at dilution of 1:5 and 1:25 weakly-to-strongly labeled control MS (for presence of MHCac in MS see Liu et al, 2003) in GG and weakly to moderately labeled extrafusal fibers positive for Ab A4.84 (Figures 2D, 2E).…”

Black wildebeest skeletal muscle exhibits high oxidative capacity and a high proportion of type IIx fibres

“…The very fast MHC IIb isoform has been detected in cheetah, pig and llama skeletal muscle, with its expression in other larger animals (bovine, human and horse) absent and restricted to specialized muscles (e.g. eye muscles) (Quiroz-Rothe and Rivero, 2001;Lefaucheur et al, 2002;Toniolo et al, 2005;Stirn Kranjc et al, 2009;Hyatt et al, 2010).…”