Dynamics of myosin heavy chain isoform transition in the longissimus muscle of domestic and wild pigs during growth: a comparative study

Abstract

Dynamics of myofiber differentiation/maturation in porcine skeletal muscle is associated with domestication, breeding and rearing conditions. This study was aimed to comparatively elucidate the age-dependent myosin heavy chain (MyHC) isoform expression and transition pattern in domestic and wild pig (WP) skeletal muscle from birth until adulthood. Domestic pigs (DPs) of Large White breed raised in conventional production system were compared with WPs reared in a large hunting enclosure. Muscle samples for immuno/enzyme histochemistry were taken from the longissimus dorsi muscle within 24 h postmortem at 24 to 48 h, 21 to 23 days, 7 months and~2 years postpartum. Based on the antibody reactivity to MyHCs (NCL-MHCs, A4.74, BF-F3) and succinate dehydrogenase activity, myofibers were classified into I, I/IIa, IIa, IIx and IIb types. In addition, foetal MyHC expression was determined with the use of F158.4C10 antibody. Maturation of the longissimus dorsi muscle in the WP was characterized by an accelerated transformation of the fast to slow MyHC during the first hours postpartum, followed by differentiation towards oxidative myofibers in which type I, IIa and IIx MyHCs predominated. In the DP, the transformation shifted towards glycolytic myofibers that expressed MyHC-IIb. The expression of foetal MyHC was higher in the DP than in the WP at 1 day of age, and the decline in the foetal MyHC during the first 3 weeks was more rapid in the WP than in the DP denoting an accelerated early postnatal muscle maturation in WP than DP piglets. All foetal MyHC-positive myofibers co-expressed IIa isoform, but not vice versa. The intense myofiber hypertrophy was evident from 3 weeks until 7 months of age. In this period, the myofiber crosssectional area increased up to 10-and 20-fold in the WP and the DP, respectively. In the DP, the hypertrophy of all myofiber types was more pronounced than in the WP, particularly the hypertrophy of IIx and IIb myofibers. To summarize, the comparison between growing DP with wild ancestors showed that genetic selection and rearing conditions lead to substantial changes in the direction and intensity of postnatal MyHC transformation as evidenced by different proportion of individual myofiber types and differences in their hypertrophic potential.

Rearing pattern alters porcine myofiber type, fat deposition, associated microbial communities and functional capacity

“…This result was consistent with the report of Fazarinc et al (2017) 16 , wherein the percentage of MyHC-I was higher in wild pigs breeding outside, which were physically active than domestic pigs indoors. Higher percentage of slow-twitch type I myofibers was also found in wild pigs kept in group housing with diminished activity and were fed ad libitum 17 or were obtained from a zoological garden 18 .…”

Rearing pattern alters porcine myofiber type, fat deposition, associated microbial communities and functional capacity

“…This result was consistent with the report of Fazarinc et al (2017) 16 , wherein the percentage of MyHC-I was higher in wild pigs breeding outside, which were physically active than domestic pigs indoors. Higher percentage of slow-twitch type I myofibers was also found in wild pigs kept in group housing with diminished activity and was fed ad libitum 17 or was obtained from a zoological garden 18 .…”

Expression of Myosin Heavy Chain and Some Energy Metabolism-Related Genes in the Longissimus Dorsi Muscle of Krškopolje Pigs: Effect of the Production System

“…Earlier studies have provided evidences for the negative influence of fiber hypertrophy on meat quality traits, such as shear force, drip loss, and cooking loss (3,9). In both groups, the CSA of type IIx and IIb fiber in the LD muscles of Krškopolje pig was observed to be considerably smaller in comparison to modern white pigs, but larger than in wild pigs of comparable age (∼7 months) (18). Data derived from immunohistochemistrybased classification of myofiber types and analysis of MyHC mRNA generally showed a strong correlation in the case of MyHC I and IIb, and moderate and weak in the case of MyHC IIa and MyHC IIx, respectively, indicating that there are still difficulties in correctly classifying the latter.…”

“…Muscle samples were collected from the central part of the longissimus dorsi muscle (LD) at the level of the last thoracic vertebrae within 2 h after slaughter, deep-frozen in liquid nitrogen, and stored at −80 • C till further analysis. Immunoenzyme histochemistry was performed on a subset of animals (6 animals per group) as previously described (18). Briefly, three different monoclonal antibodies (MAb) specific for adult MyHC isoforms were used: NLC-MHCs, specific for slow-twitch MyHC I; SC 71, specific for MyHC IIa; and BF-F3, specific for rat MyHC IIb (19).…”

“…The histomorphometric analysis of the transverse serial sections was performed using a Nikon Eclipse Ni-UM microscope equipped with a DS-Fi1 camera and the Imaging Software NIS-Elements BR 4.60 (Nikon instruments Europe B.V., Badhoevedorp, The Netherlands) as previously described (18). Approximately 500 myofibers in randomly selected complete muscle fascicles were analyzed per muscle sample to determine the average proportion of individual myofiber types according to the immunohistochemical staining and SDH activity as well as the cross-sectional area (CSA) of myofiber types.…”