The Effect of the Wooden Breast Fibrotic Myopathy in Broilers on Fibrillar Collagen Organization and Decorin-Collagen Binding

Expression and secretion of SPARC, FGF-21 and DCN in bovine muscle cells: Effects of age and differentiation

Skeletal muscle growth is an economically important trait in the cattle industry. Secreted muscle-derived proteins, referred to as myokines, have important roles in regulating the growth, metabolism, and health of skeletal muscle in human and biomedical research models. Accumulating evidence supports the importance of myokines in skeletal muscle and whole-body health, though little is known about the potential presence and functional significance of these proteins in cattle. This study evaluates and confirms that secreted proteins acidic and rich in cysteine (SPARC), fibroblast growth factor 21 (FGF-21), myostatin (MSTN), and decorin (DCN) are expressed and SPARC, FGF-21, and DCN are secreted by primary bovine satellite cells from 3- (BSC3; n = 3) and 11- (BSC11; n = 3) month -old commercial angus steers. Cells were cultured and collected at zero, 12, 24, and 48 hours to characterize temporal expression and secretion from undifferentiated and differentiated cells. The expression of SPARC was higher in the undifferentiated (p = 0.04) and differentiated (p = 0.07) BSC11 than BSC3. The same was observed with protein secretion from undifferentiated (p <0.0001) BSC11 compared to BSC3. Protein secretion of FGF-21 was higher in undifferentiated BSC11 (p < 0.0001) vs. BSC3. DCN expression was higher in differentiated BSC11 (p = 0.006) vs. BSC3. Comparing undifferentiated vs. differentiated BSC, MSTN expression was higher in differentiated BSC3 (p ≤ 0.001) for 0, 12, and 24 hours and in BSC11 (p ≤ 0.03) for 0, 12, 24, and 48 hours. There is also a change over time for SPARC expression (p ≤ 0.03) in undifferentiated and differentiated BSC and protein secretion (p < 0.0001) in undifferentiated BSC, as well as FGF-21 expression (p = 0.007) in differentiated BSC. This study confirms SPARC, FGF-21, and DCN are secreted, and SPARC, FGF-21, MSTN, and DCN are expressed in primary bovine muscle cells with age and temporal differences.

Transcriptomic Profiles of Pectoralis major Muscles Affected by Spaghetti Meat and Woody Breast in Broiler Chickens

Spaghetti meat (SM) and woody breast (WB) are breast muscle myopathies of broiler chickens, characterized by separation of myofibers and by fibrosis, respectively. This study sought to investigate the transcriptomic profiles of breast muscles affected by SM and WB. Targeted sampling was conducted on a flock to obtain 10 WB, 10 SM, and 10 Normal Pectoralis major muscle samples from 37-day-old male chickens. Total RNA was extracted, cDNA was used for pair-end sequencing, and differentially expressed genes (DEGs) were determined by a false discovery rate of <0.1 and a >1.5-fold change. Principal component and heatmap cluster analyses showed that the SM and WB samples clustered together. No DEGs were observed between SM and WB fillets, while a total of 4018 and 2323 DEGs were found when comparing SM and WB, respectively, against Normal samples. In both the SM and WB samples, Gene Ontology terms associated with extracellular environment and immune response were enriched. The KEGG analysis showed enrichment of cytokine-cytokine receptor interaction and extracellular matrix-receptor interaction pathways in both myopathies. Although SM and WB are macroscopically different, the similar transcriptomic profiles suggest that these conditions may share a common pathogenesis. This is the first study to compare the transcriptomes of SM and WB, and it showed that, while both myopathies had profiles different from the normal breast muscle, SM and WB were similar, with comparable enriched metabolic pathways and processes despite presenting markedly different macroscopic features.

Effect of freezing on the quality of breast meat from broilers affected by wooden breast myopathy

The objective of the present study was to characterize possible variations in the quality of wooden chicken breast meat during freezing for 12 mo, in order to prove whether the shelf life recommended by the industry allows the storage of that type of meat without compromising its consumption. Three hundred samples of male Cobb 500 broilers slaughtered at 42 d of age were used. Part of the samples (n = 20 normal-control group; n = 20 moderate degree; n = 20 severe degree) were analyzed on the day of collection (beginning), previously kept under refrigeration (4°C). The other samples were stored (-18°C) for up to 12 mo. At the end of each proposed freezing period (3, 6, 9, and 12 mo), physical and chemical analyses were performed (per period: n = 20 normal-control group; n = 20 moderate degree; n = 20 severe degree). Color (L*, a*, and b*), pH, water-holding capacity, cooking losses, tenderness, lipid oxidation, chemical composition, cholesterol concentration, mineral profile, and collagen concentration were evaluated. The physicochemical quality of wooden chicken breast meat is significantly altered during frozen storage for 12 mo, being of inferior quality when compared to normal chicken breast meat, which can negatively affect consumer acceptance. However, it should be noted that even after 12 mo of freezing, the meats did not show oxidative rancidity.

Insights into Intramuscular Connective Tissue Associated with Wooden Breast Myopathy in Fast-Growing Broiler Chickens

Wooden breast myopathy (WBM) is a meat abnormality affecting pectoralis majors (PMs) of fast-growing broiler chickens. WBM-affected PMs exhibited varied meat qualities with increasing WBM severity. Normal PMs (NOR), mild WBM-affected PMs (MIL), moderate WBM-affected PMs (MOD), and severe WBM-affected PMs (SEV) were selected as raw materials. The structure and organization of connective tissue and fibrillar collagen were investigated through immersing with sodium hydroxide solution, Masson trichrome staining, and using an electron microscope. The mechanical strength of intramuscular connective tissue was analyzed via the shear force of samples treated with sodium hydroxide solution. The thermal property and secondary structure of connective tissue were analyzed by differential scanning calorimetry and Fourier transform infrared spectroscopy. The obtained connective tissue was dissolved in a sodium hydroxide solution for the evaluation of the physicochemical properties of proteins, including particle size, molecular weight, surface hydrophobicity, and intrinsic fluorescence. In particular, the particle size was measured using a zeta potential instrument. The molecular weight was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The surface hydrophobicity and intrinsic fluorescence were measured by spectroscopy technology. Histologically, macrophage infiltration, myodegeneration and necrosis, regeneration, fibrous connective tissue, and thickened perimysial connective tissue were observed in WBM-affected PMs, especially SEV with fibrosis, including blood vessels. Compared with NOR, WBM led to increased average diameter of the collagen fibrils in perimysial (36.61 nm of NOR to 69.73 nm of SEV) and endomysial (34.19 nm of NOR to 56.93 nm of SEV) layers. A significant increase (p < 0.05) was observed in the mechanical strength (2.05 N to 5.55 N) of fresh PMs and the thermal transition temperature (onset temperature (T_O), 61.53 °C to 67.50 °C; maximum transition temperature (T_M), 66.46 °C to 70.18 °C; termination temperature (T_E), 77.20 °C to 80.88 °C) of connective tissue from NOR to SEV. Cooking decreased the mechanical strength, and MOD samples showed the highest mechanical strength (1.24 N, p < 0.05), followed by SEV (0.96 N), MIL (0.93 N), and NOR (0.72 N). For proteins in connective tissue, random coil (19.64% to 29.61%, p < 0.0001), particle size (p < 0.05), and surface hydrophobicity (p < 0.05) increased with the decrease in the α-helix (14.61% to 11.54%, p < 0.0001), β-sheet (45.71% to 32.80%, p < 0.0001), and intrinsic fluorescence of proteins from NOR to SEV. The molecular weights of intramuscular connective tissue proteins were in the ranges of >270 kDa, 180-270 kDa, 110-180 kDa, 95-100 kDa, and <15 kDa. Taken together, WBM resulted in thickened organization, tightly packed collagen fibrils, increased mechanical strength and thermal temperature, and increased particle size, surface hydrophobicity, and intrinsic fluorescence of proteins in connective tissue, as the WBM severity increased.

Changes of Raw Texture, Intramuscular Connective Tissue Properties and Collagen Profiles in Broiler Wooden Breast during Early Storage

A recently identified broiler myopathy known as wooden breast (WB) is predominantly found in the pectoralis major muscle of fast-growing broiler hybrids and is causing significant losses to the poultry industry. The aim of this study was to investigate the effects of WB syndrome on raw meat texture, purge loss and thermal properties of intramuscular connective tissue of pectoralis major muscle in the early postmortem period (1-3 days). Results showed that the presence of the WB muscles condition at 1 day postmortem was associated with significantly increased stiffness (27.0 N vs. 23.1 N) and significantly increased purge loss (1.8% vs. 1.0%) compared to normal breast (NB). However, on 3 days postmortem, these parameters did not differ between WB and NB groups. Insoluble and total collagen content was significantly higher in WB muscles compared to NB muscles, and the extractability of intramuscular connective tissue (IMCT) of WB was also higher (0.42% vs. 0.37%) compared to NB and remained stable in the early postmortem period. There was significantly lower protein content in the sarcoplasmic protein fraction and myofibrillar protein fraction of WB muscles compared to NB muscles (p < 0.05). The IMCT of these two groups showed different thermal properties, as the enthalpy of denaturation (ΔH) was significantly lower in WB muscles compared to NB muscles. The WB syndrome had a great effect on the texture and connective tissue properties of the meat compared to normal muscle, with a tendency for having a lower purge loss and higher raw meat hardness.

Matrix stiffness and architecture drive fibro-adipogenic progenitors' activation into myofibroblasts

Fibro-adipogenic progenitors (FAPs) are essential in supporting regeneration in skeletal muscle, but in muscle pathologies FAPs the are main source of excess extracellular matrix (ECM) resulting in fibrosis. Fibrotic ECM has altered mechanical and architectural properties, but the feedback onto FAPs of stiffness or ECM properties is largely unknown. In this study, FAPs’ sensitivity to their ECM substrate was assessed using collagen coated polyacrylamide to control substrate stiffness and collagen hydrogels to engineer concentration, crosslinking, fibril size, and alignment. FAPs on substrates of fibrotic stiffnesses had increased myofibroblast activation, depicted by αSMA expression, compared to substrates mimicking healthy muscle, which correlated strongly YAP nuclear localization. Surprisingly, fibrosis associated collagen crosslinking and larger fibril size inhibited myofibroblast activation, which was independent of YAP localization. Additionally, collagen crosslinking and larger fibril diameters were associated with decreased remodeling of the collagenous substrate as measured by second harmonic generation imaging. Inhibition of YAP activity through verteporfin reduced myofibroblast activation on stiff substrates but not substrates with altered architecture. This study is the first to demonstrate that fibrotic muscle stiffness can elicit FAP activation to myofibroblasts through YAP signaling. However, fibrotic collagen architecture actually inhibits myofibroblast activation through a YAP independent mechanism. These data expand knowledge of FAPs sensitivity to ECM and illuminate targets to block FAP’s from driving progression of muscle fibrosis.

Improving the poor texture and technological properties of chicken wooden breast by enzymatic hydrolysis and low-frequency ultrasound

Abstract

Wooden breast (WB) is a recurrent myopathy in fast‐growing birds, which alters the appearance, functionality, and the texture of the breast muscle. The objectives of this study were (i) to evaluate the effect of a combined use of papain enzyme and ultrasound on the texture of WB chicken using response surface methodology and (ii) to assess the effect of marinating on the quality of WB chicken meat. Full factorial experimental design method was used to obtain the ideal conditions to soften the WB meat. The independent variables were the concentration of papain (0.1%–0.3%) and the time in ultrasonic bath (10–30 min); shear force (SF) was the dependent variable. The optimum results were obtained at a concentration of 0.2% papain and 20 min on ultrasound. Papain enzyme had a great influence on the texture of WB meat, reducing its hardness. However, the effect of the ultrasound time on the SF response was not observed. The marinated WB meat showed similar SF values and texture profile than those from normal (N) meat, with reduction in the parameters of protein and lipid oxidation. The use of papain without ultrasound bath proved to be an efficient means for improving the tenderness of WB breasts.

Practical Application

This study shows the efficiency of the application of two technological procedures (enzymatic treatment and ultrasound) to improve the texture profile and technological properties of chicken breasts affected by the wooden breast myopathy. The economic loss caused by the world‐wide occurrence of wooden breast is enormous, and the application of papain has been found to counteract the impaired properties of this abnormal chicken breasts. Since papain is already widely used in the food industry to tenderize meat, its application in improving the quality of WB meat is straightforward.

Accumulation of lipofuscin in broiler chicken with wooden breast

Lipofuscin is one of the indicators of oxidative stress. To elucidate the role of oxidative stress in the development of wooden breast, this study investigates lipofuscin accumulation in various parts of wooden breast muscles. Sampling was performed using 46-day-old broiler chickens housed at a commercial Japanese poultry slaughterhouse. Fourteen wooden breast fillets and 13 normal breast fillets were collected in the deboning line. The samples used to measure shear force, 2-thiobarbituric acid reactive substance (TBARS), and for histological analysis were taken from the six portions of breast muscle fillets. In muscles affected by wooden breast, vacuolated muscle fibers were observed, and connective tissues appearing like perimysium were expanded with fibrosis. TBARS value and accumulation of lipofuscin were significantly higher in the wooden breast than in the normal breasts. A lot of lipofuscin granules were localized in the cytoplasm of collapsed muscle fibers of the wooden breast. The cranial portion of the wooden breast showed the highest shear force. The cranial position had a large amount of connective tissue and lipofuscin granules. The results of the present study strongly suggest that high oxidative stress, especially with a significant accumulation of lipofuscin, is associated with the development of wooden breasts.

Alpha-tocopherol acetate and alpha lipoic acid may mitigate the development of wooden breast myopathy in broilers at an early age

1. The objective of this study was to identify the effects of the antioxidant alpha-tocopherol acetate (ATA) and alpha lipoic acid (ALA) which have anti-inflammatory effects on developmental onset, severity and the progression of wooden breast (WB) based on Pectoralis major (P. major) muscle morphology and expression of genes associated with WB during the first three weeks post-hatch.2. A total of 160 newly hatched Ross 708 broiler chicks were randomly assigned in a replicated trial to either a control group or three dietary treatments (ATA 160 mg/kg feed, ALA 500 mg/kg feed or in combination).3. Microscopic changes associated with WB began at one week of age in all groups. The ATA acetate and ALA fed in combination decreased WB severity at two weeks of age (P = 0.05) and ATA alone or in combination reduced severity at three weeks of age compared to the control group (P = 0.05). Expression of myogenic determination factor 1 and peroxisome proliferator-activated receptor gamma was reduced in all dietary treatments compared to the control at three weeks of age (P ≤ 0.05), which suggested reduced muscle degeneration and lipid deposition.4. ATA and ALA fed both independently and in combination had a positive effect on mitigating WB severity microscopically as early as two weeks of age.

A critical review of the mechanisms involved in the occurrence of growth-related abnormalities affecting broiler chicken breast muscles

In the past decade, the poultry industry has faced the occurrence of growth-related muscular abnormalities that mainly affect, with a high incidence rate, the Pectoralis major of the fast-growing genotypes selected for their production performances (high growth rate and breast yield). These myopathies are termed as White Striping, Wooden Breast, and Spaghetti Meat and exhibit distinctive phenotypes. A spatiotemporal distribution has been demonstrated for these disorders as in the early stage they primarily affect the superficial area in the cranial portion of the muscle and, as the birds grow older, involve the entire tissue. Aside from their distinctive phenotypes, these myopathies share common histological features. Thus, it might be speculated that common causative mechanisms might be responsible for the physiological and structural perturbations in the muscle associated with these conditions and might underpin their occurrence. The present review paper aims to represent a critical survey of the outcomes of all the histologic and ultrastructural observations carried out on White Striping, Wooden Breast, and Spaghetti Meat affected muscles. Our analysis has been performed by combining these outcomes with the findings of the genetic studies, trying to identify possible initial causative mechanisms triggering the onset and the time-series of the events ultimately resulting in the development and progression of the growth-related myopathies currently affecting broilers Pectoralis major muscles. Several evidences support the hypothesis that sarcoplasmic reticulum stress, primarily induced an accumulation of misfolded proteins (but also driven by other factors including altered calcium homeostasis and accumulation of fatty acids), may be responsible for the onset of these growth-related myopathies in broilers. At the same time, the development of hypoxic conditions, as a direct consequence of an inadequate vascularization, triggers a time-series sequence of events (i.e., phlebitis, oxidative stress, etc.) resulting in the activation of response mechanisms (i.e., modifications in the energetic metabolism, inflammation, degeneration, and regeneration) which are all strictly related to the progression of these myopathic disorders.

Characterization of Collagen Structure in Normal, Wooden Breast and Spaghetti Meat Chicken Fillets by FTIR Microspectroscopy and Histology

Recently, two chicken breast fillet abnormalities, termed Wooden Breast (WB) and Spaghetti Meat (SM), have become a challenge for the chicken meat industry. The two abnormalities share some overlapping morphological features, including myofiber necrosis, intramuscular fat deposition, and collagen fibrosis, but display very different textural properties. WB has a hard, rigid surface, while the SM has a soft and stringy surface. Connective tissue is affected in both WB and SM, and accordingly, this study's objective was to investigate the major component of connective tissue, collagen. The collagen structure was compared with normal (NO) fillets using histological methods and Fourier transform infrared (FTIR) microspectroscopy and imaging. The histology analysis demonstrated an increase in the amount of connective tissue in the chicken abnormalities, particularly in the perimysium. The WB displayed a mixture of thin and thick collagen fibers, whereas the collagen fibers in SM were thinner, fewer, and shorter. For both, the collagen fibers were oriented in multiple directions. The FTIR data showed that WB contained more β-sheets than the NO and the SM fillets, whereas SM fillets expressed the lowest mature collagen fibers. This insight into the molecular changes can help to explain the underlying causes of the abnormalities.

Pectoralis Major (Breast) Muscle Extracellular Matrix Fibrillar Collagen Modifications Associated With the Wooden Breast Fibrotic Myopathy in Broilers

The poultry industry has placed significant emphasis on the selection of meat-type broilers for increased body weight, increased meat yield especially the pectoralis major (breast) muscle, decreased time to processing, and improved feed conversion_. Although significant improvements have occurred in fast-growing meat-type broilers, myopathies affecting meat quality especially in the pectoralis major muscle have occurred. Many of the broiler breast muscle myopathies are caused by inflammation leading to the necrosis of existing muscle fibers and resulting in replacement of the muscle fibers with extracellular matrix proteins especially fibrillar collagens, fibrosis. This review explores how the fibrotic deposition and organization of extracellular matrix proteins especially the fibrillar collagens, Types I and III, affects the phenotype of the Wooden Breast myopathy, functional properties of the pectoralis major muscle, and meat quality.

Timing Is Everything-The High Sensitivity of Avian Satellite Cells to Thermal Conditions During Embryonic and Posthatch Periods

Myofiber formation is essentially complete at hatch, but myofiber hypertrophy increases posthatch through the assimilation of satellite cell nuclei into myofibers. Satellite cell proliferation and differentiation occur during the early growth phase, which in meat-type poultry terminates at around 8 days posthatch. Thus, any factor that affects the accumulation of satellite cells during late-term embryogenesis or early posthatch will dictate long-term muscle growth. This review will focus on the intimate relationship between thermal conditions during chick embryogenesis and the early posthatch period, and satellite cell myogenesis and pectoralis growth and development. Satellite cells are highly sensitive to temperature changes, particularly when those changes occur during crucial periods of their myogenic activity. Therefore, timing, temperature, and duration of thermal treatments have a great impact on satellite cell activity and fate, affecting muscle development and growth in the long run. Short and mild thermal manipulations during embryogenesis or thermal conditioning in the early posthatch period promote myogenic cell proliferation and differentiation, and have long-term promotive effects on muscle growth. However, chronic heat stress during the first 2 weeks of life has adverse effects on these parameters and may lead to muscle myopathies.