Changes In Collagen Fibers Research Articles

Myocardial interstitial fibrosis in different cardiomyopathies as a basis of heart failure

Myocardial interstitial fibrosis (MIF) occurs in several ischemic and non-ischemic cardiomyopathies and is associated with left ventricular dysfunction and progression to heart failure (HF). MIF exists in two types – reparative and reactive with different origin and molecular mechanisms. Although MIF arises mainly because of alterations in collagen turnover leading to collagen fiber accumulation, there are also qualitative changes in collagen fibers in cardiac diseases. There are several studies for cellular and molecular mechanisms and his role in cardiac function, biomarkers and potential target therapies.

Automatic wound closure system: closure of large wounds by stretching the skin around the wound.

Large-wound treatment often requires autologous skin grafting or skin flap transfer, causing iatrogenic secondary injuries. Thus, we have developed an automatic wound closure system that consists of a stretch module, microcontroller, and touch screen. Full-thickness wounds (8 × 14cm) on Bama miniature pigs were manually closed by direct suture in control animals and with three different tension levels performed by the automatic device in the experimental animals. Wound-closure conditions, post-closure healing, and scars were evaluated. Post-operative microscopic changes in collagen fibers, local cell apoptosis, and changes in vascular density were compared between the two wound-closure techniques. In the control group and the first experimental group, which used a traction force of 15 N, primary wound closure could not be achieved. The other two experimental groups used a traction force of 30 N and 60 N and all wounds achieved primary closure. Collagen-fiber stretching was observed histologically in all groups and collagen-fiber breakdown occurred in some wounds when the traction force was 60 N. Scar hyperplasia was significantly reduced in the automatic wound closure system groups. The collagen content decreased, cell apoptosis increased, and vascular density decreased in local tissues in the early post-closure stage, but eventually recovered to normal-skin levels. In summary, we developed an automatic wound closure system that effectively and safely stretches dermal-collagen fibers under an appropriate traction force (30 N) and stretch wound-peripheral skin to cover the wound, achieve primary closure, and reduce scar hyperplasia.

Біофізичні властивості шкіри щурів із метаболічним синдромом

It is known that metabolic syndrome (MS) prolongs the healing time of the wound surface of various genesis. We hypothesized that this may be related to changes in the biophysical properties of the skin. The aim of the work was to investigate the biophysical properties of skin (content of moisture, collagen, fused gelatin in the skin, and skin thermal fusion temperature) in rats with MS. Materials and methods. Research was conducted on 40 white non-linear rats (20 – males, 20 – females). After birth, males and females were divided into 2 groups. The first group served as a control for the second groups, in which MS was simulated by administering monosodium glutamate at a dose of 4.0 mg/kg on the 2nd, 4th, 6th, 8th, and 10th postnatal days. At the age of 4 months, the animals were decapitated under ether anesthesia. Biochemical studies were conducted to confirm the development of MS. The percentage of moisture, collagen content, destructive changes in collagen fibers and resistance of skin collagen to thermal factors were determined in native skin. The results. 4-month-old rats injected with monosodium glutamate in the early neonatal period developed MS as evidenced by abdominal obesity, insulin resistance, and dyslipidemia. In comparison with animals of the control group, in the skin of male and female rats with MS, the moisture content decreased, and the collagen content did not change. At the same time, the percentage of melted gelatin doubled, which indicates the depth of destructive changes in collagen fibers. Thermal welding of skin samples of male and female rats with signs of MS occurred at rather low temperatures compared to rats of the control group. Conclusion. Changes in the biophysical properties of the skin, which are registered in rats with MS, may be the reason for the later closure of the wound surface.

The role and mechanism of macrophage autophagy in the experimental model of chronic obstructive pulmonary disease.

Macrophages play an important role in chronic obstructive pulmonary disease (COPD). Cigarette smoke (CS) impairs autophagy in alveolar macrophages from COPD patients, and autophagic impairment leads to reduced clearance of protein aggregates, dysfunctional mitochondria, and defective bacterial delivery to lysosomes. However, the exact function of lung macrophage autophagy in the pathogenesis of CS-induced COPD remains largely unknown. Western blot detected the expression of autophagy-related proteins induced by CSE. The model of COPD mice was established by CS exposure combined with CSE intraperitoneal injection. Double immunofluorescence was used to measure the CD206+LC3B+ cells. The morphological changes and effects on lung function were observed. Masson staining detected the changes in collagen fibers in lung tissue. The expression levels of E-cadherinb and N-cadherinb were detected by immunohistochemistry. Western blot detected the expression of ATP6V1E1 in lung tissue. At 24 hours of exposure to CSE, the expression levels of LC3B (microtubule-associated protein 1A/1B-light chain 3B) and P62 (nucleoporin 62) were highest at 1% CSE and AGT5 (nucleoporin 62) at 2.5% CSE; at 48 hours, the expression levels of LC3B, P62 and AGT5 were highest at 2.5% CSE, and as the intervention time increased.CD206+LC3B+ cells were significantly higher in the COPD group. Enhanced macrophage autophagy may promote emphysema formation and aggravate lung function damage. The expression of E-cadherinb in lung tissue of the COPD group was decreased, and N-cadherinb expression was increased; the expression of E-cadherinb was increased, and N-cadherinb expression was decreased in ATG5myeΔ COPD mice. The expression of ATP6V1E1 in the lung tissue was increased in the COPD group; ATP6V1E1 expression was decreased in the lung tissues of ATG5myeΔ COPD mice. CSE enhanced macrophage autophagy, leads to increased lung function impairment and collagenous fiber in lung tissue, as well as promotes epithelial-mesenchymal transition, and eventually leads to small airway remodeling, which may be achieved through the ATG5/ATP6V1E1 pathway.

Label-free assessment of pathological changes in pancreatic intraepithelial neoplasia by biomedical multiphoton microscopy.

Pancreatic intraepithelial neoplasia (PanIN) is the most common precursor lesion that has the potential to progress to invasive pancreatic cancer, and early and rapid detection may offer patients a chance for treatment before the development of invasive carcinoma. Therefore, the identification of PanIN holds significant clinical importance. In this study, we first used multiphoton microscopy (MPM) combining two-photon excitation fluorescence and second-harmonic generation imaging to label-free detect PanIN and attempted to differentiate between normal pancreatic ducts and different grades of PanIN. Then, we also developed an automatic image processing strategy to extract eight morphological features of collagen fibers from MPM images to quantify the changes in collagen fibers surrounding the ducts. Experimental results demonstrate that the combination of MPM and quantitative information can accurately identify normal pancreatic ducts and different grades of PanIN. This study may contribute to the rapid diagnosis of pancreatic diseases and may lay the foundation for further clinical application of MPM.

Histoarchitecture of stromal collagen fibers in gastrointestinal hollow organs of mice after a 30-day space flight

The digestive organs are highly sensitive to the influence of orbital flight factors and can limit the professional activities of crew members aboard the International Space Station. Connective tissue, as a system-forming matrix of the integrative-buffer metabolic environment, is of particular relevance in space biomedicine, ensuring the functioning of internal organs under an altered gravitational stimulus. However, the adaptive mechanisms of the fibrous extracellular matrix of the gastric and intestinal connective tissue have not been fully investigated under prolonged microgravity weightlessness. Using histochemical techniques, we experimentally studied the state of collagen fibers in the specific tissue microenvironment of the gastric and intestinal membranes in C57BL/6 N mice after a 30-day space flight, subsequent 7-day ground readaptation, and in animals of the relevant control groups. The 30-day stay of laboratory animals aboard the Bion-M 1 biosatellite resulted in a reduction in the fibrous extracellular matrix of connective tissue in the studied digestive organs, excepting the gastric lamina propria. Increased fibrillogenesis was revealed in the gastrointestinal mucous membranes of animals 7 days after biosatellite landing compared with the parameters of animals in the space flight group. During the experiment with ground simulated orbital flight conditions, changes in collagen fibers were not significant compared to the vivarium control group. Thus, the results obtained evidence gravisensitivity of the fibrous extracellular matrix of the intraorgan connective tissue. This fact also highlights the necessity to further improve gastrointestinal tract-related preventive measures for astronauts during orbital flight.

Effects of Flavonoid and Saponins on Protecting HaCaT Cells and Ameliorating Ultraviolet Radiation B/Ultraviolet Radiation A-Induced Skin Photoaging

The skin serves as a natural barrier in the human body, protecting against pathogenic microorganisms and ultraviolet radiation (UV). Skin photoaging is a physiological stress reaction characterized by skin relaxation, dryness, abnormal pigmentation, and increased wrinkles due to prolonged exposure to ultraviolet radiation. The search and development of natural products that can effectively prevent skin photoaging have gained significant attention. We established the photoaging model by subjecting HaCaT cells and ICR mice to UVB+UBA irradiation. We employed CCK8 to assess the impact of Totol Flavonoid of Lichi Seed (TFLS) and Lychee Seed Saponins (LSS) on cell viability. We evaluated the effects of TFLS and LSS on apoptosis using flow cytometry. We utilized SIRT-IN-1 inhibitor to suppress the activity of SIRT1 and examined the mechanism by which TFLS and LSS alleviate UV-induced photoaging damage in cells and mice. We assessed skin inflammation in photoaging ICR mice through HE staining. We evaluated changes in collagen fibers and glia in the skin of photoaging ICR mice using Masson staining. We employed TUNEL staining to evaluate the apoptosis of skin cells in photoaging ICR mice. We extracted nucleic acid using nano-magnetic beads and detected the expression of SIRT1, TGF-β1, and Smad3 in HaCaT cells and mouse skin tissues using qPCR and WB. The study results demonstrate the protective effect of TFLS and LSS against UV-induced photoaging in HaCaT cells and ICR mouse skin, mitigating the damage caused by UV exposure. The mechanism underlying the attenuation of UV-induced photoaging by TFLS and LSS may involve activation of the SIRT1-TGF-β1/Smad3 signaling pathway.

Identification of an ADAMTS2 frameshift variant in a cat family with Ehlers-Danlos syndrome.

We investigated 4 European domestic shorthair kittens with skin lesions consistent with the dermatosparaxis type of the Ehlers-Danlos syndrome, a connective tissue disorder. The kittens were sired by the same tomcat but were born by 3 different mothers. The kittens had easily torn skin resulting in nonhealing skin wounds. Both clinically and histologically, the skin showed thin epidermis in addition to inflammatory changes. Changes in collagen fibers were visible in electron micrographs. The complete genome of an affected kitten was sequenced. A one base pair duplication leading to a frameshift in the candidate gene ADAMTS2 was identified, p.(Ser235fs*3). All 4 affected cats carried the frameshift duplication in a homozygous state. Genotypes at this variant showed perfect cosegregation with the autosomal recessive Ehlers-Danlos syndrome phenotype in the available family. The mutant allele did not occur in 48 unrelated control cats. ADAMTS2 loss-of-function variants cause autosomal recessive forms of Ehlers-Danlos syndrome in humans, mice, dogs, cattle, and sheep. The available evidence from our investigation together with the functional knowledge on ADAMTS2 in other species allows to classify the identified ADAMTS2 variant as pathogenic and most likely causative variant for the observed Ehlers-Danlos syndrome.

Detection of fibrotic changes in the progression of liver diseases by label-free multiphoton imaging.

Collagen fibers play an important role in the progression of liver diseases. The formation and progression of liver fibrosis is a dynamic pathological process accompanied by morphological changes in collagen fibers. In this study, we used multiphoton microscopy for label-free imaging of liver tissues, allowing direct detection of various components including collagen fibers, tumors, blood vessels, and lymphocytes. Then, we developed a deep learning classification model to automatically identify tumor regions, and the accuracy reaches 0.998. We introduced an automated image processing method to extract eight collagen morphological features from various stages of liver diseases. Statistical analysis showed significant differences between them, indicating the potential use of these quantitative features for monitoring fibrotic changes during the progression of liver diseases. Therefore, multiphoton imaging combined with automatic image processing method would hold a promising future in rapid and label-free diagnosis of liver diseases.

#3197 A NOVEL INVESTIGATION OF AVF WITH A SECOND HARMONIC GENERATION MICROSCOPY IN PATIENTS WITH END STAGE RENAL DISEASE

Abstract Background and Aims The population of patients with end-stage renal disease is rapidly growing and hemodialysis (HD) remains the most common treatment option. In clinical practice, the formation of arteriovenous fistulas (AVFs) is considered a priority in order to ensure optimal vascular access for HD patients. One of the complications in the formation of AVF is the hyperplasia of the neointimal layer of the vein, which leads to the failure of the fistula. The impact of the arrangement of collagen fibers in the veins of AVFs is little studied and opens wide opportunities for investigations. The structural tissue can be imaged with polarimetric nonlinear microscopy. Collagen fibers have a non-centrosymmetric structure, so they can be effectively imaged by second harmonic generation (SHG) microscopy [1]. The polarimetric nonlinear microscopy, exploiting the multidimentional tensor nature of light-matter interactions, is emerging as a valuable research tool in biomedical investigations and applications to digital pathology, and is only now becoming technically feasible for potential clinical translation [2,3]. This proposal represents a novel application of multimodal polarimetric nonlinear microscopy in histopathology, and biomedical imaging. The aim of this study is to determine the influence of the arrangement of collagen fibers in veins on the formation efficiency of AVFs by using the innovative method of nonlinear SHG microscopy. Method In this prospective study, we first used a novel SHG microscopy method to investigate AVFs venous intima hyperplasia. V. Cephalica segment is being obtained during arteriovenous fistula formation surgery from patients with end stage renal disease and after the removal of aneurysmatic or fibrotic AVF. Cross-sections of venous specimens are being fixed in 10% buffered formalin and stained with hematoxylin and eosin (H&E). Further, sample investigation is being performed in Laser Research Centre, Vilnius University using a home-built multiphoton laser-scanning microscope. The investigation is being performed with the permission of Lithuanian Biomedical Research Ethics Committee. Results We determined the arrangement of collagen fibers in veins before AVF formation and after the removal of aneurysmatic AVFs. It was observed that tunica intima of V. Cephalica is dominated both by endothelial cells and connective tissue made up of high-density collagen fibers. Whereas tunica adventitia consists mainly of collagen fibers. Collagen in tunica intima and adventitia are found to be highly noncentrosymmetric. Thus a strong SHG signal, resulting in high-contrast structural visualization of the V. Cephalica segment is generated. Conclusion Our initial investigations of AVF show clearly visible collagen fibers. The future work will focus on the structural changes of collagen fibers in the vein intimal hyperplasia. Further investigations need to be done to create artificial intelligence-based identification of new predictive collagen markers.

Dynamic evaluation of pathological changes in a mouse acne model by optical imaging technology.

Acne vulgaris is a disorder of the pilosebaceous unit that is primarily caused by hyperseborrhoea, colonization with Propionibacterium acnes, hyperkeratosis and an inflammatory response. Existing pharmacodynamic assessment methods primarily focus on a single causative factor at a certain time point, making it difficult to assess multiple factors simultaneously in real time. Therefore, it is crucial to establish a dynamic and nondestructive method for the assessment of acne in vivo. This study utilized four-dimensional optical imaging techniques to assess the pathogenic factors and pathological progression of acne. LSCI was employed to measure blood flow; TPEF was used to observe inflammatory changes (NAD(P)H) in epidermal granular layer cells and structural changes in collagen fibres in the dermal layer. Additionally, the dermatoscope was used to investigate the micro-characterization of the lesions. We observed that the epidermis in the lesion area was thickened, hair follicles were keratinized, and there was obvious inflammation and blood flow aggregation by optical imaging technology. Based on these findings, the pathological progression of this acne model could be divided into the inflammation phase, accompanied by bacterial colonization, and the reparative phase. These results provide a new perspective for the assessment of acne and offer an experimental basis for the selection of precise drugs for clinical use.

Optical second-harmonic generation imaging for identifying gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors arising in the digest tract. It brings a challenge to diagnosis because it is asymptomatic clinically. It is well known that tumor development is often accompanied by the changes in the morphology of collagen fibers. Nowadays, an emerging optical imaging technique, second-harmonic generation (SHG), can directly identify collagen fibers without staining due to its noncentrosymmetric properties. Therefore, in this study, we attempt to assess the feasibility of SHG imaging for detecting GISTs by monitoring the morphological changes of collagen fibers in tumor microenvironment. We found that collagen alterations occurred obviously in the GISTs by comparing with normal tissues, and furthermore, two morphological features from SHG images were extracted to quantitatively assess the morphological difference of collagen fibers between normal muscular layer and GISTs by means of automated image analysis. Quantitative analyses show a significant difference in the two collagen features. This study demonstrates the potential of SHG imaging as an adjunctive diagnostic tool for label-free identification of GISTs.

Collagen fiber anisotropy characterization by polarized photoacoustic imaging for just-in-time quantitative evaluation of burn severity

Just-in-time burn severity assessment plays a vital role in burn treatment and care. However, it is still difficult to quantitatively and promptly evaluate burn severity by existing medical imaging methods via initial burn depth measurement since burn wounds are usually dynamically developed. As an elastic skeleton of skin, the degree of conformational changes of collagen fibers caused by overheating can reflect the burn severity in a timelier manner. Herein, the polarized photoacoustic technique (PPAT) for just-in-time quantitative evaluation of burn severity via collagen fiber anisotropy assessment is proposed. First, phantom experiments demonstrate the ability of PPAT for deep imaging in a transport mean free path and accurately quantify changes in microstructural order by thermal damage. Then, the Pearson correlation coefficient of the PPAT in assessing burn severity is shown to be up to 0.95, validated by burn skin samples. The PPAT provides a just-in-time quantitative strategy for burn severity evaluation.

Three-dimensional remodeling of collagen fibers within cervical tissues in pregnancy

The cervix is a collagen-rich connective tissue that must remain closed during pregnancy while undergoing progressive remodeling in preparation for delivery, which begins before the onset of the preterm labor process. Therefore, it is important to resolve the changes of collagen fibers during cervical remodeling for the prevention of preterm labor. Herein, we assessed the spatial organization of collagen fibers in a three-dimensional (3D) context within cervical tissues of mice on day 3, 9, 12, 15 and 18 of gestation. We found that the 3D directional variance, a novel metric of alignment, was higher on day 9 than that on day 3 and then gradually decreased from day 9 to day 18. Compared with two-dimensional (2D) approach, a higher sensitivity was achieved from 3D analysis, highlighting the importance of truly 3D quantification. Moreover, the depth-dependent variation of 3D directional variance was investigated. By combining multiple 3D directional variance-derived metrics, a high level of classification accuracy was acquired in distinguishing different periods of pregnancy. These results demonstrate that 3D directional variance is sensitive to remodeling of collagen fibers within cervical tissues, shedding new light on highly-sensitive, early detection of preterm birth (PTB).

Influence of plasma activation nanostructure collagen on process structurization without chrome a fur sheepskin

The influence of water-soluble non-isocyanate urethanglicol and plasma treatment on changes in the nanostructure of collagen in the process of organic tanning is investigated. Plasma modification leads to conformational changes in collagen fibers which contributes to increase in the diffusion of structuring agents into the sense of capillary-porous material. Input parameters of plasma processing determined. Pilot tests of the proposed technology led to the production of a semi-finished product of fur sheepskin with increased values of physical, mechanical and operational indicators in comparison with the control.

Extracellular Matrix-Oriented Proteomic Analysis of Periodontal Ligament Under Mechanical Stress.

The periodontal ligament (PDL) is a specialized connective tissue that provides structural support to the tooth and is crucial for oral functions. The mechanical properties of the PDL are mainly derived from the tissue-specific composition and structural characteristics of the extracellular matrix (ECM). The ECM also plays key roles in determining cell fate in the cellular microenvironment thus crucial in the PDL tissue homeostasis. In the present study, we determined the comprehensive ECM profile of mouse molar PDL using laser microdissection and mass spectrometry-based proteomic analysis with ECM-oriented data curation. Additionally, we evaluated changes in the ECM proteome under mechanical loading using a mouse orthodontic tooth movement (OTM) model and analyzed potential regulatory networks using a bioinformatics approach. Proteomic changes were evaluated in reference to the novel second harmonic generation (SHG)-based fiber characterization. Our ECM-oriented proteomics approach succeeded in illustrating the comprehensive ECM profile of the mouse molar PDL. We revealed the presence of type II collagen in PDL, possibly associated with the load-bearing function upon occlusal force. Mechanical loading induced unique architectural changes in collagen fibers along with dynamic compositional changes in the matrisome profile, particularly involving ECM glycoproteins and matrisome-associated proteins. We identified several unique matrisome proteins which responded to the different modes of mechanical loading in PDL. Notably, the proportion of type VI collagen significantly increased at the mesial side, contributing to collagen fibrogenesis. On the other hand, type XII collagen increased at the PDL-cementum boundary of the distal side. Furthermore, a multifaceted bioinformatics approach illustrated the potential molecular cues, including PDGF signaling, that maintain ECM homeostasis under mechanical loading. Our findings provide fundamental insights into the molecular network underlying ECM homeostasis in PDL, which is vital for clinical diagnosis and development of biomimetic tissue-regeneration strategies.

Mapping Organizational Changes of Fiber‐Like Structures in Disease Progression by Multiparametric, Quantitative Imaging

AbstractWith the progression of diseases, modified cell–matrix interactions have major effects not only upon key cellular functions but also upon the structure of extracellular matrix and vasculature, which are two of the most prevalent fiber‐like structures in biological tissues. Unfortunately, quantitative approaches to assessing these structural changes are lacking. Herein, a multiparametric imaging system is established to resolve subtle organizational changes of collagen fibers and vasculature in disease progression. The pixel‐wise, automated waviness (paWav) is developed as a novel biomarker, and a multimodal analysis system combining paWav with orientation and alignment assessments is constructed. Aggregation‐induced emission luminogens (AIEgens) with second near‐infrared excitation or emission are developed for in vivo deep‐penetration vasculature imaging. The organization remodeling of cortical blood vessels in stroke in marmosets is quantitatively characterized using biologically excretable AIE dots that highlight the clinical translation potential, and a distance dependence law in vessel morphological remodeling is identified. Finally, the multiparametric analysis relying completely on collagen fiber signatures successfully differentiates cancerous from normal pancreatic tissues using a predictive classification approach. Collectively, the combined use of these structural changes in fibrillar tissue components may enable a better understanding of cell–matrix interactions in pathogenesis and identification of new potential treatment targets.

The role of cathepsin L on structural changes of collagen fibers involved in textural deterioration of chilled grass carp (Ctenopharyngodon idella) fillets.

Textural deterioration is a serious problem in chilled fish flesh. Cysteine proteinases are proposed to participate in disintegration of collagen fibers during this process, while its mechanism remains elusive. In the present study, a cysteine proteinase was purified from grass carp muscle and identified by mass spectrometry, and its effect on structural changes of collagen fibers was investigated. During storage at 4°C, cysteine proteinase activity in fillets increased to 1.53-fold at day 5 and maintained a high level later, and this variable was related to a decline in shear force and an increase in drip loss. A 29 kDa cysteine proteinase was purified through ammonium sulfate precipitation and column chromatography, and identified as cathepsin L. Cathepsin L caused collagen fibers to partly disintegrate into fibril bundles and individual fibrils at 48 h, while the triple helical structure of collagen molecules remained stable. Release of soluble proteins and glycosaminoglycans from cathepsin L-treated collagen fibers was time dependent, coinciding with a release of 4.12 ± 0.13% and 8.57 ± 0.03% at 48 h respectively. However, 0.85 ± 0.02% of hydroxyproline was freed from cathepsin L-treated collagen fibers at 48 h. Furthermore, scanning electron microscopy revealed that the inhibitory effect of cathepsin L could retard the destruction of intramuscular connective tissues (IMCTs). These results indicated that cathepsin L might be involved in collagen fiber breakdown by degrading collagen-associated proteoglycans during textural deterioration of grass carp. © 2022 Society of Chemical Industry.

Mineral dysmetabolism in corneal diseases

Functional status and biological properties of connective tissues significantly depend on the mineral elements involved in their metabolism. Connective tissue portion of the corneal stroma makes up most of its thickness; pathological changes in collagen fibers and the stroma can cause a range of corneal diseases, some of which are specifically associated with disorders of mineral metabolism. The article considers impairments of mineral metabolism as possible pathophysiological mechanisms in certain diseases and disorders of the cornea, and describes in detail the abnormalities associated with mineral dysmetabolism observed in patients with keratoconus.

The role of endogenous serine proteinase on disintegration of collagen fibers from grass carp (Ctenopharyngodon idellus)

Softening, causing by the degradation of collagen, leads to serious quality deterioration of fish fillets during post-mortem storage. In order to study the role of endogenous enzymes in softening of fish muscle, collagen fibers from grass carp (Ctenopharyngodon idellus) were degraded by serine proteinase. The structural and biochemical changes of collagen fibers with serine proteinase digestion were investigated in terms of scanning electron microscopy, fourier transform infrared spectroscopy, electrophoresis and chemical analysis. In the present study, an endogenous proteinase (approximately 250 kDa) with gelatinolytic activity was isolated from grass carp muscle by ammonium sulfate precipitation and column chromatographies, and identified as serine proteinase. Collagen fibers were partly disaggregated into collagen fibrils after serine proteinase treatment for 48 h, coinciding with a release of hydroxyproline (5.56 ± 0.02%) and glycosaminoglycans (9.04 ± 0.03%). However, almost all gelatin and 40% of acid-soluble collagen were degraded within 1 h and 6 h, respectively. Meanwhile, serine proteinase-treated collagen fibers maintained the triple-helical structure of collagen molecule, while their thermal stability was gradually decreased with digestion time. All results indicated that disintegration of collage fibers by serine proteinase might be due to both the degradation of proteoglycans and collagen molecules during textural deterioration of chilled grass carp fillets.