Actinidain-hydrolyzed type I collagen reveals a crucial amino acid sequence in fibril formation

Defective chicken skin collagen molecules, hydrolyzed by actinidain protease, assemble to form loosely packed fibrils that promote cell spheroid formation

Cells recognize collagen fibrils as the first step in the process of adherence. Fibrils of chicken skin actinidain-hydrolyzed collagen (low adhesive scaffold collagen, LASCol), in which the telopeptide domains are almost completely removed, cause adhering cells to form spheroids instead of adopting a monolayer morphology. Our goal was to elucidate the ultrastructure of the LASCol fibrils compared with pepsin-hydrolyzed collagen (PepCol) fibrils. At low concentration of 0.2 mg/mL, the time to reach the maximum increasing rate of turbidity for LASCol was all slower than that for PepCol. Differential scanning calorimetry showed that the thermal stability of collagen self-assembly changed significantly between pH 5.5 and pH 6.6 with and without a small number of telopeptides. However, the calorimetric enthalpy change did not vary much in that pH range. The melting temperature of LASCol fibrils at pH 7.3 was 55.1 °C, whereas PepCol fibrils exhibited a peak around 56.9 °C. The D-periodicity of each fibril was the same at 67 nm. Nevertheless, the looseness of molecular packing in LASCol fibrils was demonstrated by circular dichroism measurements and immuno-scanning electron microscopy with a polyclonal antibody against type I collagen. As there is a close relationship between function and structure, loosely packed collagen fibrils would be one factor that promotes cell spheroid formation.

TGF-β promotes fetal gene expression and cell migration velocity in a wound repair model of untransformed intestinal epithelial cells

The early-phase wound repair response of the intestinal epithelium is characterized by rapid and organized cell migration. This response is regulated by several humoral factors, including TGF-β. However, due to a lack of appropriate models, the precise response of untransformed intestinal epithelial cells (IECs) to those factors is unclear. In this study, we established an in vitro wound repair model of untransformed IECs, based on native type-I collagen. In our system, IECs formed a uniform monolayer in a two-chamber culture insert and displayed a stable wound repair response. Gene expression analysis revealed significant induction of Apoa1, Apoa4, and Wnt4 during the collagen-guided wound repair response. The wound repair response was enhanced significantly by the addition of TGF-β. Surprisingly, addition of TGF-β induced a set of genes, including Slc28a2, Tubb2a, and Cpe, that were expressed preferentially in fetal IECs. Moreover, TGF-β significantly increased the peak velocity of migrating IECs and, conversely, reduced the time required to reach the peak velocity, as confirmed by the motion vector prediction (MVP) method. Our current in vitro system could be employed to assess other humoral factors involved in IEC migration and could contribute to a deeper understanding of the wound repair potentials of untransformed IECs.

Comparison of the Structural Characteristics of Native Collagen Fibrils Derived from Bovine Tendons using Two Different Methods: Modified Acid-Solubilized and Pepsin-Aided Extraction

Native collagen fibrils (CF) were successfully extracted from bovine tendons using two different methods: modified acid-solubilized extraction for A-CF and pepsin-aided method for P-CF. The yields of A-CF and P-CF were up to 64.91% (±1.07% SD) and 56.78% (±1.22% SD) (dry weight basis), respectively. The analyses of both amino acid composition and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed that A-CF and P-CF were type I collagen fibrils. Both A-CF and P-CF retained the intact crystallinity and integrity of type I collagen’s natural structure by FTIR spectra, circular dichroism spectroscopy (CD) and X-ray diffraction detection. The aggregation structures of A-CF and P-CF were displayed by UV–Vis. However, A-CF showed more intact aggregation structure than P-CF. Microstructure and D-periodicities of A-CF and P-CF were observed (SEM and TEM). The diameters of A-CF and P-CF are about 386 and 282 nm, respectively. Although both A-CF and P-CF were theoretically concordant with the Schmitt hypothesis, A-CF was of evener thickness and higher integrity in terms of aggregation structure than P-CF. Modified acid-solubilized method provides a potential non-enzyme alternative to extract native collagen fibrils with uniform thickness and integral aggregation structure.

Reduced nucleotomy-induced intervertebral disc disruption through spontaneous spheroid formation by the Low Adhesive Scaffold Collagen (LASCol)

Back pain is a global health problem with a high morbidity and socioeconomic burden. Intervertebral disc herniation and degeneration are its primary cause, further associated with neurological radiculopathy, myelopathy, and paralysis. The current surgical treatment is principally discectomy, resulting in the loss of spinal movement and shock absorption. Therefore, the development of disc regenerative therapies is essential. Here we show reduced disc damage by a new collagen type I-based scaffold through actinidain hydrolysis-Low Adhesive Scaffold Collagen (LASCol)-with a high 3D spheroid-forming capability, water-solubility, and biodegradability and low antigenicity. In human disc nucleus pulposus and annulus fibrosus cells surgically obtained, time-dependent spheroid formation with increased expression of phenotypic markers and matrix components was observed on LASCol but not atelocollagen (AC). In a rat tail nucleotomy model, LASCol-injected and AC-injected discs presented relatively similar radiographic and MRI damage control; however, LASCol, distinct from AC, decelerated histological disc disruption, showing collagen type I-comprising LASCol degradation, aggrecan-positive and collagen type II-positive endogenous cell migration, and M1-polarized and also M2-polarized macrophage infiltration. Reduced nucleotomy-induced disc disruption through spontaneous spheroid formation by LASCol warrants further investigations of whether it may be an effective treatment without stem cells and/or growth factors for intervertebral disc disease.

Self-assembly of collagen-based biomaterials: preparation, characterizations and biomedical applications

By combining regulatory parameters with characterization methods, researchers can selectively fabricate collagenous biomaterials with various functional responses for biomedical applications.

Kiwifruit cysteine protease actinidin compromises the intestinal barrier by disrupting tight junctions

BACKGROUND

The intestinal epithelium forms a barrier that food allergens must cross in order to induce sensitization. The aim of this study was to evaluate the impact of the plant-derived food cysteine protease--actinidin (Act d1) on the integrity of intestinal epithelium tight junctions (TJs).

METHODS

Effects of Act d1 on the intestinal epithelium were evaluated in Caco-2 monolayers and in a mouse model by measuring transepithelial resistance and in vivo permeability. Integrity of the tight junctions was analyzed by confocal microscopy. Proteolysis of TJ protein occludin was evaluated by mass spectrometry.

RESULTS

Actinidin (1 mg/mL) reduced the transepithelial resistance of the cell monolayer by 18.1% (after 1 h) and 25.6% (after 4 h). This loss of barrier function was associated with Act d 1 disruption of the occludin and zonula occludens (ZO)-1 network. The effect on intestinal permeability in vivo was demonstrated by the significantly higher concentration of 40 kDa FITC-dextran (2.33 μg/mL) that passed from the intestine into the serum of Act d1 treated mice in comparison to the control group (0.5 μg/mL). Human occludin was fragmented, and putative Act d1 cleavage sites were identified in extracellular loops of human occludin.

CONCLUSION

Act d1 caused protease-dependent disruption of tight junctions in confluent Caco-2 cells and increased intestinal permeability in mice.

GENERAL SIGNIFICANCE

In line with the observed effects of food cysteine proteases in occupational allergy, these results suggest that disruption of tight junctions by food cysteine proteases may contribute to the process of sensitization in food allergy.

Elusive Structural, Functional, and Immunological Features of Act d 5, the Green Kiwifruit Kiwellin

Kiwellin (Act d 5) is an allergenic protein contained in kiwifruit pulp in high amounts. The aim of this study was to investigate the three-dimensional structure of the natural molecule from green kiwifruit and its possible function. Kiwellin was crystallized, and its structure, including post-translational modifications, was elucidated. The molecular weight and structural features, in solution, were analyzed by gel filtration and circular dichroism, respectively. Although structurally similar to expansin, kiwellin lacks expansin activity and carbohydrate binding. A specific algorithm was applied to investigate any possible IgE reactivity correlation between kiwellin and a panel of 102 allergens, including expansins and other carbohydrate-binding allergens. The available data suggest a strong dependence of the kiwellin structure on the environmental/experimental conditions. This dependence therefore poses challenges in detecting the correlations between structural, functional, and immunological features of this protein.

A cisplatin derivative that inhibits collagen fibril-formation in vitro

Using an in vitro random screening of small-molecule compounds, we discovered cis-diamminedichloroplatinum(II) (cisplatin), an anticancer agent, as a potential inhibitor of collagen fibril-formation. The inhibitory effect was found only when cisplatin was dissolved in dimethylsulphoxide (DMSO), indicating that the active species were cisplatin derivatives formed in the DMSO solution. The cisplatin derivatives inhibited the formation of collagen fibrils in vitro without affecting the triple-helical conformation of the collagen molecules. Incubation with the cisplatin solution in DMSO also inhibited in situ deposition of collagen fibrils in a human umbilical vein endothelial cell (HUVEC) culture. In addition, the derivatization of cisplatin in DMSO abolished the cytotoxicity of the original compound. The platinum complex was further revealed to interact with specific sites on the collagen triple helix, and the binding sites were suggested to contain His and/or Met residues. Mass spectrometry analysis of the cisplatin solution in DMSO and a structure-activity relationship study strongly suggested that the active compound is [Pt(NH3 )2 (Cl)(DMSO)](+) . This platinum complex will be useful for investigating molecular mechanisms of collagen self-assembly and for drug development for the treatment of fibrotic diseases.

Thermal memory in self-assembled collagen fibril networks

Collagen fibrils form extracellular networks that regulate cell functions and provide mechanical strength to tissues. Collagen fibrillogenesis is an entropy-driven process promoted by warming and reversed by cooling. Here, we investigate the influence of noncovalent interactions mediated by the collagen triple helix on fibril stability. We measure the kinetics of cold-induced disassembly of fibrils formed from purified collagen I using turbimetry, probe the fibril morphology by atomic force microscopy, and measure the network connectivity by confocal microscopy and rheometry. We demonstrate that collagen fibrils disassemble by subunit release from their sides as well as their ends, with complex kinetics involving an initial fast release followed by a slow release. Surprisingly, the fibrils are gradually stabilized over time, leading to thermal memory. This dynamic stabilization may reflect structural plasticity of the collagen fibrils arising from their complex structure. In addition, we propose that the polymeric nature of collagen monomers may lead to slow kinetics of subunit desorption from the fibril surface. Dynamic stabilization of fibrils may be relevant in the initial stages of collagen assembly during embryogenesis, fibrosis, and wound healing. Moreover, our results are relevant for tissue repair and drug delivery applications, where it is crucial to control fibril stability.