丝素蛋白材料在皮肤创伤愈合中的研究进展

摘要：丝素蛋白是一种天然的高分子纤维蛋白,其结构的特殊性决定了较好的机械性能,再因其优良的生物相容性、降解产物无毒等特点,被广泛用于各种材料的研究。通过各种化学修饰和负载生长因子等,使丝素蛋白在体内外具有促进成纤维细胞增殖分化的作用,拥有诱导创面愈合的功能,同时其可部分降解,具有缓释性能好,柔韧性强,透气以及透水等较好的理化性质不但在皮肤组织工程学中的广泛的应用,并且在敷料领域的研究也显示了其治疗烧烫伤、创伤达到抑制疤痕、促进伤口快速愈合的治疗效果。总之,通过改良丝素蛋白材料的加工方法,通过化学修饰、其他物质复合等手段得到适合于皮肤修复的具有优良性能的各种材料,是具有很大潜力的极具临床价值的皮肤修复材料。本文旨在综述国内及国外学者的各种关于丝素蛋白生物材料治疗皮肤损伤的研究最新进展。     

担载神经生长因子(NGF)的乳液法涂层纤维体外缓释研究

目的:目前周围神经修复中,神经导管是研究热点,本文研究乳液法涂层纤维制备的神经导管在神经修复中应用的可能性。方法:本文采用乳液法制备担载NGF的丝素-聚乳酸(PLLA)涂层电纺纤维,观察纤维的形态,测定NGF的体外释放动力学参数,并考察纤维释放液对于PC12细胞增殖的影响。结果:担载NGF的涂层纤维具备类似于细胞外基质(ECM)的三维结构和多孔形态;涂层纤维中NGF体外有效缓释10天;细胞实验中,在含有释放液的培养基中生长的PC12细胞,与空白对照组相比,荧光强度平均多了2000-4000个荧光强度,所以释放液可以更好地促进PC12细胞的增殖。结论:担载NGF的乳液法涂层纺丝纤维具备促进缺损周围神经修复的条件,可以进一步研究在动物体内修复缺损周围神经中的效果,为以后的临床应用打下基础。     

The caddisfly Ceraclea fulva and the freshwater sponge Ephydatia fluviatilis: a successful relationship

The association between the aquatic phases of the caddisfly Ceraclea fulva (Trichoptera, Leptoceridae) and the freshwater sponge Ephydatia fluviatilis (Porifera, Spongillidae) has been investigated by means of scanning and transmission electron microscopy (SEM, TEM). Ceraclea fulva habitually feeds on sponges and builds its case by using the siliceous spicules of the sponge, which are arranged side by side, inter-crossed, cemented with silk, and organised in layers. In the newly hatched larva, the case is strengthened exclusively by cemented siliceous spicules, while during growth, the insect adds sponge fragments to it. The fine organisation of the sponge tissues growing on the case proves that the sponge is functional. Inter-spaced, small protrusions, derived from the outermost compact silk layer, form a series of "bridges" enhancing case/sponge adhesion. Tube-case shape varies according to the aquatic developmental phase of the insect: in the mature larva and pupa, this shelter carries larger sponge fragments dorsally. The caddisfly acts as carrier of the sponge, thus facilitating its dispersal and the colonisation of new habitats. This justifies regarding this association as a successful mutualistic relationship, and not as a unilateral parasitic behaviour on the part of the insect.     

Extraordinary Conservation of Cysteines Among Homologous Chironomus Silk Proteins sp185 and sp220

Aquatic larvae of the midge, Chironomus tentans, synthesize a 185-kDa silk protein (sp185) with the cysteine-containing motif Cys-X-Cys-X-Cys (where X is any residue) every 20–28 residues. We report here the cloning and full-length sequence of cDNAs encoding homologous silk proteins from Chironomus pallidivittatus (sp185) and Chironomus thummi (sp220). Deduced amino acid sequences reveal proteins of nearly identical mass composed of 72 blocks of 20–28 residues, 61% of which can be described by the motif X_5–8-Cys-X₅-(Trp/Phe/Tyr)-X₄-Cys-X-Cys-X-Cys. Spatial arrangement of these residues is preserved more than surrounding sequences. cDNA clones enabled us to map the genes on polytene chromosomes and identify for the first time the homolog of the Camptochironomus Balbiani ring 3 locus in Chironomus thummi. The apparent molecular weight difference between these proteins (185 vs 220 kDa) is not attributable to primary structure and may be due to differential N-linked glycosylation. DNA distances and codon substitutions indicate that the C. tentans and C. pallidivittatus genes are more related to each other than either is to C. thummi; however, substitution rates for the 5′- and 3′-halves of these genes are different. Blockwise sequence comparisons suggest intragenic variation in that some regions evolved slower or faster than the mean and may have been subjected to different selective pressures. Received: 30 August 1996 / Accepted: 6 November 1996     

The salivary secretion of spinning larvae ofRhynchosciara americana

Summary The secretion present at the lumen of the salivary glands of spinning larvae ofRhynchosciara americana was studied cytochemically and with microspectrophotometry and fluorescence and quantitative polarization microscopy. It was found that structural proteins, including glycoproteins and lipoproteins, occur in this secretion. Findings involving spectral absorption profiles after xylidine ponceau staining, patterns of birefringence and dispersion of birefringence, and lack of dichroism after xylidine ponceau staining and of blue fluorescence after ANS staining are highly suggestive that the secretion ofR. americana differs from classical silks not only in terms of composition but also of macromolecular array. The silk secretion ofR. americana also appears to differ from that of another sciarid,Bradysia spatitergum. Part of the glycoproteins present at the glandular lumen is assumed to be extruded from cells of the posterior zone of the glands, whereas other glycoproteins (or their glycidic radicals) are probably removed from fat body cells via cells of the anterior zone of the glands. The salivary secretion of the spinning larvae ofR. americana contains calcium and is devoid of acid glycosaminoglycans.     

Spidroin N-terminal domain promotes a pH-dependent association of silk proteins during self-assembly

Spider silks are spun from concentrated solutions of spidroin proteins. The appropriate timing of spidroin assembly into organized fibers must be highly regulated to avoid premature fiber formation. Chemical and physical signals presented to the silk proteins as they pass from the ampulle and through the tapered duct include changes in ionic environment and pH as well as the introduction of shear forces. Here, we show that the N-terminal domain of spidroins from the major ampullate gland (MaSp-NTDs) for both Nephila and Latrodectus spiders associate noncovalently as homodimers. The MaSp-NTDs are highly pH-responsive and undergo a structural transition in the physiological pH range of the spider duct. Tryptophan fluorescence of the MaSp-NTDs reveals a change in conformation when pH is decreased, and the pH at which the transition occurs is determined by the amount and type of salt present. Size exclusion chromatography and pulldown assays both indicate that the lower pH conformation is associated with a significantly increased MaSp-NTD homodimer stability. By transducing the duct pH signal into specific protein-protein interactions, this conserved spidroin domain likely contributes significantly to the silk-spinning process. Based on these results, we propose a model of spider silk assembly dynamics as mediated through the MaSp-NTD.     

Reducing blood glucose level in TIDM mice by orally administering the silk glands of transgenic hIGF-I silkworms

To realize the secretory expression of human insulin-like growth factor-I (hIGF-I) in the posterior silk glands (PSGs) of transgenic silkworms, the piggyBac transposon vector pigA3GFP-fibHS-hIGF-i.e.-neo containing a neomycin-resistance gene (neo), green fluorescent protein gene (gfp) and human insulin-like growth factor I (hIGF-I) gene controlled by the Bombyxmori fibroin heavy chain gene (fib-H) promoter with its downstream signal peptide sequence, and a helper plasmid containing the piggyBac transposase sequence under the control of the B. mori actin 3 gene (A3) promoter were transferred into silkworm eggs by sperm-mediated gene transfer. Transformed silkworms were obtained after being screened for green fluorescence and by the antibiotic G418. In the PSGs of the transformed silkworms, a specific band representing hIGF-I could be detected by Western blotting, and the content of the hIGF-I estimated by ELISA was approximately 1.84 μg/gram of cocoon and 19.18 μg/gram of freeze-dried PSG powder. To further estimate the biological activity of the expressed hIGF-I, streptozotocin-induced TIDM mice were orally administered with the PSG powder of the transgenic silkworms, the results showed the blood glucose levels of mice were significantly reduced, suggesting that the the PSGs powder of transgenic hIGF-I silkworms could possibly be used as a perorally administered medicine.     

Proteome profile of spinneret from the silkworm,Bombyx mori

The silkworm spinneret is an important tissue for silk fibrillogenesis and spinning. All biochemical processes during silk fibrillogenesis are correlated with silk properties. Understanding the role of spinneret in silk fibrillogenesis may help to reveal the mechanism of silk fibrillogenesis as well as improve silk quality for commercial purposes. Thus, we profiled the proteome of silkworm spinneret. A total of 1572 proteins and 232 differential abundance proteins were identified. Silk fibrillogenesis‐related proteins, such as cuticle proteins, ion‐transporting proteins, muscular proteins, and energy metabolic proteins, were abundant in spinneret. Metabolic pathway and GO enrichment analyses revealed that the identified proteins were involved in energy metabolism, chitin binding, and cuticle construction. Active energy metabolism may provide abundant energy for the muscle contraction as well as ion and water exchange. The chitin binding and cuticle construction process may provide sufficient shear forces for silk formation. Our data suggest that silkworm spinneret provides a suitable physiological and biochemical environment for silk fibrillogenesis. These proteins are potential targets for improving silk quality in the silk industry. Data are available via ProteomeXchange with identifier PXD004455.     

The second introduction of a non-native Embioptera to Korea via ornamental plants: Evaluating DNA barcoding to prepare for a global inflow of unfamiliar taxa

This study reports a webspinner, Aposthonia ceylonica, found in imported ornamental Tillandsia plants in greenhouse gardens in Paju and Seoul. This is the second record of a non-native Embioptera in Korea. The insects were found in the gaps between the basal leaves of the plants, and lived as a group in galleries of woven silk produced from the forelegs. The morphological characters and silk structures were investigated using scanning electron microscopy. The mitochondrial COI gene was sequenced for molecular identification, and to evaluate the validity of DNA barcoding for Embioptera. These insects can only survive and breed in greenhouse gardens because they are subtropical to tropical. However, they might ultimately settle after introduction in the Korean Peninsula if tropicalization continues.