Characterization and tissue incorporation of cross-linked human acellular dermal matrix

Here, we describe a novel human acellular dermal matrix (ADM) cross-linked using electron beam irradiation. Structural and biomechanical characteristics of the human ADM were assessed by infrared spectrometry and uni-axial tensile testing. Electron beam irradiation affects collagen secondary structure, which can be detected in the amide I spectral region (1660 cm⁻¹ and 1690 cm⁻¹). At doses exceeding 25 kGy, cross-linking of the collagen matrix results in a denser, more stratified appearance and parallel arrangement, with significantly increased tensile strength and elastic modulus. In a micropig model, the implanted ADM elicits rapid host cell infiltration and extracellular matrix deposition; however, the delayed remodeling resulted in long-term structural integrity. Furthermore, mean densities of collagen and elastin, expression of extracellular matrix proteins, and microvessel formation within the implanted ADM increased significantly, whereas the thickness of the implanted ADM did not decrease during the course of the study. Compared with normal adjacent tissue, type I collagen mRNA levels in the ADM increased 12-fold at 3 months after implantation, and transforming growth factor-β mRNA levels increased 3.3-fold at 2 months. Matrix metalloproteinase (MMP)-1 and MMP-9 mRNA levels were also elevated. Collectively, these results demonstrate that the structural and biomechanical properties of this novel cross-linked human ADM are adequate for use as a biologic tissue substitute.     

Calorimetric study of extracellular tissue matrix degradation and instability after gamma irradiation

Native extracellular tissue matrix (ECM) is increasingly used for tissue repair and regeneration. The kinetics of gamma irradiation damage on human dermis ECM was studied by differential scanning calorimetry (DSC). Dermis ECM was irradiated at a low-dose rate of 0.23 kGy h(-1) in order to study the progression of ECM damage as the gamma dose increased from 0 to 32 kGy. The study showed that the effect of gamma irradiation above 2 kGy was predominantly peptide chain scission. As the gamma dose increased, the stability of irradiated ECM decreased further, and multiple ECM domains of different stability were detected. Even a moderate gamma dose (7-12 kGy) could decrease the onset denaturation temperature of ECM to below body temperature. DSC analysis also showed partial and spontaneous protein denaturation in gamma-irradiated, rehydrated ECM at 37 degrees C. In vitro rehydration tests confirmed that a significant fraction of the irradiated ECM disintegrated into minute ECM fragments at 37 degrees C, although the irradiated ECM appeared to be normal at 4 degrees C and room temperature. DSC data were correlated well to effects of gamma irradiation on ECM microstructure, mechanical property and in vitro cell response reported earlier by us. A model was presented to describe the kinetics of gamma-irradiation-induced alterations of tissue ECM properties.     

Development and characterization of an acellular human pericardial matrix for tissue engineering

This study aimed to produce an acellular human tissue scaffold with a view to recellularization with autologous cells to produce a tissue-engineered pericardium that can be used as a patch for cardiovascular repair. Human pericardia from cadaveric donors were treated sequentially with hypotonic buffer, SDS in hypotonic buffer, and a nuclease solution. Histological analysis of decellularized matrices showed that the human pericardial tissue retained its histioarchitecture and major structural proteins. There were no whole cells or cell fragments. There were no significant differences in the hydroxyproline (normal and denatured collagen) and glycosaminoglycan content of the tissue before and after decellularization (p > 0.05). There were no significant changes in the ultimate tensile strength after decellularization (p > 0.05). However, there was an increased extensibility when the tissue strips were cut parallel to the visualized collagen bundles (p = 0.005). No indication of contact or extract cytotoxicity was found when using human dermal fibroblasts and A549 cells. In summary, successful decellularization of the human pericardium was achieved producing a biocompatible matrix that retained the major structural components and strength of the native tissue.     

Glutaraldehyde-fixed kangaroo aortic wall tissue: histology,crosslink stability and calcification potential

Stentless aortic heart valve substitutes, manufactured from biological tissues, are fixed with glutaraldehyde to cross-link collagen, reduce antigenicity, and sterilize the tissue. Despite improved cross linking, reduced antigenicity, and various anticalcification measures, the aortic wall tissue present in these prostheses tends to calcify. The aim of this study was to assess the morphology, collagen cross-link stability, and calcification potential of glutaraldehyde-preserved kangaroo aortic wall tissue as opposed to porcine aortic wall tissue. Porcine and kangaroo aortic wall tissues were fixed in 0.625% buffered glutaraldehyde. Histology and cross-link stability were examined. Calcification potential was determined in the subcutaneous rat model. Kangaroo aortic wall tissue was significantly (p < 0.01) less calcified than porcine aortic wall tissue (26.67 +/- 6.53 versus 41.959 +/- 2.75 microg/mg tissue) at 8 weeks. In conclusion, the histological differences between kangaroo and porcine aortic wall tissue correlate well with the reduced calcification potential of kangaroo aortic wall tissue. The reduced calcification potential could result in improved long-term durability of stentless kangaroo heart valves as bioprostheses.     

Functional neovascularization in tissue engineering with porcine acellular dermal matrix and human umbilical vein endothelial cells

Endothelial cells-matrix interactions play an important role in promoting and controlling network formation. In this study, porcine acellular dermal matrix (PADM) was used to guide human umbilical vein endothelial cells (HUVECs) adhesion and proliferation as a potential system for vascularization of engineered tissues. We fabricated PADM using a modified protocol and assessed their composition and ultrastructures. Subsequently, the viability of HUVECs and the formation of capillary-like networks were evaluated by seeding cells directly on PADM scaffolds or PADM digests in vitro. We further investigated the function of the HUVECs seeded on the PADM scaffolds after subcutaneous transplantation in athymic mice. Moreover, the function of the neovessels formed in the PADM scaffolds was assessed by implantation into cutaneous wounds on the backs of mice. The results showed that PADM scaffolds significantly increased proliferation of HUVECs, and the PADM digest induced HUVECs formed many tube-like structures. Moreover, HUVECs seeded on the PADM scaffolds formed numerous capillary-like networks and some perfused vascular structures after implantation into mice. PADM seeded with HUVECs and fibroblasts were also able to form many capillary-like networks in vitro. Further, these neovessels could inosculate with the murine vasculature after implantation into cutaneous wounds in mice. The advantage of this method is that the decellularized matrix not only provides signals to maintain the viability of endothelial cells but also serves as the template structure for regenerated tissue. These findings indicate that PADM seeded with HUVECs may be a potential system for successful engineering of large, thick, and complex tissues.     

Alterations in mast cell frequency and relationship to angiogenesis in the rat mammary gland during windows of physiologic tissue remodeling

Background: The mammary epithelium undergoes proliferation and regression accompanied by remodeling of the fibrocellular and vascular stroma. Mast cells are abundant in these compartments and have been implicated in remodeling during wound healing and cancer progression. The purpose of this study was to test the hypothesis that mast cell abundance correlates with physiologic mammary tissue remodeling during estrous cycling, lactogenesis (pregnancy and lactation) and involution. Results: Mast cell and capillary frequency were quantified in the stroma surrounding ducts and lobules from mammary glands of rats. During estrous cycling, periductal mast cell numbers were unchanged, but lobule‐associated mast cells significantly increased in the regressive phase of diestrus II. During lactogenesis, lobular stroma mast cells peaked early in pregnancy, at D2, followed by a significant decrease throughout lactation. Involution was associated with a rapid return in mast cell numbers, similar to diestrus II. Lobular vascularization peaked during the state of metestrus, when limited secretory differentiation occurs. Lobular angiogenesis peaked at D7 of pregnancy, regressed, and then returned to high levels during lactation and early involution, when secretory differentiation is high. Conclusions: These results suggest mast cells are predominantly associated with regressive lobular remodeling during cycling and involution, whereas angiogenesis is predominantly associated with secretory differentiation. Developmental Dynamics 241:890–900, 2012. © 2012 Wiley Periodicals, Inc.     

Effects of gamma irradiation on cultured rat and mouse microvessel endothelial cells: metastatic tumor cell adhesion,subendothelial matrix degradation,and secretion of tumor cell growth factors

The effects of-irradiation on the properties of microvessel endothelial cells were studiedin vitro. After incubating confluent endothelial cell monolayers in low serum-containing medium for 24 h, the monolayers were irradiated with¹³⁷Cs. Survival of rat lung microvessel endothelial (RLE) and mouse brain microvessel endothelial (MBE) cells were similar after irradiation (D _o=2.17 and 1.75 Gy,D _q=4.44 and 5.67 Gy, andn=7.8 and 25 for RLE and MBE cells, respectively). We examined the effects of-irradiation on endothelial cell morphology, adhesion of syngeneic rat lung or mouse brain metastasizing tumor cells, release of the subendothelial matrix-degrading enzyme heparanase, and secretion of soluble mitogenic factors that stimulated the growth of syngeneic metastatic tumor cells. The effects of-irradiation were not apparent until several hours after irradiation, and by 24 h doses of 10 Gy caused limited endothelial cell retraction and reorganization of the endothelial monolayer. By 24 h after irradiation there was also increased adhesion of metastatic tumor cells to RLE but not MBE cells. We also examined the effects of-irradiation on the release from endothelial cells of enzymes that solubilize the subendothelial matrix. Radiation resulted in a significant increase in the release of matrix-degrading enzyme (heparanase) that solubilized [³⁵S]-labeled heparan sulfate from subendothelial matrix. This was most pronounced in the 24 h sample from-irradiated endothelial cells. Finally, we examined the-irradiation-induced release of mitogenic factors from endothelial cells that could stimulate the growth of metastatic cells in serum-limiting medium. The medium from RLE but not MBE cells stimulated the growth of a rat mammary carcinoma cell line. The results suggest that-irradiation of microvessel endothelial cells can affect the interactions of tumor cells with endothelial cells and their subendothelial matrix; these processes could facilitate metastasis formation in irradiated tissues such as the lung.     

脱细胞基质制备方法及其在涎腺组织工程中的应用

背景:由脱细胞基质组成的生物支架被广泛应用于动物及临床研究,以修复和重建组织与器官,但所有的脱细胞方法都会在一定程度上破坏基质结构与功能。目的:综述脱细胞基质制备方法、优缺点及其在涎腺组织工程研究中的应用。方法:应用计算机检索CNKI数据库、中国生物医学文献数据库、PubMed数据库及Elsevier数据库2008至2019年发表的相关文献,检索词为“脱细胞基质,制备方法,涎腺,组织工程,再生;decellularization,preparation method,parotid gland tissue engineering”,共纳入74篇文献。结果与结论:大部分组织与器官脱细胞基质制备方法需要化学、生物(酶)、物理及以上几种方法联合使用,具体方法取决于组织与器官的厚度、组成和性质。虽然不是所有脱细胞方法均可去除组织与器官中的细胞成分,但完全去除细胞的组织与器官具有重塑组织特异性的优势,为接种细胞的增殖和分化提供有利的微环境。由于涎腺结构复杂和组织工程化在临床应用中的挑战,应用于患者的临床移植进展有限,该领域的体内研究仅限于动物,而基于颌下腺脱细胞基质生物支架材料方面的应用有望为涎腺组织工程提供有利的来源。     

Effect of in vitro irradiation and cell cycle-inhibitory drugs on the spontaneous human IgE synthesis in vitro

The in vitro effects of radiation, diterpine forskolin (FK), and hydrocortisone (HC) on the in vitro spontaneous IgE synthesis by peripheral blood B-lymphocytes from atopic patients were investigated. Without affecting cell viability, in vitro irradiation inhibited in a dose-dependent fashion de novo IgE synthesis in vitro by B cells from all patients examined with a mean 40% reduction of in vitro IgE product after treatment with 100 rads. In contrast, the in vitro IgE production by the U266 myeloma cell line was unaffected, even by irradiation with 1600 rads. The addition to B cell cultures from atopic patients of FK consistently resulted in a dose-dependent inhibition of the spontaneous IgE production in vitro. The addition to cultures of 10(-5) and 10(-6) molar concentrations of HC was also usually inhibitory, whereas lower HC concentrations were uneffective or even enhanced the spontaneous in vitro IgE synthesis. When 10(-6) molar concentrations of both HC and FK were combined in culture, a summation inhibitory effect on the spontaneous IgE synthesis was observed. In contrast, neither FK nor HC had inhibitory effect on the in vitro spontaneous IgE synthesis by the U266 myeloma cell line. The spontaneous in vitro IgE synthesis by B cells from patients with Hodgkin's disease, demonstrating high levels of serum IgE, was strongly reduced or virtually abolished after patients underwent total nodal irradiation to prevent the spread of the disease. In addition, the in vitro spontaneous IgE synthesis by B cells from atopic patients was markedly decreased or abolished by in vivo administration of betamethasone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Biological basis of bone formation, remodeling, and repair-part III: biomechanical forces

While it has been long appreciated that biomechanical forces are involved in bone remodeling and repair, the actual mechanism by which a physical force is translated to the corresponding intracellular signal has largely remained a mystery. To date, most biomechanical research has concentrated upon the effect on bone morphology and architecture, and it is only recently that the complex cellular and molecular pathways involved in this process (called mechanotransduction) are being described. In this paper, we review the current understanding of bone mechanobiology and highlight the implications for clinical medicine and tissue engineering research.     

Isolation of intact aortic valve scaffolds for heart-valve bioprostheses: extracellular matrix structure, prevention from calcification, and cell repopulation features

Extracellular matrix (ECM) scaffolds isolated from valvulated conduits can be useful in developing durable bioprostheses by tissue engineering provided that anatomical shape, architecture, and mechanical properties are preserved. As evidenced by SEM, intact scaffolds were derived from porcine aortic valves by the combined use of Triton X-100 and cholate (TRI-COL) or N-cetylpyridinium (CPC) and subsequent nucleic acid removal by nuclease. Both treatments were effective in removing most cells and all the cytomembranes, with preservation of (1) endothelium basal membranes, (2) ECM texture, including the D-periodical interaction of small proteoglycans with normally D-banded collagen fibrils, and (3) mechanical properties of the treated valves. Ultrastructural features agreed with DNA, hexosamine, and uronic acid biochemical estimations. Calcification potential, assessed by a 6-week rat subdermal model, was significantly reduced by TRI-COL/nuclease treatment. This was not true for CPC only, despite better proteoglycan preservation, suggesting that nucleic acids also are involved in calcification onset. Human fibroblasts, used to repopulate TRI-COL samples, formed mono- or multilayers on surfaces, and groups of cells also were scattered within the valve leaflet framework. A biocompatible scaffolds of this kind holds promise for production of durable valve bioprostheses that will be able to undergo probable turnover and/or remodeling by repopulating recipient cells.     

Heparin-chitosan-coated acellular bone matrix enhances perfusion of blood and vascularization in bone tissue engineering scaffolds

Currently, the main hurdle in the tissue engineering field is how to provide sufficient blood supply to grafted tissue substitutes in the early post-transplanted period. For three-dimensional, cell-dense, thick tissues to survive after transplantation, treatments are required for hypoxia, nutrient insufficiency, and the accumulation of waste products. In this study, a biomacromolecular layer-by-layer coating process of chitosan/heparin onto a decellularized extracellular bone matrix was designed to accelerate the blood perfusion and re-endothelialization process. The results of in vitro measurements of the activated partial thromboplastin time supported the theory that the combination of chitosan and heparin could bring both anticoagulation and hemocompatibility to the scaffold. A rabbit bone defect model was established for further evaluation of the application of this kind of surface-modified scaffold in vivo. The final results of computed tomography (CT) perfusion imaging and histological examination proved that this facile coating approach could significantly promote blood perfusion and re-endothelialization in the early post-transplanted period compared with an acellular bone matrix due to its much-improved anticoagulation property.     

Development and characterization of an acellular porcine cartilage bone matrix for use in tissue engineering

The aim of this study was to develop a technique to decellularize a porcine cartilage bone construct with view to using this as a biological scaffold for cartilage substitution. The decellularization protocol applied freeze/thaw cycles; this was followed by cyclic incubation in hypotonic tris buffer and 0.1% (w/v) sodium dodecyl sulfate in hypotonic buffer plus protease inhibitors. Nucleases (RNase and DNase) were used to digest nucleic acids followed by disinfection using 0.1% (v/v) peracetic acid. Histological analysis confirmed the absence of visible cells within the decellularized tissue. DNA analysis revealed the near-complete removal of genomic DNA from the decellularized tissues. The decellularization process had minimal effect on the collagen content of the cartilage. However, there was a significant reduction in the glycosaminoglycan content in the decellularized tissues. There was no evidence of the expression of the major xenogeneic epitope, galactose-α-1,3-galactose. Biomechanical indentation testing of decellularized tissues showed a significant change in comparison to the fresh cartilage. This was presumed to be caused by the reduction in the glycosaminoglycan content. Biocompatibility of the acellular scaffold was determined using contact cytotoxicity assays and a galactosyltransferase knockout mouse model. Decellularized porcine cartilage tissue was found to exhibit favorable compatibility in both in vitro and in vivo tests. In conclusion, this study has generated data on the production of an acellular cartilage bone matrix scaffold for use in osteochondral defect repair. To our knowledge, this is the first study that has successfully removed whole cells and α-gal from xenogeneic cartilage and bone tissue.     

Chromosomal aberrations induced by in vitro irradiation: comparisons between human sperm and lymphocytes

Types and frequencies of structural aberrations in human sperm and lymphocyte chromosomes from one donor were compared after in vitro irradiation with 100, 200, and 400 rad in order to determine if cells with dramatically different chromatin configurations are similarly affected and to investigate the feasibility of using lymphocytes as surrogates for germ cells in risk estimation. Sperm chromosomes were analyzed after fusion with eggs from the golden hamster. Total frequencies of induced aberrations were similar in the two cell types. However, the relative frequencies of rejoined lesions (dicentrics), compared with unrejoined lesions (chromosome breaks and acentric fragments), were different. At the three doses tested, a constant ratio of 5 dicentrics in lymphocytes for every dicentric in sperm was induced. Conversely, for every chromosome break or acentric fragment induced in lymphocytes, 1.7 such events were induced in sperm at the three doses tested.     

Extracellular matrix dynamics in cell migration,invasion and tissue morphogenesis

This review describes how direct visualization of the dynamic interactions of cells with different extracellular matrix microenvironments can provide novel insights into complex biological processes. Recent studies have moved characterization of cell migration and invasion from classical 2D culture systems into 1D and 3D model systems, revealing multiple differences in mechanisms of cell adhesion, migration and signalling—even though cells in 3D can still display prominent focal adhesions. Myosin II restrains cell migration speed in 2D culture but is often essential for effective 3D migration. 3D cell migration modes can switch between lamellipodial, lobopodial and/or amoeboid depending on the local matrix environment. For example, “nuclear piston” migration can be switched off by local proteolysis, and proteolytic invadopodia can be induced by a high density of fibrillar matrix. Particularly, complex remodelling of both extracellular matrix and tissues occurs during morphogenesis. Extracellular matrix supports self‐assembly of embryonic tissues, but it must also be locally actively remodelled. For example, surprisingly focal remodelling of the basement membrane occurs during branching morphogenesis—numerous tiny perforations generated by proteolysis and actomyosin contractility produce a microscopically porous, flexible basement membrane meshwork for tissue expansion. Cells extend highly active blebs or protrusions towards the surrounding mesenchyme through these perforations. Concurrently, the entire basement membrane undergoes translocation in a direction opposite to bud expansion. Underlying this slowly moving 2D basement membrane translocation are highly dynamic individual cell movements. We conclude this review by describing a variety of exciting research opportunities for discovering novel insights into cell‐matrix interactions.     

羟基丁酸-羟基辛酸共聚物/脱细胞软骨基质复合支架的制备与体外降解*

背景：羟基丁酸-羟基辛酸共聚物具有高生物相容性和降解性,但单一材料无法满足组织工程支架的要求。脱细胞软骨基质是制备复合支架的常用材料,具有良好的生物相容性和无抗原性等优点。 目的：将羟基丁酸-羟基辛酸共聚物、脱细胞软骨基质以不同比例混合制备复合支架,观察其体外降解速率。 方法：取新鲜猪关节软骨,用含有双抗的PBS液浸泡,放入含有苯甲基磺酰氟的tri-HCl缓冲液,加入DNase酶和RNase酶,用D-Hank’s液冲洗等步骤制备脱细胞软骨基质。采用溶剂浇注-颗粒沥滤的方法与羟基丁酸-羟基辛酸共聚物按不同浓度混合,制备出不同比例的复合支架。 结果与结论：脱细胞软骨基质的比例不同,复合材料的完全降解时间也不同,8%含量的脱细胞软骨基质最符合软骨组织工程支架的要求。      

Inactivation of Lassa, Marburg, and Ebola viruses by gamma irradiation.

Because of the cumbersome conditions experienced in a maximum containment laboratory, methods for inactivating highly pathogenic viruses were investigated. The infectivity of Lassa, Marburg, and Ebola viruses was inactivated without altering the immunological activity after radiation with Co60 gamma rays. At 4 degrees C, Lassa virus was the most difficult to inactivate with a rate of 5.3 X 10(-6) log 50% tissue culture infective dose per rad of CO60 radiation, as compared with 6.8 X 10(-6) log 50% tissue culture infective dose per rad for Ebola virus and 8.4 X 10(-6) log 50% tissue culture infective dose per rad for Marburg virus. Experimental inactivation curves, as well as curves giving the total radiation needed to inactivate a given concentration of any of the three viruses, are presented. We found this method of inactivation to be superior to UV light or beta-propiolactone inactivation and now routinely use it for preparation of material for protein-chemistry studies or for preparation of immunological reagents.     

Radioprotective effects of Daflon against genotoxicity induced by gamma irradiation in human cultured lymphocytes

The ability of Daflon to protect against genotoxicity induced by gamma irradiation has been investigated in vivo and in vitro in cultured lymphocytes from healthy human volunteers. Peripheral human blood samples were collected predose (10 min before) and 1, 2, and 3 hr after a single oral ingestion of 1000 mg of Daflon. At each time point, whole blood was exposed in vitro to 150 cGy of cobalt‐60 gamma rays, and then the lymphocytes were cultured with mitogenic stimulation to determine the micronuclei in cytokinesis‐blocked binucleated cells. For each volunteer, the results showed a significant increase in the incidence of micronuclei after exposure to gamma irradiation as compared to control unexposed samples. As early as 1 hr after Daflon administration, a significant decrease in the incidence of micronuclei was observed in comparison with similarly irradiated lymphocytes collected before administration. The maximum protection was reached 1 hr after administration of Daflon with a significant decrease in the frequency of micronuclei of 40%. These findings suggest the possible application of Daflon for the protection of human lymphocytes from the genetic damage and side effects induced by gamma irradiation. Environ. Mol. Mutagen. 2009. © 2009 Wiley‐Liss, Inc.