Evidence of proteoglycan/proteoglycan interactions within aggregates

Nonaggregated proteoglycan monomers, digested fragments of the monomers, as well as link proteins have been shown to self-associate. These associations have not been shown to occur on the aggregate. However, previous reports, using the Kleinschmidt technique of monolayer electron microscopy, have noted proteoglycan subunits on the aggregate that appear to interact, either as branched proteoglycans or as proteoglycan subunits that appear to share the same attachment site on the hyaluronic acid chain. Branching and shared attachments were noted in all aggregates analyzed in this study. Increasing the average space between proteoglycan subunits on the reconstituted aggregate resulted in a significant decrease in branched proteoglycans, indicating either a weak association occurring on the aggregate, or an artifact created by a three-dimensional structure being reduced to a two-dimensional monolayer image. The shared attachments were independent of both the presence of link proteins and changes in spacing between proteoglycans, suggesting a proteoglycan-proteoglycan interaction occurring before aggregation. The interactions were not influenced by proteoglycan concentration at the time of aggregation. Link proteins, however, did increase the number of proteoglycans on the aggregate that could be cross-linked with a bifunctional reagent, suggesting that link proteins facilitate proteoglycan-proteoglycan interactions.     

云芝多糖防止缺血再灌注心肌早期损伤

为了探讨云芝多糖对心肌缺血再灌注损伤的预防作用，制备犬心肌缺血再灌注损伤模型，输血再灌注组不用药物干预，云芝多糖组手术前2天每天口服云芝多糖150mg/kg。在缺血再灌注过程不同时间点测定左心室舒张压，超声心功能和冠状静脉窦血浆丙二醛浓度，心肌标本行透射电镜检查。结果发现，缺血再灌注组再灌注前和再灌注早期左心室舒张压显著升高，云芝多糖组仅再灌注前左心室舒张压升高，再灌注前两组缺血心肌节段收缩期增厚百分率显著下降，并表现为矛盾运动，再灌注期两组缺血心肌节段收缩期增厚百分率呈进行性改善，至再灌注120min两组均未恢复至结扎前水平，且云芝多糖组显著高于相应时间咪缺血再灌注组；左心室射血分数的变化趋势与缺血心肌节段收缩期增厚百分率相似，但恢复较快，云芝多糖组于再灌注90min即恢复至结扎前水平。缺血再灌注组再灌注期丙二醛浓度明显升高，至再灌注120min尚未恢复至结扎前水平。而云芝多糖组再灌注早期丙二醛浓度升高，但回降较快，于再灌注30min即恢复至结扎前水平，缺血再灌注组心肌组织水肿，心肌细胞少部分肌丝断裂，收缩带模糊，线粒体轻度肿胀，脱颗粒，胞质水肿；云芝多糖组心肌组织除轻微水肿外，未见其它明显结构改变，结果提示，云芝多糖对缺血再灌注早期心肌有显著保护作用。     

Successful treatment of earlobe keloids in the pediatric population

Background

Keloid scars present a difficult treatment challenge. Recently, intralesional steroid injection has become a common treatment modality [Akoz et al. Aesthetic Plast Surg. 2002;6:184-188; Studdiford et al. JABFM. 2008;21:149-152]. Although this has become a proven treatment technique, there is no standard injection protocol to which treating physicians commonly adhere. We hypothesize that timing of steroid injection may improve outcomes using this treatment technique in combination with lesion excision.

Methods

Fifteen patients with 16 earlobe keloids were treated using a standard steroid injection protocol with Kenalog (Bristol-Myers Squibb, New York, NY), in combination with lesion excision. Strict follow-up was enforced, with repeat injections as needed at any sign of abnormal scar formation postoperatively.

Results

Of 16 lesions, 15 (94%) were treated successfully with no sign of lesion recurrence at 6 months of follow-up. A single lesion was lost to follow-up and presented 18 months postoperatively with recurrence. This lesion was subsequently retreated successfully.

Conclusions

Kenalog injection in combination with excision is a well-tolerated and effective treatment of earlobe keloids in the pediatric population. We feel that timing of injection and adherence to a strict follow-up regimen is crucial to success.     

Tissue diffusion and retention of metalloproteinases in ascending aortic aneurysms and dissections

Histopathological alterations in human aneurysms and dissections of the thoracic ascending aorta include areas of mucoid degeneration within the medial layer, colocalized with areas of cell disappearance and disruption of extracellular matrix elastic and collagen fibers. We studied the presence of matrix metalloproteinases in relation to their capacity to diffuse through the tissue or to be retained in areas of mucoid degeneration in aneurysms and dissections of the ascending aorta. Ascending aortas from 9 controls, 33 patients with aneurysms, and 14 with acute dissections, all collected at surgery, were analyzed. The morphological aspect was similar whatever the etiology or phenotypic expression of the pathological aortas, involving areas of extracellular matrix breakdown and cell rarefaction associated with mucoid degeneration. Release of proMMP-2, constitutively expressed by smooth muscle cells, was not different between controls and aneurysmal aortas, whereas the aneurysmal aortas released more of the active form. Release of pro and active MMP-9 was also similar between controls and aneurysmal aortas. Immunohistochemical staining of MMP-2 and MMP-9 was weak in both control and pathological aortas. In contrast, released MMP-7 (matrilysin) and MMP-3 (stromelysin-1) could not be detected in conditioned media but were present in tissue extracts with no detectable quantitative difference between controls and pathological aortas. Immunohistochemical staining of MMP-7 and MMP-3 revealed their retention in areas of mucoid degeneration, and semiquantitative evaluation of immunostaining showed more MMP-7 in pathological aortas than in controls. In conclusion, areas of mucoid degeneration, the hallmark of aneurysms, and dissections of thoracic ascending aortas, whatever their etiology, are not inert and can retain specific proteases.     

Contribution of extracellular matrix to the mechanical properties of the heart

Extracellular matrix (ECM) components play essential roles in development, remodeling, and signaling in the cardiovascular system. They are also important in determining the mechanics of blood vessels, valves, pericardium, and myocardium. The goal of this brief review is to summarize available information regarding the mechanical contributions of ECM in the myocardium. Fibrillar collagen, elastin, and proteoglycans all play crucial mechanical roles in many tissues in the body generally and in the cardiovascular system specifically. The myocardium contains all three components, but their mechanical contributions are relatively poorly understood. Most studies of ECM contributions to myocardial mechanics have focused on collagen, but quantitative prediction of mechanical properties of the myocardium, or changes in those properties with disease, from measured tissue structure is not yet possible. Circumstantial evidence suggests that the mechanics of cardiac elastin and proteoglycans merit further study. Work in other tissues used a combination of correlation, modification or digestion, and mathematical modeling to establish mechanical roles for specific ECM components; this work can provide guidance for new experiments and modeling studies in myocardium.     

Biglycan protects cardiomyocytes against hypoxia/reoxygenation injury: Role of nitric oxide

Biglycan, a proteoglycan component of extracellular matrix, has been suspected to contribute to the development of atherosclerosis, but overexpression of biglycan in transgenic mice has been shown to induce cardioprotective genes including nitric oxide (NO) synthases in the heart. Therefore, here we hypothesized if exogenous administration of biglycan exerts cytoprotection. Primary cardiomyocytes from neonatal rats were subjected to 150 min hypoxia and 2 h reoxygenation. Mortality of cardiomyocytes was dose-dependently attenuated by pretreatment with 1-100 nM biglycan. Biglycan enhanced eNOS mRNA and protein, and significantly increased NO content of cardiomyocytes. The NO synthase inhibitor l-nitro-arginine-methyl-ester significantly attenuated the cytoprotective effect of biglycan. This is the first demonstration that biglycan leads to cytoprotection against hypoxia/reoxygenation injury, and that this phenomenon is partially mediated by an NO-dependent mechanism.     

A role for lipoprotein lipase during synaptic remodeling in the adult mouse brain

Lipoprotein lipase (LPL) is a member of a lipase family known to hydrolyze triglyceride molecules found in lipoprotein particles. This particular lipase also has a role in the binding of lipoprotein particles to different cell-surface receptors. LPL has been identified in the brain but has no specific function yet. This study aimed at elucidating the role of LPL in the brain in response to injury. Mice were subjected to hippocampal deafferentation using the entorhinal cortex lesion and mRNA and protein expression were assessed over a time-course of degeneration/reinnervation. Hippocampal LPL levels peaked at 2 days post-lesion (DPL) both at the mRNA and protein levels. No change was observed for receptors of the LDL-receptor family or RAP at DPL 2 in the hippocampus but the glia-specific syndecan-4 was found to be significantly upregulated at DPL 2. These results suggest that LPL is involved in the recycling of cholesterol and lipids released from degenerating terminals after a lesion through a syndecan-4-dependent pathway.     

The role of proteoglycans in pulmonaryedema development

Pulmonary gas exchange critically depends upon the hydration state and the thinness of the interstitial tissue layer within the alveolo-capillary membrane. In the interstitium, fluid freely moving within the fibrous extracellular matrix (ECM) equilibrates with water chemically bound to hyaluronic acid and proteoglycans (PGs). The dynamic equilibrium between these two phases is set and maintained by the transendothelial fluid and solutes exchanges, by the convective outflows into the lymphatic system, and by the mechanical and hydrophilic properties of the solid elements of the ECM. The fibrous ECM components, in particular the chondroitin sulfate proteoglycan (CS-PG) and the heparan-sulfate proteoglycan (HS-PG) families, play a major role in the maintenance of tissue fluid homeostasis. In fact, they provide: (a) a perivascular and interstitial highly restrictive sieve with respect to plasma proteins, thus modulating both interstitial protein concentration and transendothelial fluid filtration; (b) a mechanical support to lymphatic vessels sustaining and modulating their draining function, and (c) a rigid three-dimensional low-compliant scaffold opposing fluid accumulation into the interstitial space. Fragmentation of PG induced by increased plasma volume, by degradation through proteolytic or inflammatory agents, by exposure to inspiratory gas mixture with modified oxygen fraction, or by increased tissue strain/stress invariably results in the progressive loosening of PG intermolecular bonds with other ECM components. The loss of the PGs regulatory functions compromises the protective role of the tissue solid matrix progressively leading to interstitial and eventually severe lung edema. This article is discussed in the editorial available at:     

负荷改变对髁突骨上组织细胞及细胞外基质的影响—超微结构的研究

目的：检测髁状突骨上组织细胞及细胞外基质超微结构在负荷改变后的变化特点。方法：４只成年家兔在被拔除双侧下颌磨牙后１月和３月，用透射电镜的方法观察组织的表现。结果：细胞发生了不同程度的改建及退行性反应，如粗面内质网的扩张，线粒体肿胀，溶酶体增多等；基质中胶原原纤维的有序排列结构消失，胶原网受到破坏，同时蛋白多糖颗粒减少；基质中脂质小体及基质小囊等成分增多；负重区较非负重区的改变更显著。结论：过重的负荷会超过组织的代偿能力，使细胞产生基质的能力下降，对细胞自身产生不利的影响，引起髁状突的弹性及抗压、抗磨擦等能力的下降