Molecular cloning and relative tissue expression of decorin and lumican in embryonic quail cornea

Keratan sulfate, an electrosensory neurosentient bioresponsive cell instructive glycosaminoglycan

The roles of keratan sulfate (KS) as a proton detection glycosaminoglycan in neurosensory processes in the central and peripheral nervous systems is reviewed. The functional properties of the KS-proteoglycans aggrecan, phosphacan, podocalyxcin as components of perineuronal nets in neurosensory processes in neuronal plasticity, cognitive learning and memory are also discussed. KS-glycoconjugate neurosensory gels used in electrolocation in elasmobranch fish species and KS substituted mucin like conjugates in some tissue contexts in mammals need to be considered in sensory signalling. Parallels are drawn between KS's roles in elasmobranch fish neurosensory processes and its roles in mammalian electro mechanical transduction of acoustic liquid displacement signals in the cochlea by the tectorial membrane and stereocilia of sensory inner and outer hair cells into neural signals for sound interpretation. The sophisticated structural and functional proteins which maintain the unique high precision physical properties of stereocilia in the detection, transmittance and interpretation of acoustic signals in the hearing process are important. The maintenance of the material properties of stereocilia are essential in sound transmission processes. Specific, emerging roles for low sulfation KS in sensory bioregulation are contrasted with the properties of high charge density KS isoforms. Some speculations are made on how the molecular and electrical properties of KS may be of potential application in futuristic nanoelectronic, memristor technology in advanced ultrafast computing devices with low energy requirements in nanomachines, nanobots or molecular switches which could be potentially useful in artificial synapse development. Application of KS in such innovative areas in bioregulation are eagerly awaited.

Lumican Inhibits In Vivo Melanoma Metastasis by Altering Matrix-Effectors and Invadopodia Markers

It was reported that lumican inhibits the activity of metalloproteinase MMP-14 and melanoma cell migration in vitro and in vivo. Moreover, Snail triggers epithelial-to-mesenchymal transition and the metastatic potential of cancer cells. Therefore, the aim of this study was to examine the effect of lumican on Mock and Snail overexpressing melanoma B16F1 cells in vivo. Lung metastasis was analyzed after intravenous injections of Mock-B16F1 and Snail-B16F1 cells in Lum+/+ and Lum-/- mice. At day 14, mice were sacrificed, and lungs were collected. The number of lung metastatic nodules was significantly higher in mice injected with Snail-B16F1 cells as compared to mice injected with Mock-B16F1 cells confirming the pro-metastatic effect of Snail. This effect was stronger in Lum-/- mice as compared to Lum+/+, suggesting that endogenous lumican of wild-type mice significantly inhibits metastasis to lungs. Scanning electron and confocal microscopy investigations demonstrated that lumican inhibits the development of elongated cancer cell phenotypes which are known to develop invadopodia releasing MMPs. Moreover, lumican was shown to affect the expression of cyclin D1, cortactin, vinculin, hyaluronan synthase 2, heparanase, MMP-14 and the phosphorylation of FAK, AKT, p130 Cas and GSK3α/β. Altogether, these data demonstrated that lumican significantly inhibits lung metastasis in vivo, as well as cell invasion in vitro, suggesting that a lumican-based strategy targeting Snail-induced metastasis could be useful for melanoma treatment.

Resistance of corneal RFUVA–cross-linked collagens and small leucine-rich proteoglycans to degradation by matrix metalloproteinases

PURPOSE

Extracellular matrix metalloproteinases (MMPs) are thought to play a crucial role in corneal degradation associated with the pathological progression of keratoconus. Currently, corneal cross-linking by riboflavin and ultraviolet A (RFUVA) has received significant attention for treatment of keratoconus. However, the extent to which MMPs digest cross-linked collagen and small leucine-rich proteoglycans (SLRPs) remains unknown. In this study, the resistance of RFUVA-cross-linked collagens and SLRPs to MMPs has been investigated.

METHODS

To investigate the ability of MMPs to digest cross-linked collagen and SLRPs, a model reaction system using purified collagen type I, type IV, and nonglycosylated, commercially available recombinant SLRPs, keratocan, lumican, mimecan, decorin, and biglycan in solution in vitro has been compared using reactions inside an intact bovine cornea, ex vivo.

RESULTS

Our data demonstrate that corneal cross-linked collagen type I and type IV are resistant to cleavage by MMP-1, MMP-2, MMP-9, and MMP-13, whereas non-cross-linked collagen I, IV, and natively glycosylated SLRPs are susceptible to degradation by MMPs. In addition, both cross-linked SLRPs themselves and cross-linked polymers of SLRPs and collagen appear able to resist degradation. These results suggest that the interactions between SLRPs and collagen caused by RFUVA protect both SLRPs and collagen fibrils from cleavage by MMPs.

CONCLUSIONS

A novel approach for understanding the biochemical mechanism whereby RFUVA cross-linking stops keratoconus progression has been achieved.

The impact of visible light on the immature retina: a model of early light exposure in neonatal mice

To investigate the effects of visible light on the retinal development, we established an early-light-exposure model in neonatal mice. An incision was made on the right-sided eyelids of mice on postnatal day 4 (P4), and so that the right eyes were exposed to visible light (4000 lux) for 12h per day. The population in the retinal ganglion cells (RGCs), cellular apoptosis and lumican expression were analyzed in the retinae. The loss of the RGCs was moderately alleviated and dramatically increased by early light exposure on P9 and P12, respectively. In the light-exposed retinae, the immunoactivities of caspase-9 (p39), an active isoform of caspase-9 marking the cellular apoptosis, dropped to nearly 30% of those in the control specimens on P6; thereafter the light-induced lower levels of caspase-9 (p39) remained, while those in the control specimens dropped to the values less than 50% of the light-exposed retinae. Lumican was first ectopically detected on P9, and distributed in the inner layers of the light-exposed retinae, with the most significant accumulation in the ganglion cell layer by P12. The ectopic expression of lumican was both temporarily and spatially parallel with the aggravated loss of the RGCs. In conclusion, early light exposure inflicts a profound effect on the immature retina. Our studies may have implications for premature infant care.

Effects of ultraviolet-A and riboflavin on the interaction of collagen and proteoglycans during corneal cross-linking

Corneal cross-linking using riboflavin and ultraviolet-A (RFUVA) is a clinical treatment targeting the stroma in progressive keratoconus. The stroma contains keratocan, lumican, mimecan, and decorin, core proteins of major proteoglycans (PGs) that bind collagen fibrils, playing important roles in stromal transparency. Here, a model reaction system using purified, non-glycosylated PG core proteins in solution in vitro has been compared with reactions inside an intact cornea, ex vivo, revealing effects of RFUVA on interactions between PGs and collagen cross-linking. Irradiation with UVA and riboflavin cross-links collagen α and β chains into larger polymers. In addition, RFUVA cross-links PG core proteins, forming higher molecular weight polymers. When collagen type I is mixed with individual purified, non-glycosylated PG core proteins in solution in vitro and subjected to RFUVA, both keratocan and lumican strongly inhibit collagen cross-linking. However, mimecan and decorin do not inhibit but instead form cross-links with collagen, forming new high molecular weight polymers. In contrast, corneal glycosaminoglycans, keratan sulfate and chondroitin sulfate, in isolation from their core proteins, are not cross-linked by RFUVA and do not form cross-links with collagen. Significantly, when RFUVA is conducted on intact corneas ex vivo, both keratocan and lumican, in their natively glycosylated form, do form cross-links with collagen. Thus, RFUVA causes cross-linking of collagen molecules among themselves and PG core proteins among themselves, together with limited linkages between collagen and keratocan, lumican, mimecan, and decorin. RFUVA as a diagnostic tool reveals that keratocan and lumican core proteins interact with collagen very differently than do mimecan and decorin.

Differential expression of lumican and fatty acid binding protein-1: new insights into the histologic spectrum of nonalcoholic fatty liver disease

The basis of hepatocellular injury and progressive fibrosis in a subset of patients with nonalcoholic fatty liver disease (NAFLD) is poorly understood. We sought to identify hepatic proteins that are differentially abundant across the histologic spectrum of NAFLD. Hepatic protein abundance was measured in liver samples from four groups (n = 10 each) of obese (body mass index >30 kg/m(2)) patients: (1) obese normal group (normal liver histology), (2) simple steatosis (SS), (3) nonalcoholic steatohepatitis (NASH)-mild (steatohepatitis with fibrosis stage 0-1), and (4) NASH-progressive (steatohepatitis with fibrosis stage 2-4). Hepatic peptides were analyzed on an API Qstar XL quadrupole time-of-flight mass spectrometer using Analyst QS software. Linear trends tests were performed and used to screen for differential abundance. Nine known proteins were expressed with differential abundance between study groups. For seven proteins differential abundance is likely to have been on the basis increased hepatic lipid content and/or inflammation. Lumican, a 40-kDa keratin sulfate proteoglycan that regulates collagen fibril assembly and activates transforming growth factor-beta and smooth muscle actin, was expressed similarly in obese normal and SS but was overexpressed in a progressive manner in NASH-mild versus SS (124%, P < 0.001), NASH-progressive versus NASH-mild (156%, P < 0.001) and NASH-progressive versus obese normal (178%, P < 0.001). Fatty acid binding protein-1 (FABP-1), which is protective against the detergent effects of excess free fatty acids, facilitates intracellular free fatty acid transport and is an important ligand for peroxisome proliferator-activated receptor-mediated transcription, was overexpressed in SS when compared to the obese normal group (128%, P < 0.001), but was paradoxically underexpressed in NASH-mild versus SS (73%, P < 0.001), NASH-progressive versus NASH-mild (81%, P < 0.001), and NASH-progressive versus obese normal (59%, P < 0.001).

CONCLUSION

Histologically progressive NAFLD is associated with overexpression of lumican, an important mediator of fibrosis in nonhepatic tissues, whereas FABP-1 is paradoxically underexpressed in NASH, suggesting a new potential mechanism of lipotoxicity in NAFLD. Further studies are needed to determine the biologic basis of lumican and/or FABP-1 dysregulation in NAFLD.

Spatial and Temporal Expression of Perlecan in the Early Chick Embryo

Perlecan is a major heparan sulfate proteoglycan that binds growth factors and interacts with various extracellular matrix proteins and cell surface molecules. The expression and spatiotemporal distribution of perlecan was studied by RT-PCR, immunoprecipitation and immunofluorescence in the chick embryo from stages X (morula) to HH17 (29 somites). Combined RT-PCR and immunohistochemistry demonstrated the expression of perlecan as early as stage X and its presence may be fundamental to the first basement membrane assembly on the epiblast ventral surface at stage XIII (blastula). Perlecan fluorescence was intense in the cells ingressing through the primitive streak and was strong lining the epiblast ventral surface lateral to the streak at stage HH3-4 (gastrula). At stage HH5-6 (neurula), perlecan fluorescence was low in the neuroepithelium and stronger in the apical surface of the neural plate. At stage HH10-11 (12 somites), perlecan fluorescence was intense in the neuroepithelium and was then essentially nondetectable in the neuroepithelium, and the intensity had shifted to the basement membranes of encephalic vesicles by stage HH17. Perlecan immunofluorescence was intense in neural crest cells, strong in pharyngeal arches, intense in thymus and lung rudiments, intense in aortic arches and in dorsal aorta, strong in lens and retina and intense in intraretinal space and in optic stalk, strong in the dorsal mesocardium, myocardium and endocardium, strong in dermomyotome, low in sclerotome in somites, intense in mesonephric duct and tubule rudiments, intense in the lining of the gut luminal surface. Inhibition of the function of perlecan by blocking antibodies showed that perlecan is crucial for maintaining basement membrane integrity which mediates the epithelialization, adhesive separation and maintenance of neuroepithelium in brain, somite epithelialization, and tissue architecture during morphogenesis of the heart tube, dorsal aorta and gut. An intriguing possibility is that perlecan, as a signaling molecule that modulates the activity of growth factors and cytokines, participates in the signaling pathways that guide gastrulation movements and neural crest cell migration, proliferation and survival, cardiac cell proliferation and paraxial mesoderm (somitic) cell proliferation and segmentation.

Roles of lumican and keratocan on corneal transparency

Lumican and keratocan are members of the small leucine-rich proteoglycan (SLRP) family, and are the major keratan sulfate (KS) proteoglycans in corneal stroma. Both lumican and keratocan are essential for normal cornea morphogenesis during embryonic development and maintenance of corneal topography in adults. This is attributed to their bi-functional characteristic (protein moiety binding collagen fibrils to regulate collagen fibril diameters, and highly charged glycosaminoglycan (GAG) chains extending out to regulate interfibrillar spacings) that contributes to their regulatory role in extracellular matrix assembly. The absence of lumican leads to formation of cloudy corneas in homozygous knockout mice due to altered collagenous matrix characterized by larger fibril diameters and disorganized fibril spacing. In contrast, keratocan knockout mice exhibit thin but clear cornea with insignificant alteration of stromal collaegenous matrix. Mutations of keratocan cause cornea plana in human, which is often associated with glaucoma. These observations suggest that lumican and keratocan have different roles in regulating formation of stromal extracellular matrix. Experimental evidence indicates that lumican may have additional biological functions, such as modulation of cell migration and epithelium-mesenchyme transition in wound healing and tumorgenesis, besides regulating collagen fibrillogenesis.