Two species of dermatan sulfate proteoglycans with different molecular sizes from newborn calf skin

NG2, a common denominator for neuroinflammation, blood-brain barrier alteration, and oligodendrocyte precursor response in EAE, plays a role in dendritic cell activation

In adult CNS, nerve/glial-antigen 2 (NG2) is expressed by oligodendrocyte progenitor cells (OPCs) and is an early marker of pericyte activation in pathological conditions. NG2 could, therefore, play a role in experimental autoimmune encephalomyelitis (EAE), a disease associated with increased blood–brain barrier (BBB) permeability, inflammatory infiltrates, and CNS damage. We induced EAE in NG2 knock-out (NG2KO) mice and used laser confocal microscopy immunofluorescence and morphometry to dissect the effect of NG2 KO on CNS pathology. NG2KO mice developed milder EAE than their wild-type (WT) counterparts, with less intense neuropathology associated with a significant improvement in BBB stability. In contrast to WT mice, OPC numbers did not change in NG2KO mice during EAE. Through FACS and confocal microscopy, we found that NG2 was also expressed by immune cells, including T cells, macrophages, and dendritic cells (DCs). Assessment of recall T cell responses to the encephalitogen by proliferation assays and ELISA showed that, while WT and NG2KO T cells proliferated equally to the encephalitogenic peptide MOG35-55, NG2KO T cells were skewed towards a Th2-type response. Because DCs could be responsible for this effect, we assessed their expression of IL-12 by PCR and intracellular FACS. IL-12-expressing CD11c+ cells were significantly decreased in MOG35-55-primed NG2KO lymph node cells. Importantly, in WT mice, the proportion of IL-12-expressing cells was significantly lower in CD11c+ NG2- cells than in CD11c+ NG2+ cells. To assess the relevance of NG2 at immune system and CNS levels, we induced EAE in bone-marrow chimeric mice, generated with WT recipients of NG2KO bone-marrow cells and vice versa. Regardless of their original phenotype, mice receiving NG2KO bone marrow developed milder EAE than those receiving WT bone marrow. Our data suggest that NG2 plays a role in EAE not only at CNS/BBB level, but also at immune response level, impacting on DC activation and thereby their stimulation of reactive T cells, through controlling IL-12 expression.

Age-related changes in the proteoglycans of human skin. Specific cleavage of decorin to yield a major catabolic fragment in adult skin

Dramatic changes occur in skin as a function of age, including changes in morphology, physiology, and mechanical properties. Changes in extracellular matrix molecules also occur, and these changes likely contribute to the overall age-related changes in the physical properties of skin. The major proteoglycans detected in extracts of human skin are decorin and versican. In addition, adult human skin contains a truncated form of decorin, whereas fetal skin contains virtually undetectable levels of this truncated decorin. Analysis of this molecule, herein referred to as decorunt, indicates that it is a catabolic fragment of decorin rather than a splice variant. With antibody probes to the core protein, decorunt is found to lack the carboxyl-terminal portion of decorin. Further analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry shows that the carboxyl terminus of decorunt is at Phe(170) of decorin. This result indicates that decorunt represents the amino-terminal 43% of the mature decorin molecule. Such a structure is inconsistent with alternative splicing of decorin and suggests that decorunt is a catabolic fragment of decorin. A neoepitope antiserum, anti-VRKVTF, was generated against the carboxyl terminus of decorunt. This antiserum does not recognize intact decorin in any skin proteoglycan sample tested on immunoblots but recognizes every sample of decorunt tested. The results with anti-VRKVTF confirm the identification of the carboxyl terminus of decorunt. Analysis of collagen binding by surface plasmon resonance indicates that the affinity of decorunt for type I collagen is 100-fold less than that of decorin. This observation correlates with the structural analysis of decorunt, in that it lacks regions of decorin previously shown to be important for interaction with type I collagen. The detection of a catabolic fragment of decorin suggests the existence of a specific catabolic pathway for this proteoglycan. Because of the capacity of decorin to influence collagen fibrillogenesis, catabolism of decorin may have important functional implications with respect to the dermal collagen network.

Age-related changes in the proteoglycans of human skin

Skin undergoes dramatic age-related changes in its mechanical properties, including changes in tissue hydration and resiliency. Proteoglycans are macromolecular conjugates of protein and carbohydrate (glycosaminoglycan) which are involved in these tissue properties. In order to examine whether age-related changes in skin proteoglycans may contribute to the age-related changes in the mechanical properties of skin, proteoglycans from human skin of various ages were extracted and analyzed. Samples were obtained from two different fetal ages, from mature skin, and from senescent skin. As a function of age, there is a decrease in the proportion of large chondroitin sulfate proteoglycans (versican) and a concomitant increase in the proportion of small dermatan sulfate proteoglycans (decorin). Based on reactivity with antibodies to various chondroitin sulfate epitopes, fetal versican differs from the versican found in older skin with respect to the chondroitin sulfate chains. Also, the decorin of fetal skin is slightly larger, while the decorin of older skin shows greater polydispersity in both its size and its charge to mass ratio. There are also age-related differences in the size and polydispersity of the core proteins of decorin. The most pronounced change in skin proteoglycans is the appearance in mature skin of a proteoglycan which is smaller than decorin, but which has the same amino terminal amino acid sequence as decorin. This small proteoglycan is abundant in mature skin and may be a catabolic fragment of decorin or an alternatively spliced form of decorin. In light of the known ability of decorin to influence collagen fibrillogenesis and fibril diameter, the appearance of this small decorin-related proteoglycan may have a significant effect on skin elasticity. The observation that proteoglycans in skin show dramatic age-related differences suggests that these changes may be involved in the age-related changes in the physical properties of skin.

Connective tissue naevus with pseudo-Hurler polydystrophy

We report a 39-year-old patient with a huge connective tissue naevus on his back, in association with pseudo-Hurler polydystrophy (mucolipidosis III). As far as we are aware, this is the first report of the coexistence of these two rare conditions. The lesional skin was composed of densely packed, coarse collagen fibres, which were immunohistochemically found to consist of type I, type III and type VI collagens. The amount of elastic fibres was moderately reduced. The glycosaminoglycan content of lesional skin was similar to that in a normal control. Activities of several glycosidases were markedly decreased in cultured fibroblasts.

Purification and characterization of iduronic acid-rich and glucuronic acid-rich proteoglycans implicated in human post-burn keloid scar

Small proteoglycans (PGs), extracted from human keloid scar tissue with 4M guanidinium chloride and fractionated by DEAE-cellulose chromatography, were separated by ethanol precipitation into one L-iduronic acid-rich and one D-glucuronic acid-rich fraction. The size of the L-iduronic acid-rich PG was 102 kDa with a 27 kDa glycosaminoglycan chain, that of the D-glucuronic acid-rich PG was 90 kDa with a 26 kDa glycosaminoglycan chain, and the protein core of both PGs was 14.5 kDa. The two PGs carried sulfate groups mostly attached at C-4 of the 2-amino-2-deoxy-D-galactose units. The N-terminal amino acid sequence of both was similar to human bone PGII (decorin), normal and hypertrophic scar, and human dermal tissue PG.

Deficiency of the core proteins of dermatan sulphate proteoglycans in a variant form of Ehlers-Danlos syndrome

A variant form of Ehlers-Danlos syndrome with single adrenocorticotrophic hormone (ACTH) deficiency and mild diabetes mellitus was studied by immunohistochemical and biochemical analyses of the connective tissue. The patient exhibited features characteristic of the Ehlers-Danlos syndrome, such as fragility, hyperextensibility, and bruisability of the skin and large veins were readily seen, but no hypermobility of any joint was detectable. Biochemical studies of the connective tissue confirmed that the apparent synthesis of collagens was within normal limits, but the deposition of the major proteoglycan in the skin of this patient was markedly reduced, mainly because the synthesis of core protein of dermatan sulphate proteoglycan was defective.

Isolation and partial characterization of dermatan sulfate proteoglycans from human post-burn scar tissues

Dermatan sulfate (DS) proteoglycans (PGs) were extracted from human post-burn scar (Sc) tissues with 4M guanidinium chloride and isolated from the extracts by DEAE-cellulose chromatography and by differential ethanol precipitation. The DS.PGs were further purified by Sepharose CL-6B column chromatography. The average molecular weight (Mr) of hypertrophic scar (HSc) tissue DS.PGs was 39,000 based on sedimentation equilibrium measurements. Alkaline borohydride treatment of DS.PGs liberated glycosaminoglycan (GAG) chains and the presence of xylitol indicated that these chains were attached to protein core by xylosyl residues. The average Mr of the DS.GAG chain from HSc and normal scar (NSc) samples were 23,500 and 20,000 respectively. After digestion of the HSc and NSc, DS.PGs with chondroitinase ABC in the presence of proteinase inhibitors, two peptide components with Mr values of 21,500 and 17,000 were detected by SDS-polyacrylamide gel electrophoresis using reducing conditions. Analysis of the protein core fractions derived from NSc and HSc DS.PGs by Sepharose CL-6B column chromatography showed the presence of a single NH2-terminal amino acid (aspartic acid) and also that the fractions with different KAV values had an identical NH2-terminal sequence (A1-A5). The A1-A23 sequence of NSc DS.PG (major fraction, C): NH2Asp-Glu-Ala-O-Gly-Ile-Gly-Pro-Glu-Val-Pro-Asp-Asp-Arg-Asp-Phe-G lu-Pro- Ser-Leu-Gly-Pro-Val was the same as reported for a DS.PG isolated from human fetal membrane (HFM) tissue (Brennan et al., 1984). ELISA inhibition assay using monoclonal antibodies raised in rabbit against the NH2-terminal peptide (containing 15 amino acids) of human fetal membrane tissue were found to cross-react with HSc and NSc DS.PGs. Monoclonal antibodies to bovine skin DS.PGs protein core (Pearson et al., 1983) did not show any cross-reactivity with scar DS.PGs. These results show that the scar DS.PGs described here are different from normal bovine skin DS.PGs in the size and type of the protein core, and that in all the samples, the peptide components have the same NH2-terminal amino acid sequence.

Age-related changes of the dermatan sulfate containing small proteoglycans in bovine tendon

Sulfated proteoglycans of fetal, newborn and adult bovine tendon are extracted with neutral salt and then with 4 M guanidine HCl in the presence of proteinase inhibitors. Dermatan sulfate containing small proteoglycans are separated from chondroitin sulfate rich proteoglycans by CsCl-gradient centrifugation, by affinity chromatography using concanavalin A and by molecular sieve chromatography. These proteoglycans are comprised of a core protein with an average Mr of about 53,000 on polyacrylamide gel electrophoresis with SDS and of dermatan sulfate side chains with Mr 25,000-38,000 by gel chromatography. The tryptic peptides patterns observed in the small proteoglycans from newborn calf and adult bovine tendon are identical but are distinct from those of embryonic calf tendon. The patterns of the tryptic peptides of the core proteins from embryonic calf tendon are similar to those from the dermatan sulfate proteoglycans of calf skin. These results indicated that genetically independent genes of the core proteins from dermatan sulfate proteoglycans in tendon tissues were expressed by aging.

Acidic glycosaminoglycans, isolation and structural analysis of a proteodermatan sulfate from dermatosparactic calf skin

Dermatan sulfate and hyaluronic acid are the major glycosaminoglycan components of dermatosparactic and normal calf skin but the ratio of hyaluronic acid to dermatan sulfate is 50-70% higher in dermatosparactic calf skin than that in normal calf skin. Hyaluronic acid in normal calf skin could be extracted to 93% of the total by NaCl and guanidine hydrochloride, while in dermatosparactic calf skin 57% of hyaluronic acid remained in the insoluble material after NaCl and guanidine hydrochloride extraction. The recovery of proteodermatan sulfate in NaCl extracts was similar in normal and dermatosparactic skin. The amount of proteodermatan sulfate extracted in guanidine hydrochloride form normal calf skin was 2-4 fold higher than that from dermatosparactic calf skin. No significant difference between dermatosparactic and normal calf skin proteodermatan sulfate could be detected in terms of size of the core protein (Mr = 55,000) by sodium dodecyl sulfate polyacrylamide gel electrophoresis, amino acid analysis, immunological cross-reactivity using polyclonal antibodies against either dermatosparactic or normal calf skin core protein, tryptic peptides or size of dermatan sulfate chains (Mr = 17,000-18,000) on gel chromatography.