Structure of collagen fibril-associated, small proteoglycans of mammalian origin

Increase in the growth inhibition of bovine pulmonary artery smooth muscle cells by an O-hexanoyl low-molecular-weight heparin derivative

Proliferation of pulmonary artery smooth muscle cells (PASMCs) appears to play a significant role in chronic pulmonary hypertension. The proliferation of PASMCs is strongly inhibited by some commercial heparin preparations. Heparin fragments were prepared by periodate treatment, followed by sodium borohydride reduction, to enhance potency. The tributylammonium salt of this fragmented heparin was O-acylated with hexanoic anhydride. Gradient polyacrylamide gel electrophoresis showed that the major heparin fragment contained eight disaccharide units. NMR analysis showed that approximately one hexanoyl group per disaccharide residue was present. The O-hexanoyl heparin fragments were assayed for growth inhibitory effect on bovine PASMCs in culture. This derivative was found to be more effective in growth inhibition of bovine PASMCs in culture than the heparin from which it was derived. In the future, it is envisioned that this or similar derivatives may be an effective treatment for pulmonary hypertension.

Sulfation patterns in heparin and heparan sulfate: effects on the proliferation of bovine pulmonary artery smooth muscle cells

Heparin's (HP's) antiproliferative effect on smooth muscle cells is potentially important in defining new approaches to treat pulmonary hypertension. The commercially available HP and heparan sulfate (HS) are structurally heterogenous polymers. In order to examine which sulfonate groups are required for endogenous antiproliferative activity, we prepared the following six chemically modified porcine mucosal HP and HS, which fell into three groups. One group consisted of fully O-sulfonated-N-acetylated, the second group consisted of de-N-sulfonated and re-N-acetylated, and the third group consisted of 6-O-desulfonated HP and HS derivatives. These six preparations were assayed for their antiproliferative potency on bovine pulmonary artery smooth muscle cells. The results of this assay show that (a) over-O-sulfonation of both HP and HS increases antiproliferative activity, (b) substitution of hexosamine with N-acetyl diminishes antiproliferative activity in both HP and HS, and (c) 6-O-desulfonation of HP and HS diminishes antiproliferative potency. Surprisingly, the type of uronic acid residue present at a given level of sulfation is unimportant for antiproliferative potency. In conclusion, only the level of O- and N-sulfo group substitution correlates well with HP and HS antiproliferative activity.

Heparin inhibits SMC growth in the presence of human and fetal bovine serum

Heparin (HP) has antiproliferative as well as anticoagulant properties, but not all HP preparations are equally antiproliferative. A recent report found that HP lost its total antiproliferative activity when fetal bovine serum (FBS) was replaced with human serum (HS) in culture media. This observation led to the investigation of our most potent antiproliferative Upjohn HP preparation effects on bovine pulmonary artery smooth muscle cells (PASMC) and systemic SMC growth stimulated in the presence of either FBS or HS. Bovine PASMC, human PASMC, and bovine aortic SMC were treated with 10 microg/ml Upjohn HP in either 15% FBS or 15% HS and the cell number was determined by a Coulter counter. We found that Upjohn HP significantly inhibited bovine PASMC and systemic SMC proliferation in both HS and FBS. The antiproliferative activity of the above HP preparation in HS may lead to an effective treatment of pulmonary vascular and systemic remodeling.

Structural determinants of antiproliferative activity of heparin on pulmonary artery smooth muscle cells

In addition to its anticoagulant properties, heparin (HP), a complex polysaccharide covalently linked to a protein core, inhibits proliferation of several cell types including pulmonary artery smooth muscle cells (PASMCs). Commercial lots of HP exhibit varying degrees of antiproliferative activity on PASMCs that may due to structural differences in the lots. Fractionation of a potent antiproliferative HP preparation into high and low molecular weight components does not alter the antiproliferative effect on PASMCs, suggesting that the size of HP is not the major determinant of this biological activity. The protein core of HP obtained by cleaving the carbohydrate-protein linkage has no growth inhibition on PASMCs, demonstrating that the antiproliferative activity resides in the glycosaminoglycan component. Basic sugar residues of glucosamine can be replaced with another basic sugar, i.e., galactosamine, without affecting growth inhibition of PASMCs. N-sulfonate groups on these sugar residues of HP are not essential for growth inhibition. However, O-sulfonate groups on both sugar residues are essential for the antiproliferative activity on PASMCs. In whole HP, in contrast to an earlier finding based on a synthetic pentasaccharide of HP, 3-O-sulfonation is not critical for the antiproliferative activity against PASMCs. The amounts and distribution of sulfonate groups on both sugar residues of the glycosaminoglycan chain are the major determinant of antiproliferative activity.

Effect of fully sulfated glycosaminoglycans on pulmonary artery smooth muscle cell proliferation

Fully sulfated heparin and other glycosaminoglycans, namely heparan, chondroitin, and dermatan sulfates, and hyaluronan have been prepared by using sulfur trioxide under mild chemical conditions. All these derivatives were assayed for antiproliferative activity on cultured bovine pulmonary artery smooth muscle cells (BPASMCs). No appreciable difference was found between heparin and fully sulfated heparin. Chondroitin and dermatan sulfates actually stimulated BPASMCs growth but full sulfonation made them strongly antiproliferative. Native hyaluronan was not antiproliferative but became strongly so after sulfonation. Neither acharan sulfate nor N-sulfoacharan sulfate had any antiproliferative activity. This suggests that O-sulfonation of the polysaccharide is critical for antiproliferative activity, whereas N-sulfonation of glucosamine residues is not.

Airway smooth muscle cell proliferation: characterization of subpopulations by sensitivity to heparin inhibition

Growth and maturation state of airway smooth muscle cells (SMCs) are determinants of asthma pathophysiology. Heparin reduces airway SMC proliferation and arterial SMC replication and phenotypic modulation. Distinct arterial SMC subtypes, differing in heparin sensitivity, have been characterized. We assessed the cellular mechanisms underlying the growth and phenotype of heparin-treated canine tracheal myocytes in primary culture. Heparin reduced replication by 40%. Immunoblot assay of myosin, actin, and myosin light chain kinase revealed heparin had no effect on rapid spontaneous phenotypic modulation after the cells were plated. Heparin increased cellular protein and vimentin contents in confluent cultures, suggesting that it may induce hypertrophic growth. Cell cycle analysis revealed that heparin decreased serum-stimulated replicating myocyte number by 40%. Also, G2-M transit was 20% slower for the set of SMCs that proceeded past G1 in the presence of heparin. These data indicate that heparin does not inhibit airway SMC replication by blocking modulation from the contractile state. Moreover, airway smooth muscle is composed of distinct SMC populations differing in mitogen and antiproliferative mediator responsiveness. Identification of functionally divergent subgroups suggests that distinct sets of SMCs may contribute differentially to airway physiology and pathophysiology.

The structure of the keratan sulphate chains attached to fibromodulin from human articular cartilage

The small keratan sulphate proteoglycan, fibromodulin, has been isolated from pooled human articular cartilage. The main chain repeat region and the chain caps from the attached N-linked keratan sulphate chains have been fragmented by keratanase II digestion, and the oligosaccharides generated have been reduced and isolated. Their structures and abundance have been determined by high pH anion-exchange chromatography. These regions of the keratan sulphate from human articular cartilage fibromodulin have been found to have the following general structure: [structure: see text]. Significantly, both alpha(2-6)- and alpha(2-3)-linked N-acetyl-neuraminic acid have been found in the capping oligosaccharides. Fucose, which is alpha(1-3)-linked as a branch to N-acetylglucosamine, has also been found along the length of the repeat region and in the capping region. The chains, which have been found to be very highly sulphated, are short; the length of the repeat region and chain caps is ca. nine disaccharides. These data demonstrate that the structure of the N-linked keratan sulphate chains of human articular cartilage fibromodulin is similar, in general, to articular cartilage derived O-linked keratan sulphate chains. Further, the general structure of the keratan sulphate chains attached to human articular cartilage fibromodulin has been found to be generally similar to that of both bovine and equine articular cartilage fibromodulin.

Inseparable iduronic acid-containing proteoglycan PG(IdoA) preparations of human skin and post-burn scar tissues: evidence for elevated levels of PG(IdoA)-I in hypertrophic scar by N-terminal sequencing

Hypertrophic scarring is characterized by disordered collagen fibrils. In order to determine whether this is, in part, a result of changes in the population of proteoglycans that are thought to be involved in regulation of collagen fibril formation, we have compared PGs from post-burn normal and hypertrophic scar tissue, as well as from human dermis and epidermis. Efforts to separate the two major iduronic acid-containing proteoglycans, decorin [PG(IdoA)-II] and biglycan [PG(IdoA)-I], for quantitation were not successful. The different N-terminal sequences of these two iduronic acid-containing proteoglycans PG(IdoA-I and -II were utilized to estimate the relative amounts in the above PG(IdoA) preparations. Normal scar, dermis and epidermis were all found to contain primarily decorin with low (< 10%) levels of biglycan relative to decorin. In contrast, iduronic acid-containing proteoglycans from hypertrophic scar were found to be approximately 30% biglycan [PG(IdoA)-I]. This may be a proximal cause of altered collagen fibrils, or may result in alterations in the sequestration of growth factors, which then results in changes in collagen that effect the appearance of the scar. 1966 Elsevier Science Ltd.

Iduronic acid-rich proteoglycans (PGIdoA) and human post-burn scar maturation: isolation and characterization

Proteoglycans (PGs) were extracted from human hypertrophic and normal scar tissues from two different stages of maturation after burn injury, under dissociative conditions (4 M guanidinium chloride containing proteinase inhibitors). The extracts were fractionated by ion-exchange chromatography, followed by ethanol precipitation, to give PG-containing iduronic acid (PGIdoA). The size of the PGIdoA decreased with the maturation of scars. Glycosaminoglycan (GAG) chains from PGIdoA were released by alkaline borohydride treatment, and their M(r) values were evaluated by polyacrylamide gel electrophoresis. The M(r) values for PGIdoA protein cores of the hypertrophic scars (5+ years and 2-5 years) and normal scar (5+ years and 2-5 years) were 22.6, 25, 19 and 21 kDa, respectively. The iduronic acid content of PGIdoA from both types of scar increased in their maturation phase. The M(r) values of PGIdoA decreased with maturation. PGIdoA carried the sulfate group mainly attached at C-4 of the 2-amino-2-deoxy-D-galactose residue. The NH2-terminal amino acid sequences of all the PGIdoA were similar to those of normal human skin or bone PG II (decorin) (i.e., Asp-Glu-Ala-B-Gly-Ile-Gly-Pro-Glu-Val-Pro-Asp-Asp-Arg).

Barrier dynamics in physiological aging

Approximately 40 years ago the author initiated work which led to the 'Diffusion Theory of Aging'. Due to the net differential rate of deposition of interstitial constituents the transfer of molecules through this milieu becomes modified with advancing age so that delivery of nutrients to the interior of the cells becomes inappropriate to maintain the physiology of youthful cells. Later it was proposed that superhomeostatic events could leave irreversible residues which would further contribute to this 'malnutrition'. The role of pericellular proteins and the plasma membrane was then unknown. Now they are much better understood as final barriers to the entrance and departure of molecules into and from the cell interior and they can be modified by age. Thus is proposed the 'Barrier Dynamics Hypothesis of Aging'.

Proteoglycans in human burn hypertrophic scar from a patient with Ehlers-Danlos syndrome

Proteoglycans (PGs) from human burn hypertrophic scar of a patient with Ehlers-Danlos syndrome were extracted with 4M guanidinium chloride and purified by DEAE-cellulose chromatography. Differential ethanol precipitation of the PG fraction obtained after ion-exchange chromatography yielded two low mol.-wt. PGs, on rich in glucuronic acid (PGGLCA; Mr 66 kDa) and the other rich in iduronic acid (PGIDOA; Mr 48 kDa). In PGGLCA, 84% of the glycosaminoglycan chains are composed of GlcA----GalNAc(SO4) units, whereas in PGIDOA, the chains contain 95% IdoA----GalNAc(SO4) disaccharide units. Upon treatment with testicular hyaluronidase, the PGs gave different-sized oligosaccharides. Chondroitinase ABC digestion of PGGLCA or PGIDOA gave a single protein core (Mr approximately 20 kDa). The presence of glucosamine and sialic acid in PGGLCA and PGIDOA suggests that both contain N-linked oligosaccharides.

Proteoglycan synthesis in human skin and burn scar explant cultures

The synthesis of proteoglycans (PG) by normal human skin, and normal and hypertrophic scars were compared using tissue explants in culture. Newly synthesized PG were labelled with [35S]Na2SO4. Significant differences were found in the proportion of [35S]-radio-labelled incorporation of PG in the tissue and accumulation of [35S]PG in culture medium in the different tissues. The rate of PG biosynthesis in all three tissue types occurred in two phases. There was an initial phase of PG synthesis occurring at 0-3 h and a later phase that occurred at 3-18 h [35S]-labelled PG were isolated and characterized by Sepharose CL-6B chromatography and cellulose acetate electrophoresis. The results showed that the hypertrophic scar tissue and its culture medium contained higher proportions of dermatan sulphate (DS), chondroitin sulphate (CS) and DS' PG than the normal skin fractions. These results suggest that abnormal scarring is related to a change in the level of PG synthesis during the burn injury repair process.