Cell aggregation: role of acid mucopolysaccharides

Sericin nano-gel agglomerates mimicking the pericellular matrix induce the condensation of mesenchymal stem cells and trigger cartilage micro-tissue formation without exogenous stimulation of growth factors in vitro

Mesenchymal stem cells (MSCs) are excellent seed cells for cartilage tissue engineering and regenerative medicine. Though the condensation of MSCs is the first step of their differentiation into chondrocytes in skeletal development, the process is a challenge in cartilage repairing by MSCs. The pericellular matrix (PCM), a distinct region surrounding the chondrocytes, acts as an extracellular linker among cells and forms the microenvironment of chondrocytes. Inspired by this, sericin nano-gel soft-agglomerates were prepared and used as linkers to induce MSCs to assemble into micro-spheres and differentiate into cartilage-like micro-tissues without exogenous stimulation of growth factors. These sericin nano-gel soft-agglomerates are composed of sericin nano-gels prepared by the chelation of metal ions and sericin protein. The MSCs cultured on 2D culture plates self-assembled into cell-microspheres centered by sericin nano-gel agglomerates. The self-assembly progress of MSCs is superior to the traditional centrifugation to achieve MSC condensation due to its facility, friendliness to MSCs and avoidance of the side-effects of growth factors. The analysis of transcriptomic results suggested that sericin nano-gel agglomerates offered a soft mechanical stimulation to MSCs similar to that of the PCM to chondrocytes and triggered some signaling pathways as associated with MSC chondrogenesis. The strategy of utilizing biomaterials to mimic the PCM as a linker and as a mechanical micro-environment and to induce cell aggregation and trigger the differentiation of MSCs can be employed to drive 3D cellular organization and micro-tissue fabrication in vitro. These cartilage micro-masses reported in this study can be potential candidates for cartilage repairing, cellular building blocks for 3D bio-printing and a model for cartilage development and drug screening.

Programmable Aggregation of Artificial Cells with DNA Signals

Cell aggregation is a complex behavior that is closely related to the viability, differentiation, and migration of cells. An effort to create synthetic analogs could lead to considerable advances in cell physiology and biophysics. Rendering and modulating such a dynamic artificial cell system require mechanisms for receiving, transducing, and transmitting intercellular signals, yet effective tools are limited at present. Here we construct synthetic cells from engineered lipids and show their programmable aggregation behaviors using DNA oligonucleotides as signaling molecules. The artificial cells have transmembrane channels made of DNA origami that are used to recognize and process intercellular signals. We demonstrate that multiple small vesicles aggregate onto a giant vesicle after a transduction of external DNA signals by an intracellular enzyme and that the small vesicles dissociate when receiving "release" signals. This work provides new possibilities for building synthetic protocells capable of chemical communication and coordination.

RCT to evaluate a hyaluronic acid containing gauze pad in leg ulcers of venous or mixed aetiology

OBJECTIVE

To investigate the efficacy and safety of an hyaluronic acid (HA)-impregnated gauze pad compared with a hydrocolloid (HC) dressing, in patients with leg ulcer of venous or mixed aetiology.

METHOD

A 56-day blind-observer, randomised, multicentre, controlled, non-inferiority trial. Patients were randomised to receive either an HA gauze pad (ialuset gauze pad) or an HC dressing (DuoDERM E).The primary endpoint was the difference between the groups regarding the percentages of patients achieving a reduction of at least 40% of the initial wound surface after 56 days of treatment (visit 5). Secondary endpoints included reduction of wound area, aspect of the wound (percentage of necrotic,fibrinous or granulation tissue), rate of complete ulcer healing, pain intensity, and clinical status of the peri-ulcerous skin.

RESULTS

In total, 170 patients were included and analysed in the intention-to-treat (ITT) population; 27 patients presented at least one major protocol deviation and were excluded from the per-protocol (PP) population.Therefore, 143 patients constituted the PP population (n=72 and n=71 in the HA gauze pad group and HC dressing group, respectively).At day 56, the confidence interval of the difference between the two groups for the percentage of patients with a reduction of at least 40% of the target ulcer initial surface was [-0.128; 0.164] with a lower limit above the non-inferiority threshold (-0.15). Peri-ulcerous skin was significantly less impaired in the HA gauze pad group for oedema at day 56 (p = 0.04), purpura at day 14 (p = 0.009) and for maceration at day 14 (p = 0.003). Other secondary endpoints were not significantly different between the two groups. Overall, both treatments were well tolerated and adverse events were comparable between the two groups regarding their pattern, frequency, likely relationship to treatment and severity which was mostly mild (grade I) or moderate (grade 2). These results were confirmed in the overall ITT population.

CONCLUSION

These data support the non-inferiority of the HA gauze pad compared with HC for the primary endpoint.The significant differences in favour of HA gauze pad regarding peri-ulcerous skin changes (oedema, purpura and maceration) may suggest a trend for HA gauze pad to have a better acceptability than the reference HC dressing.

DECLARATION OF INTEREST

This study was sponsored by Laboratoires Genévrier. Authors received honoraria for their contributions to the study, but have no other conflicts of interests to declare.

Role of CD44 in tumour progression and strategies for targeting

CD44 or hyaluronan receptor is a transmembrane receptor associated with aggressive tumour growth, proliferation, and metastasis. In normal physiology, this receptor has a crucial role in cell adhesion, inflammation, and repair processes. However, many tumour cells over-express this receptor and abuse it to become progressive and perpetual units. The article comments from common functioning of the CD44 receptor, to its diabolic multi-dimensional effects in promotion of malignant cells. It also illuminates the relations of CD44 endorsed processes with other biomolecular events in cancer progression. In an end, the review focuses comprehensively at ongoing researches to exploit the CD44 over-expression as a probable target in treatment, management, and diagnosis of malignancy.

Shear stress regulates adhesion and rolling of CD44+ leukemic and hematopoietic progenitor cells on hyaluronan

Leukemic cells and human hematopoietic progenitor cells expressing CD44 receptors have the ability to attach and roll on hyaluronan. We investigated quantitatively the adhesion behavior of leukemic cell lines and hematopoietic progenitor cells on thin films of the polysaccharides hyaluronan and alginate in a microfluidic system. An applied flow enhances the interaction between CD44-positive cells and hyaluronan if a threshold shear stress of 0.2 dyn/cm(2) is exceeded. At shear stress ∼1 dyn/cm(2), the cell rolling speed reaches a maximum of 15 μm/s. Leukemic Jurkat and Kasumi-1 cells lacking CD44-expression showed no adhesion or rolling on the polysaccharides whereas the CD44-expressing leukemic cells KG-1a, HL-60, K-562, and hematopoietic progenitor cells attached and rolled on hyaluronan. Interestingly, the observations of flow-induced cell rolling are related to those found in the recruitment of leukocytes to inflammatory sites and the mechanisms of stem-cell homing into the bone marrow.

The role of the foreign surface and female parasitoid secretions on the immune response of an insect

Most successful parasitoids are able to avoid the encapsulation reaction of their host. A similar avoidance was observed with particles of a weakly acidic cation exchanger which was not encapsulated following its injection into the haemocoele of an insect. The ionic nature of the surface of the acidic cation exchanger and the two species of parasitoid eggs appeared to be similar. A weakly basic anion exchanger was readily encapsulated following injections into the haemocoele of a host. The encapsulation of the basic anion exchanger was prevented by coating the surface with fluid from the calyx region of the female parasitoid ovary. The importance of the fluid from the calyx region of the parasitoid and the ionic nature of the surface in avoiding the encapsulation reaction of the hosts haemocytes is discussed.

Hyaluronan-binding receptors: possible involvement in osteoarthritis

Our objectives were to compare the expression of the hyaluronan receptors CD44 and RHAMM in knee synovial tissue of patients with and without advanced osteoarthritis (OA). Both receptors were detected immunohistochemically; the staining appeared more intense in the tissues from the patients with advanced OA. Expression of CD44 and RHAMM were each significantly increased (p < 0.05) in synovial tissue from patients with OA, as determined by means of Western-blot analysis. The findings suggested that changes in levels of the HA-binding proteins might be implicated in the development or progression of OA.

Direct measurement of forces between cell-coating polymers and chiral crystal surfaces: the enantioselectivity of

The interactions of hyaluronan (HA), a high-molecular-weight linear polysaccharide present in many pericellular coatings, with different facets of chiral calcium tartrate (CT) crystal surfaces are investigated using a molecular force probe. Forces between {011} and {110} facets of (R,R) and (S,S) CT crystals and a HA-bearing surface have been measured in saturated CT solutions. It has been observed that hyaluronan binds most strongly to the {011} facet of the (R,R) crystal, compared with the other facets examined, which is consistent with earlier observations of the adhesion of HA-coated cells to chiral CT crystals. The variation of binding strength among the facets studied is tentatively attributed to the surface structure difference between the {011} and {110} facets as well as to the preferential matching of the local hyaluronan H-bond network to the -OH groups on the {011} facet of the (R,R) enantiomer.

Solid-state hydrolysis of cellulose and methyl α- and β-d-glucopyranosides in presence of magnesium chloride

Solid-state hydrolysis proceeded with cellulose and methyl alpha- and beta-D-glucopyranosides in the presence of hydrated magnesium chloride. This reaction was effective even at >100 degrees C since the hydrated water, which is held by MgCl(2) up to >200 degrees C, is utilized as a nucleophile. Excess water made this reaction ineffective due to the competition between water and sugar oxygen atoms in coordinating with Mg(2+), a Lewis acid. Consequently, this hydrolysis reaction is characteristic of solid-state reactions.

Characterization of hyaluronan-binding proteins on guinea pig polymorphonuclear leukocytes: possible involvement of complement receptor type 3 (CR3, CD11b/CD18) in the hyaluronan-leukocyte interaction

Hyaluronan (HA), a high-molecular-weight glycosaminoglycan ubiquitously present in the extracellular matrices (ECMs) of animals, plays important roles in ECM organization and cell behavior through binding to hyaluronan-binding proteins (HABPs). We previously reported that HA has anti-inflammatory effects on guinea pig phagocytes, although the nature of guinea pig HABPs was unknown. In this study, we characterized guinea pig HABPs on peritoneal polymorphonuclear leukocytes (PMNs) and blood neutrophils by flow cytometry and affinity chromatography. It was found that PMNs express diverse HABPs with different molecular weights. These HABPs maximally bound with HA over a wide pH range (6-8), and recognized HAs as small as the pentadisaccharide units of d-glucuronic acid and N-acetyl-d-glucosamine. Furthermore, they could be divided into Mg(2+)-dependent and Ca(2+)/Mg(2+)-independent groups. Interestingly, two proteins in the Mg(2+)-dependent group were found to be the two subunits of complement receptor type 3 (CR3, CD11b/CD18). Unlike PMNs, blood neutrophils expressed several functionally inactive HABPs. Among these inactive HABPs, Mg(2+)-dependent proteins including CR3 but not Ca(2+)/Mg(2+)-independent proteins were activated on phorbol ester-stimulation. These results show the existence of diverse HABPs on guinea pig neutrophils and the cell activation-dependent activation of HABPs. It is also suggested that the CR3-HA interaction is possibly involved in the regulation of neutrophil function.

Adsorption of biopolymers at hydrophilic cellulose-water interface

The extent of adsorption (Gamma2(1)) of bovine serum albumin (BSA), beta-lactoglobulin, lysozyme, gelatin, and DNA from aqueous solution onto the hydrophilic surface of cellulose has been measured as function of biopolymer concentration at different temperatures, pHs, and ionic strengths, and in the presence of a high concentration of inorganic salts and denaturants. In all cases, the value of Gamma2(1) increases with the increase of biopolymer concentration (X2) in bulk and it attains a maximum value at a critical mole fraction concentration X2m. The value of Gamma2m depends upon the nature of protein, temperature, pH, and ionic strength, as well as the nature of neutral salts present in excess. Gamma2m for proteins at a fixed physicochemical condition stands in the following order: Gelatin>betalactoglobulin>lysozyme>BSA. The isotherms for adsorption of DNA nucleotides on cellulose surface at pH 4.0 have been compared at different temperatures and ionic strengths, and in the presence of high concentration of inorganic salts LiCl, NaCl, KCl, and Na2SO4. Values of Gamma2m for different systems have been evaluated and critically compared. At pH 6.0 and 8.0, Gamma2(1) values of DNA nucleotides on cellulose are all negative due to the excess positive hydration of cellulose. At pH 4.0, adsorption of nucleotides of acid, alkali, and heat-denatured DNA widely differ from each other and in the presence of excess concentration of urea becomes negative. The probable mechanisms of biopolymer-cellulose adsorption in terms of polymer hydration, steric interaction, London-van der Waals, hydrophobic, and other types of interactions have been discussed qualitatively. The standard free energy change for the adsorption of protein and DNA nucleotides on the cellulose surface at the state of adsorption saturation has been calculated in kJ per kg of cellulose using an integrated form of the Gibbs adsorption equation. The relation between DeltaG degrees and maximum affinities between biopolymers and the polysaccharide interface have been discussed for various systems.

Engineering of Biomaterials Surfaces by Hyaluronan

This review addresses the area of study that defines the field of surface modification of biomedical materials and devices by hyaluronan (HA), as related to the exploitation of HA biological properties. To provide a comprehensive view of the subject matter, initial sections give a quick introduction to basic information on HA-protein and HA-cell interactions, together with some discussion on the bioactive role of HA in wound healing and related phenomena. This is followed by a description of current theories that correlate HA properties to its molecular structure in aqueous media, underlying how HA molecular details are crucial for its biological interaction and role. Finally, existing approaches to surface modification by HA are reviewed, stressing the need for HA-surface engineering founded on the knowledge and control of the surface-linked HA molecular conformation at the solid/aqueous interface.

Differentiation of mesothelioma from adenocarcinoma in serous effusions: The role of hyaluronic acid and CD44 localization

Differentiating cells of mesothelial origin from adenocarcinoma (ACA) based on morphology alone can be a diagnostic challenge, especially in cytological specimens. Malignant mesothelioma (MM) is characterized by accumulation of abundant intracellular hyaluronic acid (HA), a feature that is not reported in ACA. The purpose of this study was to evaluate the significance of cellular HA using an HA-specific binding peptide (HABP) and the expression of its principal receptor, the standard CD44 molecule (CD44S). Archival paraffin-embedded cell blocks of serous fluids from 28 cases of reactive mesothelial cells, 14 cases of MM, 20 cases of metastatic ovarian carcinomas, 17 cases of metastatic breast carcinomas, 12 cases of metastatic lung ACA, and 12 cases of metastatic gastrointestinal ACA were stained with HA using a biotinylated HABP and CD44S. Positive staining was defined as droplet to diffuse cytoplasmic staining for HA and uniform membranous staining for CD44S. All MMs and 93% (26/28) of the benign mesothelial cells were positive for intracytoplasmic HA vs. none of ACAs. CD44S was expressed in 100% (28/28) of mesothelial hyperplesia, 86% (12/14) of MMs, 70% (14/20) of ovarian carcinomas, 29% (5/17) of breast carcinomas, 25% (3/12) of gastrointestinal ACAs, and 8% (1/12) of lung ACAs. In MM and reactive mesothelial cells, CD44S stained cell membranes diffusely with highlights on the villous surfaces and in ACA it was focal and confined to cell membranes. Immunostaining with HA is a reliable marker that can distinguish between cells of mesothelial origin (reactive mesothelial cells and MM) and ACA. The CD44S staining pattern of cells of mesothelial origin is of diagnostic significance. CD44 may prove useful in conjunction with other stains in the differential diagnosis of mesothelioma and ADA.

Adhesion molecules

The exact mechanisms by which serous ovarian cancer cells invade through their underlying basement membrane or are released from the surface of the ovary have yet to be elucidated. This process undoubtedly has a complex molecular basis that most likely involves multiple cell surface receptors, basement membrane components, intercellular adhesion molecules, and signaling from the cell [137]. One possible mechanism by which ovarian carcinoma tumor cells may alter their basement membrane is by the synthesis and secretion of proteolytic enzymes that degrade their basement membranes [88-94, 138]. Alternatively, metastatic ovarian carcinoma cells may decrease their synthesis and/or secretion of ECM molecules. Additional studies are required to determine whether the more aggressive behavior of malignant ovarian carcinoma cells, compared to normal ovarian epithelial cells, is related to an altered cellular response towards ECM molecules, perhaps due to alterations in adhesion molecules/receptors. A further elucidation of the mechanisms by which serous ovarian carcinoma cells regulate their expression of ECM molecules and adhesion molecules/receptors will help in our understanding of the invasion and metastasis of tumor cells. Members of several families of adhesion molecules have been described that seem to be important in the progression of ovarian carcinoma, including CD44, integrins, and E-cadherin. Due to the complexity of this disease, it is likely that other adhesion molecules will also be implicated in the adhesion, migration, invasion, growth, proliferation, and apoptosis of ovarian carcinoma cells. Our group and others have shown that CD44 and the beta 1 integrin subunit play fundamental roles in the adhesion and migration of ovarian carcinoma cells to mesothelial cells and their associated pericellular matrix. Subsequent to the initial adhesion, the ovarian carcinoma cells may migrate through the layer of mesothelial cells, penetrate through the underlying basement membrane, invade into the tissue, and establish a secondary site of growth. Further studies will be required in order to fully understand the relationship of each adhesion molecule and their ligand(s) in the progression of this disease. Once the adhesion molecules and their ligand(s) for each step of the progression of this disease have been identified, it should be possible to develop reagents that can inhibit these interactions. Then, when ovarian carcinoma cells can no longer interact with mesothelial cells and their associated ECM, the dissemination of ovarian carcinoma cells in vivo may be prevented.

Water content, body weight and acid mucopolysaccharides, hyaluronidase and beta-glucuronidase in response to aestivation in Australian desert frogs

This study investigates the effects of aestivation on body water content, body mass, acid mucopolysaccharide (AMPS) and some of its degrading enzymes in different tissues for some Australian desert frogs. The AMPS component of the liver, kidney, skin and cocoon alter during aestivation to help retain water, which is unchanged in most tissues of all frog species, and to protect the frogs from desiccation during extended periods of aestivation. Hepatic AMPS was unaltered in Cyclorana maini, C. platycephala and Neobatrachus sutor but increased significantly after 2 months of aestivation in C. australis. The level of AMPS in the kidney was elevated in all four frog species after 5 months of aestivation. Skin AMPS content in the skin of awake frogs decreases with aestivation period and increases in the cocoon. AMPS in the cocoon probably works as a cement between the cocoons' layers and its physical presence presumably contributes to preventing water flux. Changes in AMPS content in different tissues were accompanied by significant changes in both hyaluronidase and beta-glucuronidase activities, which play an important role in AMPS metabolism. Alcian blue staining of control and digested skin of C. australis and C. platycephala with testicular hyaluronidase indicated the presence of AMPS, concentrated in a thin layer (called ground substance, GS) located between stratum compactum and stratum spongiosum, and acid mucin concentrated in the mucous glands and in a 'tubular' structure which could be observed in the epidermal layer. Hyaluronidase digestion of the cocoon slightly changed the Alcian Blue colour, suggesting the presence of a large amount of acid mucin similar to that found in the skin mucous gland. The results of this study present data for the redistribution of AMPS, which may help in reducing water loss across the cocoon and reabsorption of water in the kidney during aestivation.

Hyaluronidase as additive to induction chemotherapy in advanced squamous cell carcinoma of the head and neck

Forty-eight patients with advanced head and neck tumours were treated with irradiation and concomitant chemotherapy with cisplatin, vindesine and hyaluronidase. The disease-free survival rate at 5 years was 47%. The toxic effects were mucositis (48 patients), nausea (25 patients, vomiting in six patients), bone marrow depression (15 patients) and peripheral neuropathy (14 patients). The results warrant a randomized trial.

The normal structure and function of CD44 and its role in neoplasia

CD44 is a transmembrane glycoprotein, the variant isoforms of which are coded for by alternative splicing, with the most prolific isoform being CD44 standard. CD44 is found in a wide variety of tissues including the central nervous system, lung, epidermis, liver, and pancreas, whereas variant isoforms of CD44 (CD44v) appear to have a much more restricted distribution. Variants of CD44 are expressed in tissues during development, including embryonic epithelia. Known functions of CD44 are cellular adhesion (aggregation and migration), hyaluronate degradation, lymphocyte activation, lymph node homing, myelopoiesis and lymphopoiesis, angiogenesis, and release of cytokines. The functions of CD44 are principally dependant on cellular adhesion in one setting or another. The role of CD44 in neoplasia is less well defined, although metastatic potential can be conferred on non-metastasising cell lines by transfection with a variant of CD44 and high levels of CD44 are associated with several types of malignant tumours. The physiological functions of CD44 indicate that the molecule could be involved in the metastatic spread of tumours. Many studies have investigated the pattern of CD44 distribution in tumours and some observations suggest that certain cells do not use CD44 in tumorigenesis or in the production of metastases. However, the data are extremely conflicting, and further studies are needed to establish the prognostic value of CD44 and its variant isoforms. The precise function of CD44 in the metastatic process and the degree of involvement in human malignancies has yet to be established fully.

Interaction between Entamoeba histolytica and intestinal epithelial cells involves a CD44 cross-reactive protein expressed on the parasite surface

This study shows that Entamoeba histolytica binds hyaluronic acid. The binding molecule was identified as an 80-kDa membrane protein and was recognized by anti-CD44 monoclonal antibodies. These data indicate that a CD44 cross-reacting adherence molecule is expressed on E. histolytica.

Reduction of adhesion formation with hyaluronic acid after peritoneal surgery in rabbits

OBJECTIVE

To examine the effect of hyaluronic acid, a high-molecular-weight glucosaminoglycan found in the extracellular matrix, on the formation of adhesions, a major source of postoperative complications.

DESIGN

The ability of hyaluronic acid to reduce adhesion formation was evaluated using a standardized rabbit model. The material was administered i.p. at the end of surgery.

SETTING

University laboratory.

ANIMAL(S)

New Zealand White female rabbits.

INTERVENTION(S)

Intraperitoneal administration of various formulations of hyaluronic acid at the end of surgery.

MAIN OUTCOME MEASURE(S)

One week after surgery, a second laparotomy was performed and the extent of adhesion formation was determined.

RESULT(S)

Five separate molecular weight ranges of hyaluronic acid representing eight viscosities between 1,000 and 12,000 centipoise (CPS) were shown to reduce adhesion formation in this model. All volumes, 1 to 30 mL, of hyaluronic acid tested reduced adhesion formation. In addition, the low-viscosity, low-molecular-weight hyaluronic acid significantly reduced adhesion formation when added to the trauma site or when injected at a site remote from the trauma area.

CONCLUSION(S)

This study showed that hyaluronic acid administered at the end of surgery reduced adhesion formation.

Nectinepsin: a new extracellular matrix protein of the pexin family. Characterization of a novel cDNA encoding a protein with an RGD cell binding motif

We report the isolation and characterization of a novel cDNA from quail neuroretina encoding a putative protein named nectinepsin. The nectinepsin cDNA identifies a major 2.2-kilobase mRNA that is detected from ED 5 in neuroretina and is increasingly abundant during embryonic development. A nectinepsin mRNA is also found in quail liver, brain, and intestine and in mouse retina. The deduced nectinepsin amino acid sequence contains the RGD cell binding motif of integrin ligands. Furthermore, nectinepsin shares substantial homologies with vitronectin and structural protein similarities with most of the matricial metalloproteases. However, the presence of a specific sequence and the lack of heparin and collagen binding domains of the vitronectin indicate that nectinepsin is a new extracellular matrix protein. Furthermore, genomic Southern blot studies suggest that nectinepsin and vitronectin are encoded by different genes. Western blot analysis with an anti-human vitronectin antiserum revealed, in addition to the 65- and 70-kDa vitronectin bands, an immunoreactive protein of about 54 kDa in all tissues containing nectinepsin mRNA. It seems likely that the form of vitronectin found in chick egg yolk plasma by Nagano et al. ((1992) J. Biol. Chem. 267, 24863-24870) is the protein that corresponds to the nectinepsin cDNA. This new protein could be an important molecule involved in the early steps of the development.

The structure and function of hyaluronan: An overview

Hyaluronan is a major component of synovial tissue and fluid as well as other soft connective tissues. It is a high-Mr polysaccharide which forms entangled networks already at dilute concentrations (< 1 mg/mL) and endows its solutions with unique rheological properties. Physiological functions of hyaluronan (lubrication, water homeostasis, macromolecular filtering, exclusion, etc.) have been ascribed to the properties of these networks. Recently a number of specific interactions between hyaluronan and a group of proteins named hyaladherins have also pointed towards a role of hyaluronan in recognition and the regulation of cellular activities. Many more or less well documented hypotheses have been proposed for the function of hyaluronan in joints, for example, that it should lubricate, protect cartilage surfaces, scavenge free radicals and debris, keep the joint cavities open, form flow barriers in the synovium and prevent capillary growth.

Hyaluronan synthase immunoreactivity in the anterior segment of the primate eye

The anterior segment of human and cynomolgus monkey eyes was investigated for the presence of hyaluronan (HA) synthesizing cells using a polyclonal antibody against the enzyme HA synthase (HAS). In the chamber angle region the most intense staining was seen in the cell membranes of the corneal endothelium and in monkey eyes in the cells covering the posterior extension of the cornea (the operculum). The trabecular meshwork cells of the uveal and inner corneoscleral lamellae were also intensely stained. On the other hand, no staining was observed in the trabecular cells of the outer corneoscleral and the cribriform meshwork. The cell membranes of the inner wall endothelium of Schlemm's canal were labelled only at their luminal surface. In the iris stroma and the trabeculum ciliare (the ciliary body band), labelled cells were also found, whereas the connective tissue of the ciliary muscle and the muscle itself did not contain HAS-positive cells. In the ciliary processes immunoreactivity was seen in the non-pigmented epithelial cells (NPE) covering the anterior tips of the processes, suggesting that HA found in the aqueous humor is produced by these cells. The pars plana NPE showed the most intense staining in the cells directly adjacent to the ora serrata region. The hyalocytes found in the neighborhood of the pars plana also showed intense HAS immunoreactivity. It is likely that both hyalocytes and NPE cells of the posterior pars plana release HA into the vitreous.

Hyaluronate binding and CD44 expression in human glioblastoma cells and astrocytes

CD44 is an integral membrane glycoprotein of approximately 90 kDa which has been implicated in the binding of hyaluronate to the cell surface. The expression of CD44 in astrocytes was investigated by means of indirect immunofluorescence on cultured cells. The vast majority of these cells were found to express CD44. Western blot analysis of these cells revealed a highly polydisperse species having an M(r) corresponding to 74-86 kDa. In order to visualize hyaluronate-binding cells, living cultures were probed with fluorescein-conjugated hyaluronate (FI-HA). Some astrocytes were able to bind FI-HA, provided that they were first treated with hyaluronidase. Streptomyces hyaluronidase, which is hyaluronate-specific, was effective in exposing the hyaluronate-binding capacity of these cells. This leads one to conclude that hyaluronate is bound to the surface of these cells and that it masks their capacity to bind hyaluronate. Provided that they were first treated with hyaluronidase, the U-87 MG (glioblastoma-astrocytoma), U-373 MG (glioblastoma), and Hs 683 (glioma) cell lines were also able to bind FI-HA. The U-138 MG (glioblastoma) cell line was unable to bind FI-HA, with or without prior hyaluronidase treatment. A quantitative assay was developed with the use of [3H]hyaluronate ([3H]HA). This revealed the binding to be highly specific, inasmuch as the addition of unlabeled hyaluronate, but not other glycosaminoglycans, was effective in inhibiting the binding of the [3H]HA. An anti-CD44 monoclonal antibody, 50B4, was able to inhibit the binding of the [3H]HA to the U-373 MG cell line. In this cell line, then, CD44 functions as a hyaluronate receptor and one may infer that this is also the case in some astrocytes.

Recent advances in primary palate and midface morphogenesis research

During the sixth week of human development, the primary palate develops as facial prominences enlarge around the nasal pits to form the premaxillary region. Growth of craniofacial components changes facial morphology and affects the extent of contact between the facial prominences. Our recent studies have focused on developing methods to analyze growth of the primary palate and the craniofacial complex to define morphological phases of normal development and to determine alterations leading to cleft lip malformation. Analysis of human embryos in the Carnegie Embryology Collection and mouse embryos of cleft lip and noncleft strains showed that human and mouse embryos have similar phases of primary palate development: first, an epithelial seam, the nasal fin, forms; then a mesenchymal bridge develops through the nasal fin and enlarges rapidly. A robust mesenchymal bridge must form between the facial prominences before advancing midfacial growth patterns tend to separate the facial components as the medial nasal region narrows and elongates, the nasal pits narrow, and the primary choanae (posterior nares) open posterior to the primary palate. In mouse strains with cleft lip gene, maxillary growth, nasal fin formation, and mesenchymal replacement of the nasal fin were all delayed compared with noncleft strains of mice. Successful primary palate formation involves a sequence of local cellular events that are closely timed with spatial changes associated with craniofacial growth that must occur within a critical developmental period.

Small deletion in v-src SH3 domain of a transformation defective mutant of Rous sarcoma virus restores wild type transforming properties

RSV mutant virus PA101T was obtained while assaying the tumorigenicity of parental PA101 virus in chickens. PA101 is a transformation defective mutant of RSV which has a low src kinase activity. However, PA101 retained a temperature-sensitive ability to induce sustained proliferation of neuroretina cells. PA101T appeared as a wild-type phenotype revertant of PA101. Molecular cloning and sequencing of PA101T showed that this reversion is due to additional mutations in PA101 src gene. These mutations are a deletion eliminating three amino acids in the N-terminal region of SH3 domain and mutation of Ala 426 to Val. Analysis of the properties of chimeric src genes associating either half of PA101T with the complementary regions of PA101 or wild-type virus showed that the N-terminal moiety of PA101T src, which contains the deletion, confers wild-type transforming properties, whereas its C-terminal moiety, which contains single amino acid mutation, confers a partially temperature-sensitive phenotype. These results are consistent with other reports showing that mutations or deletions in this region of SH3 activate the transforming potential of c-src. They support the hypothesis that the N-terminal region of SH3 interacts with a cellular negative regulator of src activity.

Cell adhesion receptor expression during melanoma progression and metastasis

Many steps in melanoma metastasis involve cell-cell or cell-matrix adhesive interactions. The surface molecules which mediate these processes therefore play an important role in regulating melanoma dissemination and their level of expression may alter during the course of tumor progression. Human melanocyte strains and melanoma cell lines have been characterised with regard to levels of cell surface receptors of the integrin family. Increased amounts of at least two integrins, VLA-4 (alpha 4 beta 1) and VnR (alpha v beta 3), appeared to correlate with progression in this tumor, type. A novel VnR composed of an alpha v beta 1 association has been observed in one melanoma cell line and there is the possibility that heterogeneity of integrin composition could affect biological behavior of these tumors. CD44, a cell surface glycoprotein which functions as the major receptor for hyaluronate, is another molecule whose expression increases in transformed cells of the melanocytic lineage. Iterative sorting on the FACS for stable variants, of both human and murine melanomas, expressing low and high levels of CD44 established that lack of expression of this molecule correlated with impaired ability to form pulmonary tumor nodules subsequent to i.v. injection into appropriate recipient mice. These findings illustrate that an understanding of the regulation of melanoma adhesion receptors could provide insights into the process of tumor spread.

Characterization and purification of the hyaluronan-receptor on liver endothelial cells

In order to characterize the proteins on liver endothelial cells that bind hyaluronan (HYA), liver endothelial cells were surface-iodinated with 125I, solubilized by Triton X-100 and passed through a column containing HYA coupled to agarose. The column was washed and eluted with HYA-oligosaccharides. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the eluted material, followed by autoradiography, showed a major band with a molecular mass of 100 kDa, that upon reduction gave major bands of 20 and 35 kDa, and minor doublet bands at 60 and 80 kDa. Two-dimensional electrophoresis of liver endothelial cell membrane proteins revealed that the 100 kDa protein has a pI of 6.6-6.8. The protein was purified by preparative SDS-PAGE of liver endothelial cell membrane proteins. The 100 kDa protein was excised from the gel and used for immunization of rabbits. Antiserum from immunized rabbits specifically recognized only the 100 kDa protein on immunoblots of liver endothelial cell membrane proteins separated by SDS-PAGE. The binding of 3H-HYA to liver endothelial cells and liver endothelial cell membranes could be specifically inhibited by Fab-fragments of the antibodies. When we tried to isolate the receptor in large scale by affinity chromatography of proteins from purified liver endothelial cell membranes, the 100 kDa protein could often not be detected on immunoblots or by silver staining following SDS-PAGE of the eluted material. Instead, proteins with molecular masses of 55 and 15 kDa were detected, but the antibodies reacted specifically with these proteins. Thus the 100 kDa protein is apparently susceptible to cleavage into distinct subcomponents.

Determination of the osmotic active drug concentration in the cytoplasm of anthracycline-resistant and -sensitive K562 cells

A fluorescence method was used to follow the interaction of 4'-o-tetrahydropyranyladriamycin (THP-ADR) with drug-resistant and -sensitive K562 cells. The amounts of drug bound to the nuclei at the steady state, Cn and at the equilibrium state, CN, once the membrane has been solubilized with Triton X-100, have been determined as a function of the pH outside the cells (pHe): Cn increased and CN decreased as pHe increased. At a given pH value outside the cells, CN is the same for both sensitive and resistant cells, whereas Cn is lower in resistant cells as compared to sensitive cells. Using the observation that the essential binding characteristics of THP-ADR in nuclei are the same for both types of cell, the osmotic active drug concentration, Ci, in the cytoplasm of the cells was determined at different values of pHe. Using fluorescent dye, the cytoplasmic pH was determined and found equal to 7.2 +/- 0.1 in both types of cell. In sensitive cells, the equilibrium transmembrane concentrations verified the relation [DH+]i/[DH+]e = [H +]i/[H+]e where [DH +]i and [DH +]e stand for the concentration of protonated form of the drug inside and outside the cells, respectively. This indicates that the uptake of the drug occurs through free permeation of the neutral form of the drug in response to delta pH gradient. Such a relation is not verified in the case of resistant cells.

Hyaluronan-binding proteins on cultured J 774 macrophages

Cultivated macrophages of murine cell-line J 774 were found to bind high-molecular-weight (molecular weight average approx. 5.10(6) [3H]hyaluronan (HA) by a saturable mechanism at 4 degrees C. Half-maximal binding was observed at 7-8 microgram/ml (1.4-1.6 nM) and the maximal binding was reached at 30-40 microgram/ml. Scatchard plot analysis revealed that approx. 20,000 molecules could bind to each cell with a Kd of 1.5 nM. The binding could be effectively inhibited by unlabeled HA. Also chondroitin sulphate inhibited the binding, but only to about 50%. At 37 degrees C the J 774 cells took up and degraded the polysaccharide effectively. Affinity chromatography on HA coupled to agarose of solubilized surface-iodinated J 774 cells, revealed that a protein of approx. 60 kDa, when analyzed by sodium dodecylsulfate polyacrylamide gel electrophoresis and autoradiography, could be specifically eluted with HA-oligosaccharides. Our results suggest that J 774 macrophages can bind HA by a mechanism compatible with receptor-binding, and carry a 60 kDa HA-binding protein on their surface. This receptor-binding may mediate uptake and degradation of the polysaccharide and influence the levels and turnover of HA in interstitial fluid as well as the release of HA into the bloodstream.

Binding of hyaluronic acid to lymphoid cell lines is inhibited by monoclonal antibodies against Pgp-1

Recent biochemical and sequence data suggest a possible relationship between Pgp-1 (identical to CD44/Hermes 1/p85) and a hyaluronic acid-binding function. Here, we have studied the hyaluronic acid-binding activity of a series of murine hematopoietic cell lines using several assays: cell aggregation by hyaluronic acid, binding of fluorescein-conjugated hyaluronic acid, and cell adhesion to hyaluronic acid-coated dishes. Certain Pgp-1-positive T and B cell lines show hyaluronic acid binding that is highly specific and is not competed for by other glycosaminoglycans. Monoclonal antibodies against Pgp-1, but not antibodies against other major cell surface glycoproteins, inhibited hyaluronic acid-induced cell aggregation and cell adhesion to hyaluronic acid-coated dishes. Additionally, some anti-Pgp-1 antibodies inhibited binding of fluorescein-hyaluronic acid to hyaluronic acid-binding lines. We found no Pgp-1-negative lines that bound, but many Pgp-1-positive cell lines did not bind hyaluronic acid. Two Pgp-1-positive thymomas that did not bind hyaluronic acid were induced by phorbol ester to bind hyaluronic acid with the same specificity as other hyaluronic acid-binding lines. Normal hematopoietic cells, including those which express high levels of Pgp-1, such as bone marrow myeloid cells and splenic lymphocytes, showed no detectable hyaluronic acid-binding activity. We discuss several models that might account for these observations: (1) the hyaluronic acid receptor is Pgp-1, but it normally exists in an inactive state; (2) hyaluronic acid receptors are a subset of a family of molecules recognized by anti-Pgp-1 antibodies; (3) the hyaluronic acid receptor is not Pgp-1, but is closely associated with Pgp-1 on the surface of cells which express hyaluronic acid-binding activity.

Serum proteins enhance aggregate formation of dissociated fetal rat brain cells in an aggregating culture

Dissociated fetal rat brain cells (Day 14.5 of gestation) reaggregated into small cell clusters and formed large aggregates in a medium supplemented with serum or dialyzed serum in an aggregating culture. In contrast, only small aggregates were produced in a serum-free medium. The present results indicated that albumin, fetuin, transferrin, and alpha 1-antitrypsin enhanced the aggregate formation. Small aggregates produced in a serum-free medium elongated neurites when they were cultured within a collagen gel matrix. Total DNA per flask was almost the same in small and large aggregates. Thus, these serum proteins may well play an important role in the adhesion of small cell clusters and cause the formation of large aggregates in this short-term aggregating culture.

Aggregation of macrophages and fibroblasts is inhibited by a monoclonal antibody to the hyaluronate receptor

To examine the role of the hyaluronate receptor in cell to cell adhesion, we have employed the K-3 monoclonal antibody (MAb) which specifically binds to the hyaluronate receptor and blocks its ability to interact with hyaluronate. In the first set of experiments, we investigated the spontaneous aggregation of SV-3T3 cells, which involves two distinct mechanisms, one of which is dependent upon the presence of divalent cation and the other is independent. The divalent cation-independent aggregation was found to be completely inhibited by both intact and Fab fragments of the K-3 MAb. In contrast, the K-3 MAb had no effect on the divalent cation-dependent aggregation of cells. In a second set of experiments, we examined alveolar macrophages. The presence of hyaluronate receptors on alveolar macrophages was demonstrated by the fact that detergent extracts of these cells could bind [3H]hyaluronate, and this binding was blocked by the K-3 MAb. Immunoblot analysis of alveolar macrophages showed that the hyaluronate receptor had a Mr of 99,500, which is considerably larger than the 85,000 Mr for that on BHK cells. When hyaluronate was added to suspensions of alveolar macrophages, the cells were induced to aggregate. This effect was inhibited by the K-3 MAb, suggesting that the hyaluronate-induced aggregation was mediated by the receptor.

Hyaluronate-cell interactions during differentiation of chick embryo limb mesoderm

The mechanism of interaction of hyaluronate with the surface of cells from embryonic chick limbs was studied using cell cultures of mesoderm from various developmental stages. The mode of interaction of hyaluronate with the cell surface changed at the onset of mesodermal cell condensation prior to differentiation of cartilage and muscle. At this time hyaluronate binding sites appeared on the cells and continued to be present on differentiated chondrocytes but not on myotubes. Direct measurement of hyaluronate binding was made using stage 24 mesodermal cells and membranes isolated from cells derived from various limb stages. The stage 24 cells and membranes from stage 22, 24, and 26 cells exhibited hyaluronate binding, but not membranes from stage 19 mesoderm cultures. At stage 38, membranes from chondrocyte cultures exhibited the highest hyaluronate binding, and membranes from myoblasts and fibroblasts intermediate binding, whereas membranes from myotube-enriched cultures lacked binding activity. No significant competition of hyaluronate binding by chondroitin sulfate was observed. Occupied hyaluronate binding sites were measured by the displacement of radiolabeled cell surface hyaluronate with exogenous, unlabeled hyaluronate. Very little hyaluronate was displaced from mesodermal cells derived from the youngest embryos, namely, stage 19 or stage 20-21. However, greater than 50% of cell surface hyaluronate was displaced from stage 22 and 24 mesodermal cells. The addition of exogenous hyaluronate to stage 26 mesoderm, the stage of onset of cartilage differentiation, and to stage 38 chondrocytes resulted in displacement of large proportions of both hyaluronate and chondroitin sulfate. Addition of exogenous chondroitin sulfate did not cause displacement of significant amounts of cell surface hyaluronate or chondroitin sulfate. These results indicate the presence and developmental modulation of specific binding sites for hyaluronate on limb cells during their differentiation.

The hyaluronate receptor is associated with actin filaments

The cell-surface receptor for hyaluronate is an integral membrane glycoprotein of Mr 85,000 (Underhill, C. B., A. L. Thurn, and B. E. Lacy, 1985, J. Biol. Chem., 260:8128-8133) that is thought to mediate many of the effects that hyaluronate has on cell behavior, such as migration, angiogenesis, and phagocytosis. To determine if the receptor is associated with the underlying cytoskeleton, Swiss 3T3 cells were extracted with a solution of Triton X-100, which solubilized most of the cellular components, but which left behind an insoluble residue containing the cytoskeleton. This detergent-insoluble residue was found to contain the bulk of the hyaluronate-binding activity, suggesting that the receptor might indeed be associated with the cytoskeleton. To further define the cytoskeletal element with which the receptor interacts, 3T3 cells were extracted with Triton X-100 under a variety of different ionic conditions. In each case, the amount of hyaluronate-binding activity in the detergent-insoluble residue was related to the amount of actin present, but not to either tubulin or vimentin. In addition, the recovery of hyaluronate-binding activity was dramatically enhanced (to 100% in most cases) if the cells were extracted in the presence of phalloidin, a drug that stabilizes actin filaments. However, the recovery of binding activity was dramatically decreased when whole cells were treated with cytochalasin B before extraction, and when extracted cells were treated with DNase I, which promotes the depolymerization of actin filaments. In addition, preincubating an extract of SV-40-transformed Swiss 3T3 cell membranes with DNase I caused a change in the elution profile of the receptor as judged by molecular-sieve chromatography. Presumably this decrease in the size of the receptor is due to the loss of associated actin filaments. The results of these experiments strongly suggest that the receptor for hyaluronate is associated either directly or indirectly with cytosolic actin filaments.

Induction of proliferation of neuroretina cells by long terminal repeat activation of the carboxy-terminal part of c-mil

Expression of the P100gag-mil protein of avian retrovirus MH2 in cultured chicken embryo neuroretina cells was previously shown to result in the proliferation of normally quiescent cell populations. We show here that long terminal repeat activation of the carboxy terminus of the c-mil gene is sufficient to induce neuroretina cell proliferation.

Hyaluronate inhibition of cell proliferation

The proliferation of rabbit synovial cells, 3T3 cells, or simian virus-transformed 3T3 cells in cell culture was inhibited by the addition of hyaluronate to the culture medium. This effect was markedly dependent on the molecular weight and concentration of the hyaluronate. At the molecular weight and concentration of hyaluronate present in normal synovial fluid, proliferation was inhibited. At lower molecular weights or concentrations, as found in rheumatoid synovial fluid, hyaluronate was significantly less inhibitory. Thus, the changes in synovial fluid hyaluronate that are associated with arthropathies may contribute to a favorable environment for rheumatoid pannus expansion.

Induction of proliferation of neuroretina cells by long terminal repeat activation of the carboxy-terminal part of c-mil

Expression of the P100gag-mil protein of avian retrovirus MH2 in cultured chicken embryo neuroretina cells was previously shown to result in the proliferation of normally quiescent cell populations. We show here that long terminal repeat activation of the carboxy terminus of the c-mil gene is sufficient to induce neuroretina cell proliferation.