Incorporating strontium enriched amorphous calcium phosphate granules in collagen/collagen-magnesium-hydroxyapatite osteochondral scaffolds improves subchondral bone repair

Osteochondral defect repair with a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold has demonstrated good clinical results. However, subchondral bone repair remained suboptimal, potentially leading to damage to the regenerated overlying neocartilage. This study aimed to improve the bone repair potential of this scaffold by incorporating newly developed strontium (Sr) ion enriched amorphous calcium phosphate (Sr-ACP) granules (100-150 μm). Sr concentration of Sr-ACP was determined with ICP-MS at 2.49 ± 0.04 wt%. Then 30 wt% ACP or Sr-ACP granules were integrated into the scaffold prototypes. The ACP or Sr-ACP granules were well embedded and distributed in the collagen matrix demonstrated by micro-CT and scanning electron microscopy/energy dispersive x-ray spectrometry. Good cytocompatibility of ACP/Sr-ACP granules and ACP/Sr-ACP enriched scaffolds was confirmed with in vitro cytotoxicity assays. An overall promising early tissue response and good biocompatibility of ACP and Sr-ACP enriched scaffolds were demonstrated in a subcutaneous mouse model. In a goat osteochondral defect model, significantly more bone was observed at 6 months with the treatment of Sr-ACP enriched scaffolds compared to scaffold-only, in particular in the weight-bearing femoral condyle subchondral bone defect. Overall, the incorporation of osteogenic Sr-ACP granules in Col/Col-Mg-HAp scaffolds showed to be a feasible and promising strategy to improve subchondral bone repair.

Alternative in vitro models used in the main safety tests of cosmetic products and new challenges

BACKGROUND

Guided by ethical considerations and regulatory requirements such as the 7th Amendment to the European Cosmetics Directive N° 1223/2009, the cosmetic industry has developed and evaluated alternative test strategies such as in vitro assays, in silico approaches for toxicological endpoints and efficacy of cosmetic products and cosmetics ingredients. In consequence, the European Centre for the Validation of Alternative Methods (ECVAM) has proposed a list of validated cell-based in vitro models for predicting the safety and toxicity of cosmetic ingredients. These models have been demonstrated as valuable and effective tools to overcome the limitations of animal in vivo studies. For example, 3D human skin equivalent models are used to evaluate skin irritation potential; and excised human skin is used as the gold standard for the evaluation of dermal absorption.

OBJECTIVE

This review presents, in relation to the regulatory requirements, the main alternative in vitro models used in the safety tests of cosmetic products, focusing on skin sensitization, skin corrosion, skin irritation and skin absorption, with advantages and limitations of each model. Recent innovative 3D cell technologies such as Organ-on-a-Chip (OoC) models that can bring significant improvements for toxicology and efficacy testing are also presented.

CONCLUSION

The development of OoC technology is promising for assessing the toxicity of substances contained in cosmetics, particularly for repeated dose toxicity, for which no alternative in vitro methods are currently available. Nevertheless, aside from the challenges, the technology needs to be validated and accepted by regulatory organizations as an effective method. Collaboration between researchers, regulatory organizations and industry would be required to achieve this validation.

Biocompatible fibrous networks of cellulose nanofibres and collagen crosslinked using genipin: potential as artificial ligament/tendons

Bio-based fibrous nanocomposites of cellulose nanofibres and non-crosslinked/crosslinked collagen were prepared by in situ pH-induced fibrillation of collagen phase and sterilized using gamma rays at 25 KGy. Collagen phase is crosslinked using genipin, a bio-based crosslinker that introduces flexible crosslinks. Microscopy studies of the prepared materials showed nanostructured fibrous collagen and cellulose dispersed in collagen matrix. Mechanical performance of the sterilized nanocomposites was close to that of natural ligament and tendon, in simulated body conditions. Cytocompatibility studies indicated that these nanocomposites allowed human ligament cell and human endothelial cell adhesion, growth, and differentiation; which is eminently favourable to ligament tissue engineering.

Behavior of human cells in contact with a poly(d,l-lactic acid) porous matrix after calcification using phosphatidylserine

As part of a strategy aimed at improving bioresorbable scaffolds for the engineering of bony tissues, a route to deposit calcium phosphate onto surfaces of poly(dl-lactic acid)–based porous matrices was investigated. Porosity was generated using the NaCl-leaching technique. Calcification was achieved after deposition of phosphatidylserine, a nucleating agent of natural origin, onto pore surfaces, followed by incubation of the phospholipid-coated matrix in a pH 6.5 aqueous medium consisted of 3.5 mmol CaCl2 and 2.6 mmol KH2PO4 for 3 days. Calcified matrices were noncytotoxic according to the ISO10993-5 standard test and exhibited low inflammatory potential. To compare responses of human cells of different types, human osteogenic bone marrow cells from the femoral head, human chondrocytes from femoral cartilage collected after hip surgery, and human vascular endothelial cells isolated from an umbilical cord were allowed to grow in the presence of the calcified matrices in vitro. Articular chondrocytes adhered to and grew on the calcified matrices up to colony formation. In contrast, the other two types of cells attached and proliferated for approximately 3 days and then detached. These different cell behaviors are discussed with respect to the nature of the cells and to the release of calcium ions from the coating.

Reduction of biofilm infection risks and promotion of osteointegration for optimized surfaces of titanium implants

Titanium-based implants are widely used in modern clinical practice; however, complications associated with implants due to bacterial-induced infections arise frequently, caused mainly by staphylococci, streptococci, Pseudomonas spp. and coliform bacteria. Although increased hydrophilicity of the biomaterial surface is known to be beneficial in minimizing the biofilm, quantitative analyses between the actual implant parameters and bacterial development are scarce. Here, the results of in vitro studies of Staphylococcus aureus and Staphylococcus epidermidis proliferation on uncoated and coated titanium materials with different roughness, porosity, topology, and hydrophilicity are shown. The same materials have been tested in parallel with respect to human osteogenic and endothelial cell adhesion, proliferation, and differentiation. The experimental data processed by meta-analysis are indicating the possibility of decreasing the biofilm formation by 80-90% for flat substrates versus untreated plasma-sprayed porous titanium and by 65-95% for other porous titanium coatings. It is also shown that optimized surfaces would lead to 10-50% enhanced cell proliferation and differentiation versus reference porous titanium coatings. This presents an opportunity to manufacture implants with intrinsic reduced infection risk, yet without the additional use of antibacterial substances.

Ion exchanges in apatites for biomedical application

The modification of the composition of apatite materials can be made by several processes corresponding to ion exchange reactions which can conveniently be adapted to current coatings and ceramics and are an alternative to setting up of new synthesis methods. In addition to high temperature thermal treatments, which can partly or almost totally replace the monovalent OH- anion of stoichiometric hydroxyapatite by any halogen ion or carbonate, aqueous processes corresponding to dissolution-reprecipitation reactions have also been proposed and used. However, the most interesting possibilities are provided by aqueous ion exchange reactions involving nanocrystalline apatites. These apatites are characterised by the existence on the crystal surface of a hydrated layer of loosely bound mineral ions which can be easily exchanged in solution. This layer offers a possibility to trap mineral ions and possibly active molecules which can modify the apatite properties. Such processes are involved in mineralised tissues and could be used in biomaterials for the release of active mineral species.

Copper modulation of extracellular matrix synthesis by human articular chondrocytes

OBJECTIVE

The effects of Cu2+ on human articular chondrocytes, arising from both N (normal) and OA (osteoarthritic) cartilage, were investigated "in vitro".

METHODS

Chondrocytes, cultured in high density, were incubated with copper chloride (0.01-0.25 microM/mL). Proteoglycan and collagen were assessed by incorporation of [35S]-Sulfate and [3H]-Proline. SDS-PAGE analysis was performed to quantify the ratio of type II to type I collagen.

RESULTS

Cu2+ neither increased proteoglycan synthesis by chondrocytes. of origin N or OA, nor influenced their proliferation rate. Collagen synthesis was increased. This effect is time and concentration dependant: in cultures treated for 12 days, collagen synthesis stimulation was +20% and +26% (P < 0.02) in N and OA cultures respectively, the ratio of type II to type I collagen was slightly increased. This effect was more obvious in OA cell lines than in N ones.

CONCLUSION

The observations suggest that Cu2+ upregulates collagen anabolism in human articular chondrocytes.

In vitro kinetic evaluation of titanium alloy biodegradation

The present controlled in vitro experiment evaluated the dissolution kinetics of titanium (Ti), aluminum (Al) and vanadium (V). Titanium alloy (Ti90Al6V4) dental implants were inserted in 1.8 ml sterile tubes, containing equal volumes of NaCl 0.9% (w/v) and human serum. Metallic elements released by the atomic process of corrosion were measured at pH 7.2 and 37 C by atomic absorption spectrophotometer at 1, 3, 6, 9, 15, 21, 27, 33, 42, 51, 60, 69, 78, 87 and 96 days. Ti dissolution averaged 16+/-5 ng/cm2/day and 1565 ng/cm2 over the experimental period. Al dissolution was stable at 9+/-5 ng/cm2/day and averaged 945 ng/cm2 over the 96-day period. V dissolution was stable at 0.15+/-0.18 ng/cm2/day after the sixth day of incubation and averaged 42 ng/cm2 over the 96-day period. Major disparities in atomic dissolution were detected among implants. No local or systemic reaction to titanium has been documented. In contrast, 4% toxic V and 6% Al may suffice to elicit local and systemic reactions or inhibit cellular proliferation and differentiation.

Apoptosis in normal and osteoarthritic human articular cartilage

OBJECTIVES

To investigate whether apoptosis occurs in osteoarthritis (OA), and if this phenomenon is modulated by human recombinant interleukin 1beta (hrIL1beta).

METHODS

Human articular cartilage samples were obtained at the time of hip arthroplasty because of femoral neck fracture (normal cartilage) (n=4) or advanced coxarthrosis (OA cartilage) (n=14). Apoptotic chondrocytes, isolated by collagenase digestion and cultivated for 24 hours, or present in situ in frozen cartilage sections, were quantified by fluorescent microscopy using two apoptosis markers: the TUNEL reaction, which detects nuclear DNA fragmentation, and Annexin-V-fluos, which labels at the membrane level the externalisation of phosphatidylserine.

RESULTS

In OA cartilage 18-21% of chondrocytes showed apoptotic features, compared with 2-5% in normal cartilage. The results were similar for the two comparative studies (in situ and in vitro) and for both apoptosis markers. Moreover, hrIL1beta increased the apoptosis rate in vitro in a dose dependent manner in OA and normal chondrocytes.

CONCLUSION

These results suggest that apoptosis may be an important factor in the evolution of OA and may be a new target for treatment of OA.

In vitro comparative evaluation under static conditions of the hemocompatibility of four types of tubing for cardiopulmonary bypass

A comparative in vitro assessment of 4 types of tubing representative of the materials currently used in cardiopulmonary bypass (CPB) procedures was conducted under static conditions using liquid extracts of the materials or direct contact with fresh human blood or serum. The parameters monitored were biomarkers of coagulation and fibrinolytic cascades, the complement system and cell activation. Silicone and PVC tubing were shown to be non-cytotoxic and non-hemolytic. Heparin-coated PVC tubing did present a certain degree of cytotoxicity especially when in direct contact. Thrombosis was found to be significantly lower with the same heparin-coated material. To a lesser extent, platinum-cured silicone also showed a reduced thrombotic tendency. None of the materials activated platelets or the complement system. With platinum-cured silicone tubing, constant and lower leukocyte adhesion was evidenced at the different experimental time points. This could reflect reduced cell activation.

The effect of recombinant human basic fibroblast growth factor rhFGF-2 on human osteoblast in growth and phenotype expression

This paper describes the studies of human recombinant basic fibroblast growth factor (rhFGF-2) for its effects on human osteoblast growth and phenotype expression. During a 24-h period of treatment, rhFGF-2 highly stimulated DNA synthesis in a dose-related fashion with a maximum stimulation of 150% for 1 ng/ml. On the other hand, rhFGF-2 decreases alkaline phosphatase activity, synthesis of type I collagen, and cumulative amount of osteocalcin. Moreover, rhFGF-2 provoked a threefold increase in the amount of intracellular cAMP. Scatchard plots show the presence of two classes of [125I] rhFGF-2 receptors. This data suggests that rhFGF-2 which stimulate cell replication may act indirectly as an anabolic agent and stimulate some of the phenotypic expression markers.

In vitro study of biodegradation of a Co-Cr alloy using a human cell culture model

The evaluation of a potential biomaterial is based on two approaches: firstly, the study of the local and systemic effects of the biomaterial implanted in the host; and secondly the study of the behaviour of the biomaterial itself with increasing time. The progress achieved in human cell culturing allows in vitro evaluation of a new biomaterial using the human cell(s) system(s) characteristic of the tissue which it will be exposed to in vivo. This kind of approach permits the assessment of the biodegradation of a biomaterial whatever it is: metal; alloy; ceramic; glass; polymer; with or without specialized coating.... The experimental approach is as follows: discs representative of the biomaterial (surface state, cleaning, sterilization process) are manufactured in order to cover the bottom of the culture wells. Thereafter, they are either brought in the presence of complete culture medium alone, or in the presence of a subconfluent cell layer. A kinetic analysis is performed using various incubation periods at 37 degrees C. Released biodegradation products are identified and quantified, in both the medium and cell compartment, and on the other hand cytotoxicity is assessed. A Co-Cr alloy was studied over a 9-day period according to the experimental schedule, and showed a higher corrosion rate in the presence of osteoblasts in the range of 25-30%. Moreover, an intracellular uptake of both Cr and Co was detected, which will have physiological importance.

Effect of a derivatized dextran on human osteoblast growth and phenotype expression

Water soluble derivatized dextran named E9 with a molecular weight of 45,000 g l-1 containing 58% methyl carboxylic acid unit, 19% benzylamide unit, and 26% sulfonate with a specific anticoagulant activity of 0.29 IU mg-1 was studied for its effects on human osteoblast growth and phenotype expression for short-term treatment. At concentrations between 1 ng ml-1 and 1 microgram ml-1 E9 has no effect on DNA synthesis whereas at higher concentrations DNA synthesis is inhibited in a dose related fashion (87% for 400 micrograms ml-1). For concentrations which do not modify osteoblast growth, E9 promotes alkaline phosphatase activity, type I collagen and osteocalcin synthesis with a maximum effect for 0.1-1 microgram ml-1. It has a synergistic effect with hPTH increasing AMPc. Moreover, osteonectin synthesis was enhanced in a dose-dependent manner between 0.1 and 5 micrograms ml-1. These results seem to indicate that E9 is able to stimulate human osteoblast phenotype expression and could be useful in clinical applications.

Osteogenin (bone morphogenic protein 3) inhibits proliferation and stimulates differentiation of osteoprogenitors in human bone marrow

Treatment of human bone marrow osteoprogenitors with osteogenin (BMP-3; at 1, 2.5 and 10 ng/ml) caused dose- and time-dependent inhibition of DNA synthesis and cell proliferation. Simultaneously, osteogenin stimulated type I collagen synthesis and cAMP production. Addition of osteogenin to the cell culture increased intracellular alkaline phosphatase activity and osteocalcin synthesis, with maximal stimulation at 2.5 ng/ml. Simultaneous addition of 2.5 ng/ml osteogenin and 1,25 dihydroxy vitamin D3 (10(-8) M) enhanced the stimulation observed in osteocalcin synthesis. The experiments reported here demonstrate the significant "in vitro" influence of osteogenin in the stimulation of osteogenic phenotype in osteoprogenitor cells which have been isolated from human bone marrow and cloned. These results support a reciprocal relationship between cell growth inhibition and expression of osteoblast differentiation.

Molecular interface characterization in human bone matrix. I. Biochemical and IR spectroscopic studies

The aim of this work is the characterization of interfaces in calcified tissues. In order to separate the non-collagenous bone proteins, according to their interaction with collagen or hydroxyapatite crystals, 10 sequential bone demineralizations using EDTA alone were carried out, followed by four sequential extractions using both EDTA and GuHCl. The extracts were characterized by SDS-PAGE, IR spectrum analysis, and kinetics of demineralization and proteins released. A great proportion of non-collagenous proteins are bound to the collagen matrix, many of which have a high affinity to it. This work demonstrates that collagen is not directly linked to the mineralized phase.

Radioimmunodetection of rat and rabbit cartilage using a monoclonal antibody specific to link proteins

Biodistribution analysis using [125I]Fab-6F3 specific to link proteins from human articular cartilage performed in rats by autoradiography showed a high concentration of radioactivity in all cartilaginous tissues. Preliminary immunoscintigraphic assays were performed in rabbits. Front and side view images of whole animals exhibited high uptake in cartilage tissue of the knee articulation, in the invertebral disk and the humeral head. This fixation was still detected 24 h post-injection, although high washout of radioactivity was observed.

Human bone marrow stromal cells express an osteoblastic phenotype in culture

This study reports the selection and characterization of osteogenic precursors from human bone marrow which were isolated by two "clonings" and successive subculturing. These cell lines express alkaline phosphatase activity. Gel electrophoresis of [3H]-proline labeled cultures showed that the cloned cells produce only type I collagen. They synthetize osteocalcin and osteonectin. They respond to 1,25 dihydroxy vitamin D3 by increasing osteocalcin synthesis and secretion, and to parathyroid hormone by increasing cyclic AMP synthesis. After the third subculture in the absence of beta-glycerophosphate, these cell lines formed lots of clusters which exhibit high alkaline phosphatase activity and positive von Kossa staining. X-ray energy spectrum shows that these cells are surrounded by "budding" structures containing calcium and phosphorus with a ratio Ca:P identical to those of pure hydroxyapatite. This process was associated with 45Ca uptake into the cells. All these data support the selection of osteogenic cells which may be of considerable clinical importance.

Production of epidermal sheets in a serum free culture system: a further appraisal of the role of extracellular calcium

Rhenwald and Green's technique is currently the standard method for growing stratifying epidermal cell cultures. The serum free system developed in Ham's laboratory (MCDB 153) was designed to grow keratinocyte monolayers in clonogenic conditions. Our aim was to optimize conditions in serum-free MCDB 153 for culturing epidermal sheets from adult normal skin, and to assess the effect of extracellular calcium and temperature on proliferation and differentiation of cultured keratinocytes. Sixteen strains derived from plastic surgery specimens (mean age of donors 37 years; range 5-89) were used. Primary cultures were seeded at an optimal density of 8 x 10(4) cells/cm2 in primary cultures and 10(4) cells/cm2 in secondary cultures in complete medium including EGF, insulin, hydrocortisone and bovine pituitary extract, supplemented with isoleucine, tyrosine, methionine, phenylalanine, tryptophane and histidine. Amino acid (AA) supplementation allows a 5.8-fold increase in cell counts at confluency and monolayers with densely packed cells are obtained. In AA supplemented cultures, confluency is obtained in 16 +/- 3 days in primary cultures and in 13 +/- 0.5 days at first passages. Switches to 1.1 mM calcium at first or second passages resulted in a significant increase in cell counts (P less than 0.001), when compared with AA supplemented low calcium cultures. Low temperature/low calcium cultures resulted in a 50% decrease in cell counts. Low temperature/high calcium cultures gave similar cell counts as the 37 degrees C controls. AA and calcium supplemented cultures were evaluated for differentiation markers: involucrin expression was increased, keratins 5, 6, 14, 17 were expressed, and the sheets were 6-10 layers thick by electron microscopy, with keratohyalin granules and cornified envelopes appearing at layers 3-6 (from basal layer). Dispase treatment allowed an easy detachment of these sheets. These results show that the culture medium MCDB 153 can be adapted without serum supplementation to batch culture of human adult keratinocytes to produce epidermal sheets suitable for grafting. They also indicate that extracellular calcium in physiological range of concentration is not a sufficient signal for growth arrest when other growth conditions are optimized.

Cytocompatibility of two coating materials, amorphous alumina and silicon carbide, using human differentiated cell cultures

The cytocompatibility of two coating materials, amorphous alumina and silicon carbide deposited by radio-frequency sputtering, was studied using alveolar bone osteoblasts and gingival fibroblasts from human healthy tissues. Cytocompatibility was assessed at the level of both the basic (attachment, proliferation and cell protein content) and the specific features (intracellular alkaline phosphatase activity and the cytoskeleton) of the cells in direct contact with the coating. Titanium was used as the reference material. The results showed that both silicon carbide and amorphous alumina are cytocompatible for human fibroblasts and osteoblasts, whereas titanium appears the least cytocompatible of all the three substrates. Moreover, the amorphous alumina coating seems slightly bioactive. It seems that these coatings, particularly amorphous alumina, could be used to protect alloys against corrosion, and consequently combine the good mechanical properties of the alloys with the good biocompatibility of the coatings. These coatings seem to perform more suitably than titanium if the strength of the bond between the coating and the underlying alloys is strong enough to give a stable composite material.

Biodistribution study of a monoclonal antibody specific to link proteins from human cartilage

We report the use of monoclonal antibody 6F3 prepared against link proteins from human articular cartilage to elucidate the distribution of these glycoproteins within connective and other tissues. By immunohistochemical analysis, we showed that only the Fab fragment could reach the antigenic site in human articular sections. Cross-reactivity of the antibody 6F3 with link proteins purified from rat articular cartilage allowed us to carry out a biodistribution analysis in vivo in the rat. The time course of whole blood and plasma showed maximal activity 6 h after the 20 micrograms i.v. injection of [125I]Fab-6F3. Urinary excretion seems to be a high route of elimination. Moreover, we noticed no radioactive uptake across the blood-brain barrier. A significant fixation of labeled antibody Fab-6F3 was observed in noncartilaginous connective tissues such as aorta, skin and lung. As expected, specific and increased radioactivity was observed in all cartilage tissues, this increase was significantly higher 6 h after the [125I]Fab-6F3 injection than in the other connective tissues.

In vitro evaluation of an epoxy resin's cytocompatibility using cell lines and human differentiated cells

The cytocompatibility of a polyepoxy resin (Elf Aquitaine) has been studied using both cell lines and human differentiated cell cultures. The human models were gingival fibroblasts and bone osteoblasts, while the cell lines were Hela cells and 3T3 Balb/c cells. Basal cytocompatibility was assessed by estimation of the cell proliferation, total cell protein content, cell membrane sub-lysis, and cell attachment and spreading. Specific cytocompatibility concerning human osteoblasts, from both alveolar and trabecular bone, was determined by measuring the intracellular alkaline phosphatase activity. Resin colonization by the cells was studied by both TEM and SEM. The behaviour of the two cell lines reveals a significant level of discrepancy, whereas the behaviour of human cells, whatever the model, is comparable; however, osteoblasts look more sensitive. Moreover, the results show that this epoxy resin exhibits a moderate cytocompatibility which could be the result of the cytotoxicity of early released products, associated with the considerable surface roughness.

Fibrin seal in wound healing: effect of thrombin and [Ca2+] on human skin fibroblast growth and collagen production

To assess the interaction of a fibrin sealant with wound healing, an in vitro study using human skin fibroblasts was carried out. The effect of thrombin and calcium concentrations in the sealant on the growth parameters and collagen synthesis by normal human skin fibroblasts was examined. The fibroblast proliferation was increased 3 times for 50 and 25 IU of thrombin/ml. However for 20 mM [Ca2+], this stimulating effect of thrombin was observed after an 8 day incubation period, whereas it was observed as soon as the 2nd day in the presence of 2 mM [Ca2+]. The high rate of [Ca2+] (20 mM) partly inhibited DNA synthesis: for 2 mM [Ca2+], the incorporation of [3H]-Thymidine was 4 times greater than for 20 mM [Ca2+]. Further experiments demonstrated that human skin fibroblasts in the presence of 50 IU of thrombin/ml and 2 mM [Ca2+] in fibrin seal could increase the type I and III collagen synthesis while increasing the ratio of type III to type I. Thus, our results suggest that in vivo wound healing which required fibroblast growth and collagen synthesis can be stimulated in the presence of fibrin glue which is in good accordance with previous clinical observations.

Study of the effect of the surface state on the cytocompatibility of a Co-Cr alloy using human osteoblasts and fibroblasts

Cobalt-chromium-based alloys are widely used in oral and orthopedic implantology. Although they are relatively well tolerated, biological complications could occur which sometimes are due to the insufficient biocompatibility of the alloy. This study shows the effects of an alloy (Co (base), 28% Cr, 5.5% Mo, 1% Ni, 0.95% Si, 0.7% Fe, 0.65% Mn, 0.25% C), on differentiated human cells derived from an oral implantation site, specifically alveolar bone osteoblasts and gingival fibroblasts. The cytocompatibility of the alloy is determined by the study of cell proliferation, determination of total cell protein and intracellular alkaline phosphatase contents, cytoskeleton, and cell morphology. The alloy is presented to the cells in four different surface states: rough cast, specular polished, microbead blasted, and RF sputtered. The results demonstrate that the same material has different effects on the basal and specific cellular functions, according to its surface state. For this alloy we can classify its cytocompatibility according to its surface state in such an order: Microbead blasted much greater than specular polished greater than RF sputtered greater than rough cast.

Characterization of interfaces in human calcified tissue

Thermostimulated current spectroscopy has been applied to the investigation of molecular mobility in human calcified tissue. A comparative study of extracts at various stages of demineralization is presented. The response of an organic-mineral complex interphase has been identified.

Micromechanical spectroscopy of cartilage proteoglycans: hydration

Proteoglycan subunits extracted from calf cartilage have been studied with a high resolving power mechanical spectroscopy: the Thermostimulated Creep (TSC). The influence of hydration on TSC spectra shows the existence of two types of bound water: the weakly bound water increases the inertia of proteoglycan and stiffens their structure; the strongly bound water is responsible to a compensation law indicating the existence of a resonance phenomenon at the physiological temperature. Because of the looseness of bonds in weakly bound water, an increase of the local pressure may induce, in vivo, a release of water in tissues. This hypothesis explains perfectly the role of a water pump of proteoglycans in cartilage.

Osteoarthritis-related changes in human articular cartilage. An immunologic study

We report the use of immunologic methods for detecting specific alterations in human osteoarthritic cartilage. Monoclonal antibodies with specificities for proteoglycans and link proteins have been used to define immunogenic sites in these molecules. We have identified 1 site in the protein core, 1 site in the link proteins, and another site that is common to both proteoglycan and link proteins, which are not modified in osteoarthritic cartilage. In addition, an antigenic determinant in link proteins that is altered in osteoarthritic cartilage has been identified. These results suggest that the structure of the ternary complex (hyaluronic acid binding region-link proteins-hyaluronic acid) could be altered in osteoarthritic cartilage. These modifications may be due to a genetic defect or to partial enzymatic degradation of these sites.

Corrosion protection of metal implants by hard biocompatible ceramic coatings deposited by radio-frequency sputtering

Most metals used for orthopaedic and stomatology implants and prostheses belong to the families of titanium or nickel-based and cobalt-based superalloys designed for advanced technology industries (e.g. space, aeronautic and nuclear industries). Ideal materials should be as insoluble and biologically compatible as possible. In the present paper the corrosion behaviour of Ni-Cr and Co-Cr alloys in biological media is evaluated through potentiodynamic polarization tests. It is shown that these metals exhibit some minor release of the component elements and degradation products, which may induce cytotoxic and allergic effects. The corrosion resistance of these alloys can be strongly enhanced by hard ceramic coatings deposited by radio-frequency sputtering. The biocompatibility of coated and uncoated metals is compared from differentiated human cell cultures.

Phospholipase A2 activity in human osteoarthritic cartilage

Phospholipase A2 (PLA2) activity was measured in articular cartilage from normal and osteoarthritic (OA) human femoral heads. Protoglycanase and collagenase activity was determined in the same specimens using radiolabelled human proteoglycan subunit and type II collagen, respectively. Grossly normal and fibrillated OA cartilage samples showed a significant increase in PLA2 activity which was not found in osteophytic cartilage. PLA2 activity was found to be correlated with proteoglycanase but unrelated to collagenase activity. Tiaprofenic acid induced in vitro a concomitant increase in PLA2 and a decrease in proteoglycanase activity. PLA2 which may be activated by cytokines as well as mechanical factors is suggested as a key enzyme in chondrocyte metabolism regulation. Tiaprofenic acid is shown as a potential chondroprotective nonsteroidal anti-inflammatory drug.

Ex-vivo study of molecular interfaces in calcified tissues

The aim of this work is the characterization of interfaces in calcified tissues. Thermally Stimulated Currents and Gel Permeation Chromatography have been used for investigating extracts and residues from calf femoral diaphysis, at various stages of demineralization. In residues, the evolution of molecular mobility shows that the organic-mineral linkage is insured by several proteins: Collagen is not directly linked to apatite.

Problems in the immunolocalization of type IX collagen in fetal calf cartilage using a monoclonal antibody

Monoclonal antibodies were prepared against the pepsin-resistant fragments (X1-X3) of bovine type IX collagen. One of the five hybridomas that gave a positive reaction in an enzyme-linked immunosorbent assay was selected (H1a) for structural analysis and immunolocalization of type IX collagen. The location of the epitope for H1a was deducted from immunoblots and electron microscopic observations after rotary shadowing. The H1a antibody binds to one end of the longest X2, X3, X4 molecules, and preferentially 40-55nm from one end of X1 molecules thus, on or near the noncollagenous domain, NC2. Different immunolocalizations of type IX collagen in the superficial, middle and deep zones of fetal calf epiphyseal cartilage were observed depending on the thickness of the section and on hyaluronidase digestion conditions. In the middle and deep zones, staining with H1a throughout the matrix was obtained only with thin sections (5 microns) and digestion for 1 h at 37 degrees C. With thick sections (15 microns) or with digestion for 1 h at 24 degrees C, staining was restricted to the pericellular regions. Staining throughout the matrix was obtained in the superficial zone under all experimental conditions. Without hyaluronidase treatment, no immunofluorescent staining was seen with either H1a or polyclonal antibody to type II collagen, indicating that type IX collagen is present throughout the matrix in the different zones of fetal calf cartilage. This result is in good accordance with the recent demonstration of common cross-links between type II and type IX collagen in chicken and bovine cartilage. However, the preferential unmasking of type IX collagen antigenic sites in the pericellular regions of middle and deep zones of fetal calf cartilage does not preclude the presence in that region of a special pericellular organization of the collagenous network.

Effects of S-adenosylmethionine on human articular chondrocyte differentiation. An in vitro study

The effect of S-adenosyl-L-methionine (SAMe) on human articular osteoarthritic chondrocytes was studied using a thick-layer culture model. Three SAMe concentrations were tested (1, 10, and 100 micrograms/ml). For 10 micrograms/ml, the most efficient dose, a significant rise in the incorporation levels of 35S-sulfate and 3H-serine was observed, as was as an increase in the hexuronic acid content. All the parameters seem to express a more active protein synthesis, particularly for proteoglycans. Under the same conditions, the proliferation rate of chondrocytes does not undergo important variations. These results point to a direct action on the cell metabolism but little is known concerning the mechanism involved.

Experimental arthrosis by hyperpressure

The frequent occurrence of degenerative joint disease (DJD) pathology and the high degree of functional prejudice associated with it, justify the search for experimental models with a view to a better understanding of this pathology and its treatment. The models most commonly used resort to a sudden mechanical degradation by shock (post-contusive osteoarthritis) or to a kinematic disruption of the joint through more or less extensive menisco-capsulo-ligamentary lesions or lesions induced by toxic substances.

Cartilaginous lesions met with in human pathology are often secondary to a morphological anomaly at the origin of a hyperpressure. Maquet (1977) has suggested the bringing forward of the anterior tibial tubercle (ATT) in order to reduce the retro-patellar pressure. The drawing back by hollowing of this ATT appeared to us a suitable model for experimental osteoarthritis by hyperpressure.

In vitro stimulation of articular chondrocyte differentiated function by 1,25-dihydroxycholecalciferol or 24R,25-dihydroxycholecalciferol

The effects of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) (10(-13)M-10(-8) M) and 24R ,25-dihydroxycholecalciferol ( 24R ,25-(OH)2D3) (10(-12)M-10(-7) M) on cell proliferation and proteoglycan deposition were examined in our newly developed multilayer culture system for rabbit and human articular chondrocytes. The cells are embedded in an extracellular matrix similar to that seen in vivo and maintain their in vivo phenotype. We extracted and purified native proteoglycans and degraded material from three culture compartments: the medium, intercellular matrix, and cells. Proteoglycan synthesis and deposition were analyzed by measuring 35SO4 incorporation, hexuronic acid, and galactose contents. In both rabbit and human chondrocyte cultures, chronic 1,25-(OH)2D3 treatment inhibited chondrocyte proliferation and stimulated proteoglycan synthesis and accumulation in the three compartments at 10(-12)-10(-8) M; maximal effect was at 10(-10)M. Cell proliferation was reduced by 55% and the content of hexuronic acid (or galactose) was increased to about three times that of controls in all compartments. 1,25-(OH)2D3 did not alter the proteoglycan composition. Chronic 24R ,25-(OH)2D3 treatment induced comparable effects with a maximum at 10(-8)M. When human dermal fibroblasts were treated as above both vitamin D metabolites increase mitosis. 1,25-(OH)2D3 mainly reduced the pericellular deposition of proteoglycans, while 24R ,25-(OH)2D3 appeared to reduce their synthesis and deposition in both medium and pericellular compartments. These results suggest that both 1,25-(OH)2D3 and 24R ,25-(OH)2D3 act specifically on articular chondrocytes to promote phenotype expression.

Pharmacokinetics and metabolism of [35S]-Thiazolidine carboxylic acid in the rat. I. Elimination and distribution

The localization and elimination of 35S-Thiazolidine carboxylic acid has been studied in rats following a single oral dose (100 mg/kg) and multiple oral doses (100 mg/kg/day) over 15 days. The compound was rapidly and completely absorbed as evaluated by the time of the maximum plasma 35S-concentration (140 micrograms eq/ml at 30 min) and the amount of radioactivity in the feces (less than 1% of the dose over 48 h). Urinary excretion seems to be the unique route of elimination. There was specific tissue accumulation of drug or metabolite, particularly in liver (29% of the dose at 3 h), pancreas (7% of the dose at 3 h), adrenals (320 micrograms eq/g at 3 h), pituitary and thyroid (230 micrograms eq/g at 3h). Fixation of radioactivity appears significantly higher after chronic treatment than after acute treatment.

Proteoglycan synthesis in chondrocyte cultures from osteoarthrotic and normal human articular cartilage

Chondrocytes derived by outgrowth from normal and osteoarthrotic human femoral head cartilage were grown in high density cultures for five passages. Cultures were analysed for their sulfated macromolecular components in medium, layer-matrix and intracellular compartments. Two fractions were obtained: typical proteoglycans and glycosaminoglycan-peptides (Mr approx. 60 000) which might result from an enzymatic degradation of proteoglycans. Proteoglycans from normal and osteoarthrotic cultures exhibited similar biochemical properties (size, protein:uronic acid ratio, glycosaminoglycan composition). Slightly less proteoglycans were aggregated with hyaluronic acid in osteoarthrotic than in normal cultures. Three populations of proteoglycan subunit were obtained under dissociative conditions (Sepharose CL-2B) in both normal and osteoarthrotic cultures: proteoglycan 1 (Kav=0.04), proteoglycan 2 (Kav=0.26) which were aggregated with hyaluronic acid in associative conditions, and proteoglycan 4 (Kav=0.48). A fourth population, proteoglycan 3 (Kav=0.33, Sepharose 2B and CL-2B) was intracellular in osteoarthrotic cultures. After a 4 day incubation period, about 60% more proteoglycans were found in osteoarthrotic than in normal cultures (medium+52%, layer-matrix + 44% and 17 times the normal value inside the cells). Proteoglycan distribution kinetics in the three compartments showed a higher net accumulation of proteoglycans in osteoarthrotic-derived cultures.

15-(p[75Br]bromophenyl)pentadecanoic acid: pharmacokinetics and potential as heart agent

Preparation, quality control, and pharmacokinetics of 15-(p-[75Br]bromophenyl)pentadecanoic acid (BPPA) were studied, with particular emphasis on the fate of the label and the usefulness of BPPA as a heart agent. BPPA labeled with the positron emitter Br-75 (T 1/2 = 98 min) was prepared in 55% radiochemical yield with a specific activity of greater than or equal to 1000 Ci/mmol. While the uptake of BPPA in the heart muscle is as fast and efficient as that of aliphatic omega-halofatty acids, its elimination is delayed, owing mainly to an inhibited beta oxidation and the formation of lipophilic catabolites. The blood activity and its time course are identical to those of omega-halofatty acids, but no free bromide appears in any body fluid or organ. The complex pharmacokinetic behavior of stable lipophilic catabolites prevents a quantitative background correction. In contrast to aliphatic omega-halofatty acids, a quantitative evaluation of myocardial metabolism is not possible. Br-75 BPPA, however, is well suited for positron emission tomography of the heart.