Biological evaluation of alginate-based hydrogels, with antimicrobial features by Ce(III) incorporation, as vehicles for a bone substitute.

A novel hydrogel, based on an alginate/hyaluronate mixture and Ce(III) ions, with effective bioactive and antimicrobial ability was developed to be used as vehicle of a synthetic bone substitute producing an injectable substitute (IBS). Firstly, three different IBSs were prepared using three developed alginate-based hydrogels, the hydrogel Alg composed by alginate, the hydrogel Alg/Ch composed by an alginate/chitosan mixture and the hydrogel Alg/HA composed by an alginate/hyaluronate mixture. MG63 cells viability on the IBSs was evaluated, being observed a significantly higher cell viability on the Alg/HA_IBS at all time points, which indicates a better cell adaptation to the material, increasing their predisposition to produce extracellular matrix and thus allowing a better bone regeneration. Moreover, SEM analysis showed evident filopodia and a spreader shape of MG63 cells when seeded on Alg/HA_IBS. This way, based upon the in vitro results, the hydrogel Alg/HA was chosen to the in vivo study by subcutaneous implantation in an animal model, promoting a slight irritating tissue response and visible tissue repairing. The next step was to grant antimicrobial properties to the hydrogel that showed the best biological behavior by incorporation of Ce(III) ions into the Alg/HA, producing the hydrogel Alg/HA2. The antimicrobial activity of these hyaluronate-based hydrogels was evaluated against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Candida albicans. Results showed that Ce(III) ions can significantly enhance the hydrogel antimicrobial ability without compromising the osteoconductivity improvement promoted by the vehicle association to the synthetic bone substitute.

Human bone cell cultures in biocompatibility testing. Part II: effect of ascorbic acid, beta-glycerophosphate and dexamethasone on osteoblastic differentiation.

This work analyses the proliferation/differentiation behaviour of human bone marrow cells cultured in alpha-minimum essential medium supplemented with 10% foetal bovine serum (standard medium) and in the presence of ascorbic acid (AA, 50 microg ml(-1)), beta-glycerophosphate (betaGP, 10 mmol) and dexamethasone (Dex, 10 nmol) under selected experimental conditions. Cultures were compared concerning cell morphology, cell growth, ALP activity and ability to form calcium phosphate deposits. Cells growing in the various experimental conditions proliferated gradually with the incubation time and presented high ALP activity. Cultures grown in standard medium and in the presence of either AA or Dex failed to form calcium phosphate deposits. Cultures grown in the presence of betaGP, betaGP + AA and betaGP + AA + Dex, i.e. in the presence of a source of phosphate ions, showed the formation of a mineralised extracellular matrix. The presence of Dex resulted in a significant induction in the ALP activity and ability to form mineral deposits. The behaviour of the various cell cultures is in agreement with previous studies stating a reciprocal and functionally coupled relationship between proliferation and differentiation, i.e. cultures grown in a medium containing betaGP presented a less proliferative but more differentiated osteoblastic cell population, as compared to cultures lacking the mineralisation process.

Human bone cell cultures in biocompatibility testing. Part I: osteoblastic differentiation of serially passaged human bone marrow cells cultured in alpha-MEM and in DMEM.

Well-characterised human osteoblastic bone marrow cell cultures are a useful in vitro tool to analyse bone tissue/biomaterials interactions. In this work, human bone marrow was cultured in experimental conditions described to favour osteoblastic differentiation and, serially passaged cells were cultured in two widely used culture media, minimum essential medium Eagle, alpha modification (alpha-MEM) and Dulbecco's modified Eagle's medium (DMEM). Cultures were grown for 35 d and compared concerning morphologic appearance on scanning electron microscopy (SEM), cell viability/proliferation, total protein content, activity of alkaline phosphatase (ALP) and ability to form calcium phosphate deposits. Results showed that cell proliferation was similar in cultures grown in the two media but ALP activity and ability to form mineralised deposits were lower in DMEM cultures. In both experimental situations, osteoblastic parameters were strongly reduced on cell passage, particularly from the first to the second subculture. In the experimental conditions used (presence of ascorbic acid, sodium beta-glycerophosphate and dexamethasone in the primary and secondary cultures), osteoblastic differentiation was observed in the first and second subcultures grown in alpha-MEM and in the first subculture grown in DMEM. These results underline the importance of the definition of the experimental conditions in studies involving bone cell cultures.

Surface topography modulates the osteogenesis in human bone marrow cell cultures grown on titanium samples prepared by a combination of mechanical and acid treatments.

Titanium samples of different roughness R(a) and morphology were prepared using a combination of mechanical (grinding with a SiC paper or blasting with aluminum oxide particles with 65 or 250 microm) and chemical (attack with a sulphuric acid based solution or a hydrofluoric acid based solution) treatments. The biological performance of the prepared surfaces was evaluated using human bone marrow osteoblastic cell cultures. Mechanically treated samples presented different R(a) values and surface morphology. The hydrofluoric acid solution was more effective than the sulphuric acid solution in smoothing titanium surface and also in eliminating aluminum contamination resulting from the blasting process. Bone marrow cells seeded on the different titanium samples showed a similar pattern of behavior during cell attachment and spreading. Cells proliferated very well on all the titanium surfaces and cell growth was observed during approximately two to three weeks. The samples treated with the hydrofluoric acid solution presented higher alkaline phosphatase activity. Only the blasted samples treated with the acid solutions allowed seeded bone marrow cells to form a mineralized extracellular matrix. The best biological performance was found in the blasted samples treated with the hydrofluoric acid solution, which could be related to the characteristic microtopography of these samples that presented a homogeneous and smooth roughness.

Leri-weill dyschondrosteosis syndrome in mother and daughter

This report ilustrates a case of Leri-Weill dyschondrosteosis in mother and daughter and discusses the relationship of this bone dysplasia with Madelung's deformity

Osteopetrosis: a case report

A woman had clinicoradiological features of osteopetrosis. The dominant and recessive forms of this condition are discussed