Extension of recombinant human RANTES by a single residue at the amino terminus is sufficient to produce a potent and selective antagonist. RANTES is a proinflammatory cytokine that promotes cell accumulation and activation in chronic inflammatory diseases. When mature RANTES was expressed heterologously in Escherichia coli, the amino-terminal initiating methionine was not removed by the endogenous amino peptidases. This methionylated protein was fully folded but completely inactive in RANTES bioassays of calcium mobilization and chemotaxis of the promonocytic cell line THP-1. However, when assayed as an antagonist of both RANTES and macrophage inflammatory polypeptide-1␣ (MIP-1␣) in these assays, the methionylated RANTES (Met-RANTES) inhibited the actions of both chemokines. T cell chemotaxis was similarly inhibited. The antagonistic effect was selective since Met-RANTES had no effect on interleukin-8-or monocyte chemotractant protein-1-induced responses in these cells. Met-RANTES can compete with both [ RANTES is a member of a large family of cytokines, known as chemokines, which have the ability to recruit and activate a wide variety of proinflammatory cell types (1). They are small polypeptides of 8 -10 kDa and have been further classified into CXC or CC chemokines based on the spacings of the cysteine residues proximal to the amino terminus. CXC chemokines primarily activate neutrophils, whereas CC chemokines have effects on several leucocyte cell types. RANTES is a CC chemokine, and in vitro it can produce chemotaxis and activation of monocytes, eosinophils, and T cells, particularly CD4 ϩ CD45RO ϩ (memory) T cells (2), but not neutrophils. These results imply a role for RANTES in diseases such as allergen induced late phase skin reactions or in allergic asthma. This hypothesis is strengthened by the fact that large amounts of RANTES are found in nasal polyp tissues, which are rich in infiltrating eosinophils (3). In addition, injection of RANTES into dog skin has been shown to induce a large eosinophilic infiltrate in vivo (4), and migration of human T lymphocytes was observed on injection of human RANTES into a human/severe combined immune deficiency mouse model (5).MIP-1␣ shares an overlapping cell-type specificity with RANTES in vitro (6, 7) and has been shown to elicit an inflammatory response mediated through mast cell degranulation in vivo (8). A common receptor for these two CC chemokines has been cloned (9, 10) and is a member of the seven transmembrane G-protein linked receptor family. Recombinant expression of the receptor has shown that it can transduce a functional response on stimulation by both chemokines.We report the purification of human RANTES expressed heterologously in Escherichia coli. In this system, the protein retains its initiating methionine residue, which renders it inactive as an agonist, while enabling it to antagonize effects induced both by RANTES and MIP-1␣. It is able to compete for binding of both the radiolabeled ligands on THP-1 cells and to the recombinant RANTES/MIP-1...

Bone is a natural composite construct, with a gradient structure going from a loose interconnected cellular core to an outer dense wall, thus minimizing bone weight while keeping a high mechanical resistance. Due to this unique and complex structure, bone defects are difficult to replace or repair. Tissue engineering aims at providing artificial bone grafts. Several techniques have been proposed to produce porous structures or scaffolds, but, as yet, with no optimal solutions. This article focuses on bioresorbable ceramic-polymer composite foams obtained by supercritical fluid foaming. This flexible technique enables an adequate morphology and suitable properties for bone tissue engineering to be obtained. Composite scaffolds are biocompatible, allowing cell proliferation and differentiation.

We envision the use of human fetal bone cells for engineered regeneration of adult skeletal tissue. A description of their cellular function is then necessary. To our knowledge, there is no description of human primary fetal bone cells treated with differentiation factors. The characterization of fetal bone cells is particularly important as the pattern of secreted proteins from osteoblasts has been shown to change during aging. In the first part of this work, human primary fetal bone cells were compared to adult bone cells and mesenchymal stem cells for their ability to proliferate and to differentiate into osteoblasts in vitro. Cell proliferation, gene expression of bone markers, alkaline phosphatase (ALP) activity, and mineralization were analyzed during a time-course study. In the second part of this paper, bone fetal cells behavior exposed to osteogenic factors is further detailed. The doubling time of fetal bone cells was comparable to mesenchymal stem cells but significantly shorter than for adult bone cells. Gene expression of cbfa-1, ALP, a1 chain of type I collagen, and osteocalcin were upregulated in fetal bone cells after 12 days of treatment, with higher inductions than for adult and mesenchymal stem cells. The increase of ALP enzymatic activity was stronger for fetal than for adult bone cells reaching a maximum at day 10, but lower than for mesenchymal stem cells. Importantly, the mineralization process of bone fetal cells started earlier than adult bone and mesenchymal stem cells. Proliferation of fetal and adult bone cells was increased by dexamethasone, whereas 1a,25-dihydroxyvitamin D 3 did not show any proliferative effect. Mineralization studies clearly demonstrated the presence of calcium deposits in the extracellular matrix of fetal bone cells. Nodule formation and calcification were strongly increased by the differentiation treatment, especially by dexamethasone. This study shows for the first time that human primary fetal bone cells could be of great interest for bone research, due to their fast growth rate and their ability to differentiate into mature osteoblasts. They represent an interesting and promising potential for therapeutic use in bone tissue engineering.

The aim of this investigation was to test the biocompatibility of three-dimensional bioresorbable foams made of poly(L-lactic acid) (PLA), alone or filled with hydroxyapatite (HA) or ␤-tricalcium phosphate (␤-TCP), with human primary osteoblasts, using a direct contact method. Porous constructs were processed by supercritical gas foaming, after a melt-extrusion of ceramic/polymer mixture. Three neat polymer foams, with pore sizes of 170, 310, and 600 m, and two composite foams, PLA/5 wt% HA and PLA/5 wt% ␤-TCP, were examined over a 4-week culture period. The targeted application is the bone tissue-engineering field. For this purpose, human fetal and adult bone cells were chosen because of their highly osteogenic potential. The association of fetal bone cells and composite scaffold should lead to in vitro bone formation. The polymer and composite foams supported adhesion and intense proliferation of seeded cells, as revealed by scanning electron microscopy. Cell differentiation toward osteoblasts was demonstrated by alkaline phosphatase (ALP) enzymatic activity, ␥-carboxylated Gla-osteocalcin production, and the onset of mineralization. The addition of HA or ␤-TCP resulted in higher ALP enzymatic activity for fetal bone cells and a stronger production of Gla-osteocalcin for adult bone cells.