New materials and complications of prostheses in humans: situation in Spain.

Prostheses or implantable medical devices (IMDs) are parts made of natural or artificial materials intended to replace a body structure and therefore must be well tolerated by living tissues. The types of IMDs currently available and usable are very varied and capable of replacing almost any human organ. A high but imprecise percentage of Spaniards are carriers of one or more IMDs to which they often owe their quality of life or survival. IMDs are constructed with different types of materials that are often combined in the same prosthesis. These materials must combine harmlessness to human tissues with high wear resistance. Their durability depends on many factors both on the host and the type of prosthesis, but the vast majority last for more than 10-15 years or remain in function for the lifetime of the patient. The most frequently implanted IMDs are placed in the heart or great vessels, joints, dental arches or breast and their most frequent complications are classified as non-infectious, particularly loosening or intolerance, and infectious. Complications, when they occur, lead to a significant increase in morbidity, their repair or replacement multiplies the health care cost and, on occasions, can cause the death of the patient. The fight against IMD complications is currently focused on the design of new materials that are more resistant to wear and infection and the use of antimicrobial substances that are released from these materials. Their production requires multidisciplinary technical teams, but also a willingness on the part of industry and health authorities that is not often found in Spain or in most European nations. Scientific production on prostheses and IMD in Spain is estimated to be less than 2% of the world total, and probably below what corresponds to our level of socio-economic development. The future of IMDs involves, among other factors, examining the potential role of Artificial Intelligence in their design, knowledge of tissue regeneration, greater efficiency in preventing infections and taking alternative treatments beyond antimicrobials, such as phage therapy. For these and other reasons, the Ramón Areces Foundation convened a series of experts in different fields related to prostheses and IMDs who answered and discussed a series of questions previously formulated by the Scientific Council. The following lines are the written testimony of these questions and the answers to them.

Analgesia intravenosa domiciliaria mediante bomba elastomérica como procedimiento ambulatorio de control del dolor en la reparación del ligamento cruzado anterior / Home-based intravenous analgesia with elastomeric pump as an outpatient procedure for pain control after anterior cruciate ligament repair

Objetivo. Hacer un seguimiento del dolor en el posoperatorio inmediato, mediante el uso de bomba elastomérica en la cirugía del ligamento cruzado anterior (LCA). Material y métodos. Trescientos nueve pacientes intervenidos de ligamentoplastia del LCA mediante plastia autóloga de hueso-tendón-hueso. Durante el posoperatorio inmediato se realizó un seguimiento del dolor mediante escala visual analógica (EVA); tanto en la unidad de reanimación posoperatoria, como en la sala de adaptación al medio, y durante las primeras 24-48-72 h en el domicilio. Registramos también la necesidad de medicación de rescate, efectos adversos observados y visitas al servicio de urgencias. Resultados. Se estudió a 309 pacientes (264 varones, 45 mujeres) con una edad media de 33 años (rango: 18-55). El 44,7% de los pacientes reportaron dolor posoperatorio inmediato leve y el 38,5% no tenía dolor. Al alta, el 41,1% de los pacientes reportaron dolor leve y el 57% no tenía dolor. En domicilio, se mantuvieron los valores de dolor leve/moderado, con más del 97% de los pacientes con valores EVA ≤ 3. Se registraron efectos adversos en menos del 3% de los casos. El 8,7% de los casos tuvo que hacer uso en algún momento de medicación analgésica. Menos del 1% presentó prurito mientras llevaban la analgesia intravenosa en el domicilio y menos del 2% presentó problemas relacionados con el dispositivo. Discusión. Actualmente, no hay consenso en cuanto al manejo posoperatorio de las lesiones del LCA, aunque la tendencia es el uso de anestesia multimodal y de sistemas para reducir el dolor posoperatorio. Conclusiones. El uso de bomba elastomérica como procedimiento ambulatorio de control del dolor en la reparación del ligamiento cruzado anterior ha reportado buenos resultados (AU)

Objective. To follow up pain in the immediate postoperative period, using an elastomeric pump in anterior cruciate ligament surgery. Material and methods. 309 patients who had undergone anterior cruciate ligament repair with bone-tendon-bone allograft. Pain control was assessed with a visual analogue scale (VAS) during the immediate postoperative period, in the postoperative care unit, in the recovery room, and after the first 24-48-72hours following home discharge. The need for rescue medication, adverse effects observed and emergency visits were also registered. Results. 309 patients were assessed (264 males, 45 females), mean age 33 (range: 18 - 55). Postoperative pain was mild in 44.7% of patients, and 38.5% were pain-free. At discharge, 41.1% of patients reported mild pain and 57% were pain-free. At home, mild to moderate levels of pain were maintained and over 97% of patients presented VAS values ≤ 3. Fewer than 3% had adverse effects, 8.7% had to use analgesic medication at some point. Pruritus occurred in less than 1% of patients receiving intravenous analgesia at home, and fewer than 2% had device-related complications. Discussion. There is no consensus regarding the postoperative management of anterior cruciate ligament lesions, although most surgeons use multimode anaesthesia and different combinations of analgesics to reduce postoperative pain. Conclusions. The use of an intravenous elastomeric pump as postoperative analgesia for anterior cruciate ligamentoplasty has yielded good results (AU)

Home-based intravenous analgesia with elastomeric pump as an outpatient procedure for pain control after anterior cruciate ligament repair. / Analgesia intravenosa domiciliaria mediante bomba elastomérica como procedimiento ambulatorio de control del dolor en la reparación del ligamento cruzado anterior.

OBJECTIVE: To follow up pain in the immediate postoperative period, using an elastomeric pump in anterior cruciate ligament surgery. MATERIAL AND METHODS: 309 patients who had undergone anterior cruciate ligament repair with bone-tendon-bone allograft. Pain control was assessed with a visual analogue scale (VAS) during the immediate postoperative period, in the postoperative care unit, in the recovery room, and after the first 24-48-72hours following home discharge. The need for rescue medication, adverse effects observed and emergency visits were also registered. RESULTS: 309 patients were assessed (264 males, 45 females), mean age 33 (range: 18 - 55). Postoperative pain was mild in 44.7% of patients, and 38.5% were pain-free. At discharge, 41.1% of patients reported mild pain and 57% were pain-free. At home, mild to moderate levels of pain were maintained and over 97% of patients presented VAS values ≤ 3. Fewer than 3% had adverse effects, 8.7% had to use analgesic medication at some point. Pruritus occurred in less than 1% of patients receiving intravenous analgesia at home, and fewer than 2% had device-related complications. DISCUSSION: There is no consensus regarding the postoperative management of anterior cruciate ligament lesions, although most surgeons use multimode anaesthesia and different combinations of analgesics to reduce postoperative pain. CONCLUSIONS: The use of an intravenous elastomeric pump as postoperative analgesia for anterior cruciate ligamentoplasty has yielded good results.

A novel hybrid nanofibrous strategy to target progenitor cells for cost-effective in situ angiogenesis.

Although the impact of composites based on Ti-doped calcium phosphate glasses is low compared with that of bioglass, they have been already shown to possess great potential for bone tissue engineering. Composites made of polylactic acid (PLA) and a microparticle glass of 5TiO2-44.5CaO-44.5P2O5-6Na2O (G5) molar ratio have already demonstrated in situ osteo- and angiogenesis-triggering abilities. As many of the hybrid materials currently developed usually promote osteogenesis but still lack the ability to induce vascularization, a G5/PLA combination is a cost-effective option for obtaining new instructive scaffolds. In this study, nanostructured PLA-ORMOGLASS (organically modified glass) fibers were produced by electrospinning, in order to fabricate extra-cellular matrix (ECM)-like substrates that simultaneously promote bone formation and vascularization. Physical-chemical and surface characterization and tensile tests demonstrated that the obtained scaffolds exhibited homogeneous morphology, higher hydrophilicity and enhanced mechanical properties than pure PLA. In vitro assays with rat mesenchymal stem cells (rMSCs) and rat endothelial progenitor cells (rEPCs) also showed that rMSCs attached and proliferated on the materials influenced by the calcium content in the environment. In vivo assays showed that hybrid composite PLA-ORMOGLASS fibers were able to promote the formation of blood vessels. Thus, these novel fibers are a valid option for the design of functional materials for tissue engineering applications.

Towards 4th generation biomaterials: a covalent hybrid polymer-ormoglass architecture.

Hybrid materials are being extensively investigated with the aim of mimicking the ECM microenvironment to develop effective solutions for bone tissue engineering. However, the common drawbacks of a hybrid material are the lack of interactions between the scaffold's constituents and the masking of its bioactive phase. Conventional hybrids often degrade in a non-homogeneous manner and the biological response is far from optimal. We have developed a novel material with strong interactions between constituents. The bioactive phase is directly exposed on its surface mimicking the structure of the ECM of bone. Here, polylactic acid electrospun fibers have been successfully and reproducibly coated with a bioactive organically modified glass (ormoglass, Si-Ca-P2 system) covalently. In comparison with the pure polymeric mats, the fibers obtained showed improved hydrophilicity and mechanical properties, bioactive ion release, exhibited a nanoroughness and enabled good cell adhesion and spreading after just one day of culture (rMSCs and rEPCs). The fibers were coated with different ormoglass compositions to tailor their surface properties (roughness, stiffness, and morphology) by modifying the experimental parameters. Knowing that cells modulate their behavior according to the exposed physical and chemical signals, the development of this instructive material is a valuable advance in the design of functional regenerative biomaterials.

The relevance of biomaterials to the prevention and treatment of osteoporosis.

Osteoporosis is a worldwide disease with a very high prevalence in humans older than 50. The main clinical consequences are bone fractures, which often lead to patient disability or even death. A number of commercial biomaterials are currently used to treat osteoporotic bone fractures, but most of these have not been specifically designed for that purpose. Many drug- or cell-loaded biomaterials have been proposed in research laboratories, but very few have received approval for commercial use. In order to analyze this scenario and propose alternatives to overcome it, the Spanish and European Network of Excellence for the Prevention and Treatment of Osteoporotic Fractures, "Ageing", was created. This network integrates three communities, e.g. clinicians, materials scientists and industrial advisors, tackling the same problem from three different points of view. Keeping in mind the premise "living longer, living better", this commentary is the result of the thoughts, proposals and conclusions obtained after one year working in the framework of this network.

Bioactivation of calcium deficient hydroxyapatite with foamed gelatin gel. A new injectable self-setting bone analogue.

An alternative approach to bone repair for less invasive surgical techniques, involves the development of biomaterials directly injectable into the injury sites and able to replicate a spatially organized platform with features of bone tissue. Here, the preparation and characterization of an innovative injectable bone analogue made of calcium deficient hydroxyapatite and foamed gelatin is presented. The biopolymer features and the cement self-setting reaction were investigated by rheological analysis. The porous architecture, the evolution of surface morphology and the grains dimension were analyzed with electron microscopy (SEM/ESEM/TEM). The physico-chemical properties were characterized by X-ray diffraction and FTIR analysis. Moreover, an injection test was carried out to prove the positive effect of gelatin on the flow ensuing that cement is fully injectable. The cement mechanical properties are adequate to function as temporary substrate for bone tissue regeneration. Furthermore, MG63 cells and bone marrow-derived human mesenchymal stem cells (hMSCs) were able to migrate and proliferate inside the pores, and hMSCs differentiated to the osteoblastic phenotype. The results are paving the way for an injectable bone substitute with properties that mimic natural bone tissue allowing the successful use as bone filler for craniofacial and orthopedic reconstructions in regenerative medicine.

Modular polylactic acid microparticle-based scaffolds prepared via microfluidic emulsion/solvent displacement process: fabrication, characterization, and in vitro mesenchymal stem cells interaction study.

The present study reports a novel approach for the design and fabrication of polylactic acid (PLA) microparticle-based scaffolds with microstructural properties suitable for bone and cartilage regeneration. Macroporous PLA scaffolds with controlled shape were fabricated by means of a semicontinuous process involving (1) microfluidic emulsification of a PLA/ethyl lactate solution (5% w/v) in a span 80/paraffin oil solution (3% v/v) followed by (2) particles coagulation/assembly in an acetone/water solution for the development of a continuous matrix. Porous scaffolds prepared from particles with monomodal or bimodal size distribution, overall porosity ranges from 93 to 96%, interparticles porosity from 41 to 54%, and static compression moduli from 0.3 to 1.4 MPa were manufactured by means of flow rate modulation of of the continuous phase during emulsion. The biological response of the scaffolds was assessed in vitro by using bone marrow-derived rat mesenchymal stem cells (MSCs). The results demonstrated the ability of the scaffolds to support the extensive and uniform three-dimensional adhesion, colonization, and proliferation of MSCs within the entire construct.

Ion-selective electrodes to monitor osteoblast-like cellular influence on the extracellular concentration of calcium.

In bone tissue engineering, the composition of the ionic extracellular environment (IEE) can determine both cellular fate and a biomaterial's development and performance. Therefore, precise control of the IEE and a perfect understanding of the dynamic changes that it can be subject to due to cellular activity is highly desired. To achieve this, we initially monitored how two standard osteoblast-like cell models that expressed either high or low alkaline phosphatase activity - SAOS-2 and MG63 cells, respectively - affected the extracellular concentrations of calcium and phosphate during long-term cultures. It was observed that cellular influence on the IEE varied greatly between the two models and could be linked to the capacity of cells to deposit calcium in the extracellular matrix. Miniaturized ion-selective electrodes that could allow for real-time monitoring of calcium in a minimally invasive way were then constructed. The electrodes were characterized in standard in vitro cell culture environments, prior to being successfully applied for periods of 24 h, to record the dynamics of cell-induced deposition of calcium in the extracellular matrix, while using osteogenic media of either high or low concentrations of phosphate. As a result, this study provides the background and technological means for the non-destructive evaluation of the IEE in vitro and allows for the optimization and development of better models of bone tissue construction.

High-resolution PLA-based composite scaffolds via 3-D printing technology.

Fabrication of new biodegradable scaffolds that guide and stimulate tissue regeneration is still a major issue in tissue engineering approaches. Scaffolds that possess adequate biodegradability, pore size, interconnectivity, bioactivity and mechanical properties in accordance with the injured tissue are required. This work aimed to develop and characterize three-dimensional (3-D) scaffolds that fulfill the aforementioned requirements. For this, a nozzle-based rapid prototyping system was used to combine polylactic acid and a bioactive CaP glass to fabricate 3-D biodegradable scaffolds with two patterns (orthogonal and displaced double layer). Scanning electron microscopy and micro-computer tomography showed that 3-D scaffolds had completely interconnected porosity, uniform distribution of the glass particles, and a controlled and repetitive architecture. Surface properties were also assessed, showing that the incorporation of glass particles increased both the roughness and the hydrophilicity of the scaffolds. Mechanical tests indicated that compression strength is dependent on the scaffold geometry and the presence of glass. Preliminary cell response was studied with primary mesenchymal stem cells (MSC) and revealed that CaP glass improved cell adhesion. Overall, the results showed the suitability of the technique/materials combination to develop 3-D porous scaffolds and their initial biocompatibility, both being valuable characteristics for tissue engineering applications.

Osteoblast-like cellular response to dynamic changes in the ionic extracellular environment produced by calcium-deficient hydroxyapatite.

Solution-mediated reactions due to ionic substitutions are increasingly explored as a strategy to improve the biological performance of calcium phosphate-based materials. Yet, cellular response to well-defined dynamic changes of the ionic extracellular environment has so far not been carefully studied in a biomaterials context. In this work, we present kinetic data on how osteoblast-like SAOS-2 cellular activity and calcium-deficient hydroxyapatite (CDHA) influenced extracellular pH as well as extracellular concentrations of calcium and phosphate in standard in vitro conditions. Since cells were grown on membranes permeable to ions and proteins, they could share the same aqueous environment with CDHA, but still be physically separated from the material. In such culture conditions, it was observed that gradual material-induced adsorption of calcium and phosphate from the medium had only minor influence on cellular proliferation and alkaline phosphatase activity, but that competition for calcium and phosphate between cells and the biomaterial delayed and reduced significantly the cellular capacity to deposit calcium in the extracellular matrix. The presented work thus gives insights into how and to what extent solution-mediated reactions can influence cellular response, and this will be necessary to take into account when interpreting CDHA performance both in vitro and in vivo.

Injectable calcium-phosphate-based composites for skeletal bone treatments.

Alpha-tricalcium-phosphate-based bone cements hydrolyze and set, producing calcium-deficient hydroxyapatite. They can result in an effective solution for bone defect reconstruction due to their biocompatibility, bioactivity and adaptation to shape and bone defect sizes, together with an excellent contact between bone and graft. Moreover, the integration of hydrogel phase based on poly(vinyl alcohol) (PVA) to H-cem-composed of α-tricalcium phosphate (98% wt) and hydroxyapatite (2% wt)-allows improving the mechanical and biological properties of the cement. The aim of this work was to evaluate the influence of the PVA on relevant properties for the final use of the injectable bone substitute, such as setting, hardening, injectability and in vivo behaviour. It was shown that by using PVA it is possible to modulate the setting and hardening properties: large increase in injectability time (1 h) in relation with the plain cement (few minutes) was achieved. Moreover, in vivo tests confirmed the ability of the composite to enhance bone healing in trabecular tissue. Histological results from critical size defects produced in rabbit distal femoral condyles showed after 12 weeks implantation a greater deposition of new tissue on bone-composite interfaces in comparison to bone-cement interfaces. The quality of bone growth was confirmed through histomorphometric and microhardness analysis. Bone formation in the composite implantation sites was significantly higher than in H-cem implants at both times of evaluation.

Electrochemical microelectrodes for improved spatial and temporal characterization of aqueous environments around calcium phosphate cements.

Calcium phosphate compounds can potentially influence cellular fate through ionic substitutions. However, to be able to turn such solution-mediated processes into successful directors of cellular response, a perfect understanding of the material-induced chemical reactions in situ is required. We therefore report on the application of home-made electrochemical microelectrodes, tested as pH and chloride sensors, for precise spatial and temporal characterization of different aqueous environments around calcium phosphate-based biomaterials prepared from α-tricalcium phosphate using clinically relevant liquid to powder ratios. The small size of the electrodes allowed for online measurements in traditionally inaccessible in vitro environments, such as the immediate material-liquid interface and the interior of curing bone cement. The kinetic data obtained has been compared to theoretical sorption models, confirming that the proposed setup can provide key information for improved understanding of the biochemical environment imposed by chemically reactive biomaterials.

Ion reactivity of calcium-deficient hydroxyapatite in standard cell culture media.

Solution-mediated surface reactions occur for most calcium phosphate-based biomaterials and may influence cellular response. A reasonable extrapolation of such processes observed in vitro to in vivo performance requires a deep understanding of the underlying mechanisms. We therefore systematically investigated the nature of ion reactivity of calcium-deficient hydroxyapatite (CDHA) by exposing it for different periods of time to standard cell culture media of different chemical composition (DMEM and McCoy medium, with and without osteogenic supplements and serum proteins). Kinetic ion interaction studies of principal extracellular ions revealed non-linear sorption of Ca²âº (∼50% sorption) and K⁺ (∼8%) as well as acidification of all media during initial contact with CDHA (48h). Interestingly, inorganic phosphorus (P(i)) was sorbed from McCoy medium (∼50%) or when using osteogenic media containing ß-glycerophosphate, but not from DMEM medium. Non-linear sorption data could be perfectly described by pseudo-first-order and pseudo-second-order sorption models. At longer contact time (21 days), and with frequent renewal of culture medium, sorption of Ca²âº remained constant throughout the experiment, while sorption of P(i) gradually decreased in McCoy medium. In great contrast, CDHA began to release P(i) slowly with time when using DMEM medium. Infrared spectra showed that CDHA exposed to culture media had a carbonated surface chemistry, suggesting that carbonate plays a key role in the ion reactivity of CDHA. Our data show that different compositions of the aqueous environment may provoke opposite ion reactivity of CDHA, and this must be carefully considered when evaluating the osteoinductive potential of the material.

Effect of blasting treatment and Fn coating on MG63 adhesion and differentiation on titanium: a gene expression study using real-time RT-PCR.

Biomaterial surface properties, via alterations in the adsorbed protein layer, and the presence of specific functional groups can influence integrin binding specificity, thereby modulating cell adhesion and differentiation processes. The adsorption of fibronectin, a protein directly involved in osteoblast adhesion to the extracellular matrix, has been related to different physical and chemical properties of biomaterial surfaces. This study used blasting particles of different sizes and chemical compositions to evaluate the response of MG63 osteoblast-like cells on smooth and blasted titanium surfaces, with and without fibronectin coatings, by means of real-time reverse transcription-polymerase chain reaction (qRT-PCR) assays. This response included (a) expression of the α(5), α(v) and α(3) integrin subunits, which can bind to fibronectin through the RGD binding site, and (b) expression of alkaline phosphatase (ALP) and osteocalcin (OC) as cell-differentiation markers. ALP activity and synthesis of OC were also tested. Cells on SiC-blasted Ti surfaces expressed higher amounts of the α(5) mRNA gene than cells on Al(2)O(3)-blasted Ti surfaces. This may be related to the fact that SiC-blasted surfaces adsorbed higher amounts of fibronectin due to their higher surface free energy and therefore provided a higher number of specific cell-binding sites. Fn-coated Ti surfaces decreased α(5) mRNA gene expression, by favoring the formation of other integrins involved in adhesion over α(5)ß(1). The changes in α(5) mRNA expression induced by the presence of fibronectin coatings may moreover influence the osteoblast differentiation pathway, as fibronectin coatings on Ti surfaces also decreased both ALP mRNA expression and ALP activity after 14 and 21 days of cell culture.

Novel soybean/gelatine-based bioactive and injectable hydroxyapatite foam: material properties and cell response.

Despite their known osteoconductivity, clinical use of calcium phosphate cements is limited both by their relatively slow rate of resorption and by rheological properties incompatible with injectability. Bone in-growth and material resorption have been improved by the development of porous calcium phosphate cements. However, injectable formulations have so far only been obtained through the addition of relatively toxic surfactants. The present work describes the response of osteoblasts to a novel injectable foamed bone cement based on a composite formulation including the bioactive foaming agents soybean and gelatine. The foaming properties of both defatted soybean and gelatine gels were exploited to develop a self-hardening soy/gelatine/hydroxyapatite composite foam able to retain porosity upon injection. After setting, the foamed paste produced a calcium-deficient hydroxyapatite scaffold, showing good injectability and cohesion as well as interconnected porosity after injection. The intrinsic bioactivity of soybean and gelatine was shown to favour osteoblast adhesion and growth. These findings suggest that injectable, porous and bioactive calcium phosphate cements can be produced for bone regeneration through minimally invasive surgery.

Perfusion cell seeding on large porous PLA/calcium phosphate composite scaffolds in a perfusion bioreactor system under varying perfusion parameters.

A promising approach to bone tissue engineering lies in the use of perfusion bioreactors where cells are seeded and cultured on scaffolds under conditions of enhanced nutrient supply and removal of metabolic products. Fluid flow alterations can stimulate cell activity, making the engineering of tissue more efficient. Most bioreactor systems are used to culture cells on thin scaffold discs. In clinical use, however, bone substitutes of large dimensions are needed. In this study, MG63 osteoblast-like cells were seeded on large porous PLA/glass scaffolds with a custom developed perfusion bioreactor system. Cells were seeded by oscillating perfusion of cell suspension through the scaffolds. Applicable perfusion parameters for successful cell seeding were determined by varying fluid flow velocity and perfusion cycle number. After perfusion, cell seeding, the cell distribution, and cell seeding efficiency were determined. A fluid flow velocity of 5 mm/s had to be exceeded to achieve a uniform cell distribution throughout the scaffold interior. Cell seeding efficiencies of up to 50% were achieved. Results suggested that perfusion cycle number influenced cell seeding efficiency rather than fluid flow velocities. The cell seeding conducted is a promising basis for further long term cell culture studies in large porous scaffolds.

Dynamics of bone marrow-derived endothelial progenitor cell/mesenchymal stem cell interaction in co-culture and its implications in angiogenesis.

Tissue engineering aims to regenerate tissues and organs by using cell and biomaterial-based approaches. One of the current challenges in the field is to promote proper vascularization in the implant to prevent cell death and promote host integration. Bone marrow endothelial progenitor cells (BM-EPCs) and mesenchymal stem cells (MSCs) are bone marrow resident stem cells widely employed for proangiogenic applications. In vivo, they are likely to interact frequently both in the bone marrow and at sites of injury. In this study, the physical and biochemical interactions between BM-EPCs and MSCs in an in vitro co-culture system were investigated to further clarify their roles in vascularization. BM-EPC/MSC co-cultures established close cell-cell contacts soon after seeding and self-assembled to form elongated structures at 3days. Besides direct contact, cells also exhibited vesicle transport phenomena. When co-cultured in Matrigel, tube formation was greatly enhanced even in serum-starved, growth factor free medium. Both MSCs and BM-EPCs contributed to these tubes. However, cell proliferation was greatly reduced in co-culture and morphological differences were observed. Gene expression and cluster analysis for wide panel of angiogenesis-related transcripts demonstrated up-regulation of angiogenic markers but down-regulation of many other cytokines. These data suggest that cross-talk occurs in between BM-EPCs and MSCs through paracrine and direct cell contact mechanisms leading to modulation of the angiogenic response.

Different assembly of type IV collagen on hydrophilic and hydrophobic substrata alters endothelial cells interaction.

Considering the structural role of type IV collagen (Col IV) in the assembly of the basement membrane (BM) and the perspective of mimicking its organization for vascular tissue engineering purposes, we studied the adsorption pattern of this protein on model hydrophilic (clean glass) and hydrophobic trichloro(octadecyl)silane (ODS) surfaces known to strongly affect the behavior of other matrix proteins. The amount of fluorescently labeled Col IV was quantified showing saturation of the surface for concentration of the adsorbing solution of about 50microg/ml, but with approximately twice more adsorbed protein on ODS. AFM studies revealed a fine - nearly single molecular size - network arrangement of Col IV on hydrophilic glass, which turns into a prominent and growing polygonal network consisting of molecular aggregates on hydrophobic ODS. The protein layer forms within minutes in a concentration-dependent manner. We further found that human umbilical vein endothelial cells (HUVEC) attach less efficiently to the aggregated Col IV (on ODS), as judged by the significantly altered cell spreading, focal adhesions formation and the development of actin cytoskeleton. Conversely, the immunofluorescence studies for integrins revealed that the fine Col IV network formed on hydrophilic substrata is better recognized by the cells via both alpha1 and alpha2 heterodimers which support cellular interaction, apart from these on hydrophobic ODS where almost no clustering of integrins was observed.

Injectable and fast resorbable calcium phosphate cement for body-setting bone grafts.

In this work a calcium phosphate (CPC)/polymer blend was developed with the advantage of being moldable and capable of in situ setting to form calcium deficient hydroxyapatite under physiological conditions in an aqueous environment at body temperature. The CPC paste consists in a mix of R cement, glycerol as a liquid phase carrier and a biodegradable hydrogel such as Polyvinyl alcohol, which acts as a binder. Microstructure and mechanical analysis shows that the CPC blend can be used as an injectable implant for low loaded applications and fast adsorption requirements. The storage for commercial distribution was also evaluated and the properties of the materials obtained do not significantly change during storage at -18 degrees C.