Osteogenic-angiogenic coupled response of cobalt-containing mesoporous bioactive glasses in vivo.

The incorporation of cobalt ions into the composition of bioactive glasses has emerged as a strategy of interest for bone regeneration purposes. In the present work, we have designed a set of bioactive mesoporous glasses SiO2-CaO-P2O5-CoO (Co-MBGs) with different amounts of cobalt. The physicochemical changes introduced by the Co2+ ion, the in vitro effects of Co-MBGs on preosteoblasts and endothelial cells and their in vivo behaviour using them as bone grafts in a sheep model were studied. The results show that Co2+ ions neither destroy mesoporous ordering nor inhibit in vitro bioactive behaviour, exerting a dual role as network former and modifier for CoO concentrations above 3 % mol. On the other hand, the activity of Co-MBGs on MC3T3-E1 preosteoblasts and HUVEC vascular endothelial cells is dependent on the concentration of CoO present in the glass. For low Co-MBGs concentrations (1mg/ml) cell viability is not affected, while the expression of osteogenic (ALP, RUNX2 and OC) and angiogenic (VEGF) genes is stimulated. For Co-MBGs concentration of 5 mg/ml, cell viability decreases as a function of the CoO content. In vivo studies show that the incorporation of Co2+ ions to the MBGs improves the bone regeneration activity of these materials, despite the deleterious effect that this ion has on bone-forming cells for any of the Co-MBG compositions studied. This contradictory effect is explained by the marked increase in angiogenesis that takes place inside the bone defect, leading to an angiogenesis-osteogenesis coupling that compensates for the partial decrease in osteoblast cells. STATEMENT OF SIGNIFICANCE: The development of new bone grafts implies to address the need for osteogenesis-angiogenesis coupling that allows bone regeneration with viable tissue in the long term. In this sense the incorporation of cobalt ions into the composition of bioactive glasses has emerged as a strategy of great interest in this field. Due to the potential cytotoxic effect of cobalt ions, there is an important controversy regarding the suitability of their incorporation in bone grafts. In this work, we address this controversy after the implantation of cobalt-doped mesoporous bioactive glasses in a sheep model. The incorporation of cobalt ions in bioactive glasses improves the bone regeneration ability of these bone grafts, due to enhancement of the angiogenesis-osteogenesis coupling.

Injectable mesoporous bioactive nanoparticles regenerate bone tissue under osteoporosis conditions.

The osteogenic capability of mesoporous bioactive nanoparticles (MBNPs) in the SiO2CaO system has been assessed in vivo using an osteoporotic rabbit model. MBNPs have been prepared using a double template method, resulting in spherical nanoparticles with a porous core-shell structure that has a high surface area and the ability to incorporate the anti-osteoporotic drug ipriflavone. In vitro expression of the pro-inflammatory genes NF-κB1, IL-6, TNF-α, P38 and NOS2 in RAW-264.7 macrophages, indicates that these nanoparticles do not show adverse inflammatory effects. An injectable system has been prepared by suspending MBNPs in a hyaluronic acid-based hydrogel, which has been injected intraosseously into cavitary bone defects in osteoporotic rabbits. The histological analyses evidenced that MBNPs promote bone regeneration with a moderate inflammatory response. The incorporation of ipriflavone into these nanoparticles resulted in a higher presence of osteoblasts and enhanced angiogenesis at the defect site, but without showing significant differences in terms of new bone formation. STATEMENT OF SIGNIFICANCE: Mesoporous bioactive glass nanoparticles have emerged as one of the most interesting materials in the field of bone regeneration therapies. For the first time, injectable mesoporous bioactive nanoparticles have been tested in vivo using an osteoporotic animal model. Our findings evidence that MBG nanoparticles can be loaded with an antiosteoporotic drug, ipriflavone, and incorporated in hyaluronic acid to make up an injectable hydrogel. The incorporation of MBG nanoparticles promotes bone regeneration even under osteoporotic conditions, whereas the presence of IP enhances angiogenesis as well as the presence of osteoblast cells lining in the newly formed bone. The injectable device presented in this work opens new possibilities for the intraosseous treatment of osteoporotic bone using minimally invasive surgery.

Silicon substituted hydroxyapatite/VEGF scaffolds stimulate bone regeneration in osteoporotic sheep.

Silicon-substituted hydroxyapatite (SiHA) macroporous scaffolds have been prepared by robocasting. In order to optimize their bone regeneration properties, we have manufactured these scaffolds presenting different microstructures: nanocrystalline and crystalline. Moreover, their surfaces have been decorated with vascular endothelial growth factor (VEGF) to evaluate the potential coupling between vascularization and bone regeneration. In vitro cell culture tests evidence that nanocrystalline SiHA hinders pre-osteblast proliferation, whereas the presence of VEGF enhances the biological functions of both endothelial cells and pre-osteoblasts. The bone regeneration capability has been evaluated using an osteoporotic sheep model. In vivo observations strongly correlate with in vitro cell culture tests. Those scaffolds made of nanocrystalline SiHA were colonized by fibrous tissue, promoted inflammatory response and fostered osteoclast recruitment. These observations discard nanocystalline SiHA as a suitable material for bone regeneration purposes. On the contrary, those scaffolds made of crystalline SiHA and decorated with VEGF exhibited bone regeneration properties, with high ossification degree, thicker trabeculae and higher presence of osteoblasts and blood vessels. Considering these results, macroporous scaffolds made of SiHA and decorated with VEGF are suitable bone grafts for regeneration purposes, even in adverse pathological scenarios such as osteoporosis. STATEMENT OF SIGNIFICANCE: For the first time, the in vivo behavior of scaffolds made of silicon substituted hydroxyapatites (SiHA) has been evaluated under osteoporosis conditions. In order to optimize the bone regeneration properties of these bioceramics, 3D macroporous scaffolds have been manufactured by robocasting and implanted in osteoporotic sheep. Our experimental design shed light on the important issue of the biological response of nano-sized bioceramics vs highly crystalline bioceramics, as well as on the importance of coupling vascularization and bone growth processes by decorating SiHA scaffolds with vascular endothelial growth factor.

Mesoporous bioactive glass/ɛ-polycaprolactone scaffolds promote bone regeneration in osteoporotic sheep.

Macroporous scaffolds made of a SiO2-CaO-P2O5 mesoporous bioactive glass (MBG) and ɛ-polycaprolactone (PCL) have been prepared by robocasting. These scaffolds showed an excellent in vitro biocompatibility in contact with osteoblast like cells (Saos 2) and osteoclasts derived from RAW 264.7 macrophages. In vivo studies were carried out by implantation into cavitary defects drilled in osteoporotic sheep. The scaffolds evidenced excellent bone regeneration properties, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, thick trabeculae, high vascularization and high presence of osteoblasts and osteoclasts. In order to evaluate the effects of the local release of an antiosteoporotic drug, 1% (%wt) of zoledronic acid was incorporated to the scaffolds. The scaffolds loaded with zoledronic acid induced apoptosis in Saos 2 cells, impeded osteoclast differentiation in a time dependent manner and inhibited bone healing, promoting an intense inflammatory response in osteoporotic sheep. STATEMENT OF SIGNIFICANCE: In addition to an increase in bone fragility and susceptibility to fracture, osteoporosis also hinders the clinical success of endosseous implants and grafting materials for the treatment of bone defects. For the first time, macroporous scaffolds made of mesoporous bioactive glass and ε-caprolactone have been evaluated in a sheep model that mimics the osteoporosis conditions in humans. These implants fostered bone regeneration, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, showing thick trabeculae and a high vascularization degree. Our results indicate that macroporous structures containing highly bioactive mesoporous glasses could be excellent candidates for the regenerative treatment of bone defects in osteoporotic patients.

Histologic assessment of donor kidneys and graft outcome: multivariate analyses.

UNLABELLED: We performed a multivariate analysis to evaluate the importance of histologic parameters in donor kidney biopsies as predictors of graft outcome. METHODS: Wedge protocol biopsies from a single center were analyzed for glomerulosclerosis (GS), interstitial fibrosis (IF), tubular atrophy (TA), arteriosclerosis (AS), and arteriolar hyalinosis (AH). Alterations were quantified as percentage (GS, IF) or semiquantified according to Banff criteria (IF, TA, AS, AH). We calculated creatinine clearance (CrCl) at 1, 2, and 3 years posttransplant. Donor data included age, gender, and type: non-heart-beating donor or brain dead donors. Recipient data included age, gender, cold ischemia time, number of HLA mismatches, peak level of the panel reactive antibody (PRA), number of acute rejection episodes (ARE), and presence or absence of cytomegalovirus (CMV) disease. Univariate and multivariate analyses were performed. Follow-up range was 1 to 4.2 years. RESULTS: GS, IF, TA, and AH were associated with graft survival in the multivariate analysis. The histologic parameters were associated with CrCl at several posttransplant time intervals, but the significance of association was lost in the multivariate analysis. Donor age showed a better correlation with graft function. In the univariate analyses adjusting for donor age, only IF and AH were associated with graft function. CONCLUSIONS: Histologic parameters showed a modest association with graft function. In our study, donor age is the better predictor of graft function. IF and AH may be similar to or better than GS as predictors of graft outcome.

The perfusion pressure in non-heart-beating donors may expand the glomeruli.

INTRODUCTION: We have observed expanded glomeruli in biopsies of kidneys from non-heart-beating donors (NHBDs). We sought to determine the differences in glomerular size between NHBDs and brain-dead donors and to assess whether glomerular size impacted graft outcome. METHODS: We estimated the glomerular area using the maximal planar area (MPA) method in 198 pretransplant biopsies from 119 donors: 54 (45.4%) NHBDs and 65 (54.6%) brain-dead donors. Donor data and graft outcomes were correlated with MPA and percentage of glomerulosclerosis. The range of follow-up was 1 to 3 years. Uni- and multivariate analyses were performed. RESULTS: MPA was larger among NHBDs. MPA and GS both significantly correlated with donor age. The association between MPA and age was independent of nephron loss (ie; GS). Increased glomerular size was only observed among donors younger than 50 years. Graft survival and function were not independently associated with MPA. Donor age was a better predictor of graft outcome. CONCLUSIONS: The perfusion pressure used in NHBDs may expand the glomeruli, but this maneuver does not have any effect on graft outcome. Among donors without severe changes, glomerular size increment shows a limit around the sixth decade of life. In our study, MPA was not an independent predictor of graft survival or function.

Rechazo agudo refractario en el cuarto trasplante renal: cuando el arsenal terapéutico resulta insuficiente para una inmunosupresión adecuada / Refractary acute rejection in the fourth renal transplantation

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Rechazo agudo refractario en el cuarto trasplante renal: cuando el arsenal terapéutico resulta insuficiente para una inmunosupresión adecuada / No disponible

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[BK virus in kidney allografts: a search for histologic evidence of the infection]. / Virus BK en injertos renales: evidencia histológica de la infección.

BACKGROUND: BK virus (BKV) associated interstitial nephritis is a complication in renal transplantation recipients. Its incidence is controversial. The aim of the present study is to determine the incidence of histopathologic evidence of BKV-infection in a single centre. MATERIALS AND METHODS: Renal allograft tissue samples (n = 838) from 526 patients undergoing renal transplant were evaluated by light microscopy. Polymerase chain reaction (PCR) assay for BKV DNA was performed in 41 microdissected cell populations from cases with viral inclusions, cases with other nuclear changes, and cases without nuclear changes. RESULTS: Polyomavirus-inclusions were identified in six cases (five with interstitial nephritis and other one with only urothelial infection). In one case with interstitial nephritis the DNA was degraded. PCR confirmed BKV infection in the other five and was negative in cases without inclusions. CONCLUSIONS: Five patterns of inclusions bodies are observed and they appear to be characteristic. PCR assay seemingly have a high specificity for BKV detection and it does not usually detect latent viral infection.