This study analyses the evaluation of tomographic indicators of tibia structure, assuming that the usual loading pattern shifts from uniaxial compression close to the heel to a combined compression, torsion and bending scheme towards the knee. To this end, pQCT scans were obtained at 5% intervals of the tibia length (S5-S95 sites from heel to knee) in healthy men and women (10 ⁄ 10) aged 20-40 years. Indicators of bone mass [cortical area, cortical ⁄ total bone mineral content (BMC)], diaphyseal design (peri ⁄ endosteal perimeters, cortical thickness, circularity, bending ⁄ torsion moments of inertia -CSMIs), and material quality [(cortical vBMD (bone mineral density)] were determined. The longitudinal patterns of variation of these measures were similar between genders, but male values were always higher except for cortical vBMD. Expression of BMC data as percentages of the minimal values obtained along the bone eliminated those differences. The correlative variations in cortical area, BMC and thickness, periosteal perimeter and CSMIs along the bone showed that cortical bone mass was predominantly associated with cortical thickness toward the mid-diaphysis, and with bone diameter and CSMIs moving more proximally. Positive relationships between CSMIs (y) and total BMC (x) showed men's values shifting to the upper-right region of the graph and women's values shifting to the lower-left region. Total BMC decayed about 33% from S5 to S15 (where minimum total BMC and CSMI values and variances and maximum circularity were observed) and increased until S45, reaching the original S5 value at S40. The observed gender-related differences reflected the natural allometric relationships. However, the data also suggested that men distribute their available cortical mass more efficiently than women. The minimum amount and variance of mass indicators and CSMIs, and the largest circularity observed at S15 reflected the assumed adaptation to compression pattern at that level. The increase in CSMIs (successively for torsion, A-P bending, and lateral bending), the decrease in circularity values and the changes in cortical thickness and periosteal perimeter toward the knee described the progressive adaptation to increasing torsion and bending stresses. In agreement with the biomechanical background, the described relationships: (i) identify the sites at which some changes in tibial stresses and diaphyseal structure take place, possibly associated with fracture incidence; (ii) allow prediction of mass indicators at any site from single determinations; (iii) establish the proportionality between the total bone mass at regions with highly predominant trabecular and cortical bone of the same individual, suitable for a specific evaluation of changes in trabecular mass; and (iv) evaluate the ability of bone tissue to self-distribute the available cortical bone according to specific stress patterns, avoiding many anthropometric and gender-derived influences.

Permeability of the endothelial monolayer is increased when exposed to the bacterial endotoxin LPS. Our previous studies have shown that heat shock protein (Hsp) 90 inhibitors protect and restore LPS-mediated hyperpermeability in bovine pulmonary arterial endothelial cells. In this study, we assessed the effect of Hsp90 inhibition against LPS-mediated hyperpermeability in cultured human lung microvascular endothelial cells (HLMVECs) and delineated the underlying molecular mechanisms. We demonstrate that Hsp90 inhibition is critical in the early phase, to prevent LPS-mediated hyperpermeability, and also in the later phase, to restore LPS-mediated hyperpermeability in HLMVECs. Because RhoA is a well known mediator of endothelial hyperpermeability, we investigated the effect of Hsp90 inhibition on LPS-mediated RhoA signaling. RhoA nitration and activity were increased by LPS in HLMVECs and suppressed when pretreated with the Hsp90 inhibitor, 17-allylamino-17 demethoxy-geldanamycin (17-AAG). In addition, inhibition of Rho kinase, a downstream effector of RhoA, protected HLMVECs from LPS-mediated hyperpermeability and abolished LPS-induced myosin light chain (MLC) phosphorylation, a target of Rho kinase. In agreement with these findings, 17-AAG or dominant-negative RhoA attenuated LPSinduced MLC phosphorylation. MLC phosphorylation induced by constitutively active RhoA was also suppressed by 17-AAG, suggesting a role for Hsp90 downstream of RhoA. Inhibition of Src family kinases also suppressed RhoA activity and MLC phosphorylation. Together, these data indicate that Hsp90 inhibition prevents and repairs LPS-induced lung endothelial barrier dysfunction by suppressing Src-mediated RhoA activity and signaling.

The morbidity of bone fractures and defects is steadily increasing due to changes in the age pyramid. As such, novel biomaterials that are able to promote the healing and regeneration of injured bones are needed to overcome the limitations of auto-, allo-, and xenografts, while providing a ready-to-use product that may help to minimize surgical invasiveness and duration. In this regard, recombinant biomaterials, such as elastin-like recombinamers (ELRs), are very promising as their design can be tailored by genetic engineering, thus allowing scalable production and batch-to-batch consistency, among others. Furthermore, they can self-assemble into physically crosslinked hydrogels above a certain transition temperature, in this case body temperature, but are injectable below this temperature, thereby markedly reducing surgical invasiveness. In this study, we have developed two bioactive hydrogel-forming ELRs, one including the osteogenic and osteoinductive bone morphogenetic protein-2 (BMP-2) and the other the Arg-Gly-Asp (RGD) cell adhesion motif. The combination of these two novel ELRs results in a BMP-2-loaded extracellular matrix-like hydrogel. Moreover, elastase-sensitive domains were included in both ELR molecules, thereby conferring biodegradation as a result of enzymatic cleavage and avoiding the need for scaffold removal after bone regeneration. Both ELRs and their combination showed excellent cytocompatibility, and the culture of cells on RGD-containing ELRs resulted in optimal cell adhesion. In addition, hydrogels based on a mixture of both ELRs were implanted in a pilot study involving a femoral bone injury model in New Zealand white rabbits, showing complete regeneration in six out of seven cases, with the other showing partial closure of the defect. Moreover, bone neoformation was confirmed using different techniques, such as radiography, computed tomography, and histology. This hydrogel system therefore displays significant potential in the regeneration of bone defects, promoting self-regeneration by the surrounding tissue with no involvement of stem cells or osteogenic factors other than BMP-2, which is released in a controlled manner by elastase-mediated cleavage from the ELR backbone.

Results are coherent with previous findings in physically inactive people and with Frost's mechanostat theory. The observed group differences in cortical vBMD could reflect an increase in intracortical porosity (enhanced remodeling for damage repair), eventually compensated biomechanically by CSMI improvements. The sex specificity of exercise effects may suggest the interference by the endocrine environment. Results confirm that the mechanical environment is a strong determinant of regional tibia structure and suggest that the endocrine environment may reduce the effects of physical interventions on bone health in fertile women.

Proteins with osteoinductive potential, especially recombinant human bone morphogenetic protein (rhBMP)‐2, have large effects on cell growth and their differentiation. The aim of this study was to assess repair of bone defects in rat calvaria with different types of grafts associated with rhBMP‐2, through immunohistochemistry and micro computed tomography (CT) analyses. A total of 35 male Wistar rats were selected, each weighing ~250 g, with a waiting period of 6 weeks from the creation of the defect to the sacrifice, and divided into five groups (n = 7): autograft plus 5 μg rhBMP‐2 (AuG/BMP‐2); allograft plus 5 μg rhBMP‐2 (AlG/BMP‐2); xenograft (heterologous) plus 5 μg rhBMP‐2 (XeG/BMP‐2); 5 μg rhBMP‐2 (BMP‐2) and the control group (n = 7). The micro CT reveal that all groups associating different bone grafts with BMP‐2 showed increased bone formation compared to the control. The immunostaining show that osteocalcin and bone sialoprotein were higher in groups with BMP‐2 than control group; BMP was high expressed in AuG/BMP‐2, AlG/BMP‐2, and BMP‐2; vascular endothelial growth factor (VEGF) was more expressed in groups with BMP‐2; VEGF‐R2 was low to moderate in AuG/BMP‐2, XeG/BMP‐2, and BMP‐2, predominantly moderate in AlG/BMP‐2 and low in the control; CD‐31 was predominantly moderate in AuG/BMP‐2, AlG/BMP‐2, and XeG/BMP‐2, low to moderate in BMP‐2 and low in the control. The results revealed that rhBMP‐2 improved bone repair when administered alone, or when associated with different bone grafts.