Gait analysis: An effective tool to mechanically monitor the bone regeneration of critical-sized defects in tissue engineering applications

INTRODUCTION

Tissue engineering has emerged as an innovative approach to treat critical-size bone defects using biocompatible scaffolds, thus avoiding complex distraction surgeries or limited stock grafts. Continuous regeneration monitoring is essential in critical-size cases due to the frequent appearance of non-unions. This work evaluates the potential clinical use of gait analysis for the mechanical assessment of a tissue engineering regeneration as an alternative to the traditional and hardly conclusive manual or radiological follow-up.

MATERIALS AND METHODS

The 15-mm metatarsal fragment of eight female merino sheep was surgically replaced by a bioceramic scaffold stabilized with an external fixator. Gait tests were performed weekly by making the sheep walk on an instrumented gangway. The evolution of different kinematic and dynamic parameters was analyzed for all the animal's limbs, as well as asymmetries between limbs. Finally, potential correlation in the recovery of the gait parameters was evaluated through the linear regression models.

RESULTS

After surgery, the operated limb has an altered way of carrying body weight while walking. Its loading capacity was significantly reduced as the stance phases were shorter and less impulsive. The non-operated limbs compensated for this mobility deficit. All parameters were normalizing during the consolidation phase while the bone callus was simultaneously mineralizing. The results also showed high levels of asymmetry between the operated limb and its contralateral, which exceeded 150% when analyzing the impulse after surgery. Gait recovery significantly correlated between symmetrical limbs.

CONCLUSIONS

Gait analysis was presented as an effective, low-cost tool capable of mechanically predicting the regeneration of critical-size defects treated by tissue engineering, as comparing regeneration processes or novel scaffolds. Despite the progressive normalization as the callus mineralized, the bearing capacity reduction and the asymmetry of the operated limb were more significant than in other orthopedic alternatives.

Mechanics Predicts Effective Critical-Size Bone Regeneration Using 3D-Printed Bioceramic Scaffolds

BACKGROUND

3D-printed bioceramic scaffolds have gained popularity due to their controlled microarchitecture and their proven biocompatibility. However, their high brittleness makes their surgical implementation complex for weight-bearing bone treatments. Thus, they would require difficult-to-instrument rigid internal fixations that limit a rigorous evaluation of the regeneration progress through the analysis of mechanic-structural parameters.

METHODS

We investigated the compatibility of flexible fixations with fragile ceramic implants, and if mechanical monitoring techniques are applicable to bone tissue engineering applications. Tissue engineering experiments were performed on 8 ovine metatarsi. A 15 mm bone segment was directly replaced with a hydroxyapatite scaffold and stabilized by an instrumented Ilizarov-type external fixator. Several in vivo monitoring techniques were employed to assess the mechanical and structural progress of the tissue.

RESULTS

The applied surgical protocol succeeded in combining external fixators and subject-specific bioceramic scaffolds without causing fatal fractures of the implant due to stress concentrator. The bearing capacity of the treated limb was initially altered, quantifying a 28-56% reduction of the ground reaction force, which gradually normalized during the consolidation phase. A faster recovery was reported in the bearing capacity, stiffening and bone mineral density of the callus. It acquired a predominant mechanical role over the fixator in the distribution of internal forces after one post-surgical month.

CONCLUSION

The bioceramic scaffold significantly accelerated in vivo the bone formation compared to other traditional alternatives in the literature (e.g., distraction osteogenesis). In addition, the implemented assessment techniques allowed an accurate quantitative evaluation of the bone regeneration through mechanical and imaging parameters.

A single-center comparison of our initial experiences in treating penile and urethral cancer with video-endoscopic inguinal lymphadenectomy (VEIL) and later experiences in melanoma cases

Background

Video-endoscopic inguinal lymphadenectomy (VEIL) is a minimally invasive approach that is increasingly indicated in oncological settings, with mounting evidence for its long-term oncological safety.

Objectives

To present our single-center experience of treating penile and urethral cancer with VEIL, as well as its more recent application in melanoma patients.

Methods

We prospectively recorded our experiences with VEIL from September 2010 to July 2018, registering the patient primary indication, surgical details, complications, and follow-up.

Results

Twenty-nine patients were operated in one (24) or both (5) groins; 18 had penile cancer, 1 had urethral cancer, and 10 had melanoma. A mean 8.62 ± 4.45 lymph nodes were removed using VEIL and of these, an average of 1.00 ± 2.87 were metastatic; 16 patients developed lymphocele and 10 presented some degree of lymphedema; there were no skin or other major complications. The median follow-up was 19.35 months; there were 3 penile cancer patient recurrences in the VEIL-operated side. None of the melanoma patients presented a lymphatic inguinal recurrence.

Conclusions

VEIL is a minimally invasive technique which appears to be oncologically safe showing fewer complications than open surgery. However, complications such as lymphorrhea, lymphocele, or lymphedema were not diminished by using VEIL.

Evolution of relaxation properties of callus tissue during bone transport

Callus tissue exhibits a viscoelastic behavior that has a strong influence on the distribution of stresses and their evolution with time and, thus, it can affect tissue differentiation during distraction procedures. For this reason, a deep knowledge of that viscoelastic behavior can be very useful to improve current protocols of bone distraction and bone transport. Monitoring stress relaxation of the callus during distraction osteogenesis allows characterizing its viscoelastic behavior. Different procedures have been used in the literature to fit the response of a given viscoelastic model to the force relaxation curve. However, these procedures do not ensure the uniqueness of that fit, which is of the utmost importance for statistical purposes. This work uses a fitting procedure already validated for other tissues that ensures that uniqueness. Very importantly too, the procedure presented here allows obtaining more information from the stress relaxation tests, distinguishing relaxation in different time scales, which provides a deeper insight into the viscoelastic behavior and its evolution over time. As it was observed in the results, relaxation is faster at the first days after osteotomy and becomes slower and more gradual with time. This fact can be directly linked to the temporal evolution of the callus composition (water, organic phase, and mineral content) and also to the progression of tissue differentiation, with a prevalence of hard tissues as time passes.

Time-Dependent Collagen Fibered Structure in the Early Distraction Callus: Imaging Characterization and Mathematical Modeling

Collagen is a ubiquitous protein present in regenerating bone tissues that experiences multiple biological phenomena during distraction osteogenesis until the deposition of phosphate crystals. This work combines fluorescence techniques and mathematical modeling to shed light on the mechano-structural processes behind the maturation and accommodation-to-mineralization of the callus tissue. Ovine metatarsal bone calluses were analyzed through confocal images at different stages of the early distraction osteogenesis process, quantifying the fiber orientation distribution and mean intensity as fiber density measure. Likewise, a mathematical model based on the experimental data was defined to micromechanically characterize the apparent stiffening of the tissue within the distracted callus. A reorganization of the fibers around the distraction axis and increased fiber density were found as the bone fragments were gradually separated. Given the degree of significance between the mathematical model and previous in vivo data, reorganization, densification, and bundle maturation phenomena seem to explain the apparent mechanical maturation observed in the tissue theoretically.

Structural optimization of 3D-printed patient-specific ceramic scaffolds for in vivo bone regeneration in load-bearing defects

Tissue engineering has recently gained popularity as an alternative to autografts to stimulate bone tissue regeneration through structures called scaffolds. Most of the in vivo experiments on long-bony defects use internally-stabilized generic scaffolds. Despite the wide variety of computational methods, a standardized protocol is required to optimize ceramic scaffolds for load-bearing bony defects stabilized with flexible fixations. An optimization problem was defined for applications to sheep metatarsus defects. It covers biological parameters (porosity, pore size, and the specific surface area) and mechanical constraints based on in vivo and in vitro results reported in the literature. The optimized parameters (59.30% of porosity, 5768.91 m^-1 of specific surface area, and 360.80 μm of pore size) and the compressive strength of the selected structure were validated in vitro by means of tomographic images and compression tests of six 3D-printed samples. Divergences between the design and measured values of the optimized parameters, mainly due to manufacturing defects, are consistent with the previous studies. Using the mixed experimental-mathematical scaffold-design procedure described, they could be implanted in vivo with instrumented external fixators, therefore facilitating biomechanical monitoring of the regeneration process.

Pituitary Abscess: Two Case Reports and Review of the Literature

Pituitary abscesses are infrequent entities, often forgotten and hence rarely included in the differential diagnosis of sellar lesions. However, given that they share the clinical manifestations of other more common pathologies in this region, the treatment of pituitary abscesses is usually performed correctly without demonstrating a relevant delay in therapeutic decisions when surgical options are considered as the alternative of choice. Two patients with intrasellar expansive processes and endocrinological alterations who were diagnosed intraoperatively as having pituitary abscesses are presented. In both cases, transsphenoidal surgery was performed; adjuvant antibiotic treatment was established for just one of them. Both patients are currently without symptoms due to mass-effect; one of the patients continues exhibiting residual endocrinological alteration and no signs of relapse in imaging studies.

Mechanobiology of Bone Consolidation During Distraction Osteogenesis: Bone Lengthening Vs. Bone Transport

Bone lengthening and bone transport are regeneration processes that commonly rely on distraction osteogenesis, a widely accepted surgical procedure to deal with numerous bony pathologies. Despite the extensive study in the literature of the influence of biomechanical factors, a lack of knowledge about their mechanobiological differences prevents a clinical particularization. Bone lengthening treatments were performed on sheep metatarsus by reproducing the surgical and biomechanical protocol of previous bone transport experiments. Several in vivo monitoring techniques were employed to build an exhaustive comparison: gait analysis, radiographic and CT assessment, force measures through the fixation, or mechanical characterization of the new tissue. A significant initial loss of the bearing capacity, quantified by the ground reaction forces and the limb contact time with the ground, is suffered by the bone lengthening specimens. The potential effects of this anomaly on the musculoskeletal force distribution and the evolution of the bone callus elastic modulus over time are also analyzed. Imaging techniques also seem to reveal lower bone volume in the bone lengthening callus than in the bone transport one, but an equivalent mineralization rate. The simultaneous quantification of biological and mechanical parameters provides valuable information for the daily clinical routine and numerical tools development.

Mechanical Influence of Surrounding Soft Tissue on Bone Regeneration Processes: A Bone Lengthening Study

Bone lengthening is a bone regeneration technique with multiple clinical applications. One of the most common complications of this treatment is the lack of adaptation of the surrounding soft tissue to their extension. A better understanding of the mechanobiology of the tissues involved in distraction osteogenesis would allow better control of the clinical cases. Bone lengthening treatments were performed in vivo in the metatarsus of Merino sheep, measuring the distraction forces by means of an instrumented fixator. The tissue relaxation after distraction was analyzed in this study. A viscoelastic model was also applied to distraction data to assess the mechanical behavior of the tissues during the distraction phase. Tissue relaxation is similar to other bone regeneration processes which do not imply surrounding soft tissue extension, e.g. bone transport. The effects of this tissue on distraction forces are limited to the first minutes of distraction and elongations above 4% of the original length with the protocol applied. Moreover, the surrounding soft tissue initially loses some of its viscoelasticity and subsequently suffers strain hardening from day 5 of distraction until the end of the distraction phase, day 15. Finally, anatomical changes were also evidenced in the elongated limb of our specimens.

Real-Time Wireless Platform for In Vivo Monitoring of Bone Regeneration

For the monitoring of bone regeneration processes, the instrumentation of the fixation is an increasingly common technique to indirectly measure the evolution of bone formation instead of ex vivo measurements or traditional in vivo techniques, such as X-ray or visual review. A versatile instrumented external fixator capable of adapting to multiple bone regeneration processes was designed, as well as a wireless acquisition system for the data collection. The design and implementation of the overall architecture of such a system is described in this work, including the hardware, firmware, and mechanical components. The measurements are conditioned and subsequently sent to a PC via wireless communication to be in vivo displayed and analyzed using a developed real-time monitoring application. Moreover, a model for the in vivo estimation of the bone callus stiffness from collected data was defined. This model was validated in vitro using elastic springs, reporting promising results with respect to previous equipment, with average errors and uncertainties below 6.7% and 14.04%. The devices were also validated in vivo performing a bone lengthening treatment on a sheep metatarsus. The resulting system allowed the in vivo mechanical characterization of the bone callus during experimentation, providing a low-cost, simple, and highly reliable solution.

Expression of Siglec-1, -3, -5 and -10 in porcine cDC1 and cDC2 subsets from blood, spleen and lymph nodes and functional capabilities of these cells

Dendritic cells are professional antigen-presenting cells that play a critical role in the development of immune responses. DCs express a variety of Siglecs on their surface, which play a regulatory role modulating their activation through interaction with sialylated structures expressed by cells or pathogens. Here, we characterized the phenotype of porcine conventional dendritic cells subsets from blood, spleen and lymph nodes, emphasizing the analysis of the expression of Siglecs. Siglec-1 was detected in type 1 cDC and, at lower levels, in type 2 cDC in the spleen, being low to negative in blood and lymph node cDC. Siglec-3 and Siglec-5 were expressed in cDC1 at lower levels than in cDC2. Porcine cDCs did not express Siglec-10. cDC2 showed a higher capacity to phagocytose microspheres and to process DQ™-OVA than cDC1, but none of these functions was affected by engagement of Siglec-3 and -5 with antibodies on blood cDC.

Data-Driven Computational Simulation in Bone Mechanics

The data-driven approach was formally introduced in the field of computational mechanics just a few years ago, but it has gained increasing interest and application as disruptive technology in many other fields of physics and engineering. Although the fundamental bases of the method have been already settled, there are still many challenges to solve, which are often inherently linked to the problem at hand. In this paper, the data-driven methodology is applied to a particular problem in tissue biomechanics, a context where this approach is particularly suitable due to the difficulty in establishing accurate and general constitutive models, due to the intrinsic intra and inter-individual variability of the microstructure and associated mechanical properties of biological tissues. The problem addressed here corresponds to the characterization and mechanical simulation of a piece of cortical bone tissue. Cortical horse bone tissue was mechanically tested using a biaxial machine. The displacement field was obtained by means of digital image correlation and then transformed into strains by approximating the displacement derivatives in the bone virtual geometric image. These results, together with the approximated stress state, assumed as uniform in the small pieces tested, were used as input in the flowchart of the data-driven methodology to solve several numerical examples, which were compared with the corresponding classical model-based fitted solution. From these results, we conclude that the data-driven methodology is a useful tool to directly simulate problems of biomechanical interest without the imposition (model-free) of complex spatial and individually-varying constitutive laws. The presented data-driven approach recovers the natural spatial variation of the solution, resulting from the complex structure of bone tissue, i.e. heterogeneity, microstructural hierarchy and multifactorial architecture, making it possible to add the intrinsic stochasticity of biological tissues into the data set and into the numerical approach.

Activation of pro- and anti-inflammatory responses in lung tissue injury during the acute phase of PRRSV-1 infection with the virulent strain Lena

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Lena virulent strain caused an increase in sera levels of IFN-γ and IL-6.

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Lung viral load and PRRSV-N-protein⁺ cells were inversely correlated with CD163⁺ macrophages in the lung.

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CD14⁺ cells infiltrated interstitium to possibly replenish macrophages subsets.

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Lena-induced microscopic lung injury was linked to an increase of iNOS⁺ cells.

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The increase of CD200R1⁺ and FoxP3⁺ cells was associated with the course of lung injury.

Porcine reproductive and respiratory syndrome virus (PRRSV) plays a key role in porcine respiratory disease complex modulating the host immune response and favouring secondary bacterial infections. Pulmonary alveolar macrophages (PAMs) are the main cells supporting PRRSV replication, with CD163 as the essential receptor for viral infection. Although interstitial pneumonia is by far the representative lung lesion, suppurative bronchopneumonia is described for PRRSV virulent strains. This research explores the role of several immune markers potentially involved in the regulation of the inflammatory response and sensitisation of lung to secondary bacterial infections by PRRSV-1 strains of different virulence. Conventional pigs were intranasally inoculated with the virulent subtype 3 Lena strain or the low virulent subtype 1 3249 strain and euthanised at 1, 3, 6 and 8 dpi. Lena-infected pigs exhibited more severe clinical signs, macroscopic lung score and viraemia associated with an increase of IL-6 and IFN-γ in sera compared to 3249-infected pigs. Extensive areas of lung consolidation corresponding with suppurative bronchopneumonia were observed in Lena-infected pigs. Lung viral load and PRRSV-N-protein⁺ cells were always higher in Lena-infected animals. PRRSV-N-protein⁺ cells were linked to a marked drop of CD163⁺ macrophages. The number of CD14⁺ and iNOS⁺ cells gradually increased along PRRSV-1 infection, being more evident in Lena-infected pigs. The frequency of CD200R1⁺ and FoxP3⁺ cells peaked late in both PRRSV-1 strains, with a strong correlation between CD200R1⁺ cells and lung injury in Lena-infected pigs. These results highlight the role of molecules involved in the earlier and higher extent of lung lesions in piglets infected with the virulent Lena strain, pointing out the activation of routes potentially involved in the restraint of the local inflammatory response.

Comparison of the viscoelastic properties of human abdominal and breast adipose tissue and its incidence on breast reconstruction surgery. A pilot study

BACKGROUND

Breast cancer is the leading malignant tumor in women in the world. Reconstruction after mastectomy plays a key role in the physical and psychological recuperation, being the abdominal skin and adipose tissue the best current option for the DIEP surgery. The aim of the surgery is to obtain a reconstructed breast which looks and behaves naturally. Therefore, it would be useful to characterize the mechanical behaviour of the adipose tissue in the abdomen and breast to compare their mechanical properties, also investigating possible regional differences.

METHODS

Experimental tests have been carried out in breast and abdominal adipose tissue samples, obtaining their viscoelastic properties. The specimens have been subjected to uniaxial compression relaxation tests and a mechanical behaviour model has been fitted to the experimental curves. Afterwards, statistical analyses have been used to detect differences between different individuals' abdominal fat tissue and finally between different areas of the same individual's breast and abdominal adipose tissue.

FINDINGS

Several conclusions could be extracted from the results: 1) inter-individual differences may exist in the abdominal adipose tissue; 2) the breast fat could be regarded as a unique tissue from the mechanical point of view; 3) significant differences were detected between the superficial breast and all the locations of the abdomen, except for the superficial lateral one and 4) the mechanical properties of the abdominal adipose tissue seem to change with the depth. These conclusions can be of great value for DIEP surgeries and other surgeries in which the adipose tissue is involved.

Variability of Clinical and Angiographic Results Based on the Treatment Preference (Endovascular or Surgical) of Centers Participating in the Subarachnoid Hemorrhage Database of the Working Group of the Spanish Society of Neurosurgery

OBJECTIVES

Since the introduction of endovascular treatment for cerebral aneurysms, hospitals in which subarachnoid hemorrhage is treated show different availability and/or preferences towards both treatment modalities. The main aim is to evaluate the clinical and angiographic results according to the hospital's treatment preferences applied.

METHODS

This study was conducted based on use of the subarachnoid hemorrhage database of the Vascular Pathology Group of the Spanish Neurosurgery Society. Centers were classified into 3 subtypes according to an index in the relationship between endovascular and surgical treatment as: endovascular preference, high endovascular preference, and elevated surgical preference. The clinical results and angiographic results were evaluated among the 3 treatment strategies.

RESULTS

From November 2004 to December 2017, 4282 subarachnoid hemorrhage patients were selected for the study: 630 (14.7%) patients from centers with surgical preference, 2766 (64.6%) from centers with endovascular preference, and 886 (20.7%) from centers with high endovascular preference. The surgical preference group obtained the best angiographic results associated with a greater complete exclusion (odds ratio: 1.359; 95% confidence interval: 1.025-1.801; P = 0.033). The surgical preference subgroup obtained the best outcome at discharge (65.45%), followed by the high endovascular preference group (61.5%) and the endovascular preference group (57.8%) (odds ratio: 1.359; 95% confidence interval: 1.025-1.801; P = 0.033).

CONCLUSIONS

In Spain, there is significant variability in aneurysm exclusion treatment in aneurysmal subarachnoid hemorrhage. Surgical centers offer better results for both surgical and endovascular patients. A multidisciplinary approach and the maintenance of an elevated quality of surgical competence could be responsible for these results.

Analysis of the expression of porcine CD200R1 and CD200R1L by using newly developed monoclonal antibodies

CD200R1 and CD200R1-like are paired receptors which modulate activation of immune cells. Here, we describe the characterisation of their porcine homologues. Analysis of database porcine sequences shows an exceptionally high homology between the extracellular Ig-like domains of these receptors, being the rest more dissimilar. We have obtained two mAbs, PCT1 and PCT3, against a CD200R1-Fc recombinant protein, that bind on CHO cells expressing GFP-tagged CD200R1. The specificity of these mAbs was analysed on CD200R1 L, and also on a CD200R1 splicing variant that lacks the V-type Ig domain. PCT1 bound to both CD200R1 and CD200R1L, but not to the splicing variant, what suggests that recognises an epitope in the V-type Ig domain. PCT3 reacted with both CD200R1 variants, but not CD200R1L, probably binding to an epitope in the N-terminal sequence of CD200R1. Analysis of porcine cells with these mAbs showed expression of CD200R1/CD200R1L on B cells, monocytes and alveolar macrophages.

Comparison of methods for assigning the material properties of the distraction callus in computational models

In silico models of distraction osteogenesis and fracture healing usually assume constant mechanical properties for the new bone tissue generated. In addition, these models do not always account for the porosity of the woven bone and its evolution. In this study, finite element analyses based on computed tomography (CT) are used to predict the stiffness of the callus until 69 weeks after surgery using 15 CT images obtained at different stages of an experiment on bone transport, technique in which distraction osteogenesis is used to correct bone defects. Three different approaches were used to assign the mechanical properties to the new bone tissue. First, constant mechanical properties of the hard callus tissue and no porosity were assumed. Nevertheless, this approach did not show good correlations. Second, random variations in the elastic modulus and porosity of the woven bone were taken from previous experimental studies. Finally, the elastic properties of each element were assigned depending on gray scale in CT images. The numerically predicted callus stiffness was compared with previous in vivo measurements. It was concluded firstly that assignment depending on gray scale is the method that provides the best results and secondly that the method that considers a random distribution of porosity and elastic modulus of the callus is also suitable to predict the callus stiffness from 15 weeks after surgery. This finding provides a method for assigning the material properties of the distraction callus, which does not require CT images and may contribute to improve current in silico models.

Use of IP-10 detection in dried plasma spots for latent tuberculosis infection diagnosis in contacts via mail

The aim of this study was to test the use of IP-10 detection in dried plasma from contact studies individuals (contacts of smear positive patients), by comparing it with IP-10 and IFN-γ detection in direct plasma, to establish IP-10 detection in DPS as a useful assay for LTBI diagnosis. Whole blood samples were collected from 80 subjects: 12 with active tuberculosis (TB), and 68 from contact studies. The amount of IFN-γ produced by sensitized T cells was determined in direct plasma by QuantiFERON Gold In-Tube test. IP-10 levels were determined in direct and dried plasma by an in-house ELISA. For dried plasma IP-10 determination, two 25 µl plasma drops were dried in Whatman903 filter paper and sent by mail to the laboratory. Regarding TB patients, 100.0%, 91.7% and 75.0% were positive for IFN-γ detection and IP-10 detection in direct and dried plasma, respectively. In contacts, 69.1%, 60.3% and 48.5% had positive results after IFN-γ and IP-10 in direct and dried plasma, respectively. The agreement among in vitro tests was substantial and IP-10 levels in direct and dried plasma were strongly correlated (r = 0.897). In conclusion, IP-10 detection in dried plasma is a simple and safe method that would help improve LTBI management.

Comparison of the volumetric composition of lamellar bone and the woven bone of calluses

Woven tissue is mainly present in the bone callus, formed very rapidly either after a fracture or in distraction processes. This high formation speed is probably responsible for its disorganized microstructure and this, in turn, for its low stiffness. Nonetheless, the singular volumetric composition of this tissue may also play a key role in its mechanical properties. The volumetric composition of woven tissue extracted from the bone transport callus of sheep was investigated and compared with that of the lamellar tissue extracted from the cortical shell of the same bone. Significant differences were found in the mineral and water contents, but they can be due to the different ages of both tissues, which affects the mineral/water ratio. However, the content in organic phase remains more or less constant throughout the mineralization process and has proven to be a good variable to measure the different composition of both tissues, being that content significantly higher in woven tissue. This may be linked to the abnormally high concentration of osteocytes in this tissue, which is likely a consequence of the more abundant presence of osteoblasts secreting osteoid and burying other osteoblasts, which then differentiate into osteocytes. This would explain the high formation rate of woven tissue, useful to recover the short-term stability of the bone. Nonetheless, the more abundant presence of organic phase prevents the woven tissue from reaching a stiffness similar to that of lamellar tissue in the long term, when it is fully mineralized.

Genetic diversity of mycobacterium tuberculosis in northern Greece

The aim of the present study was to describe the genetic diversity of Mycobacterium tuberculosis (M.tuberculosis) strains circulating in the region of Northern Greece. A total of thirty-seven M. tuberculosis clinical isolates were analysed by the spoligotyping method. According to the results, six clusters comprising seventeen strains were detected, and the remaining twenty strains showed unique patterns. The M.tuberculosis families according to SITVITWEB were distributed as follows: Haarlem (H) (27.0%); T (24.3%); Beijing (13.5%); Latin-America and Mediterranean (LAM) (5.4%) and S (2.7%). The remaining isolates (27%) did not match any isolates within the database and they were characterized as orphans. Regarding GenoType MTBDRplus results, two strains (5.4%) were Multi-Drug-Resistant, four strains (10.8%), were isoniazid monoresistant, while the remaining thirty-one strains (83.8%) were susceptible. In conclusion, in the region of Macedonia-Thrace (Northern Greece), there was high phylogenetic diversity among M. tuberculosis isolates. Molecular tools used and data presented can have regional and national impact on tuberculosis control.

PyroTyping, a novel pyrosequencing-based assay for Mycobacterium tuberculosis genotyping

We developed a novel method, PyroTyping, for discrimination of Mycobacterium tuberculosis isolates combining pyrosequencing and IS6110 polymorphism. A total of 100 isolates were analysed with IS6110-restriction fragment length polymorphism (RFLP), spoligotyping, mycobacterial interspersed repetitive units - variable number tandem repeats (MIRU-VNTR), and PyroTyping. PyroTyping results regarding clustering or discrimination of the isolates were highly concordant with the other typing methods performed. PyroTyping is more rapid than RFLP and presents the same discriminatory power, thus, it may be useful for taking timely decisions for tuberculosis control.

Histological evolution of the regenerate during bone transport: an experimental study in sheep

INTRODUCTION

Bone transport (BT) for segmentary bone defects is a well-known technique as it enables correction with new bone formation, which is similar to the previous bone. Despite the high number of experimental studies of distraction osteogenesis in bone lengthening, the types of ossification and histological changes that occur in the regenerate of the bone transport process remain controversial.

OBJECTIVE

The aim of this study is to provide the complete evolution of tissues and the types of ossification in the regenerate during the different phases of bone formation after BT until the end of the remodelling period.

METHODS

A histological study was performed using ten adult sheep that were submitted to BT. The types of ossification as well as the evolution of different tissues in the regenerate were determined using histomorphometry and inmunohistochemical studies. The evolution of trabeculae thickness, osteoblast and osteoclast densities, relationship between collagen types and changes in vascularization were also studied.

RESULTS

Ossification was primarily intramembranous, with some focus of endochondral ossification in isolated animals. The cell counts showed a progression of cellular activity from the periphery to the centre, presenting the same progression as the growth of bone trabeculae, whose trabeculae thickness was quadrupled at the end of remodelling. Inmunohistochemical studies confirmed the prevalence of type I collagen and the ratio of the Type I/Type II collagen ratio was found to be 2.48. The percentages of the vascularized areas were proximally higher than distally in all animals, but distal zone obtained higher rates than the central region.

CONCLUSIONS

Bone transport regenerate exhibits a centripetal ossification model and a mixed pattern with predominance of intramembranous over endochondral ossification. The data obtained resemble partially to those found in models of bone lengthening applied to large animals. This study provides a detailed structural characterization of the newly formed tissue, which may help to explain the development of the regenerate of bone transport in humans. It will also serve for future mechanobiological models that may aid research on the effect of loading or distractor stiffness in clinical results.

A polynomial hyperelastic model for the mixture of fat and glandular tissue in female breast

In the breast of adult women, glandular and fat tissues are intermingled and cannot be clearly distinguished. This work studies if this mixture can be treated as a homogenized tissue. A mechanical model is proposed for the mixture of tissues as a function of the fat content. Different distributions of individual tissues and geometries have been tried to verify the validity of the mixture model. A multiscale modelling approach was applied in a finite element model of a representative volume element (RVE) of tissue, formed by randomly assigning fat or glandular elements to the mesh. Both types of tissues have been assumed as isotropic, quasi-incompressible hyperelastic materials, modelled with a polynomial strain energy function, like the homogenized model. The RVE was subjected to several load cases from which the constants of the polynomial function of the homogenized tissue were fitted in the least squares sense. The results confirm that the fat volume ratio is a key factor in determining the properties of the homogenized tissue, but the spatial distribution of fat is not so important. Finally, a simplified model of a breast was developed to check the validity of the homogenized model in a geometry similar to the actual one.

Molecular and functional characterization of porcine Siglec-3/CD33 and analysis of its expression in blood and tissues

A cDNA clone encoding a 380 a-a type 1 transmembrane protein with homology to human Siglec-3/CD33 was obtained from a swine small intestine library. An analysis of protein sequence identified two immunoglobulin-like domains, a transmembrane region, and a carboxi-terminal tail with two tyrosine-based signalling motifs. Binding assays of Siglec-3 transfected CHO cells to polyacrylamide glycoconjugates showed a preference for α2-6-linked sialic acids. Using mAbs raised against a fragment containing the two Ig-like domains, porcine Siglec-3 was found to be expressed on monocytes and granulocytes, and their bone marrow precursors. It was also detected in lymph node, splenic and alveolar macrophages. MAbs immunoprecipitated, from granulocyte lysates, a protein of 51-60 kDa under both non-reducing and reducing conditions. MAbs were also used to analyse functional activity of Siglec-3 on bone marrow and blood cells. Engagement of Siglec-3 by mAb had no apparent effect on cell proliferation or cytokine production.

Molecular characterization of porcine Siglec-10 and analysis of its expression in blood and tissues

Siglecs are sialic acid binding Ig-like proteins involved in the control of leukocyte responses. In this study we describe the characterization of a porcine orthologue of Siglec-10. A cDNA clone was obtained from a porcine library which encodes a protein with sequence homology to human Siglec-10. This cDNA codes for a type I transmembrane protein containing four Ig-like domains, a transmembrane region, and a cytoplasmic tail with three tyrosine-based motifs, including a membrane-proximal Grb2-binding motif, and two ITIM motifs. When expressed on transfected cells, porcine Siglec-10 was able to bind red blood cells in a sialic acid-dependent manner. Monoclonal antibodies were developed against this protein and used to examine its cell and tissue distribution in the pig. Siglec-10 was found to be expressed on blood B cells and B cell areas of the spleen and lymph nodes. A weak expression was also detected on monocytes.

Biomechanical design of less invasive stabilization system femoral plates: computational evaluation of the fracture environment

Less Invasive Stabilization System femoral plates are currently accepted as a suitable fixation technique for supra-intercondylar femoral fractures. However, general agreement does not exist regarding the optimum design of this fixator type. Therefore, the aim of this article is to reduce the intrinsic Less Invasive Stabilization System complications by clarifying, from a biomechanical point of view, how the number of screws, the screw connection type (unicortical or bicortical), or the structured position of the screws can influence the outcome of the fracture site. These studies include a specific finite element analysis that determines how several biomechanical variables, such as the movement at the fracture site, are influenced by the preconditions of bone healing. The results of this study show that the screw type affects the mechanical stabilization of the femur to a greater extent than the material type of the Less Invasive Stabilization System femoral plates. The most significant differences among all the analyzed configurations are observed in the shear interfragmentary strain between screw types. Values are approximately 50% higher with unicortical screws than with bicortical ones.

Diagnosis of tuberculosis infection by interferon-gamma release assays in patients with psoriasis

OBJECTIVE

In this study, we have performed a direct comparison between both T-cell based assays (QFN-G-IT and T-SPOT.TB) and TST in patients with psoriasis taking different immunosuppressant drug-regimens.

METHODS

We have prospectively studied 103 patients with moderate-to-severe psoriasis who required latent tuberculosis infection (LTBI) screening before starting systemic immunosuppressive treatment or during its sustained use.

RESULTS

Overall number of positive results was 16.5%, 17.5% and 8.7% using T-SPOT.TB, QFN-G-IT and TST, respectively. Differences in the percentage of positive results between TST with T-SPOT.TB and QFN-G-IT were significant (p = 0.005 and p = 0.008, respectively). A total of 24.3% of the subjects enrolled were positive for at least one of the three tests performed. Sixteen patients with negative TST (17%) were positive for one of the two IGRAs. We obtained seven indeterminate results by T-SPOT.TB and two by QFN-G-IT. Seven patients with negative TST presented indeterminate results by either of two IFN-γ assays. Positive TST, T-SPOT.TB and QFN-G-IT results were not affected by clinical therapeutic profile.

CONCLUSIONS

Our results reveal that in vitro assays are useful methods for LTBI diagnosis in patients with psoriasis, suggesting that they might be less influenced by immunosuppression than TST.

IP-10 is an accurate biomarker for the diagnosis of tuberculosis in children

OBJECTIVE

Performance of IFN-γ assays in children is compromised. Therefore, we investigated the utility of IP-10 for the detection of active tuberculosis (TB) and latent tuberculosis infection (LTBI) diagnosis in children; comparing its positivity with QuantiFERON-TB Gold In-Tube (QFN-G-IT) and T-SPOT.TB.

METHODS

We studied 230 children from three groups: active TB, screening (healthy children without known exposure to active TB patient screened at school or by their paediatrician) and contact-tracing studies. IFN-γ release was determined by QFN-G-IT and T-SPOT.TB. IP-10 was detected in QFN-G-IT supernatants by ELISA.

RESULTS

When combining QFN-G-IT and IP-10 assays, positive results improved significantly from 38.3% in QFN-G-IT and 33.9% in IP-10 to 41.3%. Age and type of contact were significant risk factors associated with positive QFN-G-IT and IP-10 results. IP-10 levels after antigen-specific stimulation were significantly higher in comparison to IFN-γ levels. Correlation between the three assays was good (κ = 0.717-0.783).

CONCLUSIONS

IP-10 cytokine is expressed in response to TB specific-antigens used in QFN-G-IT. In conclusion, the use of IFN-γ T-cell based assays in combination with an additional IP-10 assay detection could be useful for diagnosing active TB and LTBI in children.

Molecular characterization and expression of porcine Siglec-5

In this study we describe the characterization of the porcine orthologue of Siglec-5. A cDNa clone was obtained from a porcine cDNa library derived from swine small intestine which encodes a 555 a-a type 1 transmembrane protein with sequence homology to human Siglec-5. This protein consists of four Ig-like domains, a transmembrane region, and a cytoplasmic tail with two tyrosine-based signalling motifs. When expressed as a recombinant protein fused to the Fc region of human IgG1, porcine Siglec-5 was able to bind porcine red blood cells in a sialic acid-dependent manner. Monoclonal antibodies (mAb) were developed against porcine Siglec-5 and used to analyse its expression in bone marrow and blood cells, and lymphoid tissues. Porcine Siglec-5 expression was mainly restricted to myelomonocytic cells and their precursors, being detected also, although at low levels, on plasmacytoid dendritic cells and B lymphocytes. In lymphoid tissues, ellipsoids of the spleen and subcapsular and medullar sinuses of lymph nodes were positive for Siglec-5. These mAbs were able to precipitate, from granulocyte lysates, a protein of approximately 85 kDa under non-reducing conditions, indicating that porcine Siglec-5 is expressed as a monomer in the plasma membrane.

Effect of non-uniform thickness of samples in stress relaxation tests under unconfined compression of samples of articular discs

A precise information of the biomechanical properties of soft tissues is required to develop a suitable simulation model, with which the distribution of stress and strain in the complex structures can be estimated. Many soft tissues have been mechanically characterized by stress relaxation tests under unconfined or confined compression. In general, full-thickness samples are extracted to reduce the damage in the tissue as much as possible. However, it is not guaranteed that these samples have a uniform thickness or, in other words, planar parallel faces. In particular, in the articular disc of the temporomandibular joint, many studies can be found testing full-thickness samples for which that thickness is known to be non-uniform, while making the assumption of uniaxial stress state to extract the mechanical properties from those tests. That inaccuracy may have a strong influence in some cases and needs a profound revision. The main goal of this work is to quantify the error committed in that assumption and the influence of the variation of thickness on that error in a particular test: stress relaxation tests under unconfined compression. Based on this error and defining an allowable tolerance, a criterion is established to reject samples depending on their aspect ratio.

Radical prostatectomy is a reasonable treatment for patients over 70 years of age

OBJECTIVE

To compare the tumor nature and oncological course of patients operated on by radical prostatectomy in three age groups.

MATERIAL AND METHOD

From the prospective completion of the data base of our department, we analyzed 1012 patients operated on between 1986 and December 2009. Patients with neo- or adjuvant treatment and those with pre-operative PSA over 50 were excluded. The sample was divided into three groups: younger than 60, 60 to 69 and over 70. The clinical, pathological variables, biochemical course and need for rescue treatment were analyzed. We consider biochemical relapse as when the PSA values reached values greater than 0.4 in two consecutive measurements. Rescue was defined as the need for hormone treatment or radiotherapy. We then made a comparative study, a univariate survival analysis by Kaplan and Meyer Curves and multivariate by Cox's regression.

RESULTS

The median follow-up was 55.1 months. Of the 1012 patients included in the study, 317 patients (31.3%) had biochemical progression and 259 (25.6%) required rescue treatment. We observed that the groups with the older age had a significantly higher PSA and higher stages than the rest. No differences were observed in the Gleason score of the surgical specimen or in the state of the surgical margins. Biochemical relapse free survival at 5 years was 72.3% (CI 66.4-78.2) in patients under 60 years, 65.3% (CI 60.6-70.0) for patients under 70 and 62.2% (CI 53.2-71.1) for patients of 70 years or older; P<.05. In the univariate study, age was a factor that was significantly associated to biochemical relapse. However, it loses interest in the multivariate study and PSA, pathological state and Gleason score regain interest. Rescue treatment free survival did not differ by age groups.

CONCLUSIONS

In the current study, worse biochemical evolution of patients over 70 was observed. However, this worse biochemical course was conditioned by clinically more aggressive tumors that, in our opinion, justifies the decision made in regards to the surgical approach taken with these patients.

ENaC in the brain--future perspectives and pharmacological implications

The epithelial sodium channel/degenerin (ENaC/deg) family of ion channels is formed by a large number of genes with variable tissue expression patterns and physiological roles. ENaC is a non-voltage gated, constitutively active channel highly selective for sodium. ENaC is formed by three homologous subunits, α, β and γ, and a fourth subunit (δ) has been found in human and monkeys that can substitute α to form functional channels. The best-characterized role of ENaC is to serve as a rate-limiting step in transepithelial sodium reabsorption in the distal part of the kidney tubule and other tight epithelia. However, ENaC subunits are also found in the peripheral and central nervous system, where their functional roles are only beginning to be understood. In this review, we mainly focus on the putative pathophysiological roles of ENaC channels in the central nervous system and their potential value as drug targets in neurodegenerative disorders and the central control of blood pressure.

Cost-effectiveness of policies aimed at increasing organ donation: the case of Chile

BACKGROUND

In this article we present an economic evaluation of policies aimed at increasing deceased organ donation in Chile, a developing country that has low donation rates; it had 5.4 donors per million people (pmp) in 2010.

METHODS

Expert opinions of leading participants in donation and transplantation were analyzed, resulting in a set of local policies aimed at increasing donation rates. Using previous results of reported cost savings of increasing kidney transplantation in Chile, we estimated the net benefits of these policies, as a function of additional donors.

RESULTS

The main problem of the Chilean system seems to be the low capability to identify potential donors and a deficit in intensive care unit (ICU) beds. Among considered policies central to increase donation are the following: increasing human and capital resources dedicated to identifying potential donors, providing ICU beds from private centers, and developing an online information system that facilitates procurement coordination and the evaluation of performance at each hospital. Our results show that there is a linear relationship between cost savings and incremental donors pmp. For example, if these policies are capable of elevating donation rates in Chile by 6 donors pmp net estimated cost savings are approximately US $1.9 million. Likewise, considering the effect on patients' quality of life, savings would amount to around $15.0 million dollars per year.

CONCLUSIONS

Our estimates suggest that these policies have a large cost-saving potential. In fact, considering implementation costs, cost reduction is positive after 4 additional donors pmp, and increasing afterward.

Antigen targeting to APC: from mice to veterinary species

Antigen delivery to receptors expressed on antigen presenting cells (APC) has shown to improve immunogenicity of vaccines in mice. An enhancement of cytotoxic T lymphocyte (CTL), helper T cell or humoral responses was obtained depending on the type of APC and the surface molecule targeted. Although this strategy is being also evaluated in livestock animals with promising results, some discrepancies have been found between species and pathogens. The genetic diversity of livestock animals, the different pattern of expression of some receptors among species, the use of different markers to characterize APC in large animals and sometimes the lack of reagents make difficult to compare results obtained in different species. In this review, we summarize the data available regarding antigen targeting to APC receptors in cattle, sheep and pig and discuss the results found in these animals in the context of what has been obtained in mice.

A new kidney allocation policy in Chile: computer-based simulations

INTRODUCTION

Kidney allocation should reach a balance between equity and efficiency. In Chile kidneys are allocated based on ABO matching, first to medical priorities and then according to a point scheme considering human leukocyte antigen (HLA) match (60%), waiting list time (20%), and panel-reactive antibodies (PRA; 20%); pediatric recipients receive extra points. A new policy maintains ABO matching and medical priorities as the first step, but incorporates other successive steps: previous living donors donors, 0 mismatch, pediatric recipients, and finally all other recipients according to a point scheme incorporating recipient age, HLA match, PRA, and time on waiting list with similar proportions. We compared the resulting transplantations using the new versus the older allocation policy.

METHODS

We analyzed computer-generated simulations using actual patients (N = 1176) on the Chilean waiting list in 2011 with the 300 donors over the previous 3 years.

RESULTS

The new policy a significantly decreased recipient age from 43 ± 0.3 years to 41 ± 0.3 and increased the number of 0-mismatched transplantations from 3% to 4%. The mean HLA mismatch increased from 2.8 ± 0.1 to 3.6 ± 0.1. Waiting time increased from a mean of 38 ± 1 months to 40 ± 1 months, but patients remaining on the waiting list had less waiting time with the new rule.

CONCLUSIONS

With the proposed changes younger patients are being privileged and the importance of compatibility is diminished (except for 0-mismatched transplantations). The chance of a good match is directly related to the size of the recipient pool, thus an allocation policy that privileges HLA matching in a restricted recipient pool is especially unfavorable for younger patients. Including age of the recipient as a continuum can help to compensate for this lack of equity. Computer-generated simulations can help discern which policies are best suited for each country based on their local characteristics.