Approximation of extracted features enabling 3D design tuning for reproducing the mechanical behaviour of biological soft tissues.

This article describes a new method, inspired by machine learning, to mimic the mechanical behaviour of target biological soft tissues with 3D printed materials. The principle is to optimise the structure of a 3D printed composite consisting of a geometrically tunable fibre embedded in a soft matrix. Physiological features are extracted from experimental stress-strain curves of several biological soft tissues. Then, using a cubic Bézier curve as the composite inner fibre, we optimised its geometric parameters, amplitude and height, to generate a specimen that exhibits a stress-strain curve in accordance with the extracted features of tensile tests. From this first phase, we created a database of specimen geometries that can be used to reproduce a wide variety of biological soft tissues. We applied this process to two soft tissues with very different behaviours: the mandibular periosteum and the calvarial periosteum. The results show that our method can successfully reproduce the mechanical behaviour of these tissues. This highlights the versatility of this approach and demonstrates that it can be extended to mimic various biological soft tissues.

Decellularization of Massive Bone Allografts By Perfusion: A New Protocol for Tissue Engineering.

In terms of large bone defect reconstructions, massive bone allografts may sometimes be the only solution. However, they are still burdened with a high postoperative complication rate. Our hypothesis is that the immunogenicity of residual cells in the graft is involved in this issue. Decellularization by perfusion might therefore be the answer to process and create more biologically effective massive bone allografts. Seventy-two porcine bones were used to characterize the efficiency of our sodium hydroxide-based decellularization protocol. A sequence of solvent perfusion through each nutrient artery was set up to ensure the complete decellularization of whole long bones. Qualitative (histology and immunohistochemistry [IHC]) and quantitative (fluoroscopic absorbance and enzyme-linked immunosorbent assay) evaluations were performed to assess the decellularization and the preservation of the extracellular matrix in the bone grafts. Cytotoxicity and compatibility were also tested. Comparatively to nontreated bones, our experiments showed a very high decellularization quality, demonstrating that perfusion is mandatory to achieve an entire decellularization. Moreover, results showed a good preservation of the bone composition and microarchitecture, Haversian systems and vascular network included. This protocol reduces the human leukocyte antigen antigenic load of the graft by >50%. The majority of measured growth factors is still present in the same amount in the decellularized bones compared to the nontreated bones. Histology and IHC show that the bones were cell compatible, noncytotoxic, and capable of inducing osteoblastic differentiation of mesenchymal stem cells. Our decellularization/perfusion protocol allowed to create decellularized long bone graft models, thanks to their inner vascular network, ready for in vivo implantation or to be further used as seeding matrices.

Evaluation of the lower face enlargement following mandibular osteotomy: Bilateral sagittal split osteotomy (BSSO) vs supra basilar sagittal Split Osteotomy (SBSSO).

INTRODUCTION: The current most common technique for mandibular split is the sagittal split osteotomy described by Obwegeser and modified by Dalpont and Epker. Several studies have shown a lower face enlargement while employing these techniques. The supra-basilar sagittal split osteotomy described in 2017 seems to be an interesting alternative as mandibular angles remain in continuity with the internal valve. The aim of this study was to evaluate lower face enlargement by comparing two techniques: sagittal split osteotomy and supra-basilar sagittal split. MATERIALS AND METHODS: Cephalograms were analyzed before and after surgery. Bigonial distances (BGD) were measured in frontal cephalograms, ramus length and distances between upper and lower incisors on lateral cephalogram. Control of those measures was also performed by measuring the Nasion-Anterior Clinoid distance and intercanthal distance to assess the comparability and error rate. Finally, a comparison of cephalograms before and after surgery to assess bigonial enlargement, ramus elongation and advancement was performed. RESULTS: Out of the 69 patients, 18 had a Bilateral Sagittal Split (BSSO) and 52 had a Supra-Basilar Sagittal Split (SBSSO). The error rate and patients' characteristics were the same in the two groups. A statistically significant widening of the bigonial distance with the BSSO in comparison with the SBSSO was found (BGD difference: 5.82 mm (BSSO) vs - 1.47 mm (SBSSO), p < 0,001). A greater ramus elongation with the SBSSO was found (ramus elongation: 1.12 mm (BSSO) vs 5.1 mm (SBSSO)). This study has shown that the supra-basilar sagittal split is an interesting way to avoid the widening of the mandibular angles.

Decellularized vascularized bone grafts as therapeutic solution for bone reconstruction: A mechanical evaluation.

INTRODUCTION: Large bone defects are challenging for surgeons. Available reimplanted bone substitutes can't properly restore optimal function along and long term osteointegration of the bone graft. Bone substitute based on the perfusion-decellularization technique seem to be interesting in order to overcome these limitations. We present here an evaluation of the biomechanics of the bones thus obtained. MATERIAL AND METHODS: Two decellularization protocols were chosen for this study. One using Sodium Dodecyl Sulfate (SDS) (D1) and one using NaOH and H2O2 (D2). The decellularization was performed on porcine forearms. We then carried out compression, three-point bending, indentation and screw pull-out tests on each sample. Once these tests were completed, we compared the results obtained between the different decellularization protocols and with samples left native. RESULTS: The difference in the means was similar between the tests performed on bones decellularized with the SDS protocol and native bones for pull-out test: +1.4% (CI95% [-10.5%- 12.4%]) of mean differences when comparing Native vs D1, compression -14.9% (CI95% [-42.7%- 12.5%]), 3-point bending -5.7% (CI95% [-22.5%- 11.1%]) and indentation -10.8% (CI95% [-19.5%- 4.6%]). Bones decellularized with the NaOH protocol showed different results from those obtained with the SDS protocol or native bones during the pull-out screw +40.7% (CI95% [24.3%- 57%]) for Native vs D2 protocol and 3-point bending tests +39.2% (CI95% [13.7%- 64.6%]) for Native vs D2 protocol. The other tests, compression and indentation, gave similar results for all our samples. CONCLUSION: Vascularized decellularized grafts seem to be an interesting means for bone reconstruction. Our study shows that the decellularization method affects the mechanical results of our specimens. Some methods seem to limit these alterations and could be used in the future for bone decellularization.

Specific detection of Treponema pallidum in clinical samples: validation of a qPCR assay combining two genomic targets.

OBJECTIVES: We evaluated a real-time quantitative PCR (qPCR) for detection of the Treponema pallidum (TP) genome in clinical samples through simultaneous detection of two genomic targets. METHODS: We performed qPCR with TaqMan technology using two TP genes, polA and tpp47, as targets, with an internal positive control. The qPCR assay was compared with syphilis diagnosis based on a combination of clinical examination, serological results and inhouse nested PCR (nPCR). Samples were analysed at the National Reference Center for STIs at Cochin Hospital in Paris. RESULTS: In total, from October 2010 to December 2016, 320 documented clinical samples (mucosal and cutaneous swabs) were collected from patients with or without syphilis attending STI centres in France. The qPCR had an overall sensitivity of 89% (95% CI 85.1% to 92.1%), a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 88% (95% CI 84.3% to 91.5%). The agreement between qPCR and nPCR results was 94% (κ=0.88, 95% CI 0.83 to 0.93). Calibration of the qPCR assay, by cloning both the polA and tpp47 genes, defined the detection threshold as 1 copy/µL of DNA elution. CONCLUSIONS: We validated a new qPCR for detecting the TP genome in clinical samples with excellent sensitivity and specificity. The cloning of polA and tpp47 genes for calibration would be interesting in the evaluation of bacterial loads in samples.

Comparison of molecular and serological assays on cerebrospinal fluid for the diagnosis of neurosyphilis.

BACKGROUND: Many assays are available on cerebrospinal fluid (CSF) for the diagnosis of neurosyphilis (NS) but there is no 'gold standard'. OBJECTIVES: The aim of this study was to evaluate different molecular and serological assays used in NS. METHODS: We evaluated two PCR assays and three serological techniques in parallel on CSF samples collected between 2019 and 2020 from patients suspected of NS. RESULTS: The study included 143 patients comprising 30 early NS, 7 late NS and 106 patients without a diagnosis of NS. All patients with NS were symptomatic and had either neurological (67.6%) or ophthalmological signs (54.1%). The qPCR and nPCR assays had overall sensitivities (Se) of 41% and 27%, respectively; with each an overall specificity (Sp) of 100%. VDRL had a Se of 51% and a Sp of 92%. Immunoblot had a Se of 62% and a Sp of 85%. Finally, treponemal tests (TT) had a Se of 96% and a Sp of 69%. CONCLUSIONS: Our study confirms the excellent specificity of molecular techniques allowing to avoid overdiagnosis of NS, and thus, unjustified intensive antibiotic therapy protocols. CSF TT, although not very specific, has an excellent Se confirming that there is almost never NS with negative CSF TT. VDRL and immunoblot tests have better overall diagnostic performance. However, none of these techniques has sufficient diagnostic performance to represent a 'gold standard'. Thus, the diagnosis of NS relies on a combination of clinical and biological parameters with the association of PCR with serology, associating VDRL and immunoblot, in CSF.

Periosteum and fascia lata: Are they so different?

Introduction: The human fascia lata (HFL) is used widely in reconstructive surgery in indications other than fracture repair. The goal of this study was to compare microscopic, molecular, and mechanical properties of HFL and periosteum (HP) from a bone tissue engineering perspective. Material and Methods: Cadaveric HP and HFL (N = 4 each) microscopic morphology was characterized using histology and immunohistochemistry (IHC), and the extracellular matrix (ECM) ultrastructure assessed by means of scanning electron microscopy (SEM). DNA, collagen, elastin, glycosaminoglycans, major histocompatibility complex Type 1, and bone morphogenetic protein (BMP) contents were quantified. HP (N = 6) and HFL (N = 11) were submitted to stretch tests. Results: Histology and IHC highlighted similarities (Type I collagen fibers and two-layer organization) but also differences (fiber thickness and compaction and cell type) between both tissues, as confirmed using SEM. The collagen content was statistically higher in HFL than HP (735 vs. 160.2 µg/mg dry weight, respectively, p < 0.0001). On the contrary, DNA content was lower in HFL than HP (404.75 vs. 1,102.2 µg/mg dry weight, respectively, p = 0.0032), as was the immunogenic potential (p = 0.0033). BMP-2 and BMP-7 contents did not differ between both tissues (p = 0.132 and p = 0.699, respectively). HFL supported a significantly higher tension stress than HP. Conclusion: HP and HFL display morphological differences, despite their similar molecular ECM components. The stronger stretching resistance of HFL can specifically be explained by its higher collagen content. However, HFL contains many fewer cells and is less immunogenic than HP, as latter is rich in periosteal stem cells. In conclusion, HFL is likely suitable to replace HP architecture to confer a guide for bone consolidation, with an absence of osteogenicity. This study could pave the way to a bio-engineered periosteum built from HFL.

Evaluation of factors associated with sexual dysfunction in psoriasis in a cohort of 1409 patients.

We report on the sexual disorders common in patients with psoriasis, and examine the underlying reasons, including the use of psoriasis treatments that can result in sexual difficulties.