Amyloid-β aggregates activate peripheral monocytes in mild cognitive impairment

The peripheral immune system is important in neurodegenerative diseases, both in protecting and inflaming the brain, but the underlying mechanisms remain elusive. Alzheimer's Disease is commonly preceded by a prodromal period. Here, we report the presence of large Aβ aggregates in plasma from patients with mild cognitive impairment (n = 38). The aggregates are associated with low level Alzheimer's Disease-like brain pathology as observed by 11C-PiB PET and 18F-FTP PET and lowered CD18-rich monocytes. We characterize complement receptor 4 as a strong binder of amyloids and show Aβ aggregates are preferentially phagocytosed and stimulate lysosomal activity through this receptor in stem cell-derived microglia. KIM127 integrin activation in monocytes promotes size selective phagocytosis of Aβ. Hydrodynamic calculations suggest Aβ aggregates associate with vessel walls of the cortical capillaries. In turn, we hypothesize aggregates may provide an adhesion substrate for recruiting CD18-rich monocytes into the cortex. Our results support a role for complement receptor 4 in regulating amyloid homeostasis.

[Electrical stimulation against loss of muscles and function in a patient admitted with COVID-19]

This is a case report of a hospitalised 62-year-old male patient with COVID-19, who received unilateral neuromuscular electrical stimulation treatment with a customised anti-embolic compression stocking and maintained muscle mass as well as maximum voluntary quadriceps contraction and balance during six days of illness-induced immobilisation. This illustrates, that short durations of neuromuscular electrical stimulation can help maintaining muscle mass and physical function in patients with SARS-CoV-2.

The importance of collagen composition and biomechanics for the porcine aortic root

A thorough understanding of the aortic root structure and biomechanics is necessary when performing aortic valve-sparing procedures in patients with aortic root aneurysms. This study aimed to evaluate the amount of collagen and biomechanics at different levels and segments of the aortic root. Ten aortic roots from healthy pigs were excised including the aortic annulus, the sinuses of Valsalva, and the sinotubular junction (STJ). Specimens were further divided into three circumferential segments; left coronary (LC)-, right coronary (RC)-, and non-coronary (NC) sinus. Collagen was determined using hydroxyproline analysis and specimens were tested biomechanically for stress-strain relations. The annulus showed significantly larger average maximum stiffness (9.6 ± 4.5 N/mm) compared with the sinus (4.5 ± 2.0 N/mm) and STJ (4.8 ± 1.8 N/mm). The average collagen content was likewise higher in the annulus (4.0 ± 1.0 mg/ml) compared with the sinus (2.4 ± 0.6 mg/ml) and STJ (2.2 ± 0.5 mg/ml) for all three segments. The NC sinus segment exhibited a significantly larger maximum stiffness and stress under static conditions compared with the RC. These results suggest that the aortic root is heterogeneous in both structure and biomechanical properties and that it varies both in levels and segments of the aortic root. Future surgical approaches should consider enhanced strength parameters for specific areas of the aortic root to achieve the best results when performing aortic valve-sparing techniques. From this study, we conclude that the aortic annulus needs special attention to imitate normal physiologic properties during aortic valve-sparing surgery due to its higher maximum stiffness, stress, and load. Modified future surgical procedures could potentially prevent recurrent aneurysmal formation.

Aarhus Regenerative Orthopaedics Symposium (AROS)

The combination of modern interventional and preventive medicine has led to an epidemic of ageing. While this phenomenon is a positive consequence of an improved lifestyle and achievements in a society, the longer life expectancy is often accompanied by decline in quality of life due to musculoskeletal pain and disability. The Aarhus Regenerative Orthopaedics Symposium (AROS) 2015 was motivated by the need to address regenerative challenges in an ageing population by engaging clinicians, basic scientists, and engineers. In this position paper, we review our contemporary understanding of societal, patient-related, and basic science-related challenges in order to provide a reasoned roadmap for the future to deal with this compelling and urgent healthcare problem.

Accumulation of nano-sized particles in a murine model of angiogenesis

PURPOSE

To evaluate the ability of nm-scaled iron oxide particles conjugated with Azure A, a classic histological dye, to accumulate in areas of angiogenesis in a recently developed murine angiogenesis model.

MATERIALS AND METHODS

We characterised the Azure A particles with regard to their hydrodynamic size, zeta potential, and blood circulation half-life. The particles were then investigated by Magnetic Resonance Imaging (MRI) in a recently developed murine angiogenesis model along with reference particles (Ferumoxtran-10) and saline injections.

RESULTS

The Azure A particles had a mean hydrodynamic diameter of 51.8 ± 43.2 nm, a zeta potential of -17.2 ± 2.8 mV, and a blood circulation half-life of 127.8 ± 74.7 min. Comparison of MR images taken pre- and 24-h post-injection revealed a significant increase in R2(*) relaxation rates for both Azure A and Ferumoxtran-10 particles. No significant difference was found for the saline injections. The relative increase was calculated for the three groups, and showed a significant difference between the saline group and the Azure A group, and between the saline group and the Ferumoxtran-10 group. However, no significant difference was found between the two particle groups.

CONCLUSION

Ultrahigh-field MRI revealed localisation of both types of iron oxide particles to areas of neovasculature. However, the Azure A particles did not show any enhanced accumulation relative to Ferumoxtran-10, suggesting the accumulation in both cases to be passive.

Fabrication and characterization of a rapid prototyped tissue engineering scaffold with embedded multicomponent matrix for controlled drug release

Bone tissue engineering implants with sustained local drug delivery provide an opportunity for better postoperative care for bone tumor patients because these implants offer sustained drug release at the tumor site and reduce systemic side effects. A rapid prototyped macroporous polycaprolactone scaffold was embedded with a porous matrix composed of chitosan, nanoclay, and β-tricalcium phosphate by freeze-drying. This composite scaffold was evaluated on its ability to deliver an anthracycline antibiotic and to promote formation of mineralized matrix in vitro. Scanning electronic microscopy, confocal imaging, and DNA quantification confirmed that immortalized human bone marrow-derived mesenchymal stem cells (hMSC-TERT) cultured in the scaffold showed high cell viability and growth, and good cell infiltration to the pores of the scaffold. Alkaline phosphatase activity and osteocalcin staining showed that the scaffold was osteoinductive. The drug-release kinetics was investigated by loading doxorubicin into the scaffold. The scaffolds comprising nanoclay released up to 45% of the drug for up to 2 months, while the scaffold without nanoclay released 95% of the drug within 4 days. Therefore, this scaffold can fulfill the requirements for both bone tissue engineering and local sustained release of an anticancer drug in vitro. These results suggest that the scaffold can be used clinically in reconstructive surgery after bone tumor resection. Moreover, by changing the composition and amount of individual components, the scaffold can find application in other tissue engineering areas that need local sustained release of drug.

Osteopontin functionalization of hydroxyapatite nanoparticles in a PDLLA matrix promotes bone formation

We studied the osteoconductive tissue response of hydroxyapatite (HA) nanoparticles functionalized with osteopontin (OPN) in a matrix of poly-D,L-lactic-acid (PDLLA). In a canine endosseus 0.75-mm gap implant model, we tested the osteointegrative impact of the OPN functionalized composite as an implant coating, and a non-functionalized composite was used as reference control. During the four weeks of observation, the OPN functionalized composite coating significantly increased the formation of new bone in the porosities of the implant, but no differences were observed in the gap. The study provides evidence of its potential use either alone or in combination with other osteoconductive compounds.

Hydroxyapatite nanoparticles in poly-D,L-lactic acid coatings on porous titanium implants conducts bone formation

It is well established in the field of biomaterials that hydroxyapatite (HA) may provide interesting osteoconductive properties. In this study, we investigated the osseointegrational effect of a 50/50 vol % composite of HA nanoparticles and poly-D,L-lactic acid (PDLLA) coated on model titanium bone implants in an in vivo animal model. The aim is to evaluate how the addition of HA to PDLLA may improve the bone formation and initial fixation of the implant. Two titanium implants coated with the PDLLA/HA composite and pure PDLLA, respectively, were implanted bilaterally in proximal part of humeri with a 2-mm peri-implant gap in 10 sheep. After 12 weeks, the remains of the coatings were present on 20.3 and 19.8% of PDLLA/HA composite- and PDLLA-coated implants, respectively. It was observed that newly formed bone (39.3%) and fibrous tissue (58.3%) had replaced the PDLLA/HA composite, whereas pure PDLLA was replaced almost completely by fibrous tissue (96.2%). Consequently, the PDLLA/HA composite-coated implants were better fixated as confirmed by push-out tests. Using quantification of peri-implant tissue and implant fixation as parameters, the present findings, therefore, clearly reveal that the addition of nanoparticulate HA to a PDLLA coating on titanium implants increases osseointegration.

Selective isolation and differentiation of a stromal population of human embryonic stem cells with osteogenic potential

The derivation of osteogenic cells from human embryonic stem cells (hESC) has been hampered by the absence of easy and reproducible protocols. hESC grown in feeder-free conditions, often show a sub population of fibroblast-like, stromal cells growing between the colonies. Thus, we examined the possibility that these cells represent a population of stromal (mesenchymal) stem cells (hESC-stromal). Two in house derived hES cell lines (Odense3 and KMEB3) as well as an externally derived cell line (Hues8) were transitioned to feeder-free conditions. A sub population of fibroblast-like cells established between the hESC colonies were isolated by selective adherence to hyaluronic acid-coated plates (100 μg/ml) and were characterized using a combination of FACS analysis and staining. The cells were CD44(+), CD29(+), CD73(+), CD166(+), CD146(+), and CD105(+); and, Oct4⁻, CD34⁻, CD45⁻ and CXCR4⁻. When cultured in osteogenic differentiation media, up regulation of osteoblastic lineage markers (DLX5, MSX2, RUNX2, SPARC, ALP, COL1a1, BGLAP, IBSP, DCN, LOX-L4) and production of in vitro mineralized matrix was detected. hESC-stromal cells loaded on a carrier and implanted either subcutaneously or in a critical size calvarial defect in immune deficient mice for 10 weeks, resulted in new bone formation and partial repair of the calvarial defect. In conclusion, hESC-stromal can be isolated from hESC cultures and represent a good source for obtaining cells with osteogenic differentiation potential suitable for regenerative medicine protocols.

Mechanical stresses in carotid plaques using MRI-based fluid-structure interaction models

Risk assessment in patients with carotid atherosclerosis relies on the degree of luminal stenosis. Incorporating morphological information on plaque composition obtained noninvasively through the use of magnetic resonance imaging (MRI) could include other variables besides the degree of stenosis into carotid plaque risk assessment. Knowledge of the morphologic composition of the plaque allows determination of mechanic stresses exerted on the protective fibrous cap, which may be of importance in the assessment of plaque vulnerability. Based on image processing of transverse MRI scans, longitudinal 2D fluid-structure interaction (FSI) simulations of carotid atherosclerotic plaques were performed facilitating in-vivo estimation of longitudinal internal fibrous cap stresses. The FSI simulation combined finite element analysis (FEA) with computational fluid dynamics (CFD) simulations of blood-flow variables. Preliminary results from two symptomatic patients revealed longitudinal stress levels (max. 254.1 and 143.2 kPa) approaching established criteria for plaque rupture at known predilection sites of plaque rupture. Determination of longitudinal fibrous cap stresses may prove useful in assessing plaque vulnerability and improve risk stratification in patients with carotid atherosclerosis.

Characterisation of Microcellular Foams using X-Ray Microtomography and Raman Spectroscopy

Closed cell polycarbonate foam is investigated using X-ray microtomography (XRMT). A specimen is prepared using the solid state processing route and a graded microstructure is obtained containing cell sizes from 10 to 90μm. The cell size distribution was estimated by modelling the foam dynamics and compared to a reconstructed geometry obtained from a XRMT experiment. The graded specimen contains regions with a microcellular structure. These regions are not suitable for XRMT investigations since the smallest details of the structure are below the resolution limit. An alternative approach for the characterisation of microcellular foams is suggested by using carbon nanotubes and Raman spectroscopy. A polycarbonate/carbon nanotube composite is molded and microcellularly foamed. Raman investigations verify that nanotubes are present within the structure and indicate straining of the nanotubes at intermediate steps during sample preparation and sample compression.