Vascularized Tissue-Engineered Model for Studying Drug Resistance in Neuroblastoma.

Neuroblastoma is a vascularized pediatric tumor derived from neural crest stem cells that displays vasculogenic mimicry and can express a number of stemness markers, such as SOX2 and NANOG. Tumor relapse is the major cause of succumbing to this disease, and properties attributed to cancer stem-like cells (CSLC), such as drug-resistance and cell plasticity, seem to be the key mechanisms. However, the lack of controllable models that recapitulate the features of human neuroblastoma limits our understanding of the process and impedes the development of new therapies. In response to these limitations, we engineered a perfusable, vascularized in vitro model of three-dimensional human neuroblastoma to study the effects of retinoid therapy on tumor vasculature and drug-resistance. METHODS: The in vitro model of neuroblastoma was generated using cell-sheet engineering and cultured in a perfusion bioreactor. Firstly, we stacked three cell sheets containing SKNBE(2) neuroblastoma cells and HUVEC. Then, a vascular bed made of fibrin, collagen I and HUVEC cells was placed onto a collagen-gel base with 8 microchannels. After gelling, the stacked cell sheets were placed on the vascular bed and cultured in the perfusion bioreactor (perfusion rate: 0.5 mL/min) for 4 days. Neuroblastoma models were treated with 10µM isotretionin in single daily doses for 5 days. RESULTS: The bioengineered model recapitulated vasculogenic mimicry (vessel-like structure formation and tumor-derived endothelial cells-TECs), and contained CSLC expressing SOX2 and NANOG. Treatment with Isotretinoin destabilized vascular networks but failed to target vasculogenic mimicry and augmented populations of CSLCs expressing high levels of SOX2. Our results suggest that CSLCs can transdifferentiate into drug resistant CD31+-TECs, and reveal the presence of an intermediate state STEC (stem tumor-derived endothelial cell) expressing both SOX2 and CD31. CONCLUSION: Our results reveal some roles of SOX2 in drug resistance and tumor relapse, and suggest that SOX2 could be a therapeutic target in neuroblastoma.

A novel surrogate lung material for impact studies: Development and testing procedures.

This work focuses on the development of a surrogate lung material (SLM) that reproduces the dynamic response of a human lung under various loading conditions and also allows for the analysis of the extent and distribution of damage. The SLM consists of polyurethane foam used to mimic the spongy lung tissue and fluid-filled gelatine microcapsules used to simulate the damage of alveoli. The bursting pressure of the microcapsules was investigated by conducting low and high rate compression tests on single microcapsules. A bursting pressure of around 5bar was measured which is comparable to the reported lung overpressure at injury level. Low and high rate compression tests were conducted on the SLMs. From the measured mechanical properties and mass density, the stress wave speed was calculated and found to be well in the range of the reported values for human lungs (16-70m/s). In order to study the extent and distribution of damage in the SLMs, as represented by burst microcapsules, a CT scan analysis was carried out before and after the impacts. The CT scan results clearly demonstrated the magnitude and distribution of damage within the specimen. The results are then compared to the Bowen curves, the most often used criteria for predicting blast injuries in humans. An excellent agreement was found between the observed damage in the surrogate lungs and the expected damage in real human lungs. In general, the SLM showed similar stress wave speed, bursting pressure and damage to that of the real lungs.

Canine articular cartilage regeneration using mesenchymal stem cells seeded on platelet rich fibrin: Macroscopic and histological assessments.

OBJECTIVES: Mesenchymal stem cells have the ability to differentiate into various cell types, and thus have emerged as promising alternatives to chondrocytes in cell-based cartilage repair methods. The aim of this experimental study was to investigate the effect of bone marrow derived mesenchymal stem cells combined with platelet rich fibrin on osteochondral defect repair and articular cartilage regeneration in a canine model. METHODS: Osteochondral defects were created on the medial femoral condyles of 12 adult male mixed breed dogs. They were either treated with stem cells seeded on platelet rich fibrin or left empty. Macroscopic and histological evaluation of the repair tissue was conducted after four, 16 and 24 weeks using the International Cartilage Repair Society macroscopic and the O'Driscoll histological grading systems. Results were reported as mean and standard deviation (sd) and compared at different time points between the two groups using the Mann-Whitney U test, with a value < 0.05 considered statistically significant. RESULTS: Higher cumulative macroscopic and histological scores were observed in stem cell treated defects throughout the study period with significant differences noted at four and 24 weeks (9.25, sd 0.5 vs 7.25, sd 0.95, and 10, sd 0.81 vs 7.5, sd 0.57; p < 0.05) and 16 weeks (16.5, sd 4.04 vs 11, sd 1.15; p < 0.05), respectively. Superior gross and histological characteristics were also observed in stem cell treated defects. CONCLUSION: The use of autologous culture expanded bone marrow derived mesenchymal stem cells on platelet rich fibrin is a novel method for articular cartilage regeneration. It is postulated that platelet rich fibrin creates a suitable environment for proliferation and differentiation of stem cells by releasing endogenous growth factors resulting in creation of a hyaline-like reparative tissue.Cite this article: D. Kazemi, K. Shams Asenjan, N. Dehdilani, H. Parsa. Canine articular cartilage regeneration using mesenchymal stem cells seeded on platelet rich fibrin: Macroscopic and histological assessments. Bone Joint Res 2017;6:98-107. DOI: 10.1302/2046-3758.62.BJR-2016-0188.R1.

A neuroanatomical analysis of lid-eye coordination in cases of ptosis and downgaze paralysis.

Ptosis and downgaze paralysis, in a case of vascular insufficiency, were the result of a specific loss of levator palpebrae (LP) motoneurons in the oculomotor nucleus, and a partial cell loss in the rostral interstitial nucleus of the MLF (riMLF), respectively. In a previous case with similar symptoms there was a comparable riMLF cell loss, but some LP motoneurons were spared; in addition there was destruction of a cell group on the mesencephalic midline, which projects to all motoneurons involved in upward eye movements including LP. This cell group is called the M-group in the monkey. The M-group was intact in the present, but not in the previous case, which may have contributed to the ptosis and to the loss of upward ocular pursuit in the latter. The results show that there is more than one premotor cell group responsible for upward eye movements in the rostral mesencephalon.

Cyclic hormonal changes in patients with congenital abscence of the uterus.

Our studies have shown normal cyclical patterns of ovarian steroids and pituitary gonadotropines in patients with congenital absence of the uterus. It appears that the life-long abscence of a functioning uterus has no effect on the functional life span of the corpus luterum, but may have some effect in the level of estrogenes in the second half of the cycle.