Fragmented blind docking : a novel protein–ligand binding prediction protocol

International audienc

Do Bioreactor Designs with More Efficient Oxygen Supply to Ovarian Cortical Tissue Fragments Enhance Follicle Viability and Growth In Vitro?

Background: Autotransplantation of cryopreserved ovarian tissue is currently the main option to preserve fertility for cancer patients. To avoid cancer cell reintroduction at transplantation, amulti-step culture systemhas been proposed to obtain fully competent oocytes for in vitro fertilization. Current in vitro systems are limited by the low number and health of secondary follicles produced during the first step culture of ovarian tissue fragments. To overcome such limitations, bioreactor designs have been proposed to enhance oxygen supply to the tissue, with inconsistent results. This retrospective study investigates, on theoretical grounds, whether the lack of a rational design of the proposed bioreactors prevented the full exploitation of follicle growth potential. Methods: Models describing oxygen transport in bioreactors and tissue were developed and used to predict oxygen availability inside ovarian tissue in the pertinent literature. Results: The proposed theoretical analysis suggests that a successful outcome is associated with enhanced oxygen availability in the cultured tissue in the considered bioreactor designs. This suggests that a rational approach to bioreactor design for ovarian tissue culture in vitro may help exploit tissue potential to support follicle growth

A Versatile Bioreactor for Dynamic Suspension Cell Culture. Application to the Culture of Cancer Cell Spheroids

<div><p>A versatile bioreactor suitable for dynamic suspension cell culture under tunable shear stress conditions has been developed and preliminarily tested culturing cancer cell spheroids. By adopting simple technological solutions and avoiding rotating components, the bioreactor exploits the laminar hydrodynamics establishing within the culture chamber enabling dynamic cell suspension in an environment favourable to mass transport, under a wide range of tunable shear stress conditions. The design phase of the device has been supported by multiphysics modelling and has provided a comprehensive analysis of the operating principles of the bioreactor. Moreover, an explanatory example is herein presented with multiphysics simulations used to set the proper bioreactor operating conditions for preliminary <i>in vitro</i> biological tests on a human lung carcinoma cell line. The biological results demonstrate that the ultralow shear dynamic suspension provided by the device is beneficial for culturing cancer cell spheroids. In comparison to the static suspension control, dynamic cell suspension preserves morphological features, promotes intercellular connection, increases spheroid size (2.4-fold increase) and number of cycling cells (1.58-fold increase), and reduces double strand DNA damage (1.5-fold reduction). It is envisioned that the versatility of this bioreactor could allow investigation and expansion of different cell types in the future.</p></div

Flow field within the bioreactor.

<p>Flow field visualization of the mutual interaction between the medium (primary phase) and the cells/constructs (dispersed phase) within the culture chamber for ultralow (A and A1) and low-to-moderate (B and B1) shear stress conditions. Flow field is depicted using both linear integral convolution lines (A and B), and a classical streamline representation (A1 and B1). Yellow arrows indicate the flow inlet and outlet. Blue arrows indicate the primary buoyant vortices. Red arrows indicate the secondary vortices.</p

Temporal evolution of the volume fraction occupied by suspended cells inside the bioreactor culture chamber.

<p>Contour plots of the temporal evolution of the VF occupied by the suspended cells inside the bioreactor culture chamber from 0 to 60 min of simulated time, with an imposed flow rate of 5 mL/min (ultralow shear stress condition, similarly to the experimental in vitro test) and 9x10⁶ inoculated cells (initial VF = 0.48%). After a transient of about 5 min, the 95.3% of the inoculated cells are suspended at an average VF value of approximately 0.33%, very close to the initial VF value. At the bottom of the culture chamber, a small volume of about 194 μL is characterized by a VF value around 6%, more than three times lower than the set threshold value of sedimentation (20%), which dynamically involves only the 2% of the inoculated cells.</p

Quantitative comparison of cycling cells and double DNA strand breaks.

<p>(A) Bar graph of the measurement of Ki67 positive cells, showing the fraction of cycling Calu-3 cells after static and dynamic suspension culture (*: p<0.05 vs static suspension). (B) Bar graph of the measurement of γH2AX positive cells, quantifying the double DNA strand breaks in Calu-3 cells harvested from static and dynamic suspension culture.</p

Ultrastructural comparison by TEM.

<p>The TEM images show (A) a small cluster (3 cells) of Calu-3 cells grown in static suspension, and (B) a larger spheroid (9 cells) of Calu-3 cells cultured within the bioreactor, harvested both after 5 days of suspension culture. Prominent nucleoli (N: nuclei), cytoplasmic structures and longitudinally and transversally oriented microvilli are characteristic features of NSCLC cell line Calu-3. High magnification views of areas included in black rectangles in panels A and B shown, respectively, (A1) a single tiny adherence junction (arrowhead) among cells cultured under static suspension, and (B1) several well-developed adherence junctions (arrowheads) developed by Calu-3 cultured within the bioreactor. Scale bars: A and B = 5 μm; A1 and B1 = 1 μm.</p

Morphological comparison by phase contrast microscopy.

<p>After 5 days of suspension culture, (A) Calu-3 cells cultured in static suspension show individual cells or very small clusters, (B) Calu-3 cells cultured under dynamic suspension show the formation of spheroids. Scale bars 200 μm.</p

Probability density functions of volume fraction and shear stresses.

<p>Probability density functions (PDF) of cell VF (A) and shear stresses (B) values experienced by the cellular phase within the bioreactor culture chamber after 60 min, with an imposed flow rate of 5 mL/min and 9x10⁶ inoculated cells.</p