Design of a novel rotating wall bioreactor for the in vitro simulation of the mechanical environment of the endothelial function

Parametric optimization of culture chamber for cell mechanobiology research

Mechanical signals influence the morphology, function, differentiation, proliferation, and growth of cells. Due to the small size of cells, it is essential to analyze their mechanobiological responses with an in vitro mechanical loading device. Cells are cultured on an elastic silicone membrane substrate, and mechanical signals are transmitted to the cells by the substrate applying mechanical loads. However, large areas of non-uniform strain fields are generated on the elastic membrane, affecting the experiment's accuracy. In the study, finite-element analysis served as the basis of optimization, with uniform strain as the objective. The thickness of the basement membrane and loading constraints were parametrically adjusted. Through finite-element cycle iteration, the "M" profile basement membrane structure of the culture chamber was obtained to enhance the uniform strain field of the membrane. The optimized strain field of culture chamber was confirmed by three-dimensional digital image correlation (3D-DIC) technology. The results showed that the optimized chamber improved the strain uniformity factor. The uniform strain area proportion of the new chamber reached 90%, compared to approximately 70% of the current chambers. The new chamber further improved the uniformity and accuracy of the strain, demonstrating promising application prospects.

Bioreactors for Cardiac Tissue Engineering

The advances in biotechnology, biomechanics, and biomaterials can be used to develop organ models that aim to accurately emulate their natural counterparts. Heart disease, one of the leading causes of death in modern society, has attracted particular attention in the field of tissue engineering. To avoid incorrect prognosis of patients suffering from heart disease, or from adverse consequences of classical therapeutic approaches, as well as to address the shortage of heart donors, new solutions are urgently needed. Biotechnological advances in cardiac tissue engineering from a bioreactor perspective, in which recapitulation of functional, biochemical, and physiological characteristics of the cardiac tissue can be used to recreate its natural microenvironment, are reviewed. Detailed examples of functional and preclinical applications of engineered cardiac constructs and the state-of-the-art systems from a bioreactor perspective are provided. Finally, the current trends and future directions of the field for its translation to clinical settings are discussed.

Quantitative Vascular Evaluation: From Laboratory Experiments to Point-of-Care Patient (Experimental Approach)

This paper illustrates the evolution of our knowledge of arterial mechanics from our initial research works up to the present time. Several techniques focusing on this topic in terms of our experience are dis-cussed. An interdisciplinary team composed by different institutions from Argentina, Uruguay, France and Spain was created to conduct research, to train human resources and to fulfill the inevitable social role of gaining access to technological inno-vation to improve public health.

Air toxicity for primary human-cultured corneal endothelial cells: an in vitro model

PURPOSE

To investigate the possible toxic effect of air exposure for an in vitro model of primary human corneal endothelial cells (HCECs).

METHODS

Primary HCECs were isolated from donor corneal rings and cultivated at 37°C in 5% CO2 and 95% humidified air. Six groups of HCEC cultures were set up, and 4 samples were enclosed in each group: group 1 consisted of samples in which HCECs were exposed to air for 30 minutes. Group 2 consisted of HCECs exposed to air for 1 hour, group 3 for 3 hours, group 4 for 6 hours, group 5 for 12 hours, and group 6 for 24 hours.

RESULTS

Three hours after exposure, the morphology of the cells was still intact; however, a few cells within the monolayer appeared enlarged and exhibited characteristics of more senescent cells. Six hours after exposure to air, the endothelial cells started losing their typical hexagonal morphology and appeared enlarged and compromised. Viability was superior to 95% in groups 1 to 3, whereas for groups 4, 5, and 6 was 71%, 22.4%, and 6.3%, respectively.

CONCLUSION

The present study illustrates that the toxic effect of air exposure for the studied in vitro model of primary human-cultured corneal endothelial cells is not significant for the period of 3 hours, whereas after 6 hours it starts to induce major apoptotic mechanisms, leading to reduced viability until the period of 24 hours where the percentage of living cells is drastically decreased.

Perspectives on the advanced control of bioreactors for functional vascular tissue engineering in vitro

Tissue engineering aims to produce tissues using cells and materials. The action of designing tissues involves observing the process of growth to understand its underlying mechanisms. It requires manipulation of the critical parameters for cell growth and remodeling to produce structured tissues and functional organs. Tissue engineers face the challenge of orchestrating the signals in a cell's microenvironment to efficiently grow an anisotropic and hierarchical tissue. It can be performed in vivo through the design of bioactive scaffolds and manipulation of biological signals using growth factors. It can also be performed in vitro in a controlled environment called the bioreactor. This article addresses the matter of finding the optimal dynamic sequence of culture conditions in a bioreactor for the maturation of tissues. Artificial intelligence and optimal control are accelerating technologies towards an understanding of tissue regeneration. The particular example of the functional engineering of small-diameter blood vessels has been chosen to illustrate this idea.

P-selectin/ligand unbinding force measured with atomic force microscopy: comparison of two chemical protocols for the tethering of single molecules

Leukocytes, as an indispensable arm of the immune system, need to be recruited from the flowing blood and transferred to the sites of infection. Their extravasation is feasible due to their ability to tether and roll over the activated endothelium, which is much dependent on the association of their selectin molecules with ligands on the activated endothelial cells. In view of the importance of this interaction for the physiological immune functions as well as for autoimmune diseases, specifying the affinity of selectins to their ligands at the single molecule level appears a challenging task to gain insight into the mechanisms that control leukocyte-endothelial avidity. To this end we functionalized substrates with P-selectin and cantilever probes with its major ligand, the P-selectin glycoprotein ligand-1, and used atomic force microscopy to measure their unbinding force. Two different chemical protocols were used for the tethering of the molecules on the substrates, one based on a homobifunctional poly(ethylene glycol) linker and the other on the use of antibody-specific binding. The unbinding forces measured with the two methods were 312 ± 149 and 230 ± 57 pN, respectively. Measurements on activated endothelials, declaratory of single molecule interactions, gave comparable results.