A dynamic perfusion bioreactor approach for engineering respiratory tissues in-vitro

Lung tissue engineering: An update

Pulmonary disease is a worldwide public health problem that reduces the life quality and increases the need for hospital admissions as well as the risk of premature death. A common problem is the significant shortage of lungs for transplantation as well as patients must also take immunosuppressive drugs for the rest of their lives to keep the immune system from attacking transplanted organs. Recently, a new strategy has been proposed in the cellular engineering of lung tissue as decellularization approaches. The main components for the lung tissue engineering are: (1) A suitable biological or synthetic three-dimensional (3D) scaffold, (2) source of stem cells or cells, (3) growth factors required to drive cell differentiation and proliferation, and (4) bioreactor, a system that supports a 3D composite biologically active. Although a number of synthetic as well biological 3D scaffold suggested for lung tissue engineering, the current favorite scaffold is decellularized extracellular matrix scaffold. There are a large number of commercial and academic made bioreactors, the favor has been, the one easy to sterilize, physiologically stimuli and support active cell growth as well as clinically translational. The challenges would be to develop a functional lung will depend on the endothelialized microvascular network and alveolar-capillary surface area to exchange gas. A critical review of the each components of lung tissue engineering is presented, following an appraisal of the literature in the last 5 years. This is a multibillion dollar industry and consider unmet clinical need.

A method for investigating the cellular response to cyclic tension or compression in three-dimensional culture

We have an interest in the cellular response to mechanical stimuli, and here describe an in-vitro method to examine the response of cells cultured in a three-dimensional matrix to mechanical compressive and tensile stress. Synthetic aliphatic polyester scaffolds coated with 45S5 bioactive glass were seeded with human dental follicular cells (HDFC), and attached to well inserts and magnetic endplates in six well palates. Scaffolds were subjected to either cyclic 10% tensile deformation, or 8% compression, at 1 Hz and 2 Hz respectively for 6, 24 or 48 h, by uniaxial motion of magnetically-coupled endplates. It was possible to isolate high quality mRNA from cells in these scaffolds, as demonstrated by high RNA integrity numbers scores, and ability to perform meaningful cRNA microarray analysis, in which 669 and 727 genes were consistently upregulated, and 662 and 518 genes down regulated at all times studied under tensile and compressive loading conditions respectively. MetaCore analysis revealed the most regulated gene ontogenies under both loading conditions to be for: cytoskeletal remodelling; cell adhesion-chemokines and adhesion; cytoskeleton remodelling-TGF WNT and cytoskeletal remodelling pathways. We believe the method here described will be of value for analysis of the cellular response to cyclic loading.

Engineered Biomaterials to Enhance Stem Cell-Based Cardiac Tissue Engineering and Therapy

Cardiovascular disease is a leading cause of death worldwide. Since adult cardiac cells are limited in their proliferation, cardiac tissue with dead or damaged cardiac cells downstream of the occluded vessel does not regenerate after myocardial infarction. The cardiac tissue is then replaced with nonfunctional fibrotic scar tissue rather than new cardiac cells, which leaves the heart weak. The limited proliferation ability of host cardiac cells has motivated investigators to research the potential cardiac regenerative ability of stem cells. Considerable progress has been made in this endeavor. However, the optimum type of stem cells along with the most suitable matrix-material and cellular microenvironmental cues are yet to be identified or agreed upon. This review presents an overview of various types of biofunctional materials and biomaterial matrices, which in combination with stem cells, have shown promises for cardiac tissue replacement and reinforcement. Engineered biomaterials also have applications in cardiac tissue engineering, in which tissue constructs are developed in vitro by combining stem cells and biomaterial scaffolds for drug screening or eventual implantation. This review highlights the benefits of using biomaterials in conjunction with stem cells to repair damaged myocardium and give a brief description of the properties of these biomaterials that make them such valuable tools to the field.

Bioreactor Development for Lung Tissue Engineering

RATIONALE

Much recent interest in lung bioengineering by pulmonary investigators, industry and the organ transplant field has seen a rapid growth of bioreactor development ranging from the microfluidic scale to the human-sized whole lung systems. A comprehension of the findings from these models is needed to provide the basis for further bioreactor development.

OBJECTIVE

The goal was to comprehensively review the current state of bioreactor development for the lung.

METHODS

A search using PubMed was done for published, peer-reviewed papers using the keywords "lung" AND "bioreactor" or "bioengineering" or "tissue engineering" or "ex vivo perfusion".

MAIN RESULTS

Many new bioreactors ranging from the microfluidic scale to the human-sized whole lung systems have been developed by both academic and commercial entities. Microfluidic, lung-mimic and lung slice cultures have the advantages of cost-efficiency and high throughput analyses ideal for pharmaceutical and toxicity studies. Perfused/ventilated rodent whole lung systems can be adapted for mid-throughput studies of lung stem/progenitor cell development, cell behavior, understanding and treating lung injury and for preliminary work that can be translated to human lung bioengineering. Human-sized ex vivo whole lung bioreactors incorporating perfusion and ventilation are amenable to automation and have been used for whole lung decellularization and recellularization. Clinical scale ex vivo lung perfusion systems have been developed for lung preservation and reconditioning and are currently being evaluated in clinical trials.

CONCLUSIONS

Significant advances in bioreactors for lung engineering have been made at both the microfluidic and the macro scale. The most advanced are closed systems that incorporate pressure-controlled perfusion and ventilation and are amenable to automation. Ex vivo lung perfusion systems have advanced to clinical trials for lung preservation and reconditioning. The biggest challenges that lie ahead for lung bioengineering can only be overcome by future advances in technology that solve the problems of cell production and tissue incorporation.