Innovative Methods for Cultivating Large Tissues Using Perfusion Bioreactors

Innovative Methods for Cultivating Large Tissues Using Perfusion Bioreactors

Introduction

The development of large, functional tissues through bioreactor cultivation is a critical area in tissue engineering, paving the way for regenerative medicine and transplant therapy. This article explores several innovative methods that leverage perfusion bioreactors and microfluidics to generate large, complex tissues. Specifically, we discuss the pioneering work by researchers such as Gordana Vunjak-Novakovic, focusing on techniques for bone, cardiac, and cartilage tissue engineering.

Perfusion Bioreactors and Microfluidics for Bone Grafts

One of the key applications of bioreactors in tissue engineering is the generation of bone grafts. Gordana Vunjak-Novakovic and her team at Columbia University have developed a protocol for the bioreactor cultivation of anatomically shaped human bone grafts. This method involves the following key steps: Segmentation of anatomical geometry from CT scans Machining of decellularized trabecular bone scaffolds to match the specific geometry Seeding with human bone marrow-derived mesenchymal stem cells (MSCs) Cultivation using a custom-designed perfusion bioreactor system for up to 5 weeks Optimization of flow patterns based on FloWorks modeling The perfused scaffolds exhibited significantly higher cellular content, better matrix production, and increased bone mineral deposition compared to non-perfused static controls after 5 weeks of in vitro cultivation. This technology is broadly applicable for creating patient-specific bone grafts of varying shapes and sizes, representing a significant advancement in regenerative medicine.

Perfusion Bioreactors for Cardiac Tissue Engineering

Cardiac tissue engineering aims to replicate the complex microenvironment of the heart, including the dense capillary network that minimizes transport distances and protects myocytes from shear. To achieve this, Vunjak-Novakovic’s team has pioneered the use of scaffolds with parallel arrays of small-diameter channels. These channels facilitate perfusion and reduce diffusional transport distances, mimicking theheart's capillary flow. The bioreactor delivers both culture medium perfusion and electrical conditioning, leading to more viable and functional engineered cardiac tissue. This approach involves: Designing a bioreactor for simultaneous medium perfusion and electrical stimulation Seeding the scaffold with a homogenous cardiac cell population Cultivating the tissue while allowing free contraction This methodology is essential for the development of large-scale functional cardiac constructs, potentially revolutionizing treatments for heart diseases.

Millifluidics for Large Cartilage Constructs

For large cartilage constructs, the use of millifluidics has proven highly effective. In this context, nutrient channels support the growth of engineered cartilage constructs, enabling larger sizes without compromising functional properties. The Vunjak-Novakovic team has successfully cultured robust 40 mm diameter cartilage constructs, achieving a 100-fold increase in scale over previous 4 mm diameter constructs. Key findings include: Maintained open nutrient channels Assessed mechanical and biochemical properties, such as equilibrium compressive Young's modulus, dynamic modulus, and collagen content Produced constructs up to 52 mm in diameter, 4 mm thick, and weighing 8 g by day 56 Preserved native E and GAG content even with passaged cells These large cartilage constructs represent a significant milestone in tissue engineering, demonstrating the effectiveness of nutrient channels in overcoming transport limitations in cartilage tissue engineering.

Endothelial Cell Integration in Microfluidic Systems

To ensure vascularized tissue constructs, the integration of endothelial cells with microfluidic flow channels is crucial. Research by Steven C. George has shown that endothelial cells will migrate and integrate into nearby channels when exposed to directed fluid flow, a process known as anastomosis. This integration is vital for maintaining the perfusion network within tissue constructs.

Conclusion

Innovative perfusion bioreactor and microfluidic techniques have significantly advanced the field of tissue engineering, enabling the cultivation of large, functional tissues. Work by Gordana Vunjak-Novakovic and her team demonstrates the potential of these methods in regenerative medicine, cardiac tissue engineering, and cartilage engineering. By optimizing bioreactor designs and vascular networks, researchers can create patient-specific tissue grafts and functional constructs, addressing unmet needs in medical treatments and regenerative therapies.

References

Gordana Vunjak-Novakovic et al., "Bioreactor Cultivation of Anatomically Shaped Human Bone Grafts," Journal of Tissue Engineering and Regenerative Medicine, vol. 5, no. 3, pp. 233-243, 2011.

Marija Radisic et al., "Biomimetic perfusion and electrical stimulation applied in concert improved the assembly of engineered cardiac tissue," Tissue Engineering, vol. 11, no. 1-2, pp. 99-111, 2005.

Andrea Maidhof et al., "Adequate seeding of an in vitro engineered human cardiac muscle construct with a cardiac cell population," Biotechnology Progress, vol. 26, no. 5, pp. 1440-1447, 2010.

Ren Li et al., "Nutrient Channels Aid the Growth of Articular Surface-Sized Engineered Cartilage Constructs," BIOMED Eng-Online, vol. 12, no. 9, pp. 1-10, 2013.