Use of Perfusion Bioreactors and Large Animal Models for Long Bone Tissue Engineering

The translation of bone tissue engineering (BTE) research to clinical use has been absymal1. Outside of bone void filler biomaterials, only Bone Morphogenetic Protein 2 (BMP2) has made significant inroads to clinical practice, and even BMP2 use has been associated with significant complications including death, dysphagia, and ectopic bone formation. The dearth of BTE products can be attributed to two main causes: (1) the need to develop BTE systems, that successfully integrate scaffolds, growth factors like BMP2 and cells and (2) the need to adapt and implement such systems for a wide variety of clinical indications in CranioMaxilloFacial (CMF), Spine and Orthopedic Surgery. Of course, to fully develop BTE systems (Issue 1) and adapt them to realistic clinical indications, we must be able to test such systems in bone defects that are as close to the human situation as possible. Thus, the use of domestic large animals for bone tissue engineering is critical, as these animals provide challenges in both defect volume and functional loading that can mimic the human situation. In addition, FDA approval for BTE products either through a 510K or IDE/IND/PMA pathway requires the use of a large pre-clinical animal model. However, despite this need, only approximately 60 large animal bone tissue-engineering studies have been published in the past 10 years. Furthermore, NIH has funded only 8% of these studies, and of the 17 bone tissue engineering studies supported by NIH in 2010, only three utilized a large animal model, and none of these used an animal larger than a rabbit. Clearly, increased translation and regulatory approval of BTE therapies will require greater testing in large animal models. We will discuss the current dearth of relevant pre-clinical studies in BTE, and present our work addressing these issues by developing BTE systems (integrated scaffold, growth factor and stem-cell constructs) and testing these systems for realistic clinical applications using the Yorkshire and other swine species as a large pre-clinical animal model. We will detail our work in developing BTE systems for CMF reconstruction and spine fusion in the swine model. Reference Hollister S. J. and Murphy W. L. Scaffold translation: barriers between concept and clinic. Tissue Eng. B. (in press).

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3D-Printing of Hierarchically Designed and Osteoconductive Bone Tissue Engineering Scaffolds

Materials ◽

10.3390/ma13081836 ◽

2020 ◽

Vol 13 (8) ◽

pp. 1836 ◽

Cited By ~ 8

Author(s):

Nicolas Söhling ◽

Jonas Neijhoft ◽

Vinzenz Nienhaus ◽

Valentin Acker ◽

Jana Harbig ◽

...

Keyword(s):

Tissue Engineering ◽

Cell Survival ◽

Bone Tissue Engineering ◽

Bone Tissue ◽

Modular Design ◽

Negative Impact ◽

Frame Structure ◽

Large Animal ◽

Large Animal Models ◽

Novel Scaffold

In Bone Tissue Engineering (BTE), autologous bone-regenerative cells are combined with a scaffold for large bone defect treatment (LBDT). Microporous, polylactic acid (PLA) scaffolds showed good healing results in small animals. However, transfer to large animal models is not easily achieved simply by upscaling the design. Increasing diffusion distances have a negative impact on cell survival and nutrition supply, leading to cell death and ultimately implant failure. Here, a novel scaffold architecture was designed to meet all requirements for an advanced bone substitute. Biofunctional, porous subunits in a load-bearing, compression-resistant frame structure characterize this approach. An open, macro- and microporous internal architecture (100 µm–2 mm pores) optimizes conditions for oxygen and nutrient supply to the implant’s inner areas by diffusion. A prototype was 3D-printed applying Fused Filament Fabrication using PLA. After incubation with Saos-2 (Sarcoma osteogenic) cells for 14 days, cell morphology, cell distribution, cell survival (fluorescence microscopy and LDH-based cytotoxicity assay), metabolic activity (MTT test), and osteogenic gene expression were determined. The adherent cells showed colonization properties, proliferation potential, and osteogenic differentiation. The innovative design, with its porous structure, is a promising matrix for cell settlement and proliferation. The modular design allows easy upscaling and offers a solution for LBDT.

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