Creating homogenous strain distribution within 3D cell‐encapsulated constructs using a simple and cost‐effective uniaxial tensile bioreactor: Design and validation study

Abstract

Mechanical loading bioreactors capable of applying uniaxial tensile strains are emerging to be a valuable tool to investigate physiologically relevant cellular signaling pathways and biochemical expression. In this study, we have introduced a simple and cost-effective uniaxial tensile strain bioreactor for the application of precise and homogenous uniaxial strains to 3D cell-encapsulated collagen constructs at physiological loading strains (0-12%) and frequencies (0.01-1 Hz). The bioreactor employs silicone-based loading chambers specifically designed to stretch constructs without direct gripping to minimize stress concentration at the ends of the construct and preserve its integrity. The loading chambers are driven by a versatile stepper motor ball-screw actuation system to produce stretching of the constructs. Mechanical characterization of the bioreactor performed through Finite Element Analysis demonstrated that the constructs experienced predominantly uniaxial tensile strain in the longitudinal direction. The strains produced were found to be homogenous over a 15 × 4 × 2 mm region of the construct equivalent to around 60% of the effective region of characterization. The strain values were also shown to be consistent and reproducible during cyclic loading regimes. Biological characterization confirmed the ability of the bioreactor to promote cell viability, proliferation, and matrix organization of cell-encapsulated collagen constructs. This easy-to-use uniaxial tensile strain bioreactor can be employed for studying morphological, structural, and functional responses of cell-embedded matrix systems in response to physiological loading of musculoskeletal tissues. It also holds promise for tissue-engineered strategies that involve delivery of mechanically stimulated cells at the site of injury through a biological carrier to develop a clinically useful therapy for tissue healing. Biotechnol. Bioeng. 2017;114: 1878-1887. © 2017 Wiley Periodicals, Inc.

Effect of Uniaxial Tensile Cyclic Loading Regimes on Matrix Organization and Tenogenic Differentiation of Adipose-Derived Stem Cells Encapsulated within 3D Collagen Scaffolds

“…The SEM images of loaded ASC-encapsulated scaffolds showed distinct compaction of collagen fibers at each of the applied strains and frequencies, while the nonloaded control group exhibited a highly random matrix (Figures 2(a) and 3(a) ). Our previous study demonstrated that even on applying the same uniaxial tensile loading regime, the extent of collagen matrix compaction can vary significantly based on the type of cells encapsulated within the scaffold [ 28 ]. Also, higher cell densities within the scaffold are known to increase the extent of matrix compaction and increase the diameter of collagen fibers [ 50 ].…”

“…Briefly, ASCs (passage 4) were encapsulated at 750,000 cells/ml seeding density within 3 mg/ml collagen I solution and neutralized to pH 7~8 with chilled 1 N NaOH solution along with PBS and cell culture media according to the manufacturer's instructions. The cell-collagen solutions were added into the loading chambers of our custom-built uniaxial tensile strain bioreactor [ 28 ] and polymerized at 37°C for 1 hour. Then, 3D cell-encapsulated collagen scaffolds were incubated in the culture media for 48 hours in a standard cell culture incubator at 37°C and 5% CO 2 .…”

A standalone bioreactor system to deliver compressive load under perfusion flow to hBMSC-seeded 3D chitosan-graphene templates

“…The conversion of these physical stimuli into molecular signals and biological responses, which is referred to as mechanotransduction, drives molecular cascades of events triggering bone remodelling 3,4 . Accordingly, an appropriate mechanical loading of cells in culture promotes their expansion 5 , along with mineralized extracellular matrix (ECM) production 6–8 . Cell physical triggering can be obtained via dedicated actuators - usually referred to as bioreactor systems - addressing a specific tissue phenotype according to their setup configuration 9–17 .…”

Independent, Controllable Stretch-Perfusion Bioreactor Chambers to Functionalize Cell-Seeded Decellularized Tendons

“…To better distribute seeded cells onto scaffolds, others described the application of mechanical stimuli in the absence of a fluid perfusion. 1,17,18,26 Moreover, a mechanical stimulation mimicking physiological loads improves the cellular production of collagen, and fiber orientation while preserving biomechanical properties of the tendon-derived scaffolds. 25 However, to the best of our knowledge, none of the custom-made or commercial bioreactors allows a simultaneous pump-free fluid perfusion and an individual, custom mechanical stimulation.…”

“…20 Another advantage of the OSPB was the possibility to independently stimulate each chamber containing a single construct, differently from other devices that can lodge independent samples, but apply the same stimulation patterns simultaneously. 1,14,17,18 According to this approach, the OSPB advantaged both the experimental in vitro studies and the potential clinical translatability. Indeed, OSPB operates on every single construct and employs different stimulation protocols and harvesting/control time points independently, within the same experiment.…”