A theoretically-motivated biaxial tissue culture system with intravital microscopy

Abstract

Many cell types produce, remodel, and degrade extracellular matrix in response to diverse stimuli, including mechanical loads. Much is known about the molecular biology and biochemistry of the deposition and degradation of collagen, the primary structural constituent of the extracellular matrix in many tissues, yet there has been little modeling of the associated mechanobiology. For example, we do not have quantitative descriptions, or rules, for the kinetics of collagen turnover as a function of altered mechanical loading and we do not know what governs the orientation and pre-stretch at which new fibers are incorporated within extant tissue. In this paper, we use a constrained mixture theory for growth and remodeling of planar soft tissues to motivate a new experimental approach for investigating competing hypotheses on, for example, how new collagen is aligned by synthetic cells. In particular, because stress and strain fields can be homogeneous in a central region of a biaxially tested tissue, and because biaxial testing admits diverse protocols wherein equal stresses can be imposed in the presence of unequal strains or stresses can be maintained in the absence of strain, we report simulations that illustrate the potential utility of biaxial culture studies. Finally, we describe the associated design of a computer-controlled system that allows intravital microscopic quantification of collagen density, orientation, and cross-linking at various stages during the adaptation of a native tissue or the development of a tissue engineered equivalent, each subjected to well controlled biaxial loads.

Modeling collagen remodeling

“…It is proposed to start with relatively simple geometries and loading conditions, where the magnitude and direction of the applied load can be controlled to subsequently monitor the evolution of the collagen fiber architecture, as a.o. suggested in Boerboom et al (2008), Humphrey et al (2008), Rubbens et al (2009a, b).…”

Dynamic multicomponent engineered tissue reorganization and matrix deposition measured with an integrated nonlinear optical microscopy–optical coherence microscopy system

“…In the current study, this is, to our knowledge, the first visualization of collagen deposition, spatial distribution, and organization within extant fibrin matrix without staining or labeling, demonstrating NLOM-OCM ability to noninvasively and serially assess ECM development. Biaxial bioreactor having both a mechanical testing platform and a stage for NLOM-OCM imaging was designed 45 and is under development. 34 Combined with bioreactors, multimodal imaging will enable future serial measurements on individual constructs over extended time courses to better visualize and understand biological, chemical, mechanical, and materials effects on cellular responses that drive bulk tissue properties.…”

A Bioreactor to Identify the Driving Mechanical Stimuli of Tissue Growth and Remodeling

“…5,[8][9][10] As cardiovascular tissues are mainly exposed to dynamic loading conditions, other bioreactors applied dynamic deformation to the tissue engineered (TE) constructs. [11][12][13][14][15][16] For example, Rubbens et al and Gould et al applied cyclic strain to study the remodeling of 3D TE constructs. 14,16 Moreover, Engelmayer et al tested different scaffold candidates for heart valve tissue engineering by designing a bioreactor capable of applying cyclic flexure and laminar flow.…”