A Tunable, Three-Dimensional In Vitro Culture Model of Growth Plate Cartilage Using Alginate Hydrogel Scaffolds

Authors

Alek G. Erickson, University of Nebraska Medical Center
Taylor D. Laughlin, University of Nebraska - Lincoln
Sarah M. Romereim, University of Nebraska-LincolnFollow
Catherine N. Sargus-Patino, University of Nebraska - Lincoln
Angela K. Pannier, University of Nebraska - LincolnFollow
Andrew T. Dudley, University of Nebraska Medical CenterFollow

Document Type

Article

Date of this Version

2018

Citation

Tissue Eng Part A. 24(1-2): 94-105

Comments

Copyright 2018, Mary Ann Liebert, Inc.

DOI: 10.1089/ten.tea.2017.0091

Abstract

Defining the final size and geometry of engineered tissues through precise control of the scalar and vector components of tissue growth is a necessary benchmark for regenerative medicine, but it has proved to be a significant challenge for tissue engineers. The growth plate cartilage that promotes elongation of the long bones is a good model system for studying morphogenetic mechanisms because cartilage is composed of a single cell type, the chondrocyte; chondrocytes are readily maintained in culture; and growth trajectory is predominately in a single vector. In this cartilage, growth is generated via a differentiation program that is spatially and temporally regulated by an interconnected network composed of long- and short-range signaling mechanisms that together result in the formation of functionally distinct cellular zones. To facilitate investigation of the mechanisms underlying anisotropic growth, we developed an in vitro model of the growth plate cartilage by using neonatal mouse growth plate chondrocytes encapsulated in alginate hydrogel beads. In bead cultures, encapsulated chondrocytes showed high viability, cartilage matrix deposition, low levels of chondrocyte hypertrophy, and a progressive increase in cell proliferation over 7 days in culture. Exogenous factors were used to test functionality of the parathyroid-related protein–Indian hedgehog (PTHrP-IHH) signaling interaction, which is a crucial feedback loop for regulation of growth. Consistent with in vivo observations, exogenous PTHrP stimulated cell proliferation and inhibited hypertrophy, whereas IHH signaling stimulated chondrocyte hypertrophy. Importantly, the treatment of alginate bead cultures with IHH or thyroxine resulted in formation of a discrete domain of hypertrophic cells that mimics tissue architecture of native growth plate cartilage. Together, these studies are the first demonstration of a tunable in vitro system to model the signaling network interactions that are required to induce zonal architecture in growth plate chondrocytes, which could also potentially be used to grow cartilage cultures of specific geometries to meet personalized patient needs.