Cell Communication in a Coculture System Consisting of Outgrowth Endothelial Cells and Primary Osteoblasts

Abstract

Bone tissue is a highly vascularized and dynamic system with a complex construction. In order to develop a construct for implant purposes in bone tissue engineering, a proper understanding of the complex dependencies between different cells and cell types would provide further insight into the highly regulated processes during bone repair, namely, angiogenesis and osteogenesis, and might result in sufficiently equipped constructs to be beneficial to patients and thereby accomplish their task. This study is based on an in vitro coculture model consisting of outgrowth endothelial cells and primary osteoblasts and is currently being used in different studies of bone repair processes with special regard to angiogenesis and osteogenesis. Coculture systems of OECs and pOBs positively influence the angiogenic potential of endothelial cells by inducing the formation of angiogenic structures in long-term cultures. Although many studies have focused on cell communication, there are still numerous aspects which remain poorly understood. Therefore, the aim of this study is to investigate certain growth factors and cell communication molecules that are important during bone repair processes. Selected growth factors like VEGF, angiopoietins, BMPs, and IGFs were investigated during angiogenesis and osteogenesis and their expression in the cultures was observed and compared after one and four weeks of cultivation. In addition, to gain a better understanding on the origin of different growth factors, both direct and indirect coculture strategies were employed. Another important focus of this study was to investigate the role of “gap junctions,” small protein pores which connect adjacent cells. With these bridges cells are able to exchange signal molecules, growth factors, and other important mediators. It could be shown that connexins, the gap junction proteins, were located around cell nuclei, where they await their transport to the cell membrane. In addition, areas in which two cells formed gap junctions were found.

Overcoming physical constraints in bone engineering: ‘the importance of being vascularized’

“…Outgrowth of endothelial cells and primary osteoblasts in vitro enhances both angiogenesis and osteogenesis (Herzog, Dohle, Bischoff, & Kirkpatrick, 2014). A number of growth factors critically contribute to these processes, including VEGF, PDGF, angiopoietins, BMPs, and IGFs.…”

“…The addition of soluble factors has been recently explored in 2D monocultures of MSCs with innovative approaches (Honda et al, 2013). Beside the paracrine diffusible factors, also physical cell-cell contacts such as connexins are involved (Herzog et al, 2014).…”

Extensive Characterization and Comparison of Endothelial Cells Derived from Dermis and Adipose Tissue: Potential Use in Tissue Engineering

“…Regenerative medicine strategies are being explored for the treatment of several pathologies, such as cardiovascular defects [1], bone defects [2,3], skeletal muscular defects [4] and difficult to heal skin wounds [5,6]. When attempts are being made to develop living tissue-engineered constructs which can be applied to a patient, a major issue in this field is that the constructs initially lack a sufficient supply of oxygen and nutrients before they become vascularized.…”

Transdifferentiation of mouse adipose-derived stromal cells into acinar cells of the submandibular gland using a co-culture system

“…The communication between different types of cells may include unknown secreted factors which are essential for (trans) differentiation of the cells [18].…”