The importance of connexin hemichannels during chondroprogenitor cell differentiation in hydrogel versus microtissue culture models

Tissue Eng Part A. 2015 Jun;21(11-12):1785-94. doi: 10.1089/ten.TEA.2014.0691. Epub 2015 Mar 24.

Abstract

Appropriate selection of scaffold architecture is a key challenge in cartilage tissue engineering. Gap junction-mediated intercellular contacts play important roles in precartilage condensation of mesenchymal cells. However, scaffold architecture could potentially restrict cell-cell communication and differentiation. This is particularly important when choosing the appropriate culture platform as well as scaffold-based strategy for clinical translation, that is, hydrogel or microtissues, for investigating differentiation of chondroprogenitor cells in cartilage tissue engineering. We, therefore, studied the influence of gap junction-mediated cell-cell communication on chondrogenesis of bone marrow-derived mesenchymal stromal cells (BM-MSCs) and articular chondrocytes. Expanded human chondrocytes and BM-MSCs were either (re-) differentiated in micromass cell pellets or encapsulated as isolated cells in alginate hydrogels. Samples were treated with and without the gap junction inhibitor 18-α glycyrrhetinic acid (18αGCA). DNA and glycosaminoglycan (GAG) content and gene expression levels (collagen I/II/X, aggrecan, and connexin 43) were quantified at various time points. Protein localization was determined using immunofluorescence, and adenosine-5'-triphosphate (ATP) was measured in conditioned media. While GAG/DNA was higher in alginate compared with pellets for chondrocytes, there were no differences in chondrogenic gene expression between culture models. Gap junction blocking reduced collagen II and extracellular ATP in all chondrocyte cultures and in BM-MSC hydrogels. However, differentiation capacity was not abolished completely by 18αGCA. Connexin 43 levels were high throughout chondrocyte cultures and peaked only later during BM-MSC differentiation, consistent with the delayed response of BM-MSCs to 18αGCA. Alginate hydrogels and microtissues are equally suited culture platforms for the chondrogenic (re-)differentiation of expanded human articular chondrocytes and BM-MSCs. Therefore, reducing direct cell-cell contacts does not affect in vitro chondrogenesis. However, blocking gap junctions compromises cell differentiation, pointing to a prominent role for hemichannel function in this process. Therefore, scaffold design strategies that promote an increasing distance between single chondroprogenitor cells do not restrict their differentiation potential in tissue-engineered constructs.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Adult
  • Alginates
  • Bone Marrow Cells / cytology
  • Bone Marrow Cells / drug effects
  • Cartilage, Articular / cytology
  • Cell Communication
  • Cell Differentiation
  • Chondrocytes / cytology*
  • Chondrogenesis / drug effects
  • Connexin 43 / physiology*
  • DNA / metabolism
  • Extracellular Matrix Proteins / metabolism
  • Female
  • Gap Junctions / drug effects
  • Gap Junctions / physiology*
  • Gene Expression Regulation, Developmental
  • Glucuronic Acid
  • Glycosaminoglycans / metabolism
  • Glycyrrhetinic Acid / pharmacology
  • Hexuronic Acids
  • Humans
  • Hydrogels*
  • Male
  • Mesenchymal Stem Cells / cytology*
  • Mesenchymal Stem Cells / drug effects
  • Tissue Culture Techniques*
  • Young Adult

Substances

  • Alginates
  • Connexin 43
  • Extracellular Matrix Proteins
  • GJA1 protein, human
  • Glycosaminoglycans
  • Hexuronic Acids
  • Hydrogels
  • Glucuronic Acid
  • Adenosine Triphosphate
  • DNA
  • Glycyrrhetinic Acid