Extracellular matrix expression of human tenocytes in three-dimensional air-liquid and PLGA cultures compared with tendon tissue: implications for tendon tissue engineering.

Tenocyte transplantation may prove to be an approach to support healing of tendon defects. Cell-cell and cell-matrix contacts within three-dimensional (3D) cultures may prevent tenocyte dedifferentiation observed in monolayer (2D) culture. The present study compares both neotissue formation and tenocyte extracellular matrix (ECM) expression in 2D and 3D cultures directly with that of native tendon, in order to determine optimal conditions for tendon tissue engineering. Primary human tenocytes were embedded in poly[lactic-co-glycolic-acid] (PLGA)-scaffolds and high-density cultures. Neotissue formation was examined by hematoxyline-eosine (H&E) and immunofluorescence staining. Gene expression of ECM proteins and vascular endothelial growth factor (VEGF) was compared at days 0 (2D), 14, and 28 in 3D cultures and tendon. Histomorphology of 3D culture showed tendon-like tissue as tenocyte cell nuclei became more elongated and ECM accumulated. Type I collagen gene expression was higher in 2D culture than in tendon and decreased in 4-week-old 3D cultures, whereas type III collagen was only elevated in high-density culture compared with tendon. Decorin and COMP were reduced in 2D and increased in 3D culture almost to ex vivo level. These results suggest that the 3D high-density or biodegradable scaffolds cultures encourage the differentiation of expanded monolayer tenocytes in vitro to tendon-like tissue.