Recombinant irisin enhances the extracellular matrix formation, remodeling potential, and differentiation of human periodontal ligament cells cultured in 3D

Abstract

Background: Irisin is expressed in human periodontal ligament (hPDL), and its administration enhances growth, migration and matrix deposition in hPDL cells cultured in monolayers in vitro.

Objectives: To identify whether irisin affects the gene expression patterns directing the morphology, mechanical properties, extracellular matrix (ECM) formation, osteogenic activity and angiogenic potential in hPDL cell spheroids cultured in 3D.

Materials and methods: Spheroids of primary human hPDL cells were generated in a rotational 3D culture system and treated with or without irisin. The gene expression patterns were evaluated by Affymetrix microarrays. The morphology of the spheroids was characterized using histological staining. Mechanical properties were quantified by nanoindentation. The osteogenic and angiogenic potential of spheroids were assessed through immunofluorescence staining for collagen type I, periostin fibronectin and von Willebrand factor (vWF), and mRNA expression of osteogenic markers. The secretion of multiple myokines was evaluated using Luminex immunoassays.

Results: Approximately 1000 genes were differentially expressed between control and irisin-treated groups by Affymetrix. Several genes related to ECM organization were differentially expressed, and multiple deubiquitinating enzymes were upregulated in the irisin-exposed samples analyzed. These represent cellular and molecular mechanisms indicative of a role for irisin in tissue remodeling. Irisin induced a rim-like structure on the outer region of the hPDL spheroids, ECM-related protein expression and the stiffness of the spheroids were enhanced by irisin. The expression of osteogenic and angiogenetic markers was increased by irisin.

Conclusions: Irisin altered the morphology in primary hPDL cell-derived spheroids, enhanced its ECM deposition, mechanical properties, differentiation and remodeling potential.

Keywords: extracellular matrix; irisin; mechanical properties; osteogenesis; periodontal ligament cells; three-dimensional culture.