AUTHOR=Citeroni Maria Rita , Mauro Annunziata , Ciardulli Maria Camilla , Di Mattia Miriam , El Khatib Mohammad , Russo Valentina , Turriani Maura , Santer Michael , Della Porta Giovanna , Maffulli Nicola , Forsyth Nicholas R. , Barboni Barbara 

TITLE=Amnion-Derived Teno-Inductive Secretomes: A Novel Approach to Foster Tendon Differentiation and Regeneration in an Ovine Model

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2021.649288

DOI=10.3389/fbioe.2021.649288

ISSN=2296-4185

ABSTRACT=<p>Regenerative medicine has greatly progressed, but tendon regeneration mechanisms and robust <italic>in vitro</italic> tendon differentiation protocols remain to be elucidated. Recently, tendon explant co-culture (CO) has been proposed as an <italic>in vitro</italic> model to recapitulate the microenvironment driving tendon development and regeneration. Here, we explored standardized protocols for production and storage of bioactive tendon-derived secretomes with an evaluation of their teno-inductive effects on ovine amniotic epithelial cells (AECs). Teno-inductive soluble factors were released in culture-conditioned media (CM) only in response to active communication between tendon explants and stem cells (CM<sub>CO</sub>). Unsuccessful tenogenic differentiation in AECs was noted when exposed to CM collected from tendon explants (CM<sub>FT</sub>) only, whereas CM<sub>CO</sub> upregulated <italic>SCXB, COL I</italic> and <italic>TNMD</italic> transcripts, in AECs, alongside stimulation of the development of mature 3D tendon-like structures enriched in TNMD and COL I extracellular matrix proteins. Furthermore, although the tenogenic effect on AECs was partially inhibited by freezing CM<sub>CO</sub>, this effect could be recovered by application of an <italic>in vivo</italic>-like physiological oxygen (2% O<sub>2</sub>) environment during AECs tenogenesis. Therefore, CM<sub>CO</sub> can be considered as a waste tissue product with the potential to be used for the development of regenerative bio-inspired devices to innovate tissue engineering application to tendon differentiation and healing.</p>