**Critical Impact of Human Amniotic Membrane Tension on Mitochondrial Function and Cell Viability In Vitro**

**Laura Poženel 1,2, Andrea Lindenmair 2,3, Katy Schmidt 4, Andrey V. Kozlov 1,2, Johannes Grillari 1,2,5, Susanne Wolbank 1,2, Asmita Banerjee 1,2,\*,**† **and Adelheid Weidinger 1,2,**†


Received: 11 November 2019; Accepted: 13 December 2019; Published: 15 December 2019

**Abstract:** Amniotic cells show exciting stem cell features, which has led to the idea of using living cells of human amniotic membranes (hAMs) in toto for clinical applications. However, under common cell culture conditions, viability of amniotic cells decreases rapidly, whereby reasons for this decrease are unknown so far. Recently, it has been suggested that loss of tissue tension in vivo leads to apoptosis. Therefore, the aim of this study was to investigate the e ffect of tissue distention on the viability of amniotic cells in vitro. Thereby, particular focus was put on vital mitochondria-linked parameters, such as respiration and ATP synthesis. Biopsies of hAMs were incubated for 7–21 days either non-distended or distended. We observed increased B-cell lymphoma 2-associated X protein (BAX)/B-cell lymphoma (BCL)-2 ratios in non-distended hAMs at day seven, followed by increased caspase 3 expression at day 14, and, consequently, loss of viability at day 21. In contrast, under distention, caspase 3 expression increased only slightly, and mitochondrial function and cellular viability were largely maintained. Our data sugges<sup>t</sup> that a mechano-sensing pathway may control viability of hAM cells by triggering mitochondria-mediated apoptosis upon loss of tension in vitro. Further studies are required to elucidate the underlying molecular mechanisms between tissue distention and viability of hAM cells.

**Keywords:** apoptosis; human amniotic membrane; mitochondrial cell death; BAX; BCL-2; tensile strength
