In life there is death: How epithelial tissue barriers are preserved despite the challenge of apoptosis

ABSTRACT

Apoptosis is a ubiquitous mode of programmed cell death that is found in healthy organs and can be stimulated by many toxic stresses. When it occurs in epithelia, apoptosis presents major challenges to tissue integrity. Apoptotic corpses can promote inflammatory and autoimmune responses if they are retained, and the cellular fragmentation that accompanies apoptosis can potentially compromise the epithelial barrier. Here we discuss 2 homeostatic mechanisms that allow epithelia to circumvent these potential risks: clearance of apoptotic corpses by professional and non-professional phagocytes and physical expulsion of apoptotic cells by apical extrusion. Extrusion and phagocytosis may represent complementary responses that preserve epithelial integrity despite the inevitable challenge of apoptosis.

KEYWORDS:

• apoptosis
• epithelia
• extrusion
• phagocytosis
• tissue mechanics

Disclosure of potential conflicts of interest

No potential conflicts of interest were disclosed.

Funding

KD is the recipient of an International Postgraduate Research Scholarship and a UQ Centennial Scholarship; GAG and KS are Future Fellows of the Australian Research Council (FT160100366 and FT130100361, respectively); and MJS and ASY are Research Fellows of the NHMRC Australia (1107914, 1044041 respectively).