Apoptosis-associated Protein Expression in Human Salivary Gland Morphogenesis

Arch Oral Biol. 2016 Sep;69:71-81. doi: 10.1016/j.archoralbio.2016.05.013. Epub 2016 May 17.

Abstract

Objective: Salivary gland (SG) development is based on branching morphogenesis, in which programmed cell death has been proposed to play a role in cell signalling and organ shaping. In the mouse salivary gland apoptosis has been suggested to play a key role in lumen formation, removing the central cells of the epithelial stalks. Here we analyse the expression of several anti- and pro-regulators of apoptosis during human SG development in a range of developmental stages.

Design: Foetal SGs obtained from the University of São Paulo were analysed by immunohistochemistry to assess the expression of apoptosis-associated proteins: caspases (caspase-6, -7, -9 and cleaved caspase-3), Bcl-2 family members (Bax, Bak, Bad, Bid, Bcl-2, Bcl-x and Bcl-xL), Survivin (BIRC5), Cytochrome C and Apaf-1.

Results: Nuclear expression of Bax and Bak was identified in presumptive luminal areas at initial stages, while Bcl-xL showed the most relevant anti-apoptotic activity. Caspase-6, -7 and -9 were expressed during all stages, while interestingly cleaved caspase-3 showed no prominent expression, indicating that caspase-7 is the main effector. Apoptosome complex components Apaf-1 and Cytochrome C, as well as survivin were all positive in developing glands.

Conclusions: The particular expression pattern of several apoptotic regulators in human SG development suggests the existence of a fundamental role for apoptosis during duct formation. The absence of Bad and Bid expressions indicates that the instrinsic pathway is more active then the extrinsic during human gland formation. The subcellular localisation of intrinsic-apoptosis proteins correlated with apoptotic activity, but also suggested additional non-apoptotic functions.

Keywords: Apoptosis; Bcl-2 family; Caspases; Development; Human; Salivary glands.

MeSH terms

  • Animals
  • Apoptosis / genetics
  • Apoptosis / physiology*
  • Apoptosis Regulatory Proteins / metabolism*
  • Apoptotic Protease-Activating Factor 1 / metabolism
  • Caspases / biosynthesis
  • Caspases / metabolism
  • Cytochromes c / metabolism
  • Humans
  • Immunohistochemistry
  • Morphogenesis / physiology
  • Proto-Oncogene Proteins c-bcl-2 / biosynthesis
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Salivary Glands / cytology*
  • Salivary Glands / metabolism*
  • Signal Transduction
  • bcl-X Protein / biosynthesis
  • bcl-X Protein / metabolism

Substances

  • APAF1 protein, human
  • Apoptosis Regulatory Proteins
  • Apoptotic Protease-Activating Factor 1
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-X Protein
  • Cytochromes c
  • Caspases