ACE2 & TMPRSS2 Expressions in Head & Neck Tissues: A Systematic Review

Area of Science:

• Head and Neck Anatomy
• Virology
• Molecular Biology

Background:

• The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) utilizes specific host cell receptors for entry.
• Angiotensin converting enzyme-2 (ACE2) and transmembrane protease serine-2 (TMPRSS2) are critical for SARS-CoV-2 cell entry.
• Understanding the expression of these receptors in head and neck tissues is crucial for comprehending viral tropism and pathogenesis.

Purpose of the Study:

• To systematically review and synthesize data on the expression of ACE2 and TMPRSS2 in human and animal head and neck tissues.
• To identify the specific anatomical locations and cell types expressing ACE2 and TMPRSS2 within the head and neck region.
• To assess the heterogeneity in detection methods and potential biases in existing literature.

Main Methods:

• A comprehensive literature search was conducted across Scopus, Cochrane Library, Medrxiv, Google Scholar, and PubMed/MEDLINE.
• Studies investigating ACE2 or TMPRSS2 expression in head and neck tissues were selected based on predefined inclusion criteria.
• PRISMA checklist and a modified PICOTS framework were employed for systematic review and data extraction.

Main Results:

• ACE2 and TMPRSS2 were detected in human oral, pharyngeal, and sinusonasal mucosa.
• ACE2 was expressed in basal, apical, goblet, minor salivary, and endothelial cells; TMPRSS2 was found in goblet and apical respiratory cells.
• Both receptors were identified in the olfactory region, particularly in neural and sustentacular stem cells, with potential age-related variations in animal models.

Conclusions:

• ACE2 and TMPRSS2 are widely expressed across multiple head and neck tissues, serving as potential entry points for SARS-CoV-2.
• The presence of these receptors in diverse cell types, including olfactory cells, highlights the vulnerability of the head and neck region to viral infection.
• Heterogeneity in detection methodologies across studies necessitates cautious interpretation and suggests a need for standardized approaches.