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Vertebrate reproductive science and technology
RESEARCH ARTICLE (Open Access)

Inducible heat shock protein A1A (HSPA1A) is markedly expressed in rat myometrium by labour and secreted via myometrial cell-derived extracellular vesicles

M. F. Russell A B , G. C. Bailey B C , E. I. Miskiewicz B C and D. J. MacPhee https://orcid.org/0000-0001-5721-6185 B C D
+ Author Affiliations
- Author Affiliations

A Department of Anatomy, Physiology and Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, SK, S7N 5E5, Canada.

B One Reproductive Health Research Group, University of Saskatchewan, Saskatoon, SK, S7N 5B4, Canada.

C Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, S7N 5B4, Canada.

D Corresponding author. Email: d.macphee@usask.ca

Reproduction, Fertility and Development 33(4) 279-290 https://doi.org/10.1071/RD20242
Submitted: 17 September 2020  Accepted: 24 November 2020   Published: 12 February 2021

Journal Compilation © CSIRO 2021 Open Access CC BY-NC

Abstract

The myometrium goes through physiological, cellular and molecular alterations during gestation that necessitate effective cellular proteostasis. Inducible heat shock protein A1A (HSPA1A) is a member of the 70-kDa heat shock protein A (HSPA) family, which acts as a chaperone to regulate proteostasis; however, HSPA1A also participates as a cytokine in inflammatory regulation, leading to its designation as a chaperokine. This study examined the spatiotemporal expression of HSPA1A protein in the rat myometrium throughout gestation and assessed whether it is secreted as cargo of myometrial cell-derived extracellular vesicles (EVs). Immunoblot analysis demonstrated that HSPA1A expression was markedly elevated during late pregnancy and labour and increased by uterine distension. Myometrial HSPA1A expression in situ increased in myocytes of longitudinal and circular muscle layers from Day 19 through to postpartum, specifically in the cytoplasm and nuclei of myocytes from both muscle layers, but frequently detectable just outside myocyte membranes. Scanning electron microscopy examination of samples isolated from hTERT-HM cell-conditioned culture medium, using EV isolation spin columns, confirmed the presence of EVs. EV lysates contained HSPA8, HSPA1A and the EV markers apoptosis-linked gene 2-interacting protein X (Alix), the tetraspanin cluster of differentiation 63 (CD63), tumour susceptibility gene 101 (TSG101) and HSP90, but not the endoplasmic reticulum protein calnexin. These results indicate that HSPA1A may act as a chaperokine in the myometrium during pregnancy.

Graphical Abstract Image

Keywords: HSPA1A, HSP70, chaperokine, pregnancy, myometrium, extracellular vesicles.


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