Heat stress and sudden infant death syndrome—Stress gene expression after exposure to moderate heat stress Marianne Cathrine Rohde a, *, Thomas Juhl Corydon b,1 , Jakob Hansen a , Christina Bak Pedersen c , Stinne P. Schmidt c , Niels Gregersen c , Jytte Banner a a Institute of Forensic Medicine, Department of Forensic Pathology, Aarhus University, Denmark b Department of Biomedicine, Aarhus University, Denmark c Research Unit for Molecular Medicine, Aarhus University, Denmark 1. Introduction Sudden infant death syndrome (SIDS) has been investigated vigorously in numerous studies. Epidemiological and pathological studies have shown that prone sleeping is the single most important risk factor in SIDS [1], and modifiable by simple intervention [2–4]. Thermal stress has been linked to the prone position [5,6]. The front surface of a body allows greater heat loss than the back, so if placed prone, heat loss may be compromised. Additional covering by bedding and/or heavily wrapping can leave the head and face the only area of excessive heat loss [6–8]. In the later years research has increasingly focused on the genetic background of SIDS. SIDS is most likely a combination of both extrinsic and intrinsic factors, gene factors and external or environmental factors, and several gene defects may be responsi- ble for cases previously classified as SIDS [9–11]. Thermal stress causes damage to several constituents including lipids, DNA and proteins, and is associated with decreased cell viability and death [12–15]. The cellular levels of heat shock proteins increase during thermal stress through transcriptional activation of heat shock protein encoding genes, a cell protective mechanism called the heat shock response [16]. The HSP70 family is comprised of several members localized in different cellular compartments [17–21]. They serve a major role in stabilization of nascent polypeptides as well as in refolding of denatured proteins into native conformations and in preventing aggregation of mis-folded proteins [16,22,23]. HSP60 is a mitochondrial chaperone essential for the folding and assembly of newly imported proteins in the mitochondria and Forensic Science International 232 (2013) 16–24 A R T I C L E I N F O Article history: Received 8 October 2012 Received in revised form 21 April 2013 Accepted 3 June 2013 Available online 27 July 2013 Keywords: Heat stress Fibroblast culture Infant death SIDS QRT-PCR A B S T R A C T The aim of the present study was to investigate stress gene expression in cultured primary fibroblasts established from Achilles tendons collected during autopsies from sudden infant death syndrome (SIDS) cases, and age-matched controls (infants dying in a traumatic event). Expression of 4 stress responsive genes, HSPA1B, HSPD1, HMOX1, and SOD2, was studied by quantitative reverse transcriptase PCR analysis of RNA purified from cells cultured under standard or various thermal stress conditions. The expression of all 4 genes was highly influenced by thermal stress in both SIDS and control cells. High interpersonal variance found in the SIDS group indicated that they represented a more heterogeneous group than controls. The SIDS group responded to thermal stress with a higher expression of the HSPA1B and HSPD1 genes compared to the control group, whereas no significant difference was observed in the expression of SOD2 and HMOX1 between the two groups. The differences were related to the heat shock treatment as none of the genes were expressed significantly different in SIDS at base levels at 37 8C. SOD2 and HMOX1 were up regulated in both groups, for SOD2 though the expression was lower in SIDS at all time points measured, and may be less related to heat stress. Being found dead in the prone position (a known risk factor for SIDS) was related to a lower HSPA1B up-regulation in SIDS compared to SIDS found on their side or back. The study demonstrates the potential usefulness of gene expression studies using cultured fibroblasts established from deceased individuals as a tool for molecular and pathological investigations in forensic and biomedical sciences. ß 2013 Elsevier Ireland Ltd. All rights reserved. * Corresponding author. Tel.: +45 87168319. E-mail addresses: mcr@forensic.au.dk (M.C. Rohde), tjc@hum-gen.au.dk (T.J. Corydon), Jah@forensic.au.dk (J. Hansen), cbak@ki.au.dk (C.B. Pedersen), stinne.schmidt@gmail.com (S.P. Schmidt), nig@ki.au.dk (N. Gregersen), Jb@forensic.au.dk (J. Banner). 1 Tel.: +45 87167775x2. Contents lists available at SciVerse ScienceDirect Forensic Science International jou r nal h o mep age: w ww.els evier .co m/lo c ate/fo r sc iin t 0379-0738/$ – see front matter ß 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.forsciint.2013.06.003