A novel mouse model of obstructive sleep apnea by bulking agent-induced tongue enlargement results in left ventricular contractile dysfunction

Abstract

Aims Obstructive sleep apnea (OSA) is a widespread disease with high global socio-economic impact. However, detailed pathomechanisms are still unclear, partly because current animal models of OSA do not simulate spontaneous airway obstruction. We tested whether polytetrafluoroethylene (PTFE) injection into the tongue induces spontaneous obstructive apneas. Methods and results PTFE (100 μl) was injected into the tongue of 31 male C57BL/6 mice and 28 mice were used as control. Spontaneous apneas and inspiratory flow limitations were recorded by whole-body plethysmography and mRNA expression of the hypoxia marker KDM6A was quantified by qPCR. Left ventricular function was assessed by echocardiography and ventricular CaMKII expression was measured by Western blotting. After PTFE injection, mice showed features of OSA such as significantly increased tongue diameters that were associated with significantly and sustained increased frequencies of inspiratory flow limitations and apneas. Decreased KDM6A mRNA levels indicated chronic hypoxemia. 8 weeks after surgery, PTFE-treated mice showed a significantly reduced left ventricular ejection fraction. Moreover, the severity of diastolic dysfunction (measured as E/e’) correlated significantly with the frequency of apneas. Accordingly, CaMKII expression was significantly increased in PTFE mice and correlated significantly with the frequency of apneas. Conclusions We describe here the first mouse model of spontaneous inspiratory flow limitations, obstructive apneas, and hypoxia by tongue enlargement due to PTFE injection. These mice develop systolic and diastolic dysfunction and increased CaMKII expression. This mouse model offers great opportunities to investigate the effects of obstructive apneas.

Advances in animal models of obstructive sleep apnea

“…Polysomnography performed by the above method can clearly distinguish sleep and wakefulness, such as rapid eye movement (REM), non-rapid eye movement (NREM), wakefulness and arousal. Combined with EMG information and respiratory amplitude and rhythm information obtained by the whole-body plethysmograph, it can highly simulate the data obtained by human PSG (34,(44)(45)(46), which basically satisfies the judgment and analysis of OSA-related pathophysiological processes in small animals. This technique can be used to image the upper airway in small animals during supine breathing, which is closer to the natural sleeping position and can avoid breathing difficulties caused by impaired diaphragm function in anesthetized animals.…”

“…It is a feasible idea to establish an OSA animal model by injecting dilatants (such as polytetrafluoroethylene and hydrophilic polyacrylamide gel) into soft tissues of the upper airway, such as the tongue or the soft palate, which can cause persistent swelling and narrowing of the upper airway soft tissues (32)(33)(34)(35)(36)(37). Polytetrafluoroethylene (PTFE) is an inert swelling agent used in the treatment of vesicoureteral reflux.…”

“…After injection, there was no significant increase in body weight of the mice, but some typical signs of OSA appeared, such as upper airway narrowing caused by significantly increased tongue volume. The frequency of inspiratory effort and apnea increased significantly in mice (34). Similarly, Lu et al injected 2 ml hydrophilic polyacrylamide gel into the submucosal muscular layer of the soft palate 1.5 cm from the posterior edge of the hard palate in New Zealand rabbits.…”

The Effect of Gender and Sex Hormones on Cardiovascular Disease, Heart Failure, Diabetes, and Atrial Fibrillation in Sleep Apnea

“…Knowledge on this topic is limited, and further studies investigating the underlying mechanisms are needed. Therefore, our group has recently published a novel mouse model of SDB by bulking agent-induced tongue enlargement ( Lebek et al, 2020a ). These mice not only show an increased frequency of spontaneous apneas and inspiratory flow limitations but also diastolic dysfunction, which offers a great opportunity for future investigation of gender-related effects in HFpEF and SDB.…”

An Inexpensive Open-Source Chamber for Controlled Hypoxia/Hyperoxia Exposure

“…Chronic and acute hypoxia exposure has been used in the past to study many different diseases, including hypoxic-ischemic encephalopathy (HIE) ( Lacaille et al, 2019 ), intermittent sleep apnea ( Toth and Bhargava, 2013 ; Arias-Cavieres et al, 2020 ; Lebek et al, 2020 ; Arias-Cavieres et al, 2021 ), ischemic stroke ( Tsuji et al, 2013 ) and epilepsy ( Toth and Bhargava, 2013 ; Lebek et al, 2020 ). Many studies use plethysmography (whole body and head-out) to assess short-term hypoxia and acquire other physiological data ( Toth and Bhargava, 2013 ; Lebek et al, 2020 ). However, commercial plethysmography systems are comparatively expensive, typically require proprietary software for recording and monitoring pressure, volume, and flow, and may be difficult to set up without extensive technical support.…”