Kiley Meghan E, Sové Richard J, Smith Reilly H, Wells Brenda N, Russell McEvoy Gaylene M, Fraser Graham M
Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada.
Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, United States.
Front Physiol. 2025 Jul 9;16:1575776. doi: 10.3389/fphys.2025.1575776. eCollection 2025.
To develop and validate thin-film micro-outlet devices to study microvascular blood flow responses to localized changes in skeletal muscle oxygen concentration ([O]).
30 male Sprague-Dawley rats (159-194 g) were anesthetized and instrumented to maintain cardiovascular state. The extensor digitorum longus (EDL) muscle was dissected, isolated, and reflected over a gas exchange chamber (GEC) mounted in the stage of an inverted microscope. The GEC and EDL were coupled via a composite, gas permeable membrane, and a gas impermeable film fabricated with laser machined micro-outlets of specific diameters (200, 400, 600, and 1,000 μm). [O] in the EDL was dynamically manipulated with step-wise oscillations between 7% (1 min) → 12% (1 min) → 2% (1 min) → 7% (1 min), and step challenges from 7% (1 min) → 2% or 12% (2 min), while recording intravital video for capillary RBC oxygen saturation (SO) and hemodynamic measurements. Oxygen diffusion between tissue and micro-outlet devices was modelled using a finite element mass transport model to further validate experimental results.
[O] oscillations imposed on capillaries directly overlying 400 μm micro-outlets caused significant changes in RBC SO at 12% and 2% [O], compared to 7% [O] (p < 0.0001). [O] oscillations caused significant changes in capillary RBC supply rate (SR) at 2% [O] versus 7%, and were significantly different at 2% compared to 12% [O] (p < 0.0014). Similarly, [O] challenges imposed on capillaries overlying 200 μm micro-outlets also caused significant changes in RBC SO at 2% [O], compared to 7% [O] (p < 0.0001), and caused significant changes in SR at 2% [O] compared to 7% (p < 0.0001).
Our composite thin-film devices were fabricated and validated to spatially confine oxygen perturbations to capillaries using micro-outlets of varying diameters. These results demonstrate that our devices can manipulate capillary SO and alter capillary RBC SR in vessels directly overlying the micro-outlet without affecting capillary SO at a distance from the outlets. Our novel composite thin-film micro-outlet devices demonstrate that capillary blood flow responses can be provoked by manipulating [O] in tissue regions as small as ∼200 μm in diameter.
开发并验证薄膜微出口装置，以研究微血管血流对骨骼肌氧浓度（[O]）局部变化的反应。
对30只雄性Sprague-Dawley大鼠（159 - 194克）进行麻醉并安装仪器以维持心血管状态。分离出趾长伸肌（EDL），将其隔离并翻转至安装在倒置显微镜载物台上的气体交换室（GEC）上方。GEC和EDL通过复合透气膜以及用特定直径（200、400、600和1000微米）的激光加工微出口制成的不透气薄膜相连。EDL中的[O]通过在7%（1分钟）→12%（1分钟）→2%（1分钟）→7%（1分钟）之间的逐步振荡以及从7%（1分钟）→2%或12%（2分钟）的阶跃挑战进行动态调节，同时记录活体视频以测量毛细血管红细胞氧饱和度（SO）和血流动力学。使用有限元质量传输模型对组织与微出口装置之间的氧扩散进行建模，以进一步验证实验结果。
与7%[O]相比，施加在直接覆盖400微米微出口上方毛细血管上的[O]振荡在12%和2%[O]时导致红细胞SO发生显著变化（p < 0.0001）。[O]振荡在2%[O]与7%时导致毛细血管红细胞供应率（SR）发生显著变化，且在2%与12%[O]时差异显著（p < 0.0014）。同样，施加在覆盖200微米微出口上方毛细血管上的[O]挑战在2%[O]时与7%[O]相比也导致红细胞SO发生显著变化（p < 0.0001），并且在2%[O]与7%时导致SR发生显著变化（p < 0.0001）。
我们制造并验证了复合薄膜装置，通过不同直径的微出口将氧扰动在空间上限制于毛细血管。这些结果表明，我们的装置能够操纵毛细血管SO并改变直接覆盖微出口上方血管中的毛细血管红细胞SR，而不影响距出口一定距离处的毛细血管SO。我们新型的复合薄膜微出口装置表明，通过操纵直径小至约200微米的组织区域中的[O]，可以激发毛细血管血流反应。
