Tanaka Yohei, Matsuo Kiyoshi, Yuzuriha Shunsuke
Department of Plastic and Reconstructive Surgery, Shinshu University School of Medicine, Matsumoto, Nagano 390-8621, Japan.
Eplasty. 2010 May 28;10:e40.
Infrared (IR) irradiation specialized with wavelengths and contact cooling increases the amount of water in the dermis to protect the subcutaneous tissues against IR damage; thus, it is applied to smooth forehead wrinkles. However, this treatment consistently induces brow ptosis. Therefore, we investigated whether IR irradiation induces muscle thinning.
Rat central back tissues were irradiated with the specialized IR device. Histological evaluation was performed on sagittal slices that included skin, panniculus carnosus, and deep muscles.
Significant reductions in panniculus carnosus thickness were observed between controls and irradiated tissues at postirradiation day 30 (P30), P60, P90, and P180; however, no reduction was observed in nonirradiated controls from days 0 to 180. No significant changes were observed in the trunk muscle over time. From day 0, dermal thickness was significantly reduced at P90 and P180; however, no difference was observed between P180 and nonirradiated controls at day 180. DNA degradation consistent with apoptosis was detected in the panniculus carnosus at P7 and P30.
We found that IR irradiation induced long-lasting superficial muscle thinning, probably by a kind of apoptosis. The panniculus carnosus is equivalent to the superficial facial muscles of humans; thus, the changes observed here reflected those in the frontalis muscle that resulted in brow ptosis. The IR device used in this study simulated solar IR radiation that reaches the skin. Therefore, exposure to solar IR radiation may cause thinning of the superficial facial muscles. This should be prevented with sunscreen that protects against IR radiation.
特定波长的红外线（IR）照射并结合接触式冷却可增加真皮层的含水量，从而保护皮下组织免受IR损伤；因此，该方法被用于改善前额皱纹。然而，这种治疗方法始终会导致眉下垂。因此，我们研究了IR照射是否会导致肌肉变薄。
使用特定的IR设备对大鼠背部中央组织进行照射。对包含皮肤、浅筋膜和深层肌肉的矢状切片进行组织学评估。
在照射后第30天（P30）、P60、P90和P180时，观察到照射组与对照组相比，浅筋膜厚度显著降低；然而，在第0天至180天期间，未照射的对照组未观察到厚度降低。随着时间的推移，躯干肌肉未观察到显著变化。从第0天开始，在P90和P180时真皮厚度显著降低；然而，在第180天，P180组与未照射对照组之间未观察到差异。在P7和P30时，在浅筋膜中检测到与细胞凋亡一致的DNA降解。
我们发现IR照射会导致长期的浅表肌肉变薄，可能是通过一种细胞凋亡机制。浅筋膜相当于人类的面部浅表肌肉；因此，此处观察到的变化反映了额肌的变化，进而导致眉下垂。本研究中使用的IR设备模拟了到达皮肤的太阳IR辐射。因此，暴露于太阳IR辐射可能会导致面部浅表肌肉变薄。应使用能防IR辐射的防晒霜来预防这种情况。
