Xue Bo, Wen Xuejun, Kuwar Ram, Sun Dong, Zhang Ning
Institute for Engineering and Medicine, Department of Chemical and Life Science, Engineering, Virginia Commonwealth University, 601 West Main Street, Room, 403, Richmond, Virginia 23284, USA.
Institute for Engineering and Medicine, Department of Chemical and Life Science, Engineering, Virginia Commonwealth University, 601 West Main Street, Room, 403, Richmond, Virginia 23284, USA, School of Pharmaceutical Sciences, Guangzhou Medical University, Guangzhou, 511436, P. R. China, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, P. R. China.
Brain Multiphys. 2022;3. doi: 10.1016/j.brain.2022.100056. Epub 2022 Sep 14.
Recent efforts in biomaterial-assisted brain tissue engineering suggest that match of mechanical properties of biomaterials to those of native brain tissue may be crucial for brain regeneration. In particular, the mechanical properties of native brain tissue vary as a function of age. To date, detailed characterization of age-dependent viscoelastic properties of brain tissue throughout the postnatal development to adulthood is only available at sparse age points in animal studies. To fill this gap, we have characterized the linear viscoelastic properties of the cerebral cortex in rats at well-spaced ages from postnatal day 4 to 4 months old, the age range that is widely used in neural regeneration studies. Using an oscillatory rheometer, the viscoelastic properties of rat cortical slices were measured independently by storage moduli (G') and loss moduli (G″). The data demonstrated increases in both the storage moduli and the loss moduli of cortex tissue over post-natal age in rats. At all ages, the damping factor (G″/G' ratio) remained constant at low oscillatory strain frequencies (<10 rad/s) before it started to decline at medium frequency range (10-100 rad/s). Such changes were not age-dependent. The stress-relaxation response increased over post-natal age, consistent with the increasing tissue stiffness. Taken together, our study demonstrates that age is a crucial factor determining the mechanical properties of the cerebral cortex in rats during early postnatal development. This data may provide the guidelines for age-specific biomechanics study of brain tissue and help to define the mechanical properties of biomaterials for biomaterial-assisted brain tissue regeneration studies.
Studies about age-dependent viscoelastic properties of rat brain tissue throughout the postnatal development to adulthood is sparsely available. To fill up the gap of knowledge, in this study, we have characterized the age-dependent viscoelastic properties and the linear viscoelastic properties of the cerebral cortex throughout the postnatal development stage to adulthood in rats by measuring storage moduli (G'), loss moduli (G″), damping factor (G″/G' ratio) and stress-relaxation response. We have found that age is a crucial factor determining the mechanical properties of the cerebral cortex in rats during early postnatal development. The findings of this study could provide guidelines for age-specific biomechanical study of brain tissue and help to define the mechanical properties of biomaterials for biomaterial-assisted brain tissue regeneration in experimental models in rats.
生物材料辅助脑组织工程领域的近期研究表明，生物材料的机械性能与天然脑组织的机械性能相匹配对于脑再生可能至关重要。特别是，天然脑组织的机械性能会随年龄而变化。迄今为止，在动物研究中，仅在稀疏的年龄点上才有关于从出生后到成年整个发育过程中脑组织年龄依赖性粘弹性特性的详细表征。为了填补这一空白，我们对出生后第4天到4个月大（神经再生研究中广泛使用的年龄范围）的大鼠大脑皮层的线性粘弹性特性进行了表征。使用振荡流变仪，通过储能模量（G'）和损耗模量（G″）独立测量大鼠皮层切片的粘弹性特性。数据表明，大鼠出生后，皮层组织的储能模量和损耗模量均增加。在所有年龄，在低频振荡应变频率（<10弧度/秒）下，阻尼因子（G″/G'比值）保持恒定，然后在中频范围（10 - 100弧度/秒）开始下降。这种变化与年龄无关。应力松弛响应在出生后随年龄增加，这与组织硬度增加一致。综上所述，我们的研究表明年龄是决定大鼠出生后早期发育过程中大脑皮层机械性能的关键因素。这些数据可为脑组织特定年龄的生物力学研究提供指导，并有助于确定用于生物材料辅助脑组织再生研究的生物材料的机械性能。
关于大鼠从出生后到成年整个发育过程中脑组织年龄依赖性粘弹性特性的研究很少。为了填补知识空白，在本研究中，我们通过测量储能模量（G'）、损耗模量（G″）、阻尼因子（G″/G'比值）和应力松弛响应，对大鼠从出生后发育阶段到成年期大脑皮层的年龄依赖性粘弹性特性和线性粘弹性特性进行了表征。我们发现年龄是决定大鼠出生后早期发育过程中大脑皮层机械性能的关键因素。本研究结果可为脑组织特定年龄的生物力学研究提供指导，并有助于确定用于大鼠实验模型中生物材料辅助脑组织再生的生物材料的机械性能。
