The meninges act as a key mechano-biological interface—dissipating external forces, supporting neuroimmune homeostasis, and dynamically regulating the brain microenvironment—yet they remain comparatively underexplored despite their importance. Within the three-layer meningeal system, the pia–arachnoid complex (PAC, i.e., leptomeninges) interfaces closely with the subarachnoid space that contains cerebrospinal fluid, vasculature, and immune cells, making it central to both mechanical safeguarding and broader physiological/immune functions. With the growing burden of traumatic brain injury (TBI), understanding force transmission across the brain–skull interface is increasingly urgent; meanwhile, finite element (FE) head models have advanced TBI mechanistic insights, but their predictive accuracy depends strongly on high-fidelity material data. Existing experimental characterization has focused largely on the dura (easier to isolate), leaving limited systematic mechanical datasets for the pia, arachnoid, and PAC. “Although prior anatomical/computational evidence suggests regional PAC heterogeneity—and incorporating multi-scale regional variability can improve hemorrhage prediction—systematic region-by-region experimental analysis is still underdeveloped, cerebellar mechanics are often overlooked, and porcine tissue is attractive due to its anatomical homology with human brain regions.” said the author Chenyi Lei, a researcher at Tsinghua University, “Accordingly,we measure macro- and micro-mechanical properties of porcine PAC across multiple anatomical regions using rheological shear tests and AFM indentation, and links regional differences to collagen/elastin-related biochemical distributions via two-photon imaging and RNA-seq, yielding a regional mechanical difference map.”
This study investigates the porcine pia–arachnoid complex (PAC, i.e., leptomeninges) using a region-by-region, multi-scale design. PAC tissue was dissected after dura removal and partitioned into major anatomical regions to enable systematic comparison across locations. The experimental strategy couples bulk and local mechanics with compositional and molecular readouts. At the tissue (macroscale) level, the authors used oscillatory rheology to quantify viscoelastic behavior across regions, reporting standard parameters such as storage modulus (G′), loss modulus (G″), and tan δ under physiologically relevant testing conditions. At the microscale, they performed atomic force microscopy (AFM) indentation and force-relaxation measurements to capture local elastic and time-dependent responses within PAC; the resulting force curves were analyzed with established contact/viscoelastic models and appropriate statistical comparisons between regions. To connect mechanical variation with tissue composition, the work further applies two-photon microscopy to image collagen architecture via second-harmonic generation (SHG) and elastin-related signal via autofluorescence, followed by quantitative image analysis. Finally, region-specific RNA sequencing and downstream functional enrichment (e.g., GO analysis with multiple-testing correction) were conducted to provide a molecular-level view aligned with the observed regional sampling scheme, supporting integrated interpretation of mechanical heterogeneity without relying on outcome-focused reporting.
The main result of the paper is that porcine leptomeninges (the pia–arachnoid complex, PAC) exhibit clear regional mechanical heterogeneity, dominated by a distinct cerebellar signature. At the bulk scale, the authors first verify that viscoelastic measures remain stable over the relevant testing window, supporting reliable comparisons; across amplitude-based evaluations and small-strain summaries, cerebellar PAC shows significantly higher storage and loss moduli than PAC from other lobes. In the same dataset, cerebellar PAC is also significantly thicker (as inferred from rheometer gap measurements), while differences among the remaining lobes are generally not statistically pronounced. At the microscale, AFM indentation reveals higher local stiffness in cerebellar PAC, with Young’s modulus on the order of roughly twice that measured in other regions; relaxation analyses further show larger characteristic time constants in cerebellar samples, indicating slower viscoelastic relaxation. The authors also note strong local heterogeneity near vasculature (stiffer and more irregular), and therefore emphasize region-to-region comparisons away from vessel-adjacent areas. To link mechanics with composition, two-photon quantification demonstrates that cerebellar PAC contains significantly higher collagen-related SHG signal and higher elastin-associated autofluorescence than other lobes, consistent with its greater stiffness and thickness. Finally, transcriptomic analyses support this interpretation: cerebellar PAC shows enriched functional categories and upregulation of collagen genes (e.g., COL1A1/COL1A2) alongside increased expression of multiple MMPs and TIMPs, pointing to more active extracellular-matrix production and remodeling in the cerebellar region.
In conclusion, this paper synthesizes a multi-scale experimental characterization of regional mechanical variability in the porcine pia–arachnoid complex (PAC) and links the observed mechanical phenotypes to plausible structural/biochemical correlates, providing material-property evidence intended to strengthen PAC parameterization in anatomically relevant large-animal models. The principal conclusion is a coherent cerebellar “stiffer” signature: cerebellar PAC exhibits higher mechanical measures than other lobes at both bulk and local scales, consistent with regional differences in supportive constituents such as collagen- and elastin-related architecture, and discussed in relation to broader anatomical/functional context associated with cerebrospinal-fluid flow. The closing discussion consolidates methodological constraints: PAC’s two-layer membrane organization and embedded vasculature complicate in vivo or fully physiological mechanical assessment and layer separation, while practical limitations (e.g., achieving uniform staining in thick tissue and limited integrated mechanics–imaging capability) restrict deeper mechanistic linkage. “Future development directions should include establishing human PAC benchmarks, refining preparation and measurement workflows to better preserve physiological conditions, and integrating these datasets with computational pipelines (e.g., finite-element modeling) to improve TBI stress–strain and hemorrhage-risk prediction; in parallel, advancing multiscale anisotropy characterization, probing mechanics–immunity coupling mechanisms, and extending toward translational applications such as brain–computer interface materials and wearable brain devices.” said Chenyi Lei.
Authors of the paper include Chenyi Lei, Wenyuan Shao, Xi Yuan, Lulu Xu, Alexander Tuzikov, Ravshan Sabirov, Semih Calamak, H. Atakan Varol, Naila Sajjad, Ijaz Gul, and Peiwu Qin.
This work was supported by the National Natural Science Foundation of China (32350410397); the Shenzhen Medical Research Funds (D2301002); the Science, Technology, Innovation Commission of Shenzhen Municipality (JCYJ20240813112016022, JCYJ20220530143014032, JCYJ20230807113017035, and KCXFZ20211020163813019); the Tsinghua Shenzhen International Graduate School Cross-disciplinary Research and Innovation Fund Research Plan (JC2022009); and the Bureau of Planning, Land and Resources of Shenzhen Municipality (2022) (207).
The paper, “Regional Variations in Mechanical Properties of Porcine Leptomeninges” was published in the journal Cyborg and Bionic Systems on Dec. 16, 2025, at DOI: 10.34133/cbsystems.0462.
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