Engineered Nanotopographies Induce Transient Openings in the Nuclear Membrane

 

Background

Recent technological advancements have enabled the creation of diverse nanotopographical structures that mimic naturally occurring living particles such as viral spike proteins. Like these natural particles, engineered materials can respond to physical interactions with cells by eliciting specific signaling pathways and cell behaviors. Previously reported responses included cytoskeletal remodeling, plasma membrane curvature modulation, penetration, and endocytosis, which can enhance functions like cellular uptake during drug delivery. However, the effects of nanomaterial interactions with other cellular organelles remain poorly understood. To address this gap, the authors of this preprint examine nuclear responses as well as changes in its morphology and behavior elicited by physical interactions between engineered materials like nanopillars and different cell types. This may offer valuable insights for the design of targeted clinical interventions.

Key findings

Nanoscale curvature induced by nanotopographies triggers nuclear membrane breaches across different cell types

Previous studies show that nanostructures in contact with a cell can alter nuclear membrane curvature: both positive and negative curvatures and cause nuclear rupture. The authors therefore wondered if the deformed curvature induced by nanopillars could breach the nuclear membrane. To verify this, they stained cells on engineered nanopillars with a nuclear rupture reporter, known to be present in the nucleus of a normal cell and to diffuse to the cytoplasm upon a breach in the nucleus. Testing cells with diverse structural and morphological features, they found that the nuclear rupture reporter was detectable in the cytoplasm of cells sitting on nanopillars but not those on flat substrates. This confirmed the creation of nuclear membrane openings by the nanopillar substrates. Interestingly, the authors could also observe an opposite diffusion process in cells sitting on nanopillars: from the cytoplasm to the nucleus. These observations led to the conclusion that nanopillar-cell interactions can facilitate bidirectional movement of molecules between cytoplasm and nucleus by inducing nuclear breaches.

Duration of nanopillar-cell interaction and nanopillar geometry control nuclear membrane breaches

Next, the authors speculated that the nuclear breaches might be dependent on the time of contact between the nanopillars and the cells. They found that the observed nuclear openings indeed depend on the duration of this interaction. They also revealed that while the nucleus was gradually deformed (by increasing its curvature within 1 to 8 hours), it was only during the initial 1 to 5 hours that the nuclear breaches most evidently increased. Quantification of other morphological features, such as cell and nuclear circularity and spreading area under induced breaching conditions, showed that rather than cell dimensions, nuclear dimensions like spreading, and deformation are key drivers of nuclear membrane breaching on nanopillars. In addition, nanopillars of small size increased nuclear curvature, which was critical for nuclear membrane breaching phenomena.

Induced nuclear membrane openings are transient and repairable

Live imaging experiments demonstrated that the nuclear membrane, temporarily breached by the engineered nanotopographies enabling molecular exchange with the cytoplasm, is capable of self-repair. They confirmed this by expressing a nuclear rupture reporter: its cytoplasmic to nuclear ratio gradually decreased within 1.5 hours, indicating that the repair mechanism might be activated approximately within that period post-breaching. Further investigation uncovered the recruitment of a tissue-resident repair machinery, ESCRT-III, to the nuclear membrane opening sites which aided the repair process.

Why I highlight this preprint

The author’s straightforward, yet insightful approach to investigate how diverse shape and sizes of nanomaterials can affect nuclear responses is noteworthy. Evidently, nuclear membrane pores play a key role in facilitating molecular exchanges between the cytoplasm and nucleus, influencing signaling cascades crucial for cell survival and growth. Looking at the broader picture, these pathways ultimately regulate tissue development. Therefore, having control over the nuclear pores or openings -allowing more molecular exchanges and interactions without causing damage to the cells – may possibly enhance cellular mechanisms as desired. Especially the results that showed how engineered nanomaterials can create temporary openings in the nucleus, which can also be partially reversed, caught my attention. By employing a simple trick to glimpse into the nucleus and allowing exchange of essential molecular information, this study presents a promising and effective strategy for drug delivery and other targeted therapies that rely on controlled interactions while minimizing damage.

 

Questions for the authors

• During the transient openings in the nuclear membrane, do the authors believe that there might be an uncontrolled exchange of signaling molecules between the cytoplasm and nucleus, which might affect other active cellular processes? In that case, is there any way to maintain a proper balance of such molecular exchanges during the transient breaching period?
• Is there a possibility that nanotopographic materials of diverse geometry can elicit undesired host immune response whenever applied for therapeutic purposes?

 

References

Hansel, C.S. et al. (2019) ‘Nanoneedle-mediated stimulation of cell mechanotransduction machinery’, ACS Nano, 13(3), pp. 2913–2926. doi:10.1021/acsnano.8b06998.

Sarikhani, E. et al. (2024) ‘Engineering the cellular microenvironment: Integrating three-dimensional nontopographical and two-dimensional biochemical cues for precise control of cellular behavior’, ACS Nano, 18(29), pp. 19064–19076. doi:10.1021/acsnano.4c03743.

Chiappini, C. et al. (2021) ‘Tutorial: Using nanoneedles for Intracellular Delivery’, Nature Protocols, 16(10), pp. 4539–4563. doi:10.1038/s41596-021-00600-7.

Tags: membrane opening, nuclear sensing

doi: https://doi.org/10.1242/prelights.38439

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