Primary cilium-mediated mechanotransduction in cartilage chondrocytes

Structure, function, and research progress of primary cilia in reproductive physiology and reproductive diseases

Primary cilia, serving as the central hub for cellular signal transduction, possess the remarkable ability to translate diverse extracellular signals, both chemical and mechanical, into intracellular responses. Their ubiquitous presence in the reproductive system underscores their pivotal roles in various cellular processes including development, differentiation, and migration. Emerging evidence suggests primary cilia as key players in reproductive physiology and associated pathologies. Notably, primary cilia have been identified in granulosa cells within mouse ovaries and uterine stromal cells, and perturbations in their structure and function have been implicated in a spectrum of reproductive dysfunctions and ciliary-related diseases. Furthermore, disruptions in primary cilia-mediated signal transduction pathways under pathological conditions exacerbate the onset and progression of reproductive disorders. This review provides a comprehensive overview of current research progress on primary cilia and their associated signaling pathways in reproductive physiology and diseases, with the aim of furnishing theoretical groundwork for the prevention and management of primary cilia-related structural and functional abnormalities contributing to reproductive system pathologies.

[Piezo1 Mediates the Regulation of Substrate Stiffness on Primary Cilia in Chondrocytes]

Objective

To investigate how substrate stiffness regulates the morphology of primary cilia in chondrocytes and to illustrate how Piezo1 mediates the morphology regulation of primary cilia by substrate stiffness.

Methods

Polydimethylsiloxane (PDMS) curing agent and the main agent (Dow Corning, Beijing, China) were mixed at the ratio of 1∶10 (stiff), 1∶50 (medium stiffness), and 1∶70 (soft), respectively, to prepare substrate films with the thickness of 1 mm at different levels of stiffness, including stiff substrate of (2.21±0.12) MPa, medium-stiffness substrate of (54.47±6.06) kPa, and soft substrate of (2.13±0.10) kPa. Chondrocytes were cultured with the substrates of three different levels of stiffness. Then, the cells were treated with Tubastatin A (Tub A) to inhibit histone deacetylase 6 (HDAC6), Piezo1 activator Yoda1, and inhibitor GsMTx4, respectively. The effects of HDAC6, Yoda1, and GsMTx4 on chondrocyte morphology and the length of primary cilia were analyzed through immunofluorescence staining.

Results

The stiff substrate increased the spread area of the chondrocytes. Immunofluorescence assays showed that the cytoskeleton and the nuclear area of the cells on the stiff substrate were significantly increased (P<0.05) and the primary cilia were significantly extended (P<0.05) compared with those on the medium-stiffness and soft substrates. However, the presence rate of primary cilia was not affected. The HDAC6 activity of chondrocytes increased with the decrease in substrate stiffness. When the activity of HDAC6 was inhibited, the cytoskeletal area, the nuclei area, and the primary cilium length were increased more significantly on the stiff substrate (P<0.05). Further testing showed that Piezo1 activator and inhibitor could regulate the activity of HDAC6 in chondrocytes, and that the length of primary cilia was significantly increased after treatment with the activator Yoda1 (P<0.05). On the other hand, the length of primary cilia was significantly shortened on the stiff substrate after treatment with the inhibitor GsMTx4 (P<0.05).

Conclusion

Both substrate stiffness and Piezo1 may affect the morphology of chondrocyte primary cilia by regulating HDAC6 activity.