Biology subjects

Soundararajan, A.

Publications and source records attributed to Soundararajan, A..

4 recordsLinked to original sources

bioRxiv2025

Multiscale 3D whole joint cellular and molecular mapping dissects the relationship between structure and pain

Understanding musculoskeletal joints from a 3D multiscale perspective, from molecular to anatomical levels, is essential for resolving the confounding relationships between structure and pain, elucidating the intricate mechanisms regulating joint health and diseases, and developing new treatment strategies. Here, we introduce a musculoskeletal joint immunostaining and clearing (MUSIC) method specifically designed to overcome key challenges of immunostaining and optical clearing of intact joints. Coupled with large-field light sheet microscopy, our approach enables 3D high-resolution, microscale neurovascular mapping within the context of whole-joint anatomy without the need for image coregistration across various joints, including temporomandibular joints, knees, and spines, and multiple species, including mouse, rat, and pig. Our findings reveal 3D heterogeneous distributions of neurovascular networks and previously uncharacterized neurovascular pathways within joints. Using the proteoglycan 4 knockout (Prg4-/-) mouse model of joint degeneration, we identified significant alterations in joint-wide neurovascular architecture, highlighting neurovascular changes along degenerative processes. Furthermore, in a traumatic joint injury mouse model, we observed long-lasting pain behavior and a time-course 3D neurovascular remodeling preceding detectable joint morphological change, bridging microscale alterations with potential pain mechanisms. This platform offers a powerful tool for multiscale 3D analysis, enabling new insights into joint pathophysiology and intricate interplay among joint tissues.

bioengineering↗

bioRxiv2025

Loss of Cathepsin K impairs collagen biogenesis and enhances actin polymerization in trabecular meshwork

Trabecular meshwork (TM) dysfunction and extracellular matrix (ECM) dysregulation contribute to increased intraocular pressure (IOP) in primary open-angle glaucoma (POAG). Earlier, we provide a proof-of-concept study identifying the regulation and the role of Cathepsin K (CTSK), a potent collagenase, in ECM homeostasis, actin bundling, and IOP regulation. Better understanding of the loss of CTSK function in TM remains unclear. Using siRNA-mediated knockdown of CTSK (siCTSK) in human TM cells, this study investigated the role of CTSK in actin and ECM homeostasis using an unbiased proteomics approach. Loss of CTSK significantly disrupted collagen biogenesis and ECM homeostasis. CTSK depletion also increased intracellular calcium levels, with proteomics data suggesting possible involvement of calcium-regulatory proteins. Additionally, PRKD1 activation enhanced actin polymerization through the LIMK1/SSH1/cofilin pathway, promoting focal adhesion maturation. Despite increased apoptotic markers (CASP3, CASP7, TRADD, PPM1F), caspase 3/7 activation was not induced, suggesting apoptosis-independent cellular remodeling. Notably, RhoQ and myosin motor proteins were significantly downregulated, indicating altered mechanotransduction in TM cells. These findings highlight the role of CTSK in maintaining ECM homeostasis, calcium signaling, and cytoskeletal regulation in TM. Its depletion induces actin polymerization, which may influence aqueous humor outflow. Targeting CTSK-related pathways may provide novel therapeutic strategies for regulating IOP and preventing glaucoma progression.

cell biology↗

bioRxiv2024

Proteomic analysis uncovers clusterin-mediated disruption of actin-based contractile machinery in the trabecular meshwork to lower intraocular pressure

Glaucoma, a major cause of blindness, is characterized by elevated intraocular pressure (IOP) due to improper drainage of aqueous humor via the trabecular meshwork (TM) outflow pathway. Our recent work identified that loss of clusterin resulted in elevated IOP. This study delves deeper to elucidate the role of clusterin in IOP regulation. Employing an ex vivo human anterior segment perfusion model, we established that constitutive expression and secretion as well as exogenous addition of clusterin can significantly lower IOP. Interestingly, clusterin significantly lowered transforming growth factor {beta}2 (TGF{beta}2)-induced IOP elevation. This effect was linked to the suppression of extracellular matrix (ECM) deposition and, highlighting the crucial role of clusterin in maintaining ECM equilibrium. A comprehensive global proteomic approach revealed the broad impact of clusterin on TM cell structure and function by identifying alterations in protein expression related to cytoskeletal organization, protein processing, and cellular mechanics, following clusterin induction. These findings underscore the beneficial modulation of TM cell structure and functionality by clusterin. Specifically, clusterin influences the actin-cytoskeleton and focal adhesion dynamics, which are instrumental in cell contractility and adhesion processes. Additionally, it suppresses the activity of proteins critical in TGF{beta}2, G-protein, and JAK-STAT signaling pathways, which are vital for the regulation of ocular pressure. By delineating these targeted effects of clusterin within the TM outflow pathway, our findings pave the way for novel treatment strategies aimed at mitigating the progression of ocular hypertension and glaucoma through targeted molecular interventions.

cell biology↗

bioRxiv2023

Targeting sterol regulatory element binding proteins (SREBPs) activation lowers intraocular pressure by halting its mechanosensing function in the trabecular meshwork

Trabecular meshwork (TM) cells are highly contractile and mechanosensitive to aid in maintaining intraocular pressure (IOP) homeostasis. Lipids are attributed to modulating TM contractility with poor mechanistic understanding. In this study using human TM cells, we identify the mechanosensing role of the transcription factors sterol regulatory element binding proteins (SREBPs) involved in lipogenesis. By constitutively activating SREBPs and pharmacologically inactivating SREBPs, we have mechanistically deciphered the attributes of SREBPs in regulating the contractile properties of TM. The pharmacological inhibition of SREBPs by fatostatin and molecular inactivation of SREBPs ex vivo and in vivo respectively results in significant IOP lowering. As a proof of concept, fatostatin significantly decreased the SREBPs responsive genes and enzymes involved in lipogenic pathways as well as the levels of the phospholipid, cholesterol, and triglyceride. Further, we show that fatostatin mitigated actin polymerization machinery and stabilization, and decreased ECM synthesis and secretion. We thus postulate that lowering lipogenesis in the TM outflow pathway can hold the key to lowering IOP by modifying the TM biomechanics. SynopsisIn this study, we show the role of lipogenic transcription factors sterol regulatory element binding proteins (SREBPs) in the regulation of intraocular pressure (IOP). (Synopsis Figure - Created using Biorender.com) O_LISREBPs are involved in the sensing of changes in mechanical stress on the trabecular meshwork (TM). SREBPs aid in transducing the mechanical signals to induce actin polymerization and filopodia/lamellipodia formation. C_LIO_LISREBPs inactivation lowered genes and enzymes involved in lipogenesis and modified lipid levels in TM. C_LIO_LISREBPs activity is a critical regulator of ECM engagement to the matrix sites. C_LIO_LIInactivation of SCAP-SREBP pathway lowered IOP via actin relaxation and decreasing ECM production and deposition in TM outflow pathway signifying a novel relationship between SREBP activation status and achieving IOP homeostasis. C_LI

cell biology↗