Biology subjects

Singhal, D.

Publications and source records attributed to Singhal, D..

7 recordsLinked to original sources

bioRxiv2025

Selective Activation of NaV1.3 Restores Lymphatic Contractility in Age and Injury

BackgroundIntrinsic lymphatic contractility is essential for tissue fluid balance, immunity and organ function, yet no FDA-approved pharmacologic treatments specifically restore lymphatic contractility. Lymph is returned to the circulation by ion channel-driven cyclic contractions of collecting lymphatic vessels. Although voltage-gated sodium (NaV) channels drive cardiomyocyte excitability, their role in lymphatic muscle cell (LMC) physiology is not well defined. We identified NaV1.3, a NaV channel historically viewed as developmentally restricted and limited in adult tissues, as unexpectedly and selectively expressed in adult lymphatic muscle but absent from heart, vascular smooth muscle, and mature brain. We tested whether selective NaV1.3 activation restores impaired lymphatic pumping in aging and radiation injury. MethodsNaV1.3 expression in LMCs was confirmed through single-cell RNA sequencing analysis and immunostaining of mouse and human lymphatic vessels. Lymphatic contractility was quantified by in vivo fluorescence lymphangiography and interstitial fluid clearance was measured with a new bioluminescence assay. NaV1.3 function was assessed in young, aged, and radiation-injured mice. NaV1.3 knockout (Scn3a-/-) mice established the requirement of NaV1.3 for basal lymphatic excitability and responsiveness to the NaV1.3-specific activator, Tf2. ResultsIn mouse and human lymphatic vessels, NaV1.3 is expressed in adult LMCs. Although dispensable for basal lymphatic contractions, NaV1.3 acted as a pharmacologically recruitable reserve that amplified contractile output. Acute NaV1.3 activation with Tf2 increased lymphangion ejection fraction and accelerated interstitial fluid clearance. Tf2 fully restored lymphatic pumping in aged mice and partially rescued radiation-induced contractile deficits. All Tf2 responses were abolished in Scn3a-/- mice, confirming NaV1.3 dependence. ConclusionsNaV1.3 is a selectively druggable ion channel in adult lymphatic muscle that can be recruited to restore lymphatic pump function across aging and injury. Targeted NaV1.3 activation provides a molecular entry point for treating diseases characterized by lymphatic pump failure, a domain with no existing pharmacologic therapies.

physiology↗

bioRxiv2025

Multidirectional alignment of collagen fibers to guide cell orientation in 3D-printed tissue

Natural tissue comprises fibrous proteins with complex fiber alignment patterns. Here, we develop a reproducible method to fabricate biomimetic scaffolds with patterned fiber alignment along multiple orientations. While extrusion-based approaches are commonly used to align fibrous polymers in a single orientation parallel to the direction of flow, we hypothesized that extrusion-based 3D printing could be utilized to achieve more complex patterns of fiber alignment. Specifically, we show control of lateral spreading of a printed filament can induce fiber alignment that is either parallel or perpendicular to the flow direction. Theoretical prediction of the printing parameters that control fiber orientation was experimentally validated using a collagen biomaterial ink. The velocity ratio of the printhead movement relative to the ink extrusion rate was found to dictate collagen fiber alignment, allowing for the informed fabrication of collagen scaffolds with prescribed patterns of fiber alignment. For example, controlled variation of the ink extrusion rate during a single print resulted in scaffolds with specified regions of both parallel and perpendicular collagen fiber alignment. Human corneal mesenchymal stromal cells seeded onto the printed scaffolds adopted a spread morphology that aligned with the underlying collagen fiber patterns. This technique worked well for filaments either printed into air or extruded within a support bath using embedded 3D printing, enabling the fabrication of 3D structures with aligned collagen fibers. Taken together, this work demonstrates a theoretical and experimental framework to achieve the reproducible fabrication of 3D printed structures with controlled collagen fiber patterns that guide cellular alignment.

bioengineering↗

bioRxiv2025

Reinforcement of Fibrillar Collagen Hydrogels with Bioorthogonal Covalent Crosslinks

Bioorthogonal covalent crosslinking stabilizes collagen type I hydrogels, improving their structural integrity for tissue engineering applications with encapsulated living cells. The chemical modification required for crosslinking, however, interferes with the fibrillar nature of the collagen, leading instead to an amorphous network without fibers. We demonstrate an approach to perform bioconjugation chemistry on collagen with controlled localization such that the modified collagen retains its ability to self-assemble into a fibrillar network, while also displaying functional groups for covalent crosslinking with bioorthogonal click chemistry. The collagen matrix is formed through a sequential crosslinking process, in which the modified collagen first physically assembles into fibers and then is covalently crosslinked. This approach preserves the fibrous architecture of the collagen, guiding the behavior of encapsulated human corneal mesenchymal stromal cells, while also reinforcing fibers through covalent crosslinks, strengthening the stability of the cell-laden collagen hydrogel against cell-induced contraction and enzymatic degradation.

bioengineering↗

bioRxiv2025

Single-nuclear transcriptomics of lymphedema-associated adipose reveals a pro-lymphangiogenic stromal cell population

Chronic lymphedema is a progressive, disfiguring disease that results from dysfunction of the lymphatic vasculature, causing distal accumulation of interstitial fluid, localized development of tissue edema, and expansion of subcutaneous adipose tissue (SAT). As the molecular mechanisms governing SAT remodeling in this disease are unclear, we performed single-nucleus RNA sequencing on paired control and affected SAT biopsies from patients with unilateral lymphedema. Lymphedema samples were characterized by expansion of SAA+ adipocytes, pro-adipogenic stem cells, and proliferation of lymphatic capillaries. A GRIA1+ lymphedema-enriched stromal cell population expressing VEGFC, ADAMTS3, and CCBE1 was identified, suggesting an enhanced axis of communication between adipose stem and progenitor cells (ASPCs) and lymphatic endothelial cells. Furthermore, lymphedema ASPC-conditioned media promoted lymphatic endothelial tube elongation and proliferation in vitro. These findings indicate a critical role for ASPCs in regulating adipocyte differentiation and lymphatic vascular remodeling in lymphedema, and provide a valuable resource for better understanding this disease.

cell biology↗

bioRxiv2024

Interpenetrating networks of fibrillar and amorphous collagen promote cell spreading and hydrogel stability

Hydrogels composed of collagen, the most abundant protein in the human body, are widely used as scaffolds for tissue engineering due to their ability to support cellular activity. However, collagen hydrogels with encapsulated cells often experience bulk contraction due to cell-generated forces, and conventional strategies to mitigate this undesired deformation often compromise either the fibrillar microstructure or cytocompatibility of the collagen. To support the spreading of encapsulated cells while preserving the structural integrity of the gels, we present an interpenetrating network (IPN) of two distinct collagen networks with different crosslinking mechanisms and microstructures. First, a physically self-assembled collagen network preserves the fibrillar microstructure and enables the spreading of encapsulated human corneal mesenchymal stromal cells. Second, an amorphous collagen network covalently crosslinked with bioorthogonal chemistry fills the voids between fibrils and stabilizes the gel against cell-induced contraction. This collagen IPN balances the biofunctionality of natural collagen with the stability of covalently crosslinked, engineered polymers. Taken together, these data represent a new avenue for maintaining both the fiber-induced spreading of cells and the structural integrity of collagen hydrogels by leveraging an IPN of fibrillar and amorphous collagen networks. Statement of significanceCollagen hydrogels are widely used as scaffolds for tissue engineering due to their support of cellular activity. However, collagen hydrogels often undergo undesired changes in size and shape due to cell-generated forces, and conventional strategies to mitigate this deformation typically compromise either the fibrillar microstructure or cytocompatibility of the collagen. In this study, we introduce an innovative interpenetrating network (IPN) that combines physically self-assembled, fibrillar collagen--ideal for promoting cell adhesion and spreading--with covalently crosslinked, amorphous collagen--ideal for enhancing bulk hydrogel stability. Our IPN design maintains the native fibrillar structure of collagen while significantly improving resistance against cell-induced contraction, providing a promising solution to enhance the performance and reliability of collagen hydrogels for tissue engineering applications. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/612534v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@80cd61org.highwire.dtl.DTLVardef@2bc8aborg.highwire.dtl.DTLVardef@838c15org.highwire.dtl.DTLVardef@61dceb_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2024

A Multiresolution Approach with Method-Informed Statistical Analysis for Quantifying Lymphatic Pumping Dynamics

Despite significant strides in lymphatic system imaging, the timely diagnosis of lymphatic disorders remains elusive. One main cause for this is the absence of standardized, quantitative methods for real-time analysis of lymphatic contractility. Here, we address this unmet need by combining near-infrared lymphangiography imaging with an innovative analytical workflow. We combined data acquisition, signal processing, and statistical analysis to integrate traditional peak and-valley with advanced wavelet time-frequency analyses. Decision theory was used to evaluate the primary drivers of attributable variance in lymphangiography measurements to generate a strategy for optimizing the number of repeat measurements needed per subject to increase measurement reliability. This approach not only offers detailed insights into lymphatic pumping behaviors across species, sex and age, but also significantly boosts the reliability of these measurements by incorporating multiple regions of interest and evaluating the lymphatic system under various gravitational loads. By addressing the critical need for improved imaging and quantification methods, our study offers a new standard approach for the imaging and analysis of lymphatic function that can improve our understanding, diagnosis, and treatment of lymphatic diseases. The results highlight the importance of comprehensive data acquisition strategies to fully capture the dynamic behavior of the lymphatic system.

physiology↗

bioRxiv2021

A discovery-based proteomics approach identifies protein disulfide isomerase (PDIA1) as a biomarker of β cell stress in type 1 diabetes

BackgroundActivation of stress pathways intrinsic to the {beta} cell are thought to both accelerate {beta} cell death and increase {beta} cell immunogenicity in type 1 diabetes (T1D). However, information on the timing and scope of these responses is lacking. MethodsTo identify temporal and disease-related changes in islet {beta} cell protein expression, data independent acquisition-mass spectrometry was performed on islets collected longitudinally from NOD mice and NOD-SCID mice rendered diabetic through T cell adoptive transfer. FindingsIn islets collected from female NOD mice at 10, 12, and 14 weeks of age, we found a time-restricted upregulation of proteins involved in the maintenance of {beta} cell function and stress mitigation, followed by loss of expression of protective proteins that heralded diabetes onset. Pathway analysis identified EIF2 signaling and the unfolded protein response, mTOR signaling, mitochondrial function, and oxidative phosphorylation as commonly modulated pathways in both diabetic NOD mice and NOD-SCID mice rendered acutely diabetic by adoptive transfer, highlighting this core set of pathways in T1D pathogenesis. In immunofluorescence validation studies, {beta} cell expression of protein disulfide isomerase A1 (PDIA1) and 14-3-3b were found to be increased during disease progression in NOD islets, while PDIA1 plasma levels were increased in pre-diabetic NOD mice and in the serum of children with recent-onset T1D compared to age and sex-matched non-diabetic controls. InterpretationWe identified a common and core set of modulated pathways across distinct mouse models of T1D and identified PDIA1 as a potential human biomarker of {beta} cell stress in T1D.

physiology↗