Regulation of Trabecular Meshwork Contractility

Stumpff, Friederike; Wiederholt, Michael

doi:10.1159/000027471

Cited by 58 publications

(58 citation statements)

References 73 publications

(134 reference statements)

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“…5,[7][8][9][10][11][12] The structure of the TM varies from slender branching beams in the uveal meshwork, to perforated sheets in the corneoscleral meshwork, to a fine fiber network in the juxtacanalicular meshwork (JCT). 13,14 This structure, which can be imaged by autofluorescence (AF) microscopy, 13,15 represents the TM's extracellular matrix (ECM) that supports cells and the function of the aqueous drainage tract.…”

Section: Discussionmentioning

confidence: 99%

Analyzing Live Cellularity in the Human Trabecular Meshwork

González

Tan

2013

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. To directly visualize the live cellularity of the intact human trabecular meshwork (TM) and quantitatively analyze tissue viability in situ.METHODS. Human donor corneoscleral rims were sectioned immediately before intravital dye incubation to label nuclei (Hoechst 33342 & propidium iodide [PI]); cytosol (CellTracker Red CMTPX, calcein AM); and membranes (octadecyl rhodamine B chloride [R18]), followed by 2-photon microscopy. Viability was assessed by counting cells in tissue colabeled with PI and Calcein AM. Some tissues were exposed to Triton X-100 to establish dead tissue controls. Fresh postmortem eyes (within 48 hours of death) represented viable tissue controls. Tissues with live cellularity exceeding 50% were considered viable.RESULTS. Hoechst nuclear labeling was seen throughout the TM, among the autofluorescent beams, plate-like structures and fibers of the meshwork, and within tissue gaps and pores. CellTracker-labeled live cells were attached to autofluorescent TM structures and filled corneoscleral meshwork pores. R18-labeling revealed the membrane distributions of interconnected cells. Calcein-positive cells were visible in all TM layers, but not in tissues killed by Triton X-100 exposure. Dead control tissues showed PI staining in the absence of Calcein-positive cells. Two-thirds of the standard donor tissues we received possessed viable TM, having a mean live cellularity of 71% (n ¼ 14), comparable with freshly postmortem eyes (76%; n ¼ 2). Mean live cellularity of nonviable tissue was 11% (n ¼ 7). CONCLUSIONS.We have visualized and quantified the live cellularity of the TM in situ. This provided unique perspectives of live cell-matrix organization and a means of assaying tissue viability. (Invest Ophthalmol Vis Sci.

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Section: Discussionmentioning

confidence: 99%

Analyzing Live Cellularity in the Human Trabecular Meshwork

González

Tan

2013

Invest. Ophthalmol. Vis. Sci.

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“…TM cells that cover the beams display an endothelial cell-like morphology and lining property but are of a unique cell type (1,2). They are avid phagocytes (3), possess contractile and migratory apparatus (4,5), have the capacity to produce ECM elements (2), and can transduce signals upon attachment to the ECM (6).…”

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confidence: 99%

Rho GTPase and cAMP/Protein Kinase A Signaling Mediates Myocilin-induced Alterations in Cultured Human Trabecular Meshwork Cells

Shen

Koga

Park

et al. 2008

Journal of Biological Chemistry

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Myocilin is a gene linked to the most common form of glaucoma, a major blinding disease. The trabecular meshwork (TM), a specialized eye tissue, is believed to be involved, at least in part, in the development of glaucoma. The myocilin expression is known to be up-regulated by glucocorticoids in TM cells, and an altered myocilin level may be the culprit in conditions such as corticosteroid glaucoma. Wild type myocilin, when transfected into cultured human TM cells, induced a dramatic loss of actin stress fibers and focal adhesions. Myocilin transfectants displayed a heightened sensitivity to trypsin. Adhesion to fibronectin, collagens, and vitronectin was compromised. The fibronectin deposition and the levels of fibronectin protein and mRNA were also reduced in myocilin transfectants. The fibronectin deposition could be restored by treatment with lysophosphatidic acid, a Rho stimulator. Assays further revealed that upon myocilin overexpression, the activity of RhoA was diminished, whereas the cAMP level and the protein kinase A (PKA) activity were augmented. Myocilin protein did not affect actin polymerization. The collapse of actin stress fibers and increased trypsin sensitivity from myocilin transfection could be reverted by coexpression of constitutively active RhoA or by treatment with PKA inhibitor H-89. The PKA activity, however, was not modified by co-expression of either constitutively active or dominant negative RhoA. These results demonstrate that myocilin has a deadhesive activity and triggers signaling events. cAMP/PKA activation and the downstream Rho inhibition are possible mechanisms by which myocilin in overabundance may lead to TM cell or tissue damage.

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“…This indicated that the working mechanism of the IOP-increase of PlGF probably is not correlated with the uveoscleral outflow, but might be rather linked to the conventional outflow regulated by the trabecular meshwork (TM). Nothing has been described about PlGF and the TM, but the TM cells do possesses smooth muscle-like properties, such as their contractility, 31 as evidenced by the expression of a-smooth muscle actin. 32 It is known that PlGF can induce contractile effects in vascular smooth muscle cells by the activation of VEGF-R1.…”

Section: Discussionmentioning

confidence: 99%