Identification, quantification and age-related changes of human trabecular meshwork stem cells

Abstract

Background Loss of cells in the human trabecular meshwork (TM) has been reported with ageing and in glaucoma. This study aims to identify, quantify and determine the age-related changes of human TM stem cells (TMSCs). Methods Isolation of TM cells/ paraffin sectioning was carried out using human corneoscleral rings and whole globes. The TM cells/ sections were immunostained for the stem cell markers ATP-binding cassette protein G2 (ABCG2), nerve growth factor receptor p75 and AnkyrinG (AnkG). Images were acquired using Leica SP8 confocal microscope. The isolated cells were analyzed for two parameters- ABCG2 expression and nucleus to cytoplasmic ratio (N/C ratio). The total number of TM cells and those positive for ABCG2 and p75 in each section were quantified. Spearman rank order correlation was used to determine the association between age and the cell counts. Results The TMSCs were identified based on two parameters- high ABCG2 expression and high N/C ratio > 0.7. These stem cells were also positive for p75 and AnkG. The TMSC content based on the two parameters was 21.0 ± 1.4% in < 30 years age group, 12.6 ± 6.6% in 30–60 years and 4.0 ± 3.5% in > 60 years. The stem cells with high ABCG2 and p75 expression were restricted to the Schwalbe’s line region of the TM. A significant correlation was observed between the reduction in TMSC content and TM cell count during ageing. Conclusion The human TMSCs were identified and quantified based on two parameter analysis. This study established a significant association between age-related reduction in TMSC content and TM cell loss.

The Primary Cilium as a Therapeutic Target in Ocular Diseases

“…The anterior chamber contains a specialized structure known as the trabecular meshwork, which controls the flow of aqueous humor and on which primary cilia are found ( Sacca et al., 2016 ). Primary cilia on trabecular meshwork cells can sense aqueous humor flow and therefore play an important role in regulating intraocular pressure, and excessive intraocular pressure caused by obstruction of aqueous humor outflow underlies glaucoma ( Figure 2B ) ( Sundaresan et al., 2019 ). When the intraocular pressure is too high, primary cilia shorten, promoting the expression of tumor necrosis factor α (TNF-α), and transforming growth factor β (TGF-β), thereby initiating the molecular mechanisms underpinning glaucoma ( Luo et al., 2014 ).…”

A Biomimetic, Stem Cell‐Derived In Vitro Ocular Outflow Model

“…With advance in stem cell technology, TM stem cells [ 9–16 ] and iPSC‐derived TM cells [ 21 ] present potentially valuable cell sources for study and treatment of glaucoma by HTM regeneration to restore outflow function and IOP regulation. In addition, bone marrow‐derived mesenchymal stem cells show potential to promote HTM regeneration and IOP reduction.…”

“…TM stem cells represent a promising stem cell source that can be used for human trabecular meshwork (HTM) regeneration. [ 9 ] These multipotent TM stem cells, which occupy the nonfiltering region of the TM, [ 10–12 ] can migrate toward the injury site after laser trabeculoplasty. [ 13 ] A number of protocols have been developed to isolate, [ 10–16 ] expand, and differentiate them to express an HTM phenotype, [ 14,16 ] demonstrating its utility for TM regeneration.…”

“…[ 9 ] These multipotent TM stem cells, which occupy the nonfiltering region of the TM, [ 10–12 ] can migrate toward the injury site after laser trabeculoplasty. [ 13 ] A number of protocols have been developed to isolate, [ 10–16 ] expand, and differentiate them to express an HTM phenotype, [ 14,16 ] demonstrating its utility for TM regeneration. [ 17,18 ] Unfortunately, since only 2–5% of the total cell population in this region is stem‐like, it is hard to imagine that they can be used for autologous cell replacement therapy.…”

Stem cell transplantation rescued a primary open-angle glaucoma mouse model

“…Trabecular meshwork stem cells (TMSCs) have their special niche located at the anterior TM tissue beneath the Schwalbe’s line ( Braunger et al, 2014 ; Raviola, 1982 ; Sundaresan et al, 2019 ; Yun et al, 2016 ) and have been successfully isolated and characterized ( Castro and Du, 2019 ; Du et al, 2012 ). TMSCs maintain stem cell characteristics and regenerative capacity after long-term cryopreservation ( Kumar et al, 2020 ), which can be an effective source for cell-based therapy.…”