Pericytes of Indirect Contact Coculture Decrease Integrity of Inner Blood-Retina Barrier Model In Vitro by Upgrading MMP-2/9 Activity.

Tianye Yang,Guanghui Liu,Yongzheng Zheng,Mingdong Pan,Liang Guo,Chun Meng,Mingli Liang,Yuan Fang,Ting Su

doi:10.1155/2021/7124835

Abstract

Inner blood-retina barrier (iBRB) is primarily formed of retinal microvascular endothelial cells (ECs) with tight junctions, which are surrounded and supported by retinal microvascular pericytes (RMPs) and basement membrane. Pericytes are believed to be critically involved in the physiology and pathology of iBRB. However, the underlying mechanism remains to be fully elucidated. We developed a novel in vitro iBRB model which was composed of primary cultures of rat retinal ECs and RMPs based on Transwell system. We tested the involvement of pericytes in the migration and invasion of ECs, examined the expression and activity of matrix metalloproteinase- (MMP-) 2/MMP-9 in the culture, evaluated the TEER and permeability of iBRB, and assessed the expression of ZO-1, occludin, claudin-5, and VE-cadherin of endothelial junctions. We found that RMPs with indirect contact of ECs can increase the expression of MMP-2 and upgrade the activity of MMP-2/9 in the coculture, which subsequently decreased TJ protein abundance of ZO-1 and occludin in ECs, promoted the migration of ECs, and finally reduced the integrity of iBRB. Taken together, our data show that RMP relative location with ECs is involved in the integrity of iBRB via MMP-2/9 and has important implications for treating diabetic retinopathy and other retinal disorders involving iBRB dysfunction.

Highlights

Inner blood-retina barrier, mainly consisting of endothelial cells (ECs), retinal microvascular pericytes (RMPs), and basement membrane, plays a key role in retinal homeostasis [1]
No difference of claudin-5 and VE-cadherin expression was observed among the 3 Inner blood-retina barrier (iBRB) models (Figure 6). These results suggest that RMPs may reduce the iBRB integrity under condition of indirect contact coculture by upregulating matrix metalloproteinase- (MMP-)2/9 activity, which subsequently, at least in part, decrease the abundance of ZO-1 and occludin directly or indirectly
We showed that RMPs decreased the expression of ZO-1 and occludin of ECs, downgraded transendothelial electrical resistance (TEER), and upgraded permeability of iBRB in indirect contact coculture by increasing the expression of Matrix metalloproteinases (MMPs)-2 and activity of MMP-2/9

Summary

Introduction

Inner blood-retina barrier (iBRB), mainly consisting of endothelial cells (ECs), retinal microvascular pericytes (RMPs), and basement membrane, plays a key role in retinal homeostasis [1]. Blood-retina barrier (BRB) restricts nonspecific transport between neural retina and peripheral blood and prevents the passage of pathogens, toxins, toxicants, proteins, and neurotransmitters into the retina [2] Under pathological conditions, such as hyperglycemia, hypoxia, oxidative stress, or inflammation, disruption of integrity of interendothelial junctions leads to the increase of iBRB permeability and gathering of harmful substances in the retina [3]. The sophisticated junctions between adjacent ECs, including tight junctions (TJs), adherens junctions (AJs), gap junctions, and desmosomes, are the basis of iBRB [4] Besides their involvement in cell to cell adhesion, these structures sustain cell survival, cell polarity, and paracellular permeability [5]. It has previously been demonstrated that increasing of iBRB permeability is related

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