Understanding the role of electrostatic force, van der Waals force, and osmotic pressure in retinal function and barrier integrity

Abstract

The retina's intricate interplay of forces and structures, with a focus on the retinal pigment epithelium (RPE) and photoreceptors, is essential for retinal health and function. Among these forces, electrostatic forces play a crucial role, working alongside van der Waals forces and oncotic pressure to maintain the retina's attachment to the RPE and ensure the integrity of the blood-retina barrier (BRB). The composition of the interphotoreceptor matrix (IPM), influenced by molecules like Retbindin secreted by rod photoreceptors, further modulates these forces, affecting processes like visual pigment regeneration and metabolite exchange. In the context of retinal tissue engineering and new technologies for support and cells-based treatments, electrostatic forces are harnessed to optimize nutrient supply to transplanted RPE cells by reducing pore size in electrospun polymer membranes. Scaffold-based strategies for retinal repair also utilize electrostatic, hydrophobic, van der Waals, and hydrogen bonding forces to enhance cell adhesion and growth, mimicking the basement membrane. Understanding the complex dynamics of these forces in retinal-RPE interactions holds promise for innovative treatments for retinal disorders, emphasizing the intricate balance between electrostatic forces, van der Waals forces, oncotic pressure, and more. These insights open exciting avenues for research and therapeutic interventions in ophthalmology. Additionally, van der Waals forces are explored in the context of cell adhesion, and their potential role in retinal health is discussed, particularly in relation to melanin's protective properties against blue light-induced damage. Tissue engineering approaches, both scaffold-free and scaffold-based, are discussed, highlighting the importance of physical surface treatments and adhesive forces in preserving engineered RPE tissue. Overall, this abstract provides a comprehensive overview of the multifaceted role of electrostatic and other forces in retinal biology and their implications for future research and clinical applications in ophthalmology.

Keywords: Electrostatic Force; Osmotic pressure; Outer segment photoreceptor; Retinal epithelium; Van Der Waals Force.

Fig. 1

The retinal pigment epithelium (RPE) and the Bruch membrane have a significant relationship. (A, C) The Bruch membrane is a barrier separating the RPE from the choriocapillaris. It is important to observe the intricate interdigitation of the apical processes of the RPE with the photoreceptor outer segments, as well as the infoldings of the basal surface. (B) The diagram illustrates the thickness of the various layers of the Bruch membrane, starting from the top: the basement membrane of the RPE, the inner collagenous layer, an elastic layer, an outer collagenous layer, and the basement membrane of the choriocapillaris. The apical processes of the RPE are identified as APRPE

Fig. 2

Diagram Illustrating the cells and structures that make up the inner and outer blood-retina barriers

Fig. 3

The positioning of the Inner and outer blood-retina barriers. The I nner blood-retina barrier (iBRB) Is created by the endothelial cells that line the blood vessels in the inner part of the retina. These blood vessels supply the retina up to the outer plexiform layer (OPL), and the layer of photoreceptor cells remains without blood vessels. The outer blood-retina barrier (oBRB) is formed by the retinal pigment epithelial cells (RPE) and controls the movement of substances between the retina and the choroid. In this context, we also have the Inner limiting membrane (ILM), ganglion cell layer (GCL), inner nuclear layer (INL), outer nuclear layer (ONL), and outer segments (OS)

Fig. 4

Light micrograph of a 2-week old argon laser burn in a pigmented rabbit retina

Fig. 5

Diagram showing the breakdown of the blood-retina barrier. This breakdown affects the ganglion cell layer (GCL), inner nuclear layer (INL), outer nuclear layer (ONL), and outer plexiform layer (OPL). The outer blood-retina barrier (oBRB) is established by the retinal pigment epithelial cells (RPE)

Fig. 6

(a) Black contact spot of smooth rubber sphere viewed in microscope as shown in (b) [98]

Fig. 7

Smooth rubber adhesion results showing the contact circle radius as a function of normal applied force fitting JKR adhesion theory to compare with Hertz pure elastic contact. The adhesion pull-off force of 20.6 g was evident [98]

Fig. 8

Scaffold-based tissue engineering