Age-related increases in eye lens stiffness are linked to presbyopia. This protocol describes a simple, cost-effective method for measuring mouse lens stiffness. Mouse lenses, like human lenses, become stiffer with age. This method is precise and can be adapted for lenses from larger animals.
La lentille de l'œil est un organe transparent qui réfracte et se concentre la lumière pour former une image claire sur la rétine. Chez l'homme, les muscles ciliaires se contractent pour déformer la lentille, ce qui conduit à une augmentation de la puissance optique de la lentille de se concentrer sur des objets proches, un processus connu sous le nom d'hébergement. les changements liés à l'âge de la rigidité de la lentille ont été liés à la presbytie, une réduction de la lentille 'capacité à accueillir, et, par extension, le besoin de lunettes de lecture. Même si les lentilles de souris ne peuvent accueillir ou de développer la presbytie, des modèles de souris peuvent fournir un outil génétique inestimable pour la compréhension des pathologies de l'objectif, et le vieillissement accéléré observé chez la souris permet l'étude des changements liés à l'âge dans la lentille. Ce protocole présente un procédé simple, précise et économique pour la détermination de la rigidité de la lentille de la souris, en utilisant des lamelles de verre pour appliquer séquentiellement des charges de compression croissante sur la lentille. Les données représentatives confirment que les lentilles de souris deviennent plus rigide avec l'âge, commeLentilles humaines. Ce procédé est très reproductible et peut potentiellement être étendu par des moyens mécaniques des lentilles d'essai à partir des animaux plus gros.
The lens is a transparent and avascular organ in the anterior chamber of the eye that is responsible for fine focusing of light onto the retina. A clear basement membrane, called the lens capsule, surrounds a bulk of elongated fiber cells covered by an anterior monolayer of epithelial cells1,2. Life-long growth of the lens depends on the continuous proliferation and differentiation of epithelial cells at the lens equator into new fiber cells that are added onto previous generations of fiber cells in a concentric manner2. Over time, lens fiber cells undergo compaction, resulting in a rigid center in the middle of the lens called the nucleus1. Accommodation, defined as a dioptric change in the optical power of the eye, occurs in humans when the ciliary muscles contract to deform the lens and allow a true increase in optical power to focus on near objects3-5. In the unaccommodated eye, the lens is held in a relatively flattened state due to tension from zonular fibers. When the ciliary muscles contract, the tension on the lens is released, leading to decreased lens equatorial diameter and increased axial thickness. Age-related changes in the lens cause presbyopia, a progressive loss of lens accommodation, which leads to the need for reading glasses.
Several studies have linked presbyopia to age-related increase in the intrinsic stiffness of the lens6-11. Stiffness is defined as the resistance of an elastic object to deform under applied load. A variety of methods have been used to examine stiffness of human lenses, including spin compression12-14, actuator compression15, probe indentation16, dynamic mechanical analysis 6,10 and bubble-based acoustic radiation force17. While mouse lenses do not accommodate or develop presbyopia, mouse models for lens pathologies are valuable tools because mice are less expensive than larger animals, well characterized genetically and undergo accelerated age-related changes due to rapid aging. A handful of studies have examined mouse lens stiffness with compression methods and demonstrated changes in lens stiffness due to aging or targeted genetic disruptions18-21. Thus, mouse lenses are good models for studying age-related changes in lens stiffness.
This protocol describes a simple and inexpensive, yet precise and reproducible, compression method for determining mouse lens stiffness based on application of glass coverslips onto the lens in conjunction with photographing the lens through a dissection microscope and mirror. This method yields robust strain and morphometric data with an easily fabricated and assembled apparatus. The representative results confirm that mouse lenses increase in stiffness with age.
Il y a plusieurs considérations clés lors de l'utilisation de cette méthode pour mesurer la rigidité de la lentille. En premier lieu, les lamelles sont appliquées à la lentille à un angle légèrement oblique (8 à 8,5 °) par rapport au fond de la chambre (θ). Il en sera une très petite partie de la charge équatorial plutôt que axialement. Cependant, cette charge équatoriale est considéré comme négligeable parce que le péché θ ≈ 0,1 19. Si cette méthode est adaptée pour des lentille…
The authors have nothing to disclose.
This work was supported by National Eye Institute Grant R01 EY017724 (VMF) and National Institute of Arthritis and Musculoskeletal and Skin Diseases Grant K99 AR066534 (DSG).
Fine tip straight forceps | Fine Scientific Tools | 11252-40 | |
Microdissection scissors, straight edge | Fine Scientific Tools | 15000-00 | |
Curved forceps | Fine Scientific Tools | 11272-40 | |
Seizing forceps | Hammacher | HSC 702-93 | Optional |
Dissection dish | Fisher Scientific | 12565154 | |
60mm petri dish | Fisher Scientific | 0875713A | |
1X phosphate buffered saline (PBS) | Life Technologies | 14190 | |
18mm x 18mm glass coverslips | Fisher Scientific | 12-542A | |
Measurement chamber with divots to hold lenses | Custom-made (see Figure 1) | ||
Right-angle mirror | Edmund Optics | 45-591 | |
Light source | Schott/Fostec | 8375 | |
Illuminated dissecting microscope | Olympus | SZX-ILLD100 | With SZ-PT phototube |
Digital camera | Nikon | Coolpix 990 |