Development of a macromolecular diffusion pathway in the lens

Area of Science:

• Ophthalmology
• Cell Biology
• Biophysics

Background:

• The mammalian lens comprises quiescent core cells and active surface cells.
• Gap junctions facilitate electrical syncytium and small molecule exchange in the lens.
• An additional, macromolecule-permeable pathway in the lens core is investigated.

Purpose of the Study:

• To characterize a macromolecule-permeable intercellular pathway in the mammalian lens core.
• To investigate the co-existence of this pathway with gap-junction-mediated communication.
• To determine the functional significance of this pathway in lens physiology.

Main Methods:

• Utilized a transgenic mouse model (TgN(GFPU)5Nagy) expressing green fluorescent protein (GFP).
• Observed GFP diffusion patterns in developing and adult lenses to identify distinct labeling patterns.
• Microinjected 10 kDa fluorescent dextran into individual fiber cells and tracked diffusion via time-lapse microscopy.

Main Results:

• Variegated GFP expression revealed distinct fluorescence patterns in superficial and core lens cells.
• Macromolecule (dextran) diffusion was observed between cells deeper than 100 microm.
• Superficial fiber cells retained injected dextran, indicating a barrier to diffusion in the outer lens layer.
• A macromolecule-permeable pathway was identified in the lens core, distinct from gap junctions.

Conclusions:

• The mammalian lens core possesses a macromolecule-permeable intercellular pathway alongside gap junctions.
• This pathway allows for the transport of larger molecules within the lens core.
• A significant portion of nucleated fiber cells resides within this permeable region, suggesting functional importance.