Eyes are one of the most magical organs in human body. They provide us vast amounts of information from the moment we wake up to when we return to sleep.
When you look at the cornea — the outer layer of the eye — you can see through it! The cornea does three basic tasks for the eye:
- chemical and mechanical protection
- transparency for transmission of light
- refraction of light
The cornea serves as a window through which we enjoy the colorful and dynamic world. If this window is damaged or broken, we need a new one to replace it. I am playing the role of a “window maker,” making a new window.
In my toolbox, I have “human cornea stromal stem cells.” This is the most efficient tool I have to make an artificial cornea. I believe that by combining these stem cells with a special framework of “extracellular matrix” the stem cells will grow on it and the framework will dissolve after the stem cells are in place!
I am working to identify the best environment to make this process occur. After I find that environment, I will test this new cornea to insure it works as a replacement for the natural cornea. Very exciting!
Human corneal stromal stem cells (hCSSCs) were induced into high alignment (b) once seeded on highly oriented PEUU nanofibrous substrate (a). After 6 week culture in keratocyte differentiation medium (KDM), hCSSCs generated abundant collagen-based construct with global alignment, which was revealed by two-photon harmonic generation (SHG) signals (c). Scanning electron microscopy (SEM) investigation (d) showed the collagen fibrils were parallel to each other and a characteristic periodic banded structure can be observed consistent with the D-band feature found in type-I collagen fibrils. Between the fibrils, there are numerous side branches to crosslink the fibrils into an integrated collagen construct. The micrographs (e and f) of transmission electron microscopy revealed that collagen-based nano-structured construct featured the uniform fibril diameter and interfibrillar spacing, and periodic banding along each collagen fibril.
In the past year, we successfully prepared an orderly nano-construct by employing a substrate with fibrillar morphology on a sub-micron scale.
This amenable microenvironment facilitated the secretion of human corneal stromal stem cells (hCSSCs) of a type-I collagen-based ECM that exhibited many of the key structural characteristics of native human cornea stromal tissue. Substrate topography appeared to play a critical role in initiating this ECM expression since a material equivalent, non-aligned fibrillar substrate and smooth film did not recapitulate the overall structural and compositional morphology of the ECM, and cellular phonotype of these substrates varied.
Importantly, it was not necessary for the substrate to maintain contact with the cells to achieve this effect. These results therefore provide new insights into the role of extracellular environment in instructing cellular behavior and ECM nano-assembly. The study also represents an important step in a bottom-upstrategy to bioengineer spatially complex collagen-based nano-structured constructs for corneal repair and regeneration.