Abstract
Purpose: :
Our previous studies have shown the presence of a subpopulation of cells in the lens with repair function that respond to injury associated with cataract surgery and are a source of myofibroblasts that cause Posterior Capsule Opacification. We have now investigated whether any cells in the embryonic lens express molecules associated with a mesenchymal phenotype.
Methods: :
Cryosections prepared from embryonic day (E)3.5 chicken lenses, or wounded ex vivo explants resulting from mock cataract surgery of E15 lenses were immunostained for mesenchymal and neural crest cell markers including the transcription factors Pax 7, Pax 3, and the HNK-1 carbohydrate epitope expressed by neural crest cells and recently linked to maintenance of stemness in cells with a neural lineage.
Results: :
At E3.5, an early stage of lens development when the lens vesicle still remains open, there exist subpopulations of cells that immunolabeled for antigens that are classically expressed by cells of mesenchymal and neural crest lineages including Pax7, Pax3 and HNK-1. HNK-1 labels a distinct population of cells that are found between and stretching all along lens cells in both the epithelium and primary lens fiber zones. The pattern of staining for Pax7 and Pax3 is different from HNK-1, but similar to one another. The greatest concentration Pax7 and Pax3 labeled cells were found among the cells of the anterior lens epithelium, where they are located in-between the lateral surfaces of the lens epithelial cells, but more concentrated towards their basolateral aspects. Staining for Pax7 also reveal a population of Pax7 positive cells just outside the anterior lens that appear to be moving toward an ultimate destination in the lens. Following mock cataract surgery of E15 lenses, Pax7 and Pax3 label the expanding niches of vimentin-positive repair cells that quickly migrate to the leading edge of the wound, shown previously to have an important role in the repair process.
Conclusions: :
Unique subpopulations of cells are present in the early embryonic lens that may be the precursors of cells that modulate wound repair and have the potential to become the myofibroblasts associated with lens disease.
Keywords: wound healing • transcription factors • development