Abstract
Keratocytes, the quiescent cells of the corneal stroma, play a crucial role in corneal wound healing. Neuropeptides and neurotransmitters are usually associated with neuronal signaling, but have recently been shown to be produced also by non-neuronal cells and to be involved in many cellular processes. The aim of this study was to assess the endogenous intracellular and secreted levels of the neuropeptides substance P (SP) and neurokinin A (NKA), and of the neurotransmitters acetylcholine (ACh), catecholamines (adrenaline, noradrenaline and dopamine), and glutamate, as well as the expression profiles of their receptors, in human primary keratocytes in vitro and in keratocytes of human corneal tissue sections in situ. Cultured keratocytes expressed genes encoding for SP and NKA, and for catecholamine and glutamate synthesizing enzymes, as well as genes for neuropeptide, adrenergic and ACh (muscarinic) receptors. Keratocytes in culture produced SP, NKA, catecholamines, ACh, and glutamate, and expressed neurokinin-1 and -2 receptors (NK-1R and NK-2R), dopamine receptor D2, muscarinic ACh receptors, and NDMAR1 glutamate receptor. Human corneal sections expressed SP, NKA, NK-1R, NK-2R, receptor D2, choline acetyl transferase (ChAT), M3, M4 and M5 muscarinic ACh receptors, glutamate, and NMDAR1, but not catecholamine synthesizing enzyme or the α1 and β2 adrenoreceptors, nor M1 receptor. In addition, expression profiles assumed significant differences between keratocytes from the peripheral cornea as compared to those from the central cornea, as well as differences between keratocytes cultured under various serum concentrations. In conclusion, human keratocytes express an array of neuropeptides and neurotransmitters. The cells furthermore express receptors for neuropeptides/neurotransmitters, which suggests that they are susceptible to stimulation by these substances in the cornea, whether of neuronal or non-neuronal origin. As it has been shown that neuropeptides/neurotransmitters are involved in cell proliferation, migration, and angiogenesis, it is possible that they play a role in corneal wound healing.
Highlights
The cornea is composed of the outer stratified squamous epithelium, the intermediate stroma, and the inner endothelium.[1]
Central and peripheral keratocytes were cultured in either DMEM/F12 medium supplemented with 2% Fetal Bovine Serum (FBS) or 0% FBS
Central keratocytes grown in these two conditions, as well as peripheral keratocytes grown in these two conditions, were compared
Summary
The cornea is composed of the outer stratified squamous epithelium, the intermediate stroma, and the inner endothelium.[1]. The keratocytes may either undergo apoptosis or transdifferentiate into an activated fibroblastic repair phenotype. This fibroblastic phenotype seen in corneal wound healing resembles the phenotype that is seen under culture conditions in vitro. Standard culture conditions for corneal stromal cells (10% Fetal Calf Serum) alter the keratocytes from their in situ phenotype [6]. Stromal cells derived from bovine, rabbit and human corneas, cultured under standard conditions, have been reported to produce moderate (15%), little (3%), or no keratan sulfates, respectively [6, 8,9,10]. When primary cultures of corneal stromal cells are cultured in serum-free medium, they exhibit a dendritic morphology and extensive dendritic processes [14], and their appearance is similar to keratocytes in situ and distinctly different from the fibroblastic or myofibroblastic appearance of keratocytes grown in serum-containing medium [5, 14]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call