Cultures of limbal stem cells represent a source of cells for transplantation in the treatment of destruction of the human cornea due to burns.

We have analyzed the proliferative and differentiation potential of human ocular keratinocytes. Holoclones, meroclones, and paraclones, previously identified in skin, constitute also the proliferative compartment of the ocular epithelium. Ocular holoclones have the expected properties of stem cells, while transient amplifying cells have variable proliferative potential. Corneal stem cells are segregated in the limbus, while conjunctival stem cells are uniformly distributed in bulbar and forniceal conjunctiva. Conjunctival keratinocytes and goblet cells derive from a common bipotent progenitor. Goblet cells were found in cultures of transient amplifying cells, suggesting that commitment for goblet cell differentiation can occur late in the life of a single conjunctival clone. We found that conjunctival keratinocytes with high proliferative capacity give rise to goblet cells at least twice in their life and, more importantly, at rather precise times of their life history, namely at 45–50 cell doublings and at ∼15 cell doublings before senescence. Thus, the decision of conjunctival keratinocytes to differentiate into goblet cells appears to be dependent upon an intrinsic “cell doubling clock.” These data open new perspectives in the surgical treatment of severe defects of the anterior ocular surface with autologous cultured conjunctival epithelium.

Neurotrophic keratopathy is a degenerative corneal disease induced by an impairment of trigeminal nerve. Impairment of loss of corneal sensory innervation is responsible for corneal epithelial defects, ulcer, and perforation. In the present report, we reviewed the pathogenesis, diagnosis, and therapeutic aspects of this disease. An accurate history and clinical examination, including the function of cranial nerves, together with the clinical features of the ocular surface are essential for a prompt diagnosis. The evaluation of the corneal sensitivity and tear film function are important diagnostic steps as well. Specific medical and surgical treatments, based on the clinical staging of the disease, are often able to halt its progression. Future developments in the medical treatment including the administration of neuropeptide and growth factors are presented.

Neurotrophic Keratopathy (NK) refers to a condition where corneal epitheliopathy leading to frank epithelial defect with or without stromal ulceration (melting) is associated with reduced or absent corneal sensations. Sensory nerves serve nociceptor and trophic functions, which can be affected independently or simultaneously. Loss of trophic function and consequent epithelial breakdown exposes the stroma making it susceptible to enzymatic degradation. Nerve pathology can range from attrition to aberrant re-generation with corresponding symptoms from anaesthesia to hyperaesthesia/allodynia. Many systemic and ocular conditions, including surgery and preserved medications can lead to NK. NK can be mild (epithelium and tear film changes), moderate (non-healing epithelial defect) or severe (stromal melting and perforation). Moderate and severe NK can profoundly affect vision and adversely impact on the quality of life. Medical management with lubricating agents from artificial tears to serum/plasma drops, anti-inflammatory agents, antibiotics and anti-proteases all provide non-specific relief, which may be temporary. Contact lenses, punctal plugs, lid closure with botulinum toxin and surgical interventions like tarsorrhaphy, conjunctival flaps and amniotic membrane provide greater success but often at the cost of obscuring sight. Corneal surgery in a dry ocular surface with reduced sensation is at high risk of failure. The recent advent of biologicals such as biopolymers mimicking heparan sulfate; coenzyme Q10 and antisense oligonucleotide that suppress connexin 43 expression, all offer promise. Recombinant nerve growth factor (cenegermin), recently approved for human use targets the nerve pathology and has the potential of addressing the underlying deficit and becoming a specific therapy for NK.