The limbus is a narrow band of tissue that encircles the cornea, the transparent 'window' into the eye. The outermost layer of the cornea is the epithelium, which is necessary for clear vision. The limbus acts as a 'reservoir' for limbal stem cells which maintain and regenerate the corneal epithelium. It also functions as a barrier to the conjunctiva and its blood vessels. Limbal stem cell deficiency is a general term for diseases which are characterised by the impairment of the limbus, limbal stem cells and their ability to replenish the corneal epithelium through proliferation and differentiation. Consequently, sufferers experience chronic pain and progressive blindness. This paper will highlight the salient milestones of limbal stem cell biology and potential future treatments for limbal stem cell deficiency.

The cornea is the clear front of the eye and its surface is composed of an epithelium. This is renewed by stem cells located at the limbus, which encircles the periphery of the cornea. These limbal stem cells become lost or deficient in the blinding disease of limbal stem cell deficiency. In this review article, we discuss the historical perspective in managing limbal stem cell deficiency as well as describing the more contemporary treatment options, and in particular the culture and transplantation of human limbal stem cells. This treatment was first proposed 13 years ago and many case series have been presented to date showing promising outcomes of this technique. However, challenges still remain in treating the debilitating disease of limbal stem cell deficiency. Here we discuss some of the questions, which remain to be answered in this field.

Limbal-derived MSC exhibited plasticity, could maintain limbal markers expression and demonstrated viable growth on amniotic membrane.

The cornea at the front of the eye is covered by an epithelium. This epithelium is maintained by stem cells located at the periphery of the cornea, in a region known as the limbus. Because this region harbors the stem cells for the corneal epithelium, the so-called limbal stem cells, its culture provides considerable interest. Limbal epithelial culture is used for two main reasons. The first is to further our understanding of limbal stem-cell biology. The second is for the culture expansion of limbal stem cells for transplantation purposes in patients with limbal stem-cell deficiency. However, considerable variations in the culture methods for limbal epithelium exist. These include culture media, sera used in the culture, use of 3T3 fibroblasts or amniotic membrane or both, the culture of whole pieces of limbal tissue or enzymatically digested tissue, and the use of airlifting.

Limbal stem cell (LSC) deficiency causes progressive loss of vision but may be treated by transplant of autologous LSCs. Cryopreservation has the potential to indefinitely extend the lifespan of LSCs allowing re-transplant in case of graft failure. In this study, we aimed to identify the optimal cryoprotectant and cryoprotectant concentration for LSC cultures. Suspension cultures derived from cadaveric corneoscleral rims were cooled to 4 °C with Me2SO, propylene glycol or ethylene glycol at a concentration of 5%, 10% or 15%. Cell tolerance was measured in terms of membrane integrity, colony-forming efficiency and alamarBlue® reduction. Increasing cryoprotectant concentration above 5% reduced membrane integrity, metabolism and colony-forming efficiency. Cryoprotectant choice did not significantly influence these characteristics. Cells demonstrating Side Population were maintained after cryopreservation with 5% propylene glycol in vapour phase liquid nitrogen for 1 week, indicating that cryopreservation of LSCs with relatively low cryoprotectant concentration (5%) has promise in low-temperature eye banking.

BackgroundWe have investigated the behaviour of a newly characterised population of haemarthrosis fluid-derived human mesenchymal stem cells (HF-hMSCs) with titanium (Ti) surfaces.MethodsHF-hMSCs were seeded onto round cannulated interference (RCI; Smith and Nephew) screws or control Ti discs and cultured under pro-osteogenic conditions.ResultsElectron microscopy showed the attachment and spreading of HF-hMSCs across both Ti surfaces during the early stages of osteogenic culture; however, cells were exclusively localised to the basal regions within the vertex of the Ti screws. In the later stages of culture, an osteoid matrix was deposited on the Ti surfaces with progressive culture expansion and matrix deposition up the sides and the top of the Ti Screws. Quantification of cellular content revealed a significantly higher number of cells within the Ti screw cultures; however, there was no difference in the cellular health. Conversely, alizarin red staining used as both a qualitative and quantitative measure of matrix calcification was significantly increased in Ti disc cultures compared to those of Ti screws.ConclusionsOur results suggest that the gross topography of the metal implant is able to create microenvironment niches that have an influence on cellular behaviour. These results have implications for the design of advanced tissue engineering strategies that seek to use cellular material to enhance biological remodelling and healing following tissue reconstruction.

DESCRIPTIONA 15-year-old boy presented after being attacked by a 'Lightsaber' wielded by his friend. The device in question was a blue laser pointer (450 nm 8000 mW) reflected by his friend off a mirror-the beam caught the patient in the left eye for a mere 1 or 2 s. His vision dropped immediately and he presented the next day with a macular haemorrhage (figure 1) and a vision of 6/60. We treated via observation only and, fortunately, his vision improved slowly over the next 4 weeks: day 7, 6/36; day 14, 6/18 and day 30, 6/12. In the absence of any evidence for an active choroidal neovascular membrane, we felt that intravitreal antivascular endothelial growth factor therapy was not indicated.It is common knowledge that lasers can cause retinal injury, 1 but we would like to share these Figure 1 Fundus photos and optical coherence tomography images capturing the natural history of the foveal haemorrhage following the laser injury.

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