Corneal renewal and repair are mediated by stem cells of the limbus, the narrow zone between the cornea and the bulbar conjunctiva. Ocular burns may destroy the limbus, causing limbal stem-cell ...deficiency. We investigated the long-term clinical results of cell therapy in patients with burn-related corneal destruction associated with limbal stem-cell deficiency, a highly disabling ocular disease.
We used autologous limbal stem cells cultivated on fibrin to treat 112 patients with corneal damage, most of whom had burn-dependent limbal stem-cell deficiency. Clinical results were assessed by means of Kaplan-Meier, Kruskal-Wallis, and univariate and multivariate logistic-regression analyses. We also assessed the clinical outcome according to the percentage of holoclone-forming stem cells, detected as cells that stain intensely (p63-bright cells) in the cultures.
Permanent restoration of a transparent, renewing corneal epithelium was attained in 76.6% of eyes. The failures occurred within the first year. Restored eyes remained stable over time, with up to 10 years of follow-up (mean, 2.91+/-1.99; median, 1.93). In post hoc analyses, success--that is, the generation of normal epithelium on donor stroma--was associated with the percentage of p63-bright holoclone-forming stem cells in culture. Cultures in which p63-bright cells constituted more than 3% of the total number of clonogenic cells were associated with successful transplantation in 78% of patients. In contrast, cultures in which such cells made up 3% or less of the total number of cells were associated with successful transplantation in only 11% of patients. Graft failure was also associated with the type of initial ocular damage and postoperative complications.
Cultures of limbal stem cells represent a source of cells for transplantation in the treatment of destruction of the human cornea due to burns.
To evaluate the safety and efficacy of topical recombinant human nerve growth factor (rhNGF) for treating moderate-to-severe neurotrophic keratitis (NK), a rare degenerative corneal disease resulting ...from impaired corneal innervation.
Phase II multicenter, randomized, double-masked, vehicle-controlled trial.
Patients with stage 2 (moderate) or stage 3 (severe) NK in 1 eye.
The REPARO phase II study assessed safety and efficacy in 156 patients randomized 1:1:1 to rhNGF 10 μg/ml, 20 μg/ml, or vehicle. Treatment was administered 6 drops per day for 8 weeks. Patients then entered a 48- or 56-week follow-up period. Safety was assessed in all patients who received study treatment, whereas efficacy was by intention to treat.
Corneal healing (defined as <0.5-mm maximum diameter of fluorescein staining in the lesion area) was assessed by masked central readers at week 4 (primary efficacy end point) and week 8 (key secondary end point) of controlled treatment. Corneal healing was reassessed post hoc by masked central readers using a more conservative measure (0-mm staining in the lesion area and no other persistent staining).
At week 4 (primary end point), 19.6% of vehicle-treated patients achieved corneal healing (<0.5-mm lesion staining) versus 54.9% receiving rhNGF 10 μg/ml (+35.3%; 97.06% confidence interval CI, 15.88–54.71; P < 0.001) and 58.0% receiving rhNGF 20 μg/ml (+38.4%; 97.06% CI, 18.96–57.83; P < 0.001). At week 8 (key secondary end point), 43.1% of vehicle-treated patients achieved less than 0.5-mm lesion staining versus 74.5% receiving rhNGF 10 μg/ml (+31.4%; 97.06% CI, 11.25–51.49; P = 0.001) and 74.0% receiving rhNGF 20 μg/ml (+30.9%; 97.06% CI, 10.60–51.13; P = 0.002). Post hoc analysis of corneal healing by the more conservative measure (0-mm lesion staining and no other persistent staining) maintained statistically significant differences between rhNGF and vehicle at weeks 4 and 8. More than 96% of patients who healed after controlled rhNGF treatment remained recurrence free during follow-up. Treatment with rhNGF was well tolerated; adverse effects were mostly local, mild, and transient.
Topical rhNGF is safe and more effective than vehicle in promoting healing of moderate-to-severe NK.
Limbal stem cell deficiency (LSCD) is a clinical condition characterized by damage of cornea limbal stem cells, which results in an impairment of corneal epithelium turnover and in an invasion of the ...cornea by the conjunctival epithelium. In these patients, the conjunctivalization of the cornea is associated with visual impairment and cornea transplantation has poor prognosis for recurrence of the conjunctivalization. Current treatments of LSCD are aimed at replacing the damaged corneal stem cells in order to restore a healthy corneal epithelium. The autotransplantation of limbal tissue from the healthy, fellow eye is effective in unilateral LSCD but leads to depauperation of the stem cell reservoir. In the last decades, novel techniques such as cultivated limbal epithelial transplantation (CLET) have been proposed in order to reduce the damage of the healthy fellow eye. Clinical and experimental evidence showed that CLET is effective in inducing long-term regeneration of a healthy corneal epithelium in patients with LSCD with a success rate of 70%–80%. Current limitations for the treatment of LSCD are represented by the lack of a marker able to unequivocally identify limbal stem cells and the treatment of total, bilateral LSCD which requires other sources of stem cells for ocular surface reconstruction.
Recent breakthroughs in regenerative medicine have generated enthusiasm and many efforts to explore new therapeutic potentials of both somatic and pluripotent stem cells. About 30 years passed since ...a discovery of a method of producing a great number of human epidermal keratinocytes by cultivation from a small skin biopsy, many possibilities are now envisaged for therapeutic application of different cultured cell types. The importance of stem cell content was proven for many tissues or organs in different pathologies. Ocular burns cause depletion of limbal stem cells, which lead to corneal opacification and visual loss. Most of available treatments are palliative and focused on the relief of the devastating clinical picture. This review is focused on recent developments in cell-based therapy of limbal stem cell deficiency. All findings can provide support for improvement and standardization of the cure for this disabling disease.
Aging impairs corneal nerve density and sensitivity. Substance P (SP), a neuropeptide secreted by sensory nerves, regulates nerve morphology and nociception. Here, we investigate the relationship ...between aging, nerve morphology, and SP expression in mouse and human corneas.
SP levels in mouse corneas (wild type and substance P-knockout) and human corneas and tears were quantified with an ELISA assay. Corneal total nerve length (TNL) was measured with whole-mount β3-tubulin immunofluorescence in mouse and in vivo laser corneal confocal microscopy in humans. SP and β3-tubulin stained cross-sections were used to assess the colocalization of SP and nerves in human and mouse corneas. Ocular surface nociception was assessed with a wiping test in mice.
SP colocalizes with sub-basal neurons in mice and humans. In WT mice, SP levels decrease with age (P = 0.0045, 8 vs. 52 weeks; P = 0.004, 26 vs. 52 weeks) as well as TNL (P = 0.018, 8 vs. 26 weeks; P = 0.0001, 8 vs. 52 weeks). Knockout mice show a greater TNL reduction (8 vs. 26 weeks, P = 0.0016) than WT mice. In the oldest WT and age-matched KO mice, nociception is impaired (P = 0.007 and P < 0.0001, respectively), and KO mice sensitivity is restored by topical SP treatment. In humans, SP levels are reduced in old subject corneas and correlate, in tears, with age (P = 0.0368); TNL also decreases in older patients (P = 0.0002).
Age-associated corneal nerve loss is paralleled by reduction of SP expression in mice and humans. SP promotes the maintenance of normal nerve morphology in the long term and modulates nociception in the cornea.
To evaluate the safety/efficacy of topical infliximab, an anti-TNF-α monoclonal antibody, in a mouse model of ocular surface scarring.
Twenty alkali burn mice were treated with infliximab (10 mg/mL) ...topically 6 times a day, while 20 alkali burn mice received saline for 7 days. Corneal opacity, epithelial wound healing, and ocular phimosis were examined at the slit-lamp. Tear production was quantified with phenol red thread test. Immunofluorescence for infliximab penetration, TNF-α localization, CD45+ cell infiltration, PAS, and Masson's trichrome staining were evaluated on ocular globes and eyelids. TNF-α and IL-1β expression levels were measured on treated murine corneas and eyelids. Finally, quantification of corneal CD31+ blood vessels and LYVE1+ lymphatic vessels were evaluated on 10 additional alkali burn mice receiving either infliximab or saline, after 14 days.
Topical infliximab penetrated the cornea and the conjunctiva and was not toxic (negative fluorescein stain). Its molecular target, TNF-α, was detected in the cornea after injury. Infliximab significantly reduced corneal perforation, opacity index, phimosis, leukocyte infiltration, and fibrosis in the eyelids. It also significantly prevented goblet cell infiltration in epithelial cornea and loss in the conjunctiva (P < 0.05), improved tear secretion and epithelial healing (P < 0.05). Finally, it significantly reduced both corneal hem- (P < 0.05) and lymphangiogenesis (P < 0.01).
Infliximab penetrates the cornea and is safe to the ocular surface in an animal model of ocular surface scarring. We suggest that topical application of infliximab may be a useful treatment in ocular caustications.
Neuropeptides, and specifically Substance P (SP), can crucially contribute to the ocular inflammatory response. SP is an undecapeptide that is secreted from sensory nerve endings and from various ...immune cells during inflammation. SP modulates ocular inflammation through its binding with the high-affinity neurokinin-1 receptor (NK-1R). This receptor is expressed on nerves, immune cells, and epithelial cells. SP is a key mediator of neurogenic inflammation as it induces increased microvascular permeability, vasodilatation, plasma extravasation, and subsequent tissue edema. In addition, macrophages can release inflammatory mediators such as interleukins, chemokines, and growth factors in response to SP stimulation. Inhibition of SP activity, either through blockade of the neuropeptide release or the use of SP receptor antagonists, ameliorates ocular inflammation, it restores immune privilege and improves a number of clinical endpoints associated with inflammation, such as corneal opacity, ocular perforation, and angiogenesis. This review of the literature will summarize the role of SP in the ocular inflammatory response (with an emphasis on the ocular surface). In addition, it will review the therapeutic effects of SP blockade to control ocular inflammation (i) in animal models and (ii) in highly prevalent human diseases.
Keratoconus (KC) is a progressive corneal degeneration characterized by structural changes consisting of progressive thinning and steepening of the cornea. These alterations result in biomechanical ...weakening and, clinically, in vision loss. While the etiology of KC has been the object of study for over a century, no single agent has been found. Recent reviews suggest that KC is a multifactorial disease that is associated with a wide variety of genetic and environmental factors. While KC is typically considered a disease of the cornea, associations with systemic conditions have been well described over the years. In particular, nutritional and metabolic imbalance, such as the redox status, hormones, metabolites, and micronutrients (vitamins and metal ions), can deeply influence KC initiation and progression. In this paper, we comprehensively review the different nutritional (vitamins and minerals) and metabolic (hormones and metabolites) factors that are altered in KC, discussing their possible implication in the pathophysiology of the disease.
There is growing evidence that Müller glia cells (MGCs) might act as regenerative elements in injured retinas of fishes and amniotes. However, their differentiation potential in humans is yet ...unknown. We isolated Müller glia from adult human retinas and propagated them in vitro revealing for the first time their ability to differentiate into rod photoreceptors. These results were also confirmed with mice retinas. Here, we describe conditions by which human MGCs adopt a rod photoreceptor commitment with a surprising efficiency as high as 54%. Functional characterization of Müller glia-derived photoreceptors by patch-clamp recordings revealed that their electrical properties are comparable to those of adult rods. Interestingly, our procedure allowed efficient derivation of MGC cultures starting from both injured and degenerating and postmortem human retinas. Human transplanted Müller glia-derived photoreceptors integrate and survive within immunodeficient mouse retinas. These data provide evidence that Müller glia retains an unpredicted plasticity and multipotent potential into adulthood, and it is therefore a promising source of novel therapeutic applications in retinal repair.
To test whether a corneal injury can stimulate inflammation in the trigeminal ganglion (TG), a structure located in the brain.
At 4 and 8 days after alkali burn induced in the right eyes of mice, in ...vivo magnetic resonance imaging (MRI) of the brain was done before and after ultrasmall superparamagnetic iron oxide nanoparticle (USPIO) contrast to track macrophages. Trigeminal ganglia were stained for Prussian Blue and inflammatory cell markers. Interleukin-1β, TNF-α, and VEGF-A transcripts were quantified on days 1, 4, and 8, and 4 days after corneal topical anti-inflammatory treatment with 0.2% dexamethasone. The expression of Substance P and its receptor NK-1R was also measured in the TG on day 4.
Corneal alkali burn induced leukocyte infiltration, including T cells, in the right TG at 4 and 8 days. In vivo MRI showed an increased contrast uptake in the right TG, which peaked at day 8. Prussian Blue(+) USPIO(+) macrophages were observed in the right TG and exhibited an M2 phenotype. The M2-macrophage infiltration was preponderant in the TG after damage. The proinflammatory cytokines Substance P and NK-1R were significantly increased in both the TGs. The expression of IL-1β and VEGF-A was significantly reduced in the right TG with dexamethasone treatment.
We suggest, for the first time, inflammatory involvement of brain structures following ocular surface damage. Our findings support the hypothesis that the neuropeptide Substance P may be involved in the propagation of inflammation from the cornea to the TG through corneal nerves.
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