Corneal opacification or scarring is one of the leading causes of blindness worldwide. Human limbus-derived stromal/mesenchymal stem cells (hLMSCs) have the potential of clearing corneal scarring. In the current preclinical studies, we aimed to determine their ability to heal the scarred corneas, in a murine model of corneal scar, and examined their ocular and systemic toxicity after topical administration to rabbit eyes. The hLMSCs were derived from human donor corneas and were cultivated in a clean room facility in compliance with the current good manufacturing practices (cGMP). Before the administration, the hLMSCs were analyzed for their characteristic properties including immunostaining, and were further subjected to sterility and stability analysis. The corneas (right eye) of C57BL/6 mice (n = 56) were stripped of their central epithelium and superficial anterior stroma using a rotary burr (Alger Brush® II). Few mice were left untreated (n = 8), while few (n = 24) were treated immediately with hLMSCs after debridement (prophylaxis group). The rest (n = 24, scar group) were allowed to develop corneal scarring for 2 weeks and then treated with hLMSCs. In both groups, the treatment modalities included encapsulated (En+) and non-encapsulated (En−) hLMSCs and sham (vehicle) treatment. The follow-up (4 weeks) after the treatment or debridement included clinical photography, fluorescein staining, and optical coherence tomography at regular intervals. All the images and scans were analyzed using ImageJ software to assess the changes in corneal haze, scar area, and the reflectivity ratio of the epithelium to the stroma. The scar area and the scar intensity were found to be decreased in the groups that received hLMSCs. The reflectivity of the stroma was found to be normalized to the baseline levels before the debridement in the eyes that were treated with hLMSCs, relative to the untreated. In the safety study, the central corneas of the left eye of 18 New Zealand rabbits were scraped with a needle and then treated with En+ hLMSCs, En− hLMSCs, and the sham (n = 6 each). Rabbits were then followed up for 4 weeks, during which blood and tear samples were collected at regular intervals. These rabbits were then assessed for changes in the quantities of inflammatory markers (TNF-α, IL-6, and IgE) in the sera and tears, changes in the ocular surface observations such as intraocular pressure (IOP), and the hematological and clinical chemistry parameters. Four weeks later, the rabbits were euthanized and examined histopathologically. No significant changes in conjunctival congestion, corneal clarity, or IOP were noticed during the ophthalmic examination. The level of inflammatory molecules (TNF-α and IL-6 TNF-α) and the hematological parameters were similar in all groups without any significant changes. Histological examination of the internal organs and ocular tissues did not reveal any abnormalities. The results of these studies summarize that the En+ and En− hLMSCs are not harmful to the recipient and potentially restore the transparency of debrided or scarred corneas, indicating that hLMSCs can be assessed for clinical use in humans.
Background The purpose of this study was to assess the ocular and systemic toxicity of topically applied human limbus-derived stromal/mesenchymal stem cells (hLMSCs) with and without alginate encapsulation as per Indian regulatory guidelines for stem cell therapy. Methods The hLMSCs were obtained from cadaveric corneoscleral rims and expanded in a current good manufacturing practice compliant laboratory. The hLMSCs were checked for viability, chromosomal stability, growth kinetics, contamination, and endotoxin levels. Cells with (En+ hLMSCs) or without (En− hLMSCs) alginate encapsulation were used for the animal experiments. The study involved 3 groups of 6 New Zealand white rabbits each, which underwent corneal wounding followed by treatment with sham (G1), En− hLMSCs (G2), and En+ hLMSCs cells (G3). Ophthalmic assessment including intraocular pressure (IOP), blood investigations and inflammatory marker (IL-6, TNF-α, IgE) expression in serum and tears were assessed on days 1, 7, 14, 21, and day 28. At the end of 28 days, the animals were sacrificed, and the organs were subjected to histopathological examination. Results The hLMSCs had 88.33 ± 2.37% viability at the end of 6 hours and 78.21 ± 1.47% at the end of 24 hours. The cells showed positive expression for the stem-cell biomarkers (p63α, Pax6, and ABCG2), extracellular matrix marker (Col-III) and mesenchymal biomarkers (VIM, CD73, CD90 and CD105). No contamination by the Mycoplasma species was found in either of the En-/En + hLMSCs and the levels of bacterial endotoxins in the En- hLMSCs and En + hLMSCs cell suspension was found be within the permissible levels (≤ 0.12 EU/mL). Ophthalmic examination showed no significant difference in IOP, corneal clarity and conjunctival congestion between the three groups at every time point. Haematological parameters were comparable between the three groups. The inflammatory markers in tear and serum (TNF-α and IL-6) were not significantly elevated in the groups receiving En+/En− hLMSCs. Histological examination did not show any abnormality in the ocular or corneal tissue, and the viscera. Conclusions The results of the study show that hLMSCs do not cause any local or systemic toxicity in recipients, implying that these cells are safe for clinical use and their efficacy can be assessed in human clinical trials.
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