Molecular and cellular characterization of expanded and cryopreserved human limbal epithelial stem cells reveal unique immunological properties

Genetic Modification of Limbal Stem Cells to Decrease Allogeneic Immune Responses

Limbal stem cell (LSC) transplantation is the only efficient treatment for patients affected by LSC deficiency (LSCD). Allogeneic LSC transplantation is one of the most successful alternative for patients with bilateral LSCD. Nevertheless, the high variability of the human leukocyte antigens (HLA) remains a relevant obstacle to long-term allogeneic graft survival. This study characterized the immunologic properties of LSCs and proposed a genetic engineering strategy to reduce the immunogenicity of LSCs and of their derivatives. Hence, LSC HLA expression was silenced using lentiviral vectors encoding for short hairpin (sh) RNAs targeting β2-microglobulin (β2M) or class II major histocompatibility complex transactivator (CIITA) to silence HLA class I and II respectively. Beside the constitutive expression of HLA class I, LSCs showed the capability to upregulate HLA class II expression under inflammatory conditions. Furthermore, LSCs demonstrated the capability to induce T-cell mediated immune responses. LSCs phenotypical and functional characteristics are not disturbed after genetic modification. However, HLA silenced LSC showed to prevent T cell activation, proliferation and cytotoxicity in comparison to fully HLA-expressing LSCs. Additionally; HLA-silenced LSCs were protected against antibody-mediated cellular-dependent cytotoxicity. Our data is a proof-of-concept of the feasibility to generate low immunogenic human LSCs without affecting their typical features. The use of low immunogenic LSCs may support for long-term survival of LSCs and their derivatives after allogeneic transplantation.

Identification and characterization of dendritic cell subtypes in preserved and cultured cadaveric human corneolimbal tissue on amniotic membrane

PURPOSE

Rejection is the leading cause of failure of limbal allogafts. Resident dendritic cell (DC) maturation plays a critical role in host allosensitization. There are two lineages: myeloid (mDC) and lymphoid (pDC), with different biological properties. The aim was to analyse the distribution of DC subtypes in limbal explant cultures on amniotic membrane (AM), cultivated on either the epithelial or stromal side and to compare the results with directly isolated cells from cadaveric whole corneoscleral tissue divided into specific areas.

METHODS

The expression of CD11c (mDC), CD303/CD123 (pDC) and costimulatory molecules CD80, CD86 and activation markers HLA-DR, CD83 was investigated by flow cytometry. Additionally, the corneal epithelium marker CK12 and ABCB5, a new epithelial stem cell marker, were investigated.

RESULTS

Cells positive for pDC and mDC markers were found in all examined areas, with a nonsignificant prevalence of pDC. In limbal explant cultures on AM, the percentage of pDC and mDC was similar, with no statistically significant difference between cultures on epithelial or stromal sides of AM. However, with ex vivo limbal explant cultivation on AM, the pDC content declined significantly (p < 0.05) and the ABCB5 marker was likewise statistically significantly reduced.

CONCLUSION

This is the first study to characterize the distribution of pDC and mDC subsets in cultured and noncultured human corneolimbal tissue. Additionally, ABCB5 positive cells were identified. These findings might be important for future strategies, allowing preparation of corneolimbal allografts with optimal stem cell content for a longer lasting therapeutic effect.

Concise Review: Stem Cells for Corneal Wound Healing

Corneal wound healing is a complex process that occurs in response to various injuries and commonly used refractive surgery. It is a significant clinical problem, which may lead to serious complications due to either incomplete (epithelial) or excessive (stromal) healing. Epithelial stem cells clearly play a role in this process, whereas the contribution of stromal and endothelial progenitors is less well studied. The available evidence on stem cell participation in corneal wound healing is reviewed, together with the data on the use of corneal and non-corneal stem cells to facilitate this process in diseased or postsurgical conditions. Important aspects of corneal stem cell generation from alternative cell sources, including pluripotent stem cells, for possible transplantation upon corneal injuries or in disease conditions are also presented. Stem Cells 2017;35:2105-2114.

Key Issues Related to Cryopreservation and Storage of Stem Cells and Cancer Stem Cells: Protecting Biological Integrity

Cryopreservation and biobanking of stem cells are becoming increasingly important as stem cell technology and application attract the interest of industry, academic research, healthcare and patient organisations. Stem cell are already being used in the treatment of some diseases and it is anticipated that stem cell therapy will play a central role in future medicine. Similarly, the discovery of both hematopoietic and solid tumor stem cells and their clinical relevance have profoundly altered paradigms for cancer research as the cancer stem cells are considered promising new targets against cancer. Consequently, long-term cryopreservation and banking of normal and malignant stem cells is crucial and will inevitably become a routine procedure that requires highly regulated and safe methods of specimen storage. There is, however, an increasing amount of evidence showing contradictory results on the impact of cryopreservation and thawing of stem cells, including extensive physical and biological stresses, apoptosis and necrosis, mitochondrial injuries, changes to basal respiration and ATP production, cellular structural damage, telomere shortening and cellular senescence, and DNA damage and oxidative stress. Notably, cell surface proteins that play a major role in stem cell fate and are used as the biomarkers of stem cells are more vulnerable to cold stress than other proteins. There are also data supporting the alteration in some biological features and genetic integrity at the molecular level of the post-thawed stem cells. This article reviews the current and future challenges of cryopreservation of stem cells and stresses the need for further rigorous research on the methodologies for freezing and utilizing cancer stem cells following long-term storage.

Transplantation of Autologous Ex Vivo Expanded Human Conjunctival Epithelial Cells for Treatment of Pterygia: A Prospective Open-label Single Arm Multicentric Clinical Trial

Purpose:

To establish the efficacy and safety of ex vivo cultured autologous human conjunctival epithelial cell (hCjEC) transplantation for treatment of pterygia.

Methods:

Twenty-five patients with pterygia were recruited at different centers across the country. Autologous hCjEC grafts were prepared from conjunctival biopsy specimens excised from the healthy eye and cultured ex vivo on human amniotic membrane mounted on inserts using a unique mounting device. The hCjEC grafts were then transported in an in-house designed transport container for transplantation. Post-surgery, the patients were followed up on days 1, 7, 14, 30, 90, and 180 as per the approved study protocol. Clinical outcomes were assessed by slit lamp examination, visual acuity, imprint cytology, fluorescein/rose bengal staining, Schirmer's test, and photographic evaluation three and 6 months post-transplantation.

Results:

Two patients were lost to follow-up and final analysis included 23 cases. No recurrence of pterygium was observed in 18 (78.3%) patients; all of these eyes showed a smooth conjunctival surface without epithelial defects. Recurrence was observed in 5 (21.7%) patients at 3 months post-treatment. No conjunctival inflammation, secondary infections or other complications were reported. Adequate goblet cells were present in 19 (82.6%) patients at the site of transplantation.

Conclusion:

We have, for the 1^st time, standardized a protocol for preparing autologous hCjEC grafts that can be safely transported to multiple centers across the country for transplantation. The clinical outcome was satisfactory for treating pterygia.

Effect of stem cell therapy on induced diabetic keratopathy in albino rat

BACKGROUND AND OBJECTIVES

Type 2 diabetes mellitus (DM) is a prevalent disorder. Diabetic keratopathy is a well-known ocular complication secondary to type 2 DM. Topical insulin application did not affect apoptosis and necrosis levels in corneal epithelium. Autologous cell transplantation is not a viable option for diabetic patients with bilateral limbal stem cell deficiency. The present study aimed at assessing the possible effect of hemopoeitic stem cell (HSC) therapy on induced diabetic keratopathy in albino rat.

METHODS AND RESULTS

Fifteen male albino rats were divided into control group of 2 rats, diabetic group of 8 rats receiving single intraperitoneal (IP) injection of 50 mg/kg streptozotocin (STZ). 3 animals were sacrificed 6 weeks following confirmation of diabetes to confirm keratopathy and 5 rats were sacrificed 4 weeks following confirmation of keratopathy. SC therapy group included 5 rats injected with HSCs 6 weeks following confirmation of diabetes and sacrificed 4 weeks following SC therapy. Cord blood collection, stem cells isolation and labeling were performed. Eye specimens were subjected to histological, histochemical, immunohistochemical, morphometric and statistical studies. In diabetic group, the central cornea showed multiple cells with vacuolated cytoplasm and dark nuclei, focal epithelial discontinuity, reduced corneal thickness and less number of layers of corneal and conjunctival epithelia. In stem cell therapy group, few cells with vacuolated cytoplasm and dark nuclei were found in the corneal and conjunctival epithelia with more number of epithelial layers.

CONCLUSIONS

A definite ameliorating effect of HSC therapy was detected on diabetic keratopathy. The therapeutic cells were effective in limiting corneal epithelial changes.

Human limbal epithelial progenitor cells express αvβ5-integrin and the interferon-inducible chemokine CXCL10/IP-10

Stem cell (SC) therapy is the main treatment modality for patients with limbal stem cell deficiency. If limbal epithelial stem cells (LESC) can be more readily identified, isolated and maintained ex vivo, patients could be treated with better quality grafts. With prior knowledge that vitronectin (VN) is present within the LESC niche and that it supports LESC in vitro, we postulated that VN receptors (integrins αvβ3/5) are expressed by, and can be used to identify and isolate LESC. Immunolocalization studies were conducted on human corneas. Corneas were also used to expand limbal epithelial cells from either biopsies or enzyme-dissociated tissue and αvβ3/5 expression determined by flow cytometry. Integrin expressing cells were isolated by magnetic activated cell sorting then assessed by immunocytology, colony forming efficiency, RT-PCR and microarray analysis. Integrin αvβ5(+) cells co-localized to N-cadherin(+)/CK-15(+) putative LESC. αvβ5 was restricted to less than 4% of the total limbal epithelial cells, which expressed higher levels of CK-15 and formed more colonies compared to αvβ5(-) cells. Transcriptional profiling of αvβ5(+/-) cells by microarray identified several highly expressed interferon-inducible genes, which localize to putative LESC. Integrin αvβ5 is a candidate LESC marker since its expression is restricted to the limbus and αvβ5(+) limbal epithelial cells have phenotypic and functional properties of LESC. Knowledge of the niche's molecular composition and the genes expressed by its SC will facilitate isolation and maintenance of these cells for therapeutic purposes.

Cell-based therapies for ocular inflammation

Since the plasticity and the potential for re-programming cells has become widely accepted, there has been great interest in cell-based therapies. These are being applied to a range of diseases, not least ocular diseases, where it is assumed that there is a reduced risk of immune rejection although this may be more perceived than real. There are two broad classes of cell-based therapies: those aimed at restoring structure and function of specific tissues and cells; and those directed towards restoring immunological homeostasis by controlling the damaging effects of inflammatory disease. Stem cells of all types represent the first group and prototypically have been used with the aim of regenerating failing cells. In contrast, immune cells have been suggested as potential modulators of inflammation. However, there is functional overlap in these two applications, with some types of stem cells, such as mesenchymal stem cells, demonstrating a potent immunomodulatory effect. This review summarises recent information on cell based therapies for ocular disease, with special emphasis on ocular inflammatory disease, and explores current uses, potential and limitations.

The effect of topical pranoprofen 0.1% on the clinical evaluation and conjunctival HLA-DR expression in dry eyes

PURPOSE

To investigate the effect of topical pranoprofen 0.1% on the clinical evaluation and conjunctival human leukocyte antigen II (HLA-DR) expression in dry eyes.

METHODS

Sixty patients with dry eyes were randomized to 2 groups. Patients in group 1 received topical pranoprofen 0.1% plus topical sodium hyaluronate 0.1%; and patients in group 2 received sodium hyaluronate without pranoprofen. Ocular surface disease index (OSDI), tear &filig;lm break-up time (TBUT), Schirmer I test, ocular surface staining (OSS), and conjunctival HLA-DR expression were evaluated before treatment and at 15 and 30 days after treatment.

RESULTS

On day 15, patients in group 1 had significantly lower OSDI, OSS, and HLA-DR-positive cells compared with patients in group 2 (P < 0.01), and the TBUT was significantly longer in patients in group 1 than that of patients in group 2 (P < 0.01). On day 30, the difference between the 2 groups in OSS lost significance; however, there continued to be significant differences in the OSDI, TBUT, and HLA-DR expression between the 2 groups (P < 0.01). On days 15 and 30, the values in group 1 patients had significant improvement compared with their baseline values in terms of the above-mentioned parameters. The comparisons within group 2 did not reveal any significant differences. There was no significant effect in the Schirmer I test value in eyes of patients in group 1 or group 2 at days 15 or 30 (P > 0.05).

CONCLUSIONS

Topical pranoprofen 0.1% has a beneficial effect in reducing the ocular signs and symptoms of dry eyes and decreasing the inflammatory markers of conjunctival epithelial cells.

Long-term cryopreservation model of rat salivary gland stem cells for future therapy in irradiated head and neck cancer patients

Irradiated head and neck cancer patients suffer from irreversible loss of salivary gland (SG) function, along with significant morbidity and compromised quality of life. To date there is no biologically-based treatment for this distress. Adult salivary gland stem cells are promising candidates for autologous transplantation therapy in the context of tissue-engineered artificial SGs or direct cell therapy. The major restrictions in handling such cells are their limited lifespan during in vitro cultivation, resulting in a narrow time-window for implantation and a risk of tumorigenic changes during culture. To overcome these difficulties, we tested in a rat model the possibility of establishing a personal/autologous SG stem cell bank. SG's integrin-α6β1-expressing cells were shown to hold a subpopulation of SG-specific progenitor-cells. Explanted and cultured single cell-originated clones were cryopreserved for up to 3 years and shown to exhibit genetic and functional stability similar to noncryopreserved cells, as was emphasized by soft agar assay, division potential assessment, flow cytometric analysis, real-time reverse transcriptase-polymerase chain reaction, in vitro three-dimensional differentiation assay, and immunofluorescence confocal microscopy. Future integration of the novel strategies presented herein to a clinical therapeutic model will allow safe preservation until transplantation and repeated transplantation if needed. These tools open a new venue for adult autologous stem-cell transplantation-based SG regeneration.

Molecular integrity and global gene expression of breast and lung cancer stem cells under long-term storage and recovery

Cryopreservation is a common procedure widely used in biological and clinical sciences. Similar protocols are also applied in preserving cancer stem cells, a field with high promises and challenges. Specific cell surface membrane proteins are considered to be biomarkers of cancer stem cells and they may play a critical role in differentiating stem cells from non stem cells. We have looked at the possible effect of long-term cryopreservation on the molecular integrity of breast MCF7 and lung, A549 and H460, cancer stem cells and to assess if these cells are more sensitive to long-term storage process. We analyzed the expression of CD24 and CD38 as two potent biomarkers of lung cancer stem cells and EpCAM and ALDH that are used as biomarkers of a wide range of cancer stem cells. We also selected three genes essential for the normal functioning of the cells, Fos, MUC1, and HLA. Our results indicate a pattern of down-regulation in the expression of the genes following freezing, in particular among cell surface marker proteins. Global gene expression of the post-thaw breast and lung cancer stem cells also reveals a significant down-regulation in freeze-thaw cells independent from each other. Analyzing the canonical pathways between two populations reveals a significant alteration in the gene expression of the pathways involved in cell cycle, mitosis, and ataxia telangiectasia mutated pathways. Overall, our results indicate that current protocols for long-term storage of lung and breast cancer stem cells may substantially influence the activity and function of genes.