Umbilical cord stem cells in the treatment of corneal disease

Extracellular vesicles secreted from mesenchymal stem cells ameliorate renal ischemia reperfusion injury by delivering miR-100-5p targeting FKBP5/AKT axis

The incidence of acute kidney injury (AKI) due to ischemia-reperfusion (IR) injury is increasing. There is no effective treatment for AKI, and because of this clinical challenge, AKI often progresses to chronic kidney disease, which is closely associated with poor patient outcomes and high mortality rates. Small extracellular vesicles from human umbilical cord mesenchymal stem cells (hUCMSC-sEVs) play increasingly vital roles in protecting tissue function from the effects of various harmful stimuli owing to their specific biological features. In this study, we found that miR-100-5p was enriched in hUCMSC-sEVs, and miR-100-5p targeted FKBP5 and inhibited HK-2 cell apoptosis by activating the AKT pathway. HK-2 cells that were exposed to IR injury were cocultured with hUCMSC-sEVs, leading to an increase in miR-100-5p levels, a decrease in FKBP5 levels, and an increase in AKT phosphorylation at Ser 473 (AKT-473 phosphorylation). Notably, these effects were significantly reversed by transfecting hUCMSCs with an miR-100-5p inhibitor. Moreover, miR-100-5p targeted FKBP5, as confirmed by a dual luciferase reporter assay. In vivo, intravenous infusion of hUCMSC-sEVs into mice suffering from IR injury resulted in significant apoptosis inhibition, functional maintenance and renal histological protection, which in turn decreased FKBP5 expression levels. Overall, this study revealed an effect of hUCMSC-sEVs on inhibiting apoptosis; hUCMSC-sEVs reduced renal IR injury by delivering miR-100-5p to HK-2 cells, targeting FKBP5 and thereby promoting AKT-473 phosphorylation to activate the AKT pathway. This study provides novel insights into the role of hUCMSC-sEVs in the treatment of AKI.

Corneal Epithelial Development and the Role of Induced Pluripotent Stem Cells for Regeneration

Severe corneal disorders due to infective aetiologies, trauma, chemical injuries, and chronic cicatricial inflammations, are among vision-threatening pathologies leading to permanent corneal scarring. The whole cornea or lamellar corneal transplantation is often used as a last resort to restore vision. However, limited autologous tissue sources and potential adverse post-allotransplantation sequalae urge the need for more robust and strategic alternatives. Contemporary management using cultivated corneal epithelial transplantation has paved the way for utilizing stem cells as a regenerative potential. Humaninduced pluripotent stem cells (hiPSCs) can generate ectodermal progenitors and potentially be used for ocular surface regeneration. This review summarizes the process of corneal morphogenesis and the signaling pathways underlying the development of corneal epithelium, which is key to translating the maturation and differentiation process of hiPSCs in vitro. The current state of knowledge and methodology for driving efficient corneal epithelial cell differentiation from pluripotent stem cells are highlighted.

Recent Advances of Adipose-Tissue-Derived Mesenchymal Stem Cell-Based Therapy for Retinal Diseases

With the rapid development of stem cell research in modern times, stem cell-based therapy has opened a new era of tissue regeneration, becoming one of the most promising strategies for currently untreatable retinal diseases. Among the various sources of stem cells, adipose tissue-derived mesenchymal stem cells (ADSCs) have emerged as a promising therapeutic modality due to their characteristics and multiple functions, which include immunoregulation, anti-apoptosis of neurons, cytokine and growth factor secretion, and antioxidative activities. Studies have shown that ADSCs can facilitate the replacement of dying cells, promote tissue remodeling and regeneration, and support the survival and growth of retinal cells. Recent studies in this field have provided numerous experiments using different preclinical models. The aim of our review is to provide an overview of the therapeutic strategies, modern-day clinical trials, experimental models, and potential clinical use of this fascinating class of cells in addressing retinal disorders and diseases.

Cell-based Therapies for Corneal and Retinal Disorders

Maintenance of the visual function is the desired outcome of ophthalmologic therapies. The shortcomings of the current treatment options, like partial recovery, post-operation failure, rigorous post-operative care, complications, etc., which are usually encountered with the conventional treatment options has warranted newer treatment options that may eliminate the root cause of diseases and minimize the side effects. Cell therapies, a class of regenerative medicines, have emerged as cutting-edge treatment option. The corneal and retinal dystrophies during the ocular disorders are the major cause of blindness, worldwide. Corneal disorders are mainly categorized mainly into corneal epithelial, stromal, and endothelial disorders. On the other hand, glaucoma, retinitis pigmentosa, age-related macular degeneration, diabetic retinopathy, Stargardt Disease, choroideremia, Leber congenital amaurosis are then major retinal degenerative disorders. In this manuscript, we have presented a detailed overview of the development of cell-based therapies, using embryonic stem cells, bone marrow stem cells, mesenchymal stem cells, dental pulp stem cells, induced pluripotent stem cells, limbal stem cells, corneal epithelial, stromal and endothelial, embryonic stem cell-derived differentiated cells (like retinal pigment epithelium or RPE), neural progenitor cells, photoreceptor precursors, and bone marrow-derived hematopoietic stem/progenitor cells etc. The manuscript highlights their efficiency, drawbacks and the strategies that have been explored to regain visual function in the preclinical and clinical state associated with them which can be considered for their potential application in the development of treatment.

[Corneal regeneration: is there a place for tissues of perinatal origin?]

The article reviews the main properties of the cornea and the mechanisms of its physiological regeneration and repair in response to damage and describes the most promising methods of treatment aimed at stimulating limbal stem cells and based on the use of native tissues of perinatal origin, umbilical cord mesenchymal stromal cells, and cell-free therapeutic products.

Mesenchymal Stromal Cell-Based Therapy for Dry Eye: Current Status and Future Perspectives

Dry eye is one of the most common chronic diseases in ophthalmology. It affects quality of life and has become a public health problem that cannot be ignored. The current treatment methods mainly include artificial tear replacement therapy, anti-inflammatory therapy, and local immunosuppressive therapy. These treatments are mainly limited to improvement of ocular surface discomfort and other symptoms. In recent years, regenerative medicine has developed rapidly, and ophthalmologists are working on new methods to treat dry eye. Mesenchymal stromal cells (MSCs) have anti-inflammatory, tissue repair, and immune regulatory effects, and have become a promising tool for the treatment of dry eye. These effects can also be produced by MSC-derived exosomes (MSC-Exos). As a cell-free therapy, MSC-Exos are hypoimmunogenic, serve more stable entities, and compared with MSCs, reduce the safety risks associated with the injection of live cells. This article reviews current knowledge about MSCs and MSC-Exos, and highlights the latest progress and future prospects of MSC-based therapy in dry eye treatment.

Autoimmune Epithelitis and Chronic Inflammation in Sjögren's Syndrome-Related Dry Eye Disease

Autoimmune epithelitis and chronic inflammation are one of the characteristic features of the immune pathogenesis of Sjögren’s syndrome (SS)-related dry eye disease. Autoimmune epithelitis can cause the dysfunction of the excretion of tear fluid and mucin from the lacrimal glands and conjunctival epithelia and meibum from the meibomian glands. The lacrimal gland and conjunctival epithelia express major histocompatibility complex class II or human leukocyte antigen-DR and costimulatory molecules, acting as nonprofessional antigen-presenting cells for T cell and B cell activation in SS. Ocular surface epithelium dysfunction can lead to dry eye disease in SS. Considering the mechanisms underlying SS-related dry eye disease, this review highlights autoimmune epithelitis of the ocular surface, chronic inflammation, and several other molecules in the tear film, cornea, conjunctiva, lacrimal glands, and meibomian glands that represent potential targets in the treatment of SS-related dry eye disease.

Integration and remodelling of a collagen anterior lamellar keratoplasty graft in an animal model - A preliminary report

There is an international shortage of donor corneas for transplantation to treat the 1.5-2.0 million new cases of blindness secondary to corneal disease. Research has therefore been directed towards the development of artificial corneas using alternative materials such as collagen. The biocompatibility of an acellular collagen-based scaffold for anterior lamellar keratoplasty was investigated in vivo in a rabbit model. This scaffold has previously shown promise as a corneal substitute in vitro. Slit-lamp and Optical Coherence Tomography examinations were carried out at 2 weeks, 1, 2, 3, and 6 months post-operatively. Graft-host integration was investigated using immunohistochemistry of the cornea at 6 months. Results showed that the graft was biocompatible, supported corneal re-epithelialisation, and showed no signs of rejection. Migration of stromal cells into areas of the graft was observed, however this was accompanied by extensive graft digestion. Whilst the scaffold was biocompatible, further modifications to the material or supplementation with matrix metalloproteinase inhibitors are required to bring us closer to a stable and fully integrated corneal substitute.

Stem cell therapy in ocular pathologies in the past 20 years

Stem cell therapies are successfully used in various fields of medicine. This new approach of research is also expanding in ophthalmology. Huge investments, resources and important clinical trials have been performed in stem cell research and in potential therapies. In recent years, great strides have been made in genetic research, which permitted and enhanced the differentiation of stem cells. Moreover, the possibility of exploiting stem cells from other districts (such as adipose, dental pulp, bone marrow stem cells, etc.) for the treatment of ophthalmic diseases, renders this topic fascinating. Furthermore, great strides have been made in biomedical engineering, which have proposed new materials and three-dimensional structures useful for cell therapy of the eye. The encouraging results obtained on clinical trials conducted on animals have given a significant boost in the creation of study protocols also in humans. Results are limited to date, but clinical trials continue to evolve. Our attention is centered on the literature reported over the past 20 years, considering animal (the most represented in literature) and human clinical trials, which are limiting. The aim of our review is to present a brief overview of the main types of treatments based on stem cells in the field of ophthalmic pathologies.

Measurement of In Vivo Biomechanical Changes Attributable to Epithelial Removal in Keratoconus Using a Noncontact Tonometer

PURPOSE

To compare the biomechanical properties of the cornea after epithelial removal in eyes with keratoconus undergoing corneal cross-linking.

METHODS

Prospective interventional case series at a university hospital tertiary referral center. Corneal biomechanical properties were measured in patients with keratoconus undergoing corneal cross-linking, immediately before and after epithelial debridement by using a dynamic ultrahigh-speed Scheimpflug camera equipped with a noncontact tonometer.

RESULTS

The study comprised 45 eyes of 45 patients with a mean age of 19.6 ± 4.9 years (range 14-34). The cornea was found to be 23.7 ± 15.7 μm thinner after epithelial removal (P < 0.01). Corneal stiffness was reduced after epithelial removal as demonstrated by a significant decrease of parameters such as stiffness parameter A1 (12.31, P < 0.01), stiffness parameter-highest concavity (2.25, P < 0.01), A1 length (0.13 mm, P = 0.04), highest concavity radius of curvature (0.26 mm, P = 0.01), highest concavity time (0.22 ms, P = 0.04) and an increase in A1 velocity (-0.01 m/s, P = 0.01), A1 deformation amplitude (-0.03 mm, P ≤ 0.01), A1 deflection length (-0.32 mm, P < 0.01), A2 deformation amplitude (-0.03 mm, P = 0.01), and A2 deflection length (-1.00 mm, P < 0.01). There were no significant differences in biomechanical intraocular pressure (0.15 mm Hg, P = 0.78), deformation amplitude (0.03, P = 0.54), maximum inverse radius (-0.01 mm, P = 0.57), and whole eye movement length (-0.02 mm, P = 0.12).

CONCLUSIONS

Dynamic ultrahigh-speed Scheimpflug camera equipped with a noncontact tonometer offers an alternative method for in vivo measurements of the epithelial layer's contribution to corneal biomechanical properties. Our results suggest that corneal epithelium may play a more significant role in corneal biomechanical properties in patients with keratoconus than previously described.

Human Umbilical Cord-Derived Mesenchymal Stem Cells Promote Corneal Epithelial Repair In Vitro

Corneal injuries are among the leading causes of blindness and vision impairment. Trauma, infectious keratitis, thermal and chemical (acids and alkali burn) injuries may lead to irreversible corneal scarring, neovascularization, conjunctivalization, and limbal stem cell deficiency. Bilateral blindness constitutes 12% of total global blindness and corneal transplantation remains a stand-alone treatment modality for the majority of end-stage corneal diseases. However, global shortage of donor corneas, the potential risk of graft rejection, and severe side effects arising from long-term use of immunosuppressive medications, demands alternative therapeutic approaches. Umbilical cord-derived mesenchymal stem cells can be isolated in large numbers using a relatively less invasive procedure. However, their role in injury induced corneal repair is largely unexplored. Here, we isolated, cultured and characterized mesenchymal stem cells from human umbilical cord, and studied the expression of mesenchymal (CD73, CD90, CD105, and CD34), ocular surface and epithelial (PAX6, WNT7A, and CK-8/18) lineage markers through immunofluorescence. The cultured human limbal and corneal epithelial cells were used as controls. Scratch assay was used to study the corneal epithelial repair potential of umbilical cord-derived mesenchymal stem cells, in vitro. The in vitro cultured umbilical cord-derived mesenchymal stem cells were plastic adherent, showed trilineage differentiation and expressed: mesenchymal markers CD90, CD105, CD73; epithelial marker CK-8/18, and ocular lineage developmental markers PAX6 and WNT-7A. Our findings suggest that umbilical cord-derived mesenchymal stem cells promote repair of the injured corneal epithelium by stimulating the proliferation of corneal epithelial cells, in vitro. They may serve as a potential non-ocular source of stem cells for treating injury induced bilateral corneal diseases.

Safety of grafting acellular human corneal lenticule seeded with Wharton's Jelly-Derived Mesenchymal Stem Cells in an experimental animal model

The present study was conducted to evaluate safety of grafting acellular human corneal lenticule seeded with Wharton's Jelly-derived Mesenchymal Stem Cells (WJSC) in an experimental animal model. Human corneal lenticules were decellularized with a rate of about 97% with an acceptable lack of cytotoxicity and relatively intact ultrastructure of the lenticules. 12 rabbits underwent unilateral stromal pocketing with implantation of decellularized lenticules. Implantation was performed for 6 rabbits along with graft recellularization with WJSCs. Rabbits were euthanized after 1 month (n = 6) and 3 months (n = 6) to evaluate progression of graft bio-integration. No clinical rejection sign was detected during the study. Histopathological analysis showed that, grafts were integrated well with the least distortion of surrounding collagen bundles. After 3 months, labeled WJCS was detected representing viability of stem cells in the host. Increased expression of keratocyte-specific markers showed the potential of recruiting WJSCs as keratocyte progenitor cells to reinforce corneal ultrastructure.

The progress in corneal translational medicine

Cornea tissue is in high demand by tissue donation centres globally, and thus tissue engineering cornea, which is the main topic of corneal translational medicine, can serve as a limitless alternative to a donated human cornea tissue. Tissue engineering aims to produce solutions to the challenges associated with conventional cornea tissue, including transplantation and use of human amniotic membrane (HAM), which have issues with storage and immune rejection in patients. Accordingly, by carefully selecting biomaterials and fabrication methods to produce these therapeutic tissues, the demand for cornea tissue can be met, with an improved healing outcome for recipients with less associated harmful risks. In this review paper, we aim to present the recent advancements in the research and clinical applications of cornea tissue, applications including biomaterial selection, fabrication methods, scaffold structure, cellular response to these scaffolds, and future advancements of these techniques.

Corneal stroma regeneration: Preclinical studies

Corneal grafting is one of the most common and successful forms of human tissue transplantation in the world, but the need for corneal grafting is growing and availability of human corneal donor tissue to fulfill this increasing demand is not assured worldwide. The stroma is responsible for many features of the cornea, including its strength, refractive power and transparency, so enormous efforts have been put into replicating the corneal stroma in the laboratory to find an alternative to classical corneal transplantation. Unfortunately this has not been yet accomplished due to the extreme difficulty in mimicking the highly complex ultrastructure of the corneal stroma, and none of the obtained substitutes that have been assayed has been able to replicate this complexity yet. In general, they can neither match the mechanical properties nor recreate the local nanoscale organization and thus the transparency and optical properties of a normal cornea. In this context, there is an increasing interest in cellular therapy of the corneal stroma using Induced Pluripotent Stem Cells (iPSCs) or mesenchymal stem cells (MSCs) from either ocular or extraocular sources, as they have proven to be capable of producing new collagen within the host stroma, modulate preexisting scars and enhance transparency by corneal stroma remodeling. Despite some early clinical data is already available, in the current article we will summary the available preclinical evidence about the topic corneal stroma regeneration. Both, in vitro and in vivo experiments in the animal model will be shown.

Mesenchymal Stem/Progenitor Cells: The Prospect of Human Clinical Translation

Mesenchymal stem/progenitor cells (MSCs) are key players in regenerative medicine, relying principally on their differentiation/regeneration potential, immunomodulatory properties, paracrine effects, and potent homing ability with minimal if any ethical concerns. Even though multiple preclinical and clinical studies have demonstrated remarkable properties for MSCs, the clinical applicability of MSC-based therapies is still questionable. Several challenges exist that critically hinder a successful clinical translation of MSC-based therapies, including but not limited to heterogeneity of their populations, variability in their quality and quantity, donor-related factors, discrepancies in protocols for isolation, in vitro expansion and premodification, and variability in methods of cell delivery, dosing, and cell homing. Alterations of MSC viability, proliferation, properties, and/or function are also affected by various drugs and chemicals. Moreover, significant safety concerns exist due to possible teratogenic/neoplastic potential and transmission of infectious diseases. Through the current review, we aim to highlight the major challenges facing MSCs' human clinical translation and shed light on the undergoing strategies to overcome them.

Measurement of refractive, wavefront, topographic, and keratometric changes attributable to epithelial removal in keratoconus

OBJECTIVE

The corneal epithelium is able to mask topographic and keratometric abnormalities of the underlying Bowman layer in keratoconus, but its contribution to refractive and wavefront parameters has not yet been studied. This study compared the refractive and aberrometric features of the corneal epithelium and Bowman layer in eyes with keratoconus before and after epithelial debridement.

METHODS

Corneal refractive and wavefront variables were measured in patients with keratoconus undergoing corneal crosslinking-immediately before and after epithelial debridement using a third-generation combined corneal topographer, autorefractor, and aberrometer.

RESULTS

After epithelial debridement, there were significant changes in spherical equivalent (-1.37 D; p < 0.01) and asphericity (-0.64; p = 0.03). The mean difference in the magnitude of epithelium-induced astigmatism in the 3rd and 5th central millimeter rings was 0.44 ± 3.20 D × 8 and 0.43 ± 2.75 D × 21 (positive cylinder), respectively. Corneal astigmatism axis shifted in the against-the-rule orientation after epithelial debridement. There were no significant changes in any corneal higher-order aberration parameter after epithelial debridement (p > 0.05).

CONCLUSIONS

In eyes with keratoconus, epithelial debridement increased the magnitude of anterior corneal prolateness and tended to increase astigmatism and shift its axis toward the against-the-rule orientation. This study supports the notion that the corneal epithelium smooths underlying Bowman layer irregularity in keratoconus.

Progress in the treatment of osteoarthritis with umbilical cord stem cells

Osteoarthritis is a chronic degenerative joint disease with an incidence of 81% among people aged over 65 years in China. Osteoarthritis significantly decreases the quality of life of patients, causing physical and psychological damage and posing a serious economic burden. Clinical treatments for osteoarthritis include drug and surgical treatments. Drug treatment can successfully alleviate pain but not satisfactorily reverse joint damage, while surgical intervention is typically used to treat end-stage disease. Stem cells are multi-potential progenitor cells with self-renewal and multi-lineage differentiation abilities, and can differentiate into many kinds of cells, including chondrocytes. Umbilical cord stem cells, also known as Wharton’s jelly mesenchymal stem cells (WJ-MSCs), have become the first choice for cartilage regeneration engineering owing to their availability and convenience of collection. This article reviews the biological characterization of WJ-MSCs in recent years, their advantages compared with other stem cells, and their application in the treatment of osteoarthritis in animal experiments and clinical trials.

Human umbilical cord-mesenchymal stem cells: a promising strategy for corneal epithelial regeneration

Aim: As a strategy to improve the outcome of ex vivo cultivated corneal epithelial transplantation, the role of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) is investigated in promoting corneal epithelial growth and functions. Materials & methods: Human telomerase-immortalized corneal epithelial cells were characterized and its functions evaluated by scratch migration assay, cellular senescence, HLA expression and spheres formation with hUC-MSC. Results: Expression of corneal epithelial markers was influenced by the duration and method of co-culture. Indirect co-culture improved cellular migration and delayed senescence when treated after 3 and 5 days. hUC-MSC downregulated expression of HLA Class I and II in IFN-γ-stimulated human telomerase-immortalized corneal epithelial cells. Conclusion: hUC-MSC promote corneal epithelial growth and functions after treatment with hUC-MSC.

Umbilical cord stem cells: Background, processing and applications

Stem cells have currently gained attention in the field of medicine not only due to their ability to repair dysfunctional or damaged cells, but also they could be used as drug delivery system after being engineered to do so. Human umbilical cord is attractive source for autologous and allogenic stem cells that are currently amenable to treatment of various diseases. Human umbilical cord stem cells are -in contrast to embryonic and fetal stem cells- ethically noncontroversial, inexpensive and readily available source of cells. Umbilical cord, umbilical cord vein, amnion/placenta and Wharton's jelly are all rich of many types of multipotent stem cell populations capable of forming many different cell types. This review will focus on umbilical cord stem cells processing and current application in medicine.

The TRIM protein Mitsugumin 53 enhances survival and therapeutic efficacy of stem cells in murine traumatic brain injury

Background

Traumatic brain injury (TBI) is a common neurotrauma leading to brain dysfunction and death. Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) hold promise in the treatment of TBI. However, their efficacy is modest due to low survival and differentiation under the harsh microenvironment of the injured brain. MG53, a member of TRIM family protein, plays a vital role in cell and tissue damage repair. The present study aims to test whether MG53 preserves hUC-MSCs against oxidative stress and enhances stem cell survival and efficacy in TBI treatment.

Methods

In this study, we performed a series of in vitro and in vivo experiments in hUC-MSCs and mice to define the function of MG53 enhancing survival, neurogenesis, and therapeutic efficacy of stem cells in murine traumatic brain injury.

Results

We found that recombinant human MG53 (rhMG53) protein protected hUC-MSCs against H₂O₂-induced oxidative damage and stimulated hUC-MSC proliferation and migration. In a mouse model of contusion-induced TBI, intravenous administration of MG53 protein preserved the survival of transplanted hUC-MSCs, mitigated brain edema, reduced neurological deficits, and relieved anxiety and depressive-like behaviors. Co-treatment of MG53 and hUC-MSCs enhanced neurogenesis by reducing apoptosis and improving PI3K/Akt-GSK3β signaling.

Conclusion

MG53 enhances the efficacy of hUC-MSCs in the recovery of TBI, indicating that such adjunctive therapy may provide a novel strategy to lessen damage and optimize recovery for brain injury.

Direct measurement of anterior corneal curvature changes attributable to epithelial removal in keratoconus

PURPOSE

To compare the tomography of the corneal epithelium and Bowman layer in eyes with moderate to severe keratoconus before and after epithelial debridement.

SETTING

University hospital tertiary referral center.

DESIGN

Prospective case series.

METHODS

Dual-channel Scheimpflug combined with Placido-disk tomography was used to measure the corneal variables in eyes with keratoconus having corneal crosslinking immediately before and after epithelial debridement. The differences in pachymetry, axial keratometry, astigmatism magnitude, asphericity, total corneal power, and spherical aberrations were computed.

RESULTS

The study comprised 30 eyes of 30 patients. After epithelial removal, the central (0.0 to 4.0 mm) and midperipheral (4.0 to 7.0 mm) corneal zones were significantly thinner mean (21 μm ± 14 [SD] and 35 ± 44 μm, respectively). The mean anterior axial flat keratometry (K) (+1.71 diopters [D]), steep K (+2.14 D), maximum K (+2.13 D), corneal astigmatism (+1.11 D), asphericity (-0.31), and total corneal power changes (+2.03 D) were significantly different after epithelial debridement. There were no significant changes in posterior corneal flat K or steep K, posterior corneal astigmatism, or posterior asphericity. There were no significant differences in the mean astigmatic axis (anterior or posterior corneal surface) or spherical aberration after epithelial debridement.

CONCLUSIONS

In eyes with moderate to severe keratoconus, the tomography of Bowman layer was significantly steeper than that of the epithelium; thus, epithelial debridement increased the magnitude of anterior corneal keratometry, astigmatism, and prolateness. These data suggest that the corneal epithelium smooths the underlying Bowman layer irregularity in keratoconus.

Cellular therapy of the corneal stroma: a new type of corneal surgery for keratoconus and corneal dystrophies

Cellular therapy of the corneal stroma, with either ocular or extraocular stem cells, has been gaining a lot of interest over the last decade. Multiple publications from different research groups are showing its potential benefits in relation to its capacity to improve or alleviate corneal scars, improve corneal transparency in metabolic diseases by enhancing the catabolism of the accumulated molecules, generate new organized collagen within the host stroma, and its immunosuppressive and immunomodulatory properties. Autologous extraocular stem cells do not require a healthy contralateral eye and they do not involve any ophthalmic procedures for their isolation. Mesenchymal stem cells have been the most widely assayed and have the best potential to differentiate into functional adult keratocytes in vivo and in vitro. While embryonic stem cells have been partially abandoned due to ethical implications, the discovery of the induced pluripotent stem cells (iPSC) has opened a new and very promising field for future research as they are pluripotent cells with the capacity to theoretically differentiate into any cell type, with the special advantage that they are obtained from adult differentiated cells. Cellular delivery into the corneal stroma has been experimentally assayed in vivo in multiple ways: systemic versus local injections with or without a carrier. Encouraging preliminary human clinical data is already available although still very limited, and further research is necessary in order to consolidate the clinical applications of this novel therapeutic line.