Purpose: Tear film disorders, particularly dry eye disease (DED), are among the most common ocular surface conditions and arise from dysfunction of the lacrimal functional unit, including the lacrimal gland, meibomian glands, and conjunctival goblet cells.Despite the recent advancements in the management of the tear film disorders, the treatment still remains palliative. Hence there is a need for research focusing on regenerative approaches to restore the physiological functions and homeostasis of the tear film.Methods: A selective literature review was performed using PubMed, Google Scholar, and Medline. The review is based on 127 relevant publications published up to January 2026, with emphasis on experimental and translational approaches for restoring tear film homeostasis. In addition, the latest advances in lacrimal gland regeneration are described, including recent studies conducted by our research group.Results: This review aims to first give an overview about the underlying diseases which alters the tear film composition, secondly highlighting the current treatment methods and their limitation and finally analyze recent experimental strategies that promotes tear film regeneration including stem cell-based therapies, tissue engineering of the lacrimal gland, neurotrophic factor supplementation, gene therapy, and biomaterial-assisted delivery systems.Conclusion: Regenerative approaches for tear film disorders are evolving from symptomatic management toward restoration of functional tissue. Although most strategies remain in preclinical or early translational stages, advances in stem cell biology, biomaterials, secretome research, and tissue engineering provide a promising foundation for future therapies targeting the lacrimal functional unit and long-term tear film homeostasis. By summarizing current findings and identifying research gaps, this review can highlight promising approaches for translational research and potential clinical applications.

PURPOSE:Dry eye disease (DED), a multifactorial disease of the lacrimal system, manifests itself in patients with various symptoms such as itching, inflammation, discomfort and visual impairment. In its most severe forms, it results in the breakdown of the vital tissues of lacrimal functional unit and carries the risk of vision loss. Despite the frequency of occurrence of the disease, there are no effective curative treatment options available to date. Treatment using stem cells and its secreted factors could be a promising approach in the regeneration of damaged tissues of ocular surface. The treatment using secreted factors as well as extracellular vesicles has been demonstrated beneficial effects in various ocular surface diseases. This review provides insights on the usage of stem cell derived exosomes as a promising therapy against LG dysfunction induced ADDE for ocular surface repair. METHODS:In order to gain an overview of the existing research in this field, literature search was carried out using the PubMed, Medline, Scopus and Web of Science databases. This review is based on 164 publications until June 2024 and the literature search was carried out using the key words "exosomes", "lacrimal gland regeneration", "exosomes in lacrimal dysfunction". RESULTS:The literature and studies till date suggest that exosomes and other secreted factors from stem cells have demonstrated beneficial effects on damaged ocular tissues in various ocular surface diseases. Exosomal cargo plays a crucial role in regenerating tissues by promoting homeostasis in the lacrimal system, which is often compromised in severe cases of dry eye disease. Exosome therapy shows promise as a regenerative therapy, potentially addressing the lack of effective curative treatments available for patients with dry eye disease. CONCLUSION:Stem cell-derived exosomes represent a promising, innovative approach as a new treatment option for ADDE. By targeting lacrimal gland dysfunction and enhancing ocular surface repair, exosome therapy offers potential for significant advances in dry eye disease management. Future research is needed to refine the application of this therapy, optimize delivery methods, and fully understand its long-term efficacy in restoring ocular health.

The integrity of corneal nerves is critical for ocular surface health, and damages can lead to Neurotrophic Keratopathy (NK). Despite the regenerative abilities of the peripheral nerve system (PNS), corneal nerve regeneration is often incomplete, and the underlying mechanisms are poorly understood. This study aims to identify potential factors that can enhance corneal nerve regeneration for NK treatment, with a focus on Lysophosphatidic acid (LPA).Thus, the effect of LPA and its underlying pathways in nerve regeneration is investigated in detail using in vitro mouse sensory neurons. To elucidate the impact of LPA as well as to reveal the responsible receptor, several functional assays as well as siRNA-based knock-down experiments were conducted. Additionally, possible changes in underlying pathways were investigated on mRNA levels.LPA-treated neurons significantly reduced fiber growth. However, LPAR2 knockdown neurons (Lpar2-KD) following LPA treatment showed a significant increase in fiber length. Additionally, LPA-treated neurons demonstrated enhanced levels of Lpar2 mRNA. On the other hand, nerve regeneration indicators such as Ngf, Gap-43, and Cdc42, along with LPA downstream signaling components like Pi3k and Ras, were elevated in Lpar2-KD neurons.In conclusion, this study elucidates the inhibitory effects of LPA on fiber outgrowth of sensory neurons. Furthermore, LPAR2 was identified as the responsible receptor for the LPA effect. Thus, Lpar2 knockdown might be a promising therapeutic approach to enhance neuronal regeneration in patients with NK.

Einleitung Das sog. „stromale vaskuläre Fraktion (SVF-) Gel“ ist ein mechanisch prozessiertes Produkt aus Fettgewebe, das aus Extrazellularmatrix und mesenchymalen stromalen Zellen (ASC) besteht. In vorliegender Arbeit wurde die Gewinnung von SVF-Gel mit Hilfe des VoiceInject-Systems zur Anwendung für regenerative Therapieansätze im Kopf-Hals-Gebiet untersucht.

Supplementary Table S1 from The Transcription Factor Evi-1 Is Overexpressed, Promotes Proliferation, and Is Prognostically Unfavorable in Infratentorial Ependymomas

Supplementary Table 1 from TWIST-1 Is Overexpressed in Neoplastic Choroid Plexus Epithelial Cells and Promotes Proliferation and Invasion

Introduction The so-called "stromal vascular fraction (SVF) gel" is a mechanically processed product of adipose tissue consisting of extracellular matrix and mesenchymal stromal cells (ASC). In the present work, the extraction of SVF-gel using the VoiceInject system was investigated for use in regenerative therapeutic approaches in the head and neck region.

Dry eye disease (DED) is a common multifactorial disease of the tear film and the ocular surface. The problem of DED has gained attention globally, with millions of people affected by the disorder. Although the treatment strategies for DED have significantly evolved over time, most of the existing modalities fall under the category of standard palliative care when viewed from a long-term perspective. To address these limitations, different approaches have been explored by various groups to uncover alternative treatment strategies that can contribute to a full regeneration of the damaged lacrimal gland, which is responsible for producing the major aqueous component of the tear film. For this, multiple groups have investigated the role of lacrimal gland cells in DED based on their regenerating, homing, and differentiating capabilities. In this review, we discuss in detail the therapeutic mechanisms and regenerative strategies that can potentially be applied for lacrimal gland regeneration as well as their therapeutic applications. This review mainly focuses on aqueous deficiency dry eye disease (ADDE) caused by lacrimal gland dysfunction and possible future treatment strategies. The current key findings from cell and tissue-based regenerative therapy modalities that could be utilised to achieve lacrimal gland tissue regeneration are summarized. In addition, this review summarises the available literature from in vitro to in vivo studies, their limitations in relation to lacrimal gland regeneration and the possible clinical applications. Finally, current issues and unmet needs of cell-based therapies in providing complete lacrimal gland tissue regeneration are discussed.

PURPOSE:Impairment of corneal nerves can lead to neurotrophic keratopathy accompanied with severe ocular surface damage, which due to limited treatment options, can result in severe visual deterioration. This study evaluates a possible new treatment by enhancing the corneal nerve regeneration using a Rho Kinase inhibitor (Y27632). ROCK is known to play an important role in regulating cell morphology, adhesion and motility but little is known about its role in corneal nerve regeneration.METHODS:Effects of ROCK inhibition on murine peripheral nerves was assessed in single cell- and wound healing assays as well as a 3D in vitro model. Furthermore, Sholl analysis evaluating neuronal branching and life-death assays evaluating toxicity of the inhibitor were performed. An in vivo mouse model was established, with monitoring weekly corneal nerve regrowth using confocal microscopy. Additionally, corneal nerve fiber length was evaluated by immunofluorescence staining. Underlying pathways were examined by qrtPCR.RESULTS:ROCK inhibition leads to a significant enhancement of fiber growth in vitro. Sholl analysis revealed a higher degree of branching of treated fibers. Cytotoxicity assay showed no influence of Y27632 on cellular survival. In vivo measurement revealed significant enhanced regeneration after injury in the treated group. QrtPCR of trigeminal ganglia confirmed ROCK knock-down as well as altered pathways.CONCLUSION:The inhibition of ROCK after corneal nerve injury resulted in an enhanced regrowth of fibers in vitro and in vivo. This might be a step towards a new therapeutic concept for the treatment of impaired corneal nerves in diseases such as neurotrophic keratopathy.

The in vitro reconstruction of stromal tissue by long-term cultivation of corneal fibroblasts is a smart approach for regenerative therapies of ocular surface diseases. However, systematic investigations evaluating optimized cultivation protocols for the realization of a biomaterial are lacking. This study investigated the influence of supplements to the culture media of human corneal fibroblasts on the formation of a cell sheet consisting of cells and extracellular matrix. Among the supplements studied are vitamin C, fetal bovine serum, L-glutamine, components of collagen such as L-proline, L-4-hydroxyproline and glycine, and TGF-β1, bFGF, IGF-2, PDGF-BB and insulin. After long-term cultivation, the proliferation, collagen and glycosaminoglycan content and light transmission of the cell sheets were examined. Biomechanical properties were investigated by tensile tests and the ultrastructure was characterized by electron microscopy, small-angle X-ray scattering, antibody staining and ELISA. The synthesis of extracellular matrix was significantly increased by cultivation with insulin or TGF-β1, each with vitamin C. The sheets exhibited a high transparency and suitable material properties. The production of a transparent, scaffold-free, potentially autologous, in vitro-generated construct by culturing fibroblasts with extracellular matrix synthesis-stimulating supplements represents a promising approach for a biomaterial that can be used for ocular surface reconstruction in slowly progressing diseases.

Purpose: The long-term success of visual rehabilitation in patients with severe conjunctival scarring is reliant on the reconstruction of the conjunctiva with a suitable substitute. The purpose of this study is the development and investigation of a re-epithelialized conjunctival substitute based on porcine decellularized conjunctiva (PDC). Methods: PDC was re-epithelialized either with pre-expanded human conjunctival epithelial cells (PDC + HCEC) or with a human conjunctival explant placed directly on PDC (PDC + HCEx). Histology and immunohistochemistry were performed to evaluate epithelial thickness, proliferation (Ki67), apoptosis (Caspase 3), goblet cells (MUC5AC), and progenitor cells (CK15, Delta Np63, ABCG2). The superior construct (PDC + HCEx) was transplanted into a conjunctival defect of a rabbit (n = 6). Lissamine green staining verified the epithelialization in vivo. Orbital tissue was exenterated on day 10 and processed for histological and immunohistochemical analysis to examine the engrafted PDC + HCEx. A human-specific antibody was used to detect the transplanted cells. Results: From day-14 in vitro onward, a significantly thicker epithelium and greater number of cells expressing Ki67, CK15, Delta Np63, and ABCG2 were noted for PDC + HCEx versus PDC + HCEC. MUC5AC-positive cells were found only in PDC + HCEx. The PDC + HCEx-grafted rabbit conjunctivas were lissamine-negative during the evaluation period, indicating epithelial integrity. Engrafted PDC + HCEx showed preserved progenitor cell properties and an increased number of goblet cells comparable to those of native conjunctiva. Conclusion: Placing and culturing a human conjunctival explant directly on PDC (PDC + HCEx) enables the generation of a stable, stratified, goblet cell-rich construct that could provide a promising alternative conjunctival substitute for patients with extensive conjunctival stem and goblet cell loss.

Diabetic retinopathy (DR) is one of the most severe clinical manifestations of diabetes mellitus and a major cause of blindness. DR is principally a microvascular disease, although the pathogenesis also involves metabolic reactive intermediates which induce neuronal and glial activation resulting in disruption of the neurovascular unit and regulation of the microvasculature. However, the impact of neural/glial activation in DR remains controversial, notwithstanding our understanding as to when neural/glial activation occurs in the course of disease. The objective of this study was to determine a potential protective role of neuropeptide Y (NPY) using an established model of DR permissive to N-methyl-D-aspartate (NMDA)-induced excitotoxic apoptosis of retinal ganglion cells (RGC) and vascular endothelial growth factor (VEGF)-induced vascular leakage. In vitro evaluation using primary retinal endothelial cells demonstrates that NPY promotes vascular integrity, demonstrated by maintained tight junction protein expression and reduced permeability in response to VEGF treatment. Furthermore, ex vivo assessment of retinal tissue explants shows that NPY can protect RGC from excitotoxic-induced apoptosis. In vivo clinical imaging and ex vivo tissue analysis in the diabetic model permitted assessment of NPY treatment in relation to neural and endothelial changes. The neuroprotective effects of NPY were confirmed by attenuating NMDA-induced retinal neural apoptosis and able to maintain inner retinal vascular integrity. These findings could have important clinical implications and offer novel therapeutic approaches for the treatment in the early stages of DR.

The shortage of donor corneas as well as the limitations of tissue substitutes leads to the necessity to develop alternative materials for ocular surface reconstruction. Corneal surface substitutes must fulfill specific requirements such as high transparency, low immunogenicity, and mechanical stability combined with elasticity. This in vitro study evaluates a decellularized matrix secreted from human corneal fibroblasts (HCF) as an alternative material for ocular surface reconstruction. HCF from human donors were cultivated with the supplementation of vitamin C to form a stable and thick matrix. Furthermore, due to enhanced cultivation time, a three-dimensional like multilayered construct which partly mimics the complex structure of the corneal stroma could be generated. The formed human cell-based matrices (so-called cell sheets [CS]) were subsequently decellularized. The complete cell removal, collagen content, ultrastructure, and cell toxicity of the decellularized CS (DCS) as well as biomechanical properties were analyzed. Surgical feasibility was tested on enucleated porcine eyes. After decellularization and sterilization, a transparent, thick, cell free, and sterile tissue substitute resulted, which allowed expansion of limbal epithelial stem cells with no signs of cytotoxicity, and good surgical feasibility. DCS seem to be a promising new corneal tissue substitute derived from human cells without the limitation of donor material; however, futurein vivostudies are necessary to further elucidate its potential for ocular surface reconstruction.

In situ regeneration of lacrimal gland (LG) tissue would be a promising approach to curatively treat dry eye disease (DED). Mesenchymal stem cells (MSC) exhibit therapeutic effects in a variety of pathological conditions and our group recently reported that their number increases in regenerating mouse LG. Since the therapeutic effects are suggested to arise from secreted trophic factors, the application of MSC-secreted proteins seems to be a promising approach to induce/enhance LG regeneration. Therefore, this study aims to optimize the isolation of murine LG-MSC and analyze their secretome to investigate its potential for LG epithelial cell survival in vitro. For optimization, LG-MSC were isolated by an explant technique or cell sorting and their secretome was investigated under normal and inflammatory conditions. Results showed that the secretome of MSC had beneficial effects on the viability of ethanol-damaged LG epithelial cells. Additional, Lipocalin-2, prosaposin, ras GTPase-activating protein-binding protein 1 (Rac1) and signal transducer and activator of transcription 1 (STAT1), proteins that were up-regulated under inflammatory conditions, further improved the cell survival of ethanol-damaged LG epithelial cells. Interestingly, recovery of cell viability was highest, when the cells were incubated with STAT1. Summarizing, this study identified promising proteins for further studies on LG regeneration.