Molecular mechanisms regulating wound repair: Evidence for paracrine signaling from corneal epithelial cells to fibroblasts and immune cells following transient epithelial cell treatment with Mitomycin C

Mechanisms Regulating Mitochondrial Transfer in Human Corneal Epithelial Cells

Purpose

The intraepithelial corneal nerves (ICNs) innervating the cornea are essential to corneal epithelial cell homeostasis. Rho-associated kinase (ROCK) inhibitors (RIs) have been reported to play roles in neuron survival after injury and in mitochondrial transfer between corneal epithelial cells. In this study, the mechanisms human corneal limbal epithelial (HCLE) cells use to control intercellular mitochondrial transfer are assessed.

Methods

Mitotracker and AAV1 mitotag eGFPmCherry were used to allow us to study mitochondrial transfer between HCLE cells and neurons in co-cultures and in HCLE cultures. A mitochondrial transfer assay was developed using HCLE cells to quantify the impact of cell stress and inhibition of phagocytosis, gap junctions, and ROCK on mitochondrial transfer, cell adhesion, migration, matrix deposition, and mitochondrial content.

Results

Bidirectional mitochondrial transfer occurs between HCLE cells and neurons. Mitochondrial transfer among HCLE cells is inhibited when gap junction function is reduced and enhanced by acid stress and by inhibition of either phagocytosis or ROCK. Media conditioned by RI-treated cells stimulates cell adhesion and mitochondrial transfer.

Conclusions

Maximal mitochondrial transfer takes place when gap junctions are functional, when ROCK and phagocytosis are inhibited, and when cells are stressed by low pH media. Treatments that reduce mitochondrial content increase HCLE cell mitochondrial transfer. ROCK inhibition in co-cultures causes the release and adhesion of mitochondria to substrates where they can be engulfed by migrating HCLE cells and growing axons and their growth cones.

ROCK Inhibitor Enhances Neurite Outgrowth In Vitro and Corneal Sensory Nerve Reinnervation In Vivo

Purpose

The intraepithelial corneal nerves are essential to corneal health. Rho kinase or ROCK inhibitors (RIs) have been reported to play a role in neuron survival after injury. Here we assess integrin and extracellular matrix expression in primary mouse neurons and determine whether treating cells with RI impacts neurite outgrowth in vitro and reinnervation after trephine and debridement injury in mice in vivo.

Methods

Cocultures of human corneal limbal epithelial cells and E11.5 mouse trigeminal neurons and neurons alone were grown on glass coverslips. High-resolution imaging was performed to localize integrins and laminin on neurons and to determine whether RI impacts neurite outgrowth in vitro and in vivo after both 1.5-mm trephine and 1.5-mm debridement injuries.

Results

Several integrin α (α3, α6, αv) chains as well as β4 integrin are expressed on neuron axons and growth cones in cocultures. RI treatment of isolated neurons, cocultures, and in conditioned media increases neurite outgrowth. In vivo, RI positively impacts sensory nerve reinnervation after trephine and debridement injury.

Conclusions

These studies are the first to demonstrate expression of β4 integrin on trigeminal sensory neurons and preferential adhesion of neurons to the laminin-enriched matrices found in footprints deposited by human corneal limbal epithelial cells. In addition, we also document for the first time the positive impact of RI on neurite outgrowth in vitro and reinnervation in vivo.

Current Advances in Corneal Stromal Stem Cell Biology and Therapeutic Applications

Corneal stromal stem cells (CSSCs) are of particular interest in regenerative ophthalmology, offering a new therapeutic target for corneal injuries and diseases. This review provides a comprehensive examination of CSSCs, exploring their anatomy, functions, and role in maintaining corneal integrity. Molecular markers, wound healing mechanisms, and potential therapeutic applications are discussed. Global corneal blindness, especially in more resource-limited regions, underscores the need for innovative solutions. Challenges posed by corneal defects, emphasizing the urgent need for advanced therapeutic interventions, are discussed. The review places a spotlight on exosome therapy as a potential therapy. CSSC-derived exosomes exhibit significant potential for modulating inflammation, promoting tissue repair, and addressing corneal transparency. Additionally, the rejuvenation potential of CSSCs through epigenetic reprogramming adds to the evolving regenerative landscape. The imperative for clinical trials and human studies to seamlessly integrate these strategies into practice is emphasized. This points towards a future where CSSC-based therapies, particularly leveraging exosomes, play a central role in diversifying ophthalmic regenerative medicine.

Nanofiber Scaffolds as Drug Delivery Systems Promoting Wound Healing

Nanofiber scaffolds have emerged as a revolutionary drug delivery platform for promoting wound healing, due to their unique properties, including high surface area, interconnected porosity, excellent breathability, and moisture absorption, as well as their spatial structure which mimics the extracellular matrix. However, the use of nanofibers to achieve controlled drug loading and release still presents many challenges, with ongoing research still exploring how to load drugs onto nanofiber scaffolds without loss of activity and how to control their release in a specific spatiotemporal manner. This comprehensive study systematically reviews the applications and recent advances related to drug-laden nanofiber scaffolds for skin-wound management. First, we introduce commonly used methods for nanofiber preparation, including electrostatic spinning, sol-gel, molecular self-assembly, thermally induced phase separation, and 3D-printing techniques. Next, we summarize the polymers used in the preparation of nanofibers and drug delivery methods utilizing nanofiber scaffolds. We then review the application of drug-loaded nanofiber scaffolds for wound healing, considering the different stages of wound healing in which the drug acts. Finally, we briefly describe stimulus-responsive drug delivery schemes for nanofiber scaffolds, as well as other exciting drug delivery systems.