Human cornea-derived extracellular matrix hydrogel for prevention of post-traumatic corneal scarring: A translational approach

Risk of Permanent Corneal Injury in Microgravity: Spaceflight-Associated Hazards, Challenges to Vision Restoration, and Role of Biotechnology in Long-Term Planetary Missions

Human space exploration presents an unparalleled opportunity to study life in extreme environments-but it also exposes astronauts to physiological stressors that jeopardize key systems like vision. Corneal health, essential for maintaining precise visual acuity, is threatened by microgravity-induced fluid shifts, cosmic radiation, and the confined nature of spacecraft living environments. These conditions elevate the risk of corneal abrasions, infections, and structural damage. In addition, Spaceflight-Associated Neuro-Ocular Syndrome (SANS)-while primarily affecting the posterior segment-has also been potentially linked to anterior segment alterations such as corneal edema and tear film instability. This review examines these ocular challenges and assesses current mitigation strategies. Traditional approaches, such as terrestrial eye banking and corneal transplantation, are impractical for spaceflight due to the limited viability of preserved tissues, surgical complexities, anesthetic risks, infection potential, and logistical constraints. The paper explores emerging technologies like 3D bioprinting and stem cell-based tissue engineering, which offer promising solutions by enabling the on-demand production of personalized corneal constructs. Complementary advancements, including adaptive protective eyewear, bioengineered tear substitutes, telemedicine, and AI-driven diagnostic tools, also show potential in autonomously managing ocular health during long-duration missions. By addressing the complex interplay of environmental stressors and biological vulnerabilities, these innovations not only safeguard astronaut vision and mission performance but also catalyze new pathways for regenerative medicine on Earth. The evolution of space-based ophthalmic care underscores the dual impact of space medicine investments across planetary exploration and terrestrial health systems.

Natural Extracellular Matrix Scaffold-Based Hydrogel Corneal Patch with Temperature and Light-Responsiveness for Penetrating Keratoplasty and Sutureless Stromal Defect Repair

Corneal transplantation remains the gold standard for treating corneal blindness; however, it is hampered globally by donor shortages and the complexity of suture-dependent procedures. Tissue-engineered corneas have demonstrated potential as corneal equivalents. Nevertheless, the development of adhesive corneal patches and full-thickness corneal substitutes remains challenging. In this study, a multifunctional hydrogel corneal patch (MHCP) is constructed by integrating a dual-crosslinked hybrid hydrogel with temperature and light responsiveness with a natural extracellular matrix scaffold. When applied to the ocular surface, MHCP spontaneously releases adhesives at body temperature and forms a stable adhesion with the recipient cornea through photocuring. In addition to its inherent mechanical, optical, and ultrastructural characteristics, which are similar to those of the natural stroma, MHCP demonstrates excellent suture resistance, anti-swelling, and anti-degradation properties after curing. MHCP promotes the proliferation and migration of corneal epithelial cells in vitro and maintains the phenotype of corneal stromal cells. In vivo, MHCP maintains graft hydration and restores corneal structural integrity and transparency during penetrating keratoplasty of various sizes and sutureless lamellar keratoplasty. Collectively, given the advantages of native stroma-like characteristics, operation-facilitating multiple functions, and convenient preparation, MHCP is a promising corneal substitute for clinical applications.

In Vitro Evaluation of Gelatin-Based Hydrogels as Potential Fillers for Corneal Wounds

Corneal persistent epithelial defects are common ophthalmic injuries that can cause significant visual and structural damage. While diagnosis is straightforward, treatment remains challenging. Noninvasive therapies like eye drops are preferred, but severe neurotrophic keratopathy may require surgical interventions. This study explores gelatin-based hydrogels as noninvasive alternatives for corneal repair. Four photo-cross-linkable hydrogels with gelatin and riboflavin phosphate (RFP) were evaluated: a control and variants incorporating 2.5% dextran (D), 0.4% hyaluronic acid (HA), or 1% methylcellulose (MC). In vitro assessments included physicochemical properties, biocompatibility, and release kinetics alongside ex vivo wound healing assays. The gelatin-RFP hydrogel maintained corneal transparency, while additives reduced it. Dextran slowed compound release, and HA and MC reduced the release rate of larger molecules. All hydrogels showed excellent biocompatibility, and ex vivo models confirmed re-epithelialization, though slower than controls. The unmodified gelatin-RFP hydrogel demonstrated the best potential for corneal tissue engineering, supporting its future clinical translation.

Enhanced wound healing properties by sodium alginate-carboxymethyl cellulose hydrogel enriched with decellularized amniotic membrane

Skin, as the primary interface with the external environment, is susceptible to damage, posing a formidable challenge for complete restoration in adult skin injuries. Wound healing remains a clinical challenge, necessitating advanced biomaterials to support cell proliferation, modulate inflammation, and combat infections. Among several options, hydrogel can be a capable contender for biological dressings. Here, we developed and evaluated a novel hydrogel composed of sodium alginate (SA) and carboxymethyl cellulose (CMC), enriched with decellularized extracellular matrix of amniotic membrane (dAM), using calcium chloride (CaCl2) as a crosslinker. An incorporation of dAM imparted biomimetic qualities, as evidenced by SEM, showing a fibrous extracellular matrix-like structure. Rheological studies demonstrated the optimal viscosity of SA-CMC-dAM for cell proliferation and adhesion, overcoming limitations of SA and CMC alone. The hydrogel exhibited the highest moisture absorption (12.27±0.59 %) and enhanced hydrophilicity, as confirmed by the contact angle assay, ensuring suitability for wound applications. Biological assessments revealed superior fibroblast migration in scratch assays and significant anti-biofilm activity (∼70 % reduction in E. coli biofilms) alongside antimicrobial efficacy, supported by FDA/PI assays. The zebrafish embryo studies validated its biocompatibility (20 μg/ml) and demonstrated potent anti-inflammatory effects, with a marked reduction in neutrophil recruitment (∼25 %) in tail transection models compared to controls. These findings suggest that the SA-CMC-dAM hydrogel synergises structural, antibacterial, and anti-inflammatory properties, making it a promising candidate for wound healing applications. The biomimetic and multifunctional design provides a strong basis for further translational studies in mammalian systems.

Artificial Cornea Substitute Based on Hydrogel Skeletons with Natural Stromal Hierarchical Structure and Extracellular Matrix for Sutureless Transplantation

Corneal substitutes with structural and compositional characteristics resembling those of natural corneas have attracted considerable attention. However, biomimicking the complex hierarchical organization of corneal stroma is challenging. In this study, humanized corneal stroma-like adhesive patches (HCSPs) are prepared through a multi-step process. First, polyethylene glycol diacrylate is cast and cured within decellularized porcine cornea (DPC) templates. The DPCs are then enzymatically digested to obtain hydrogel skeletons, which are finally integrated with human corneal extracellular matrix and methacrylate gelatin. HCSPs replicate the ultrastructure, protein components, and optical properties of human corneas and exhibit improved anti-swelling and anti-degradation capabilities compared with conventional DPCs and recombinant human collagen patches. HCSPs can deliver methacrylate gelatin at the ocular surface temperature (37 °C) and achieve stable adhesion to the corneal stroma upon 405 nm light irradiation. Furthermore, HCSPs promote the survival and migration of corneal epithelial and stromal cells while preserving their phenotypes. In rabbit models of lamellar keratoplasty and microperforation repair, HCSPs accelerate epithelial healing, minimize suture-associated complications, and maintain structural stability. These findings suggest that HCSPs are promising donor corneal substitutes for clinical applications.

Repair effects of thermosensitive hydrogels combined with iPSC-derived corneal endothelial cells on rabbit corneal endothelial dysfunction

Considering the limitations of human corneal endothelial cell proliferation as well as the severe shortage of corneal donations, it is imperative to develop improved methods of corneal endothelial cell transplantation. The purpose of this study was to construct a modified corneal endothelial cell transplantation approach using thermosensitive hydrogels combined with induced pluripotent stem cells (iPSCs)-derived human corneal endothelial cells (hCECs). In this study, thermosensitive hydrogels hydroxypropyl chitin/carboxymethyl chitosan (HPCH/CMCS) were fabricated, and their hydrogels properties and biocompatibility were investigated. Our results demonstrated that HPCH/CMCS hydrogels exhibited superior transparency, appropriate mechanical properties and favorable biocompatibility. A two-step induction method of small molecule compounds was employed, by which iPSCs were differentiated into hCECs via neural crest cells (NCCs). Additionally, a rabbit corneal endothelial dysfunction model was established in vivo, aiming to evaluate the safety and effectiveness of the combined method. Slit lamp microscope results indicated that significant transparency improvement could be noted in HPCH/CMCS/hCECs group (P = 0.006), whereas the corneal transparency was not homogeneous in different areas. Moreover, histological examinations and immunofluorescence analysis revealed that HPCH/CMCS/hCECs group showed a higher density of corneal endothelial cells and positive expressions of related markers. This study may provide ideas and experimental basis for the combined application of hydrogels and iPSC-derived corneal endothelial cells for corneal endothelial dysfunction. STATEMENT OF SIGNIFICANCE: Corneal transplantation is the most effective treatment for corneal endothelial dysfunction, which is challenged by issues such as corneal donor shortages and immune rejection. In this study, we proposed a combined transplantation method of cells and hydrogels for corneal endothelial dysfunction. We modified the protocols to obtain corneal endothelial cells from iPSCs by a two-step induction method. Besides, thermosensitive hydrogels with satisfactory biocompatibility and degradability were fabricated as fixation and support carriers of iPSC-derived corneal endothelial cells for in vivo transplantation. Experimental results demonstrated that this method could locally repair corneal endothelial dysfunction in rabbits, with the repaired corneas expressing relevant markers. This study presented a preliminary attempt to combine hydrogels and cells for corneal endothelial dysfunction.

Impact of increasingly complex cell culture conditions on the proteome of human periodontal ligament stem cells

AIMS

Human periodontal ligament stem cells (hPDLSCs) exhibit an enormous potential to regenerate periodontal tissue. However, their translatability to the clinical setting is constrained by technical difficulties in standardizing culture conditions. The aim was to assess complex culture conditions using a proteomic-based protocol to standardize multi-layer hPDLSC cultivation methodology.

MATERIALS AND METHODS

hPDLSC-derived constructs were created with varying biological complexity. The simplest constructs were monolayer sheets of hPDLSCs cultured with fetal bovine serum (FBS) or Plasma Rich in Growth Factors supernatant (PRGFsn). The most complex constructs were triple-layered cell structures cultured with PRGFsn, with or without PRGF fibrin membrane (mPRGF). Ultrastructure and proteomic analyses were performed on these constructs.

RESULTS

PRGF supernatant improved protein expression related to extracellular matrix, adhesion, proliferation, and migration in hPDLSCs. PRGF fibrin scaffold upregulates proteins for cell activation, respiration, and electron transport. hPDLSCs on fibrin membrane show robust osteogenic potential through differential protein expression (ossification, tissue remodeling, morphogenesis, or cell migration) and overall homeostasis relative to less complex structures.

CONCLUSION

Our data reveal the far-reaching potential of 3-dimensional constructs in combination with PRGF technology in periodontal regenerative applications.

Paradigm Shift in Eye Banking: From Tissue Retrieval to Cellular Harvesting and Bioengineering

ABSTRACT

An integrated cell, tissue, and eye bank is vital to meet the evolving needs of ocular transplant therapies. In addition to traditional corneal transplant tissues, it encompasses processing and delivery of transplant materials for newer treatments like cell-based therapies and gene-modified products, adhering to rigorous standards, optimizing tissue utilization with comprehensive services for surgeons.

Current and emerging strategies for the manufacture, implantation, and clinical management of corneal tissue allografts

Approximately 40,000 Australians have received a donor corneal tissue transplant over the last 40 years, with the primary indications being keratoconus, Fuchs' endothelial dystrophy, bullous keratopathy, and failure of a prior corneal transplant. Although corneal cross-linking and rigid contact lenses have emerged as alternative strategies for the management of keratoconus, the demand for donor corneas is increasing in-line with the ageing population in Australia. Moreover, owing to the lack of tissue banking resources in less-developed countries, the global demand for donor corneas exceeds supply by 70-fold. These supply issues, combined with evolving tissue banking and surgical techniques, have led to the emergence of new strategies for the storage, processing and implantation of corneal cells and tissues. Organ culture techniques have been developed that support the storage of donor corneas for up to 30 days, facilitating improvements in tissue supply and surgery scheduling. Bespoke surgical methods have been developed that are tailored to the requirements of specific conditions, allowing reductions in both the volume of tissue required to be transplanted and the size of the necessary surgical incision. Further efficiencies and improvements in patient care may be achieved via exploitation of cell culture technologies as exemplified through use of cultured corneal epithelial cells for the treatment of limbal stem cell deficiency. Promising progress has also been made in developing a cultured corneal endothelial cell therapy for patients with corneal endothelial dysfunction. These evolving strategies are discussed with respect to their potential impact on the clinical presentation and management of patients who have received an implant of donor corneal tissue or cells.

Bioprinting of anisotropic functional corneal stroma using mechanically robust multi-material bioink based on decellularized cornea matrix

Corneal scarring is a common cause of blindness, affecting millions globally each year. A huge gap between the demand and supply of donor tissue currently limits corneal transplantation, the only definitive therapy for patients with corneal scarring. To overcome this challenge, researchers have harnessed the efficacy of 3D bioprinting to fabricate artificial corneal stromal constructs. With all the different bioinks available, the decellularized corneal matrix-based bioprinted construct can fulfill the required biological functionality but is limited by the lack of mechanical stiffness. Additionally, from a biophysical standpoint, it is necessary for an ideal corneal substitute to mimic the anisotropy of the cornea from the central optic zone to the surrounding periphery. In this study, we enhanced the mechanical robustness of decellularized cornea matrix (DCM) hydrogel by blending it with another natural polymer, sonicated silk fibroin solution in a defined ratio. Although hybrid hydrogel has an increased complex modulus than DCM hydrogel, it has a lower in vitro degradation rate and increased opaqueness due to the presence of crystalline beta-sheet conformation within the hydrogel. Therefore, we used this multi-material bioink-based approach to fabricate a corneal stromal equivalent where the outer peripheral corneal rim was printed with a mechanically robust polymeric blend of DCM and sonicated silk fibroin and the central optic zone was printed with only DCM. The bioprinted corneal stroma thus maintained its structural integrity and did not break when lifted with forceps. The two different bioinks were encapsulated with human limbus-derived mesenchymal stem cells (hLMSC) individually and 3D bioprinted in different patterns (concentric and parallel) to attain a native-like structure in terms of architecture and transparency. Thus, the bilayer cornea constructs maintained high cell viability and expressed keratocyte core proteins indicating optimal functionality. This approach helped to gain insight into bioprinting corneas with heterogeneous mechanical property without disturbing the structural clarity of the central optic zone.

Engineering a Biomimetic Glomerular Filtration Barrier: Coculturing Endothelial Podocytes on Kidney ECM-Bacterial Cellulose Membrane Hybrid

A novel avenue for advancing our understanding of kidney disease mechanisms and developing targeted therapeutics lies in overcoming the limitations of the existing in vitro models. Traditional animal models, while useful, do not fully capture the intricacies of human kidney physiology and pathophysiology. Tissue engineering offers a promising solution, yet current models often fall short in replicating the complex microarchitecture and biochemical milieu of the kidney. To address this challenge, we propose the development of a sophisticated in vitro glomerular filtration barrier (GFB) utilizing advanced biomaterials and a kidney decellularized extracellular matrix (kdECM). In our approach, we employ a bacterial cellulose membrane (BC) as a scaffold, providing a robust framework for cell growth and interaction. Coating this scaffold with kdECM hydrogel derived from caprine kidney tissue via a detergent-free decellularization method ensures the preservation of vital extracellular matrix proteins crucial for cellular compatibility and signaling. Our engineered GFB not only supports the growth of endothelial and podocyte cells but also exhibits the presence of key markers such as CD31 and nephrin, indicating successful cellular integration. Furthermore, the expression of collagen IV, an essential extracellular matrix (ECM) protein, validates the fidelity of our model in simulating cellular interactions within a kdECM matrix. Additionally, we assessed the filtration efficiency of the developed GFB model using albumin, a standard protein, to evaluate its performance under conditions that closely mimic the native physiological environment. This innovative approach, which faithfully recapitulates the native microenvironment of the glomerulus, holds immense promise for elucidating kidney disease mechanisms, conducting permeability studies, and advancing personalized therapeutic strategies. By leveraging cutting-edge biomaterials and tissue-specific coculture technology, this study can be further extended to develop GFB for the treatment of renal diseases, ultimately improving patient outcomes and quality of life.

Developing fibrin-based biomaterials/scaffolds in tissue engineering

Tissue engineering technology has advanced rapidly in recent years, offering opportunities to construct biologically active tissues or organ substitutes to repair or even enhance the functions of diseased tissues and organs. Tissue-engineered scaffolds rebuild the extracellular microenvironment by mimicking the extracellular matrix. Fibrin-based scaffolds possess numerous advantages, including hemostasis, high biocompatibility, and good degradability. Fibrin scaffolds provide an initial matrix that facilitates cell migration, differentiation, proliferation, and adhesion, and also play a critical role in cell-matrix interactions. Fibrin scaffolds are now widely recognized as a key component in tissue engineering, where they can facilitate tissue and organ defect repair. This review introduces the properties of fibrin, including its composition, structure, and biology. In addition, the modification and cross-linking modes of fibrin are discussed, along with various forms commonly used in tissue engineering. We also describe the biofunctionalization of fibrin. This review provides a detailed overview of the use and applications of fibrin in skin, bone, and nervous tissues, and provides novel insights into future research directions for clinical treatment.

Nanohydroxyapatite Coating Attenuates Fibrotic and Immune Responses to Promote Keratoprosthesis Biointegration in Advanced Ocular Surface Disorders

Keratoprosthesis (KPro) implantation is frequently the only recourse for patients with severe corneal disease. However, problems arise due to inadequate biointegration of the KPro, particularly the PMMA optical cylinder, such as tissue detachment, tissue melting, or eye-threatening infection in the interface. Here, using the AuroKPro as a model prosthesis, a surface functionalization approach─coating the optical cylinder with nanohydroxyapatite (nHAp)─was trialed in rabbit eyes with and without a proceeding chemical injury. In chemically injured eyes, which simulated total limbal epithelial stem cell deficiency, clear benefits were conferred by the coating. The total modified Hackett-McDonald score and area of tissue apposition differences 12 weeks after implantation were 5.0 and 22.5%, respectively. Mechanical push-in tests revealed that 31.8% greater work was required to detach the tissues. These differences were less marked in uninjured eyes, which showed total score and tissue apposition differences of 2.5 and 11.5%, respectively, and a work difference of 23.5%. The improved biointegration could be contributed by the attenuated expression of fibronectin (p = 0.036), collagen 3A1 (p = 0.033), and α-smooth muscle actin (p = 0.045)─proteins typically upregulated during nonadherent fibrous capsule envelopment of bioinert material─adjacent to the optical cylinders. The coating also appeared to induce a less immunogenic milieu in the ocular surface tissue, evidenced by the markedly lower expression of tear proteins associated with immune and stimulus responses. Collectively, the level of these tear proteins in eyes with coated prostheses was 1.1 ± 13.0% of naïve eyes: substantially lower than with noncoated KPros (246.5 ± 79.3% of naïve, p = 0.038). Together, our results indicated that nHAp coating may reduce the risk of prosthesis failure in severely injured eyes, which are representative of the cohort of KPro patients.

ECM-based bioadhesive hydrogel for sutureless repair of deep anterior corneal defects

Corneal transplantation is the gold standard treatment for corneal-related blindness; however, this strategy faces challenges such as limited donor cornea, graft rejection, suture-related complications, and the need for specialized equipment and advanced surgical skills. Development of tissue adhesives for corneal regeneration is of great clinical value. However, currently available corneal tissue sealants pose challenges, such as lack of safety, biocompatibility, and desired mechanical properties. To meet these requirements simultaneously, a bovine stromal corneal extracellular matrix (dCor) was used to design a bioadhesive photocurable hydrogel based on gelatin methacrylate (GelMA) and polyethylene glycol diacrylate (PEGDA) hydrogels (dCor/Gel-PEG). Integration of dCor into the dual networks of GelMA and PEGDA (Gel-PEG) led to a bioadhesive hydrogel for curing corneal defects, which could be crosslinked by Irgacure 2959 within 5 min ultraviolet irradiation. The viability of corneal stromal stem cells (CSSCs) was improved on the dCor/Gel-PEG hydrogel in comparison to the Gel-PEG hydrogel. The gene expression profile supported the keratocyte differentiation of CSSCs seeded on dCor/Gel-PEG via increased KERA and ALDH, with inhibited myofibroblast transdifferentiation via decreased α-SMA due to the presence of dCor. Interestingly, the dCor/Gel-PEG hydrogel exhibited favorable mechanical performance in terms of elasticity and bioadherence to the host corneal stroma. Ex vivo and in vivo examinations proved the feasibility of this hydrogel for the sutureless reconstruction of deep anterior corneal defects with promising histopathological results.

Emerging strategy towards mucosal healing in inflammatory bowel disease: what the future holds?

For decades, the therapeutic goal of conventional treatment among inflammatory bowel disease (IBD) patients is alleviating exacerbations in acute phase, maintaining remission, reducing recurrence, preventing complications, and increasing quality of life. However, the persistent mucosal/submucosal inflammation tends to cause irreversible changes in the intestinal structure, which can barely be redressed by conventional treatment. In the late 1990s, monoclonal biologics, mainly anti-TNF (tumor necrosis factor) drugs, were proven significantly helpful in inhibiting mucosal inflammation and improving prognosis in clinical trials. Meanwhile, mucosal healing (MH), as a key endoscopic and histological measurement closely associated with the severity of symptoms, has been proposed as primary outcome measures. With deeper comprehension of the mucosal microenvironment, stem cell niche, and underlying mucosal repair mechanisms, diverse potential strategies apart from monoclonal antibodies have been arising or undergoing clinical trials. Herein, we elucidate key steps or targets during the course of MH and review some promising treatment strategies capable of promoting MH in IBD.