An injectable peptide hydrogel for reconstruction of the human trabecular meshwork

Glaucoma is a leading cause of irreversible blindness worldwide. Current treatments of glaucoma involve lowering the IOP by means of decreasing aqueous humor production or increasing non-trabecular aqueous humor outflow with the help of IOP-lowering eye drops, nanotechnology enabled glaucoma drainage implants, and trabeculectomy. However, there is currently no effective and permanent cure for this disease. In order to investigate new therapeutic strategies, three dimensional (3D) biomimetic trabecular meshwork (TM) models are in demand. Therefore, we adapted MAX8B, a peptide hydrogel system to bioengineer a 3D trabecular meshwork scaffold. We assessed mechanical and bio-instructive properties of this engineered tissue matrix by using rheological analysis, 3D cell culture and imaging techniques. The scaffold material exhibited shear-thinning ability and biocompatibility for proper hTM growth and proliferation indicating a potential utilization as an injectable implant. Additionally, by using a perfusion system, MAX8B scaffold was tested as an in vitro platform for investigating the effect of Dexamethasone (Dex) on trabecular meshwork outflow facility. The physiological response of hTM cells within the scaffold to Dex treatment clearly supported the effectiveness of this 3D model as a drug-testing platform, which can accelerate discovery of new therapeutic targets for glaucoma. Statement of significance: Artificial 3D-TM (3-dimentional Trabecular Meshwork) developed here with hTM (human TM) cells seeded on peptide-hydrogel scaffolds exhibits the mechanical strength and physiological properties mimicking the native TM tissue. Besides serving a novel and effective 3D-TM model, the MAX8B hydrogel could potentially function as an injectable trabecular meshwork implant

Towards preventing exfoliation glaucoma by targeting and removing fibrillar aggregates associated with exfoliation syndrome

Exfoliation syndrome presents as an accumulation of insoluble fibrillar aggregates that commonly correlates with age and causes ocular complications, most notably open-angle glaucoma. Despite advances in understanding the pathogenesis and risk factors associated with exfoliation syndrome, there has been no significant progress in curative pharmacotherapy of this disease. It is thought that the ability to target the fibrillar aggregates associated with exfoliation may offer a new therapeutic approach, facilitating their direct removal from affected tissues. Phage display techniques yielded two peptides (LPSYNLHPHVPP, IPLLNPGSMQLS) that could differentiate between exfoliative and non-affected regions of the human lens capsule. These peptides were conjugated to magnetic particles using click chemistry to investigate their ability in targeting and removing exfoliation materials from the anterior human lens capsule. The behavior of the fibrillar materials upon binding to these magnetic particles was assessed using magnetic pins and rotating magnetic fields of various strengths. Ex vivo studies showed that the magnetic particle-peptide conjugates could generate enough mechanical force to remove large aggregates of exfoliation materials from the lens capsule when exposed to a low-frequency rotating magnetic field (5000 G, 20 Hz). Biocompatibility of targeting peptides with and without conjugated magnetic particles was confirmed using MTT cell toxicity assay, live/dead cell viability assay, and DNA fragmentation studies on primary cultured human trabecular meshwork cells. This is a novel, minimally invasive, therapeutic approach for the treatment of exfoliation glaucoma via the targeting and removal of exfoliation materials that could be applied to all tissues within the anterior segment of the eye

Molecular Retention Limitations for Prevascularized Subcutaneous Sites for Islet Transplantation

Beta cell replacement therapies utilizing the subcutaneous space have inherent advantages to other sites: the potential for increased accessibility, noninvasive monitoring, and graft extraction. Site prevascularization has been developed to enhance islet survivability in the subcutaneous zone while minimizing potential foreign body immune responses. Molecular communication between the host and prevascularized implant site remains ill-defined. Poly(ethylene oxide)s (PEOs) of various hydrated radii (i.e., ∼11–62 Å) were injected into prevascularized subcutaneous sites in C57BL/6 mice, and the clearance and organ biodistribution were characterized. Prevascularization formed a barrier that confined the molecules compared with the unmodified site. Molecular clearance from the prevascularized site was inversely proportional to the molecular weight. The upper limit in molecular size for entering the vasculature to be cleared was determined to be 35 kDa MW PEO. These findings provide insight into the impact of vascularization on molecular retention at the injection site and the effect of molecular size on the mobility of hydrophilic molecules from the prevascularized site to the host. This information is necessary for optimizing the transplantation site for increasing the beta cell graft survival