Retinitis pigmentosa (RP) is a form of retinal degeneration characterized by primary degeneration of rod photoreceptors followed by a secondary cone loss that leads to vision impairment and finally blindness. This is a rare disease with mutations in several genes and high genetic heterogeneity. A challenging effort has been the characterization of the molecular mechanisms underlying photoreceptor cell death during the progression of the disease. Some of the cell death pathways have been identified and comprise stress events found in several neurodegenerative diseases such as oxidative stress, inflammation, calcium imbalance and endoplasmic reticulum stress. Other cell death mechanisms appear more relevant to photoreceptor cells, such as high levels of cGMP and metabolic changes. Here we review some of the cell death pathways characterized in the RP mutant retina and discuss preclinical studies of therapeutic approaches targeting the molecular outcomes that lead to photoreceptor cell demise.

A drawback in the development of treatments that can reach the retina is the presence of barriers in the eye that restrain compounds from reaching the target. Intravitreal injections hold promise for retinal delivery, but the natural defenses in the vitreous can rapidly degrade or eliminate therapeutic molecules. Injectable hydrogel implants, which act as a reservoir, can allow for long-term drug delivery with a single injection into the eye, but still suffer due to the fast clearance of the released drugs when traversing the vitreous and random diffusion that leads to lower pharmaceutic efficacy. A combination with HA-covered nanoparticles, which can be released from the gel and more readily pass through the vitreous to increase the delivery of therapeutic agents to the retina, represents an advanced and elegant way to overcome some of the limitations in eye drug delivery. In this article, we developed hybrid PLGA-Dotap NPs that, due to their hyaluronic acid coating, can improve in vivo distribution throughout the vitreous and delivery to retinal cells. Moreover, a hydrogel implant was developed to act as a depot for the hybrid NPs to better control and slow their release. These results are a first step to improve the treatment of retinal diseases by protecting and transporting the therapeutic treatment across the vitreous and to improve treatment options by creating a depot system for long-term treatments.

Myelin is the main component of the white matter of the central nervous system (CNS), allowing the proper electrical function of the neurons by ensheathing and insulating the axons. The extensive use of magnetic resonance imaging has highlighted the white matter alterations in Alzheimer’s dementia (AD) and other neurodegenerative diseases, alterations which are early, extended, and regionally selective. Given that the white matter turnover is considerable in the adulthood, and that myelin repair is currently recognized as being the only true reparative capability of the mature CNS, oligodendrocyte precursor cells (OPCs), the cells that differentiate in oligodendrocyte, responsible for myelin formation and repair, are regarded as a potential target for neuroprotection. In this review, several aspects of the OPC biology are reviewed. The histology and functional role of OPCs in the neurovascular-neuroglial unit as described in preclinical and clinical studies on AD is discussed, such as the OPC vulnerability to hypoxia-ischemia, neuroinflammation, and amyloid deposition. Finally, the position of OPCs in drug discovery strategies for dementia is discussed.

Background: Photoreceptor death leads to inherited blinding retinal diseases, such as retinitis pigmentosa (RP). As disease progression often outpaces therapeutic advances, developing effective treatments is urgent. This study evaluates the efficacy of small peptides derived from pigment epithelium-derived factor (PEDF), which are known to restrict common cell death pathways associated with retinal diseases. Methods: We tested chemically synthesized peptides (17-mer and H105A) with affinity for the PEDF receptor, PEDF-R, delivered as eye drops to two RP mouse models: rd10 (phosphodiesterase 6b mutation) and Rho ^P23H/+ (rhodopsin P23H mutation). Additionally, we engineered AAV-H105A vectors for intravitreal delivery in Rho ^P23H/+ mice. To assess peptide effects in human tissue, we used retinal organoids exposed to cigarette smoke extract, a model of oxidative stress. Photoreceptor survival, morphology and function were evaluated. Results: Here we show that peptides 17-mer and H105A delivered via eye drops successfully reach the retina, promote photoreceptor survival, and improve retinal function in both RP mouse models. Intravitreal delivery of a AAV-H105A vector delays photoreceptor degeneration in Rho ^P23H/+ mice up to six months. In human retinal organoids, peptide H105A specifically prevents photoreceptor death induced by oxidative stress, a contributing factor to RP progression. Conclusions: PEDF peptide-based eye drops offer a promising, minimally invasive therapy to prevent photoreceptor degeneration in retinal disorders, with a favorable safety profile.

Spinal cord injury (SCI) is an incurable condition, in which a cascade of cellular and molecular events triggered by inflammation and excitotoxicity impairs endogenous regeneration, namely remyelination and axonal outgrowth. We designed a treatment solution based on an implantable biomaterial (electrospun poly (l-lactic acid) [PLLA]) loaded with ibuprofen and triiodothyronine (T3) to counteract inflammation, thus improving endogenous regeneration. In vivo efficacy was tested by implanting the drug-loaded PLLA in the rat model of T8 contusion SCI. We observed the expected recovery of locomotion beginning on day 7. In PLLA-implanted rats (i.e., controls), the recovery stabilized at 21 days post-lesion (DPL), after which no further improvement was observed. On the contrary, in PLLA + ibuprofen (Ibu) + T3 (PLLA-Ibu-T3) rats a further recovery and a significant treatment effect were observed, also confirmed by the gait analysis on 49 DPL. Glutamate release at 24 h and 8 DPL was reduced in PLLA-Ibu-T3– compared to PLLA-implanted rats, such as the estimated lesion volume at 60 DPL. The myelin- and 200-neurofilament–positive area fraction was higher in PLLA-Ibu-T3–implanted rats, where the percentage of astrocytes was significantly reduced. The implant of a PLLA electrospun scaffold loaded with Ibu and T3 significantly improves the endogenous regeneration, leading to an improvement of functional locomotion outcome in the SCI.

The involvement of the extracellular matrix (ECM) in lesion evolution and functional outcome is well recognized in spinal cord injury. Most attention has been dedicated to the “core” area of the lesion and scar formation, while only scattered reports consider ECM modification based on the temporal evolution and the segments adjacent to the lesion. In this study, we investigated the expression profile of 100 genes encoding for ECM proteins at 1, 8 and 45 days post-injury, in the spinal cord segments rostral and caudal to the lesion and in the scar segment, in a rat model. During both the active lesion phases and the lesion stabilization, we observed an asymmetric gene expression induced by the injury, with a higher regulation in the rostral segment of genes involved in ECM remodeling, adhesion and cell migration. Using bioinformatic approaches, the metalloproteases inhibitor Timp1 and the hyaluronan receptor Cd44 emerged as the hub genes at all post-lesion times. Results from the bioinformatic gene expression analysis were then confirmed at protein level by tissue analysis and by cell culture using primary astrocytes. These results indicated that ECM regulation also takes place outside of the lesion area in spinal cord injury.