Paracrine effects of intraocularly implanted cells on degenerating retinas in mice

Safety Results for Geographic Atrophy Associated with Age-Related Macular Degeneration Using Subretinal Cord Blood Platelet-Rich Plasma

Purpose

To evaluate the safety of subretinal injection of cord blood platelet-rich plasma (CB-PRP) and its possible effect in eyes affected by geographic atrophy (GA) associated with dry age-related macular degeneration (d-AMD).

Design

Interventional, open-label study started in January 2021 with follow-up at 12 months (the Si.Cord Study). This study was a single-center, nonrandomized, sequential-assigned clinical trial conducted in Rome, Italy, at Fondazione Policlinico Universitario Agostino Gemelli IRCCS (ClinicalTrials.gov NCT04636853).

Participants

Thirteen patients (26 eyes) with bilateral d-AMD-related GA were enrolled. One eye from each patient (with more advanced GA) underwent CB-PRP treatment, and the fellow eye was considered the control. All patients participated in follow-up at 12 months.

Intervention

All 13 eyes received 23-gauge (G) vitrectomy and subretinal injection of CB-PRP using a 41-gauge needle.

Main Outcomes and Measures

Best-corrected visual acuity (BCVA) with ETDRS letters, central macular thickness using OCT, and atrophic area measured on en face OCT images were assessed at baseline, 1, 3, 6, and 12 months.

Results

The BCVA in the treated group was 34.46 ± 20.8 ETDRS at baseline, 40.84 ± 20.52 at 1 month, 40.07 ± 20.34 at 3 months, 39.38 ± 19.84 at 6 months, and 35.84 ± 18.38 at 12 months. In the untreated group, the BCVA was 53 ± 21.1 ETDRS letters at baseline, 51.54 ± 20.99 at 1 month, 46.62 ± 19.47 at 3 months, 46.85 ± 18.58 at 6 months, and 43.92 ± 17.97 at 12 months (2-way analysis of variance: interaction of treatment by eye or time, P = 0.084). Central macular thickness did not show a significant intereye difference at 12 months (P = 0.97). The atrophic geographic areas tended to increase in both treated and fellow eyes at 12 months (P < 0.0001). No inflammatory reaction, endophthalmitis, retinal detachment, uveitis, or other complications due to the subretinal injection of CB-PRP were observed during the follow-up.

Conclusions

Subretinal injection of CB-PRP could be safely used for d-AMD in its GA form. Despite its safety, a larger cohort of patients, and probably a new way of administration, will be needed to understand whether the CB-PRP could have a role in the GA treatment.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Comparison of retinal degeneration treatment with four types of different mesenchymal stem cells, human induced pluripotent stem cells and RPE cells in a rat retinal degeneration model

BACKGROUND

Retinal degeneration (RD) is a group of disorders on irreversible vision loss. Multiple types of stem cells were used in clinical trials for RD treatment. However, it remains unknown what kinds of stem cells are most effective for the treatment. Therefore, we investigated the subretinal transplantation of several types of stem cells, human adipose-derived stem cells (hADSCs), amniotic fluid stem cells (hAFSCs), bone marrow stem cells (hBMSCs), dental pulp stem cells (hDPSCs), induced pluripotent stem cell (hiPSC), and hiPSC-derived retinal pigment epithelium (RPE) cells for protection effects, paracrine effects and treatment efficiency in an RD disease model rats.

METHODS

The generation and characterization of these stem cells and hiPSC-derived RPE cells were performed before transplantation. The stem cells or hiPSC-derived RPE cell suspension labelled with CellTracker Green to detect transplanted cells were delivered into the subretinal space of 3-week-old RCS rats. The control group received subretinal PBS injection or non-injection. A series of detections including fundus photography, optomotor response (OMR) evaluations, light-dark box testing, electroretinography (ERG), and hematoxylin and eosin (HE) staining of retinal sections were conducted after subretinal injection of the cells.

RESULTS

Each stem cell, hiPSC-derived RPE cell or PBS (blank experiment) was successfully transplanted into at least six RCS rats subretinally. Compared with the control rats, RCS rats subjected to subretinal transplantation of any stem cells except hiPSCs showed higher ERG waves (p < 0.05) and quantitative OMR (qOMR) index values (hADSCs: 1.166, hAFSCs: 1.249, hBMSCs: 1.098, hDPSCs: 1.238, hiPSCs: 1.208, hiPSC-RPE cells: 1.294, non-injection: 1.03, PBS: 1.06), which indicated better visual function, at 4 weeks post-injection. However, only rats that received hiPSC-derived RPE cells maintained their visual function at 8 weeks post-injection (p < 0.05). The outer nuclear layer thickness observed in histological sections after HE staining showed the same pattern as the ERG and qOMR results.

CONCLUSIONS

Compared to hiPSC-derived RPE cells, adult and fetal stem cells yielded improvements in visual function for up to 4 weeks post-injection; this outcome was mainly based on the paracrine effects of several types of growth factors secreted by the stem cells. Patients with RD will benefit from the stem cell therapy.

Applying stem cell therapy in intractable diseases: a narrative review of decades of progress and challenges

Background and Objective

Stem cell therapy (SCT) is one of the vastly researched branches of regenerative medicine as a therapeutic tool to treat incurable diseases. With the use of human stem cells such as embryonic stem cells (ESCs), adult stem cells (ASCs) and induced pluripotent stem cells (iPSCs), stem cell therapy aims to regenerate or repair damaged tissues and congenital defects. As stem cells are able to undergo infinite self-renewal, differentiate into various types of cells and secrete protective paracrine factors, many researchers have investigated the potential of SCT in regenerative medicine. Therefore, this review aims to provide a comprehensive review on the recent application of SCT in various intractable diseases, namely, haematological diseases, neurological diseases, diabetes mellitus, retinal degenerative disorders and COVID-19 infections along with the challenges faced in the clinical translation of SCT.

Methods

An extensive search was conducted on Google scholar, PubMed and Clinicaltrials.gov using related keywords. Latest articles on stem cell therapy application in selected diseases along with their challenges in clinical applications were selected.

Key content and findings

In vitro and in vivo studies involving SCT are shown to be safe and efficacious in treating various diseases covered in this review. There are also a number of small-scale clinical trials that validated the positive therapeutic outcomes of SCT. Nevertheless, the effectiveness of SCT are highly variable as some SCT works best in patients with early-stage diseases while in other diseases, SCT is more likely to work in patients in late stages of illnesses. Among the challenges identified in SCT translation are uncertainty in the underlying stem cell mechanism, ethical issues, genetic instability and immune rejection.

Conclusions

SCT will be a revolutionary treatment in the future that will provide hope to patients with intractable diseases. Therefore, studies ought to be done to ascertain the long-term effects of SCT while addressing the challenges faced in validating SCT for clinical use. Moreover, as there are many studies investigating the safety and efficacy of SCT, future studies should look into elucidating the regenerative and reparative capabilities of stem cells which largely remains unknown.

Retinal cell transplantation in retinitis pigmentosa

Retinitis pigmentosa is the most common hereditary retinal disease. Dietary supplements, neuroprotective agents, cytokines, and lately, prosthetic devices, gene therapy, and optogenetics have been employed to slow down the retinal degeneration or improve light perception. Completing retinal circuitry by transplanting photoreceptors has always been an appealing idea in retinitis pigmentosa. Recent developments in stem cell technology, retinal imaging techniques, tissue engineering, and transplantation techniques have brought us closer to accomplish this goal. The eye is an ideal organ for cell transplantation due to a low number of cells required to restore vision, availability of safe surgical and imaging techniques to transplant and track the cells in vivo, and partial immune privilege provided by the subretinal space. Human embryonic stem cells, induced pluripotential stem cells, and especially retinal organoids provide an adequate number of cells at a desired developmental stage which may maximize integration of the graft to host retina. However, stem cells must be manufactured under strict good manufacturing practice protocols due to known tumorigenicity as well as possible genetic and epigenetic stabilities that may pose a danger to the recipient. Immune compatibility of stem cells still stands as a problem for their widespread use for retinitis pigmentosa. Transplantation of stem cells from different sources revealed that some of the transplanted cells may not integrate the host retina but slow down the retinal degeneration through paracrine mechanisms. Discovery of a similar paracrine mechanism has recently opened a new therapeutic path for reversing the cone dormancy and restoring the sight in retinitis pigmentosa.

Biotechnology and Biomaterial-Based Therapeutic Strategies for Age-Related Macular Degeneration. Part II: Cell and Tissue Engineering Therapies

Age-related Macular Degeneration (AMD) is an up-to-date untreatable chronic neurodegenerative eye disease of multifactorial origin, and the main causes of blindness in over 65 y.o. people. It is characterized by a slow progression and the presence of a multitude of factors, highlighting those related to diet, genetic heritage and environmental conditions, present throughout each of the stages of the illness. Current therapeutic approaches, mainly consisting on intraocular drug delivery, are only used for symptoms relief and/or to decelerate the progression of the disease. Furthermore, they are overly simplistic and ignore the complexity of the disease and the enormous differences in the symptomatology between patients. Due to the wide impact of the AMD and the up-to-date absence of clinical solutions, Due to the wide impact of the AMD and the up-to-date absence of clinical solutions, different treatment options have to be considered. Cell therapy is a very promising alternative to drug-based approaches for AMD treatment. Cells delivered to the affected tissue as a suspension have shown poor retention and low survival rate. A solution to these inconveniences has been the encapsulation of these cells on biomaterials, which contrive to their protection, gives them support, and favor their retention of the desired area. We offer a two-papers critical review of the available and under development AMD therapeutic approaches, from a biomaterials and biotechnological point of view. We highlight benefits and limitations and we forecast forthcoming alternatives based on novel biomaterials and biotechnology methods. In this second part we review the preclinical and clinical cell-replacement approaches aiming at the development of efficient AMD-therapies, the employed cell types, as well as the cell-encapsulation and cell-implant systems. We discuss their advantages and disadvantages and how they could improve the survival and integration of the implanted cells.

First steps for the development of silk fibroin-based 3D biohybrid retina for age-related macular degeneration (AMD)

Age-related macular degeneration is an incurable chronic neurodegenerative disease, causing progressive loss of the central vision and even blindness. Up-to-date therapeutic approaches can only slow down he progression of the disease.

OBJECTIVE

Feasibility study for a multilayered, silk fibroin-based, 3D biohybrid retina.

APPROACH

Fabrication of silk fibroin-based biofilms; culture of different types of cells: retinal pigment epithelium, retinal neurons, Müller and mesenchymal stem cells ; creation of a layered structure glued with silk fibroin hydrogel.

MAIN RESULTS

In vitro evidence for the feasibility of layered 3D biohybrid retinas; primary culture neurons grow and develop neurites on silk fibroin biofilms, either alone or in presence of other cells cultivated on the same biomaterial; cell organization and cellular phenotypes are maintained in vitro for the seven days of the experiment.

SIGNIFICANCE

3D biohybrid retina can be built using silk silkworm fibroin films and hydrogels to be used in cell replacement therapy for AMD and similar retinal neurodegenerative diseases.