LONG-TERM RESULTS OF AUTOLOGOUS RETINAL PIGMENT EPITHELIUM AND CHOROID TRANSPLANTATION FOR THE TREATMENT OF EXUDATIVE AND ATROPHIC MACULOPATHIES

Incisional choroidal surgery

The choroid is a thin layer of highly vascular uveal tissue enclosed externally by sclera and internally by neurosensory retinal tissue. The choroid is a "middle layer" ocular tissue with anatomically challenging surgical access. The primary functional role of the choroid is to provide rapid, oxygenated, and nutrient-rich blood flow to both the highly metabolic retinal pigment epithelium and outer retina (i.e. photoreceptors) while simultaneously removing waste products. Historically, incisional choroidal surgery (ICS) has involved tumor biopsy or excision, removal of choroidal neovascular complex or autologous choroidal translocations; however, ICS also holds unique potential for novel and innovative approaches to address macular pathology. Using large-animal surgical studies, researchers have explored ICS with the objective of finding safer and more effective techniques to reduce surgical risks such as bleeding, tissue contraction, and scar tissue formation. We explore the relevant anatomy and embryology, existing surgical techniques, discuss the implications for retinal drug delivery, define ICS guiding principles, and offer a rationale for implementation of ICS into a vitreoretinal surgical practice. We also identify other future challenges and anticipate future innovations that will advance ICS.

Retinotomies and retinectomies: A review of indications, techniques, results, and complications

Retinotomy refers to "cutting" or "incising" the retina, whereas retinectomy denotes "excising" the retina. Retinotomies and retinectomies aid in tackling traction and retinal shortening that persist following membrane dissection and scleral buckling. We performed a literature search using Google Scholar and PubMed, followed by a review of the references procured. All relevant literature was studied in detail and summarized. We discuss the indications of retinotomies and retinectomies for relaxing retinal stiffness, accessing the subretinal space for choroidal neovascular membrane, hemorrhage and abscess clearance, drainage retinotomies to allow retinal flattening, radial retinotomies to release circumferential traction, harvesting free retinal grafts, and prophylactic chorioretinectomies in trauma.

Clinical results of neurorestorative cell therapies and therapeutic indications according to cellular bio-proprieties

Cell therapies have been explored to treat patients with nervous diseases for over 20 years. Even though most kinds of cell therapies demonstrated neurorestorative effects in non-randomized clinical trials; the effects of the majority type cells could not be confirmed by randomized controlled trials. In this review, clinical therapeutic results of neurorestorative cell therapies according to cellular bio-proprieties or cellular functions were introduced. Currently it was demonstrated from analysis of this review that some indications of cell therapies were not appropriate, they might be reasons why their neurorestorative effects could not be proved by multicenter, randomized, double blind, placebo-controlled clinical trials. Theoretically if one kind of cell therapy has neurorestorative effects according to its cellular bio-proprieties, it should have appropriate indications. The cell therapies with special bio-properties is promising if the indication selections are appropriate, such as olfactory ensheathing cells for chronic ischemic stroke, and their neurorestorative effects can be confirmed by higher level clinical trials of evidence-based medicine.

Subretinal Transplant of Human Amniotic Membrane in Advanced Age-Related Macular Degeneration

Macular neovascularization (MNV) and geographic atrophy can complicate age-related macular degeneration (AMD) and lead to severe visual acuity reduction. Despite the medical treatments available, with a defect in the retinal pigmented epithelium (RPE) there is no possibility of restoring acceptable visual acuity. We evaluated postoperative outcomes in patients affected by advanced AMD who underwent subretinal implant of the human amniotic membrane (hAM) as a source of pluripotent stem cells. This retrospective, consecutive, non-randomized interventional study included 23 eyes of 21 patients affected by AMD complicated by MNV, and five eyes of five patients affected by geographic atrophy. All eyes underwent a pars plana vitrectomy, neovascular membrane removal for the MNV group, a subretinal implant of hAM, and gas tamponade, and were followed for 12 months. The primary study outcome was visual acuity improvement. Secondary outcomes were postoperative complications, OCT-angiography parameters correlated with best-corrected visual acuity (BCVA) and MNV recurrence. The mean preoperative BCVA was 1.9 logMAR, and the mean final BCVA value was 1.2 logMAR. In the MNV group, the mean BCVA improved from 1.84 logMAR to 1.26 logMAR, and from 1.84 logMAR to 1.32 logMAR in the geographic atrophy group. No MNV recurrence was evident in 12 months of follow-up. An OCT-angiography scan was used to evaluate the retinal vascularization in the treated eye, which showed a high correlation between BCVA and deep vascular density. This study demonstrates the hAM potential and safety in promoting a partial restoration of retinal function together with an increase in visual acuity.

Transcriptional comparison of adult human primary Retinal Pigment Epithelium, human pluripotent stem cell-derived Retinal Pigment Epithelium, and ARPE19 cells

The therapeutic potential of pluripotent stem cells is great as they promise to usher in a new era of medicine where cells or organs may be prescribed to replace dysfunctional tissue. At the forefront are efforts in the eye to develop this technology as it lends itself to in vivo monitoring and sophisticated non-invasive imaging modalities. In the retina, retinal pigment epithelium (RPE) is the most promising replacement cell as it has a single layer, is relatively simple to transplant, and is associated with several eye diseases. However, after transplantation, the cells may transform and cause complications. This transformation may be partially due to incomplete maturation. With the goal of learning how to mature RPE, we compared induced pluripotent stem cell-derived RPE (iPSC-RPE) cells with adult human primary RPE (ahRPE) cells and the immortalized human ARPE-19 line. We cultured ARPE-19, iPSC-RPE, and ahRPE cells for one month, and evaluated morphology, RPE marker staining, and transepithelial electrical resistance (TEER) as quality control indicators. We then isolated RNA for bulk RNA-sequencing and DNA for genotyping. We genotyped ahRPE lines for the top age-related macular degeneration (AMD) and proliferative vitreoretinopathy (PVR) risk allele polymorphisms. Transcriptome data verified that both adult and iPSC-RPE exhibit similar RPE gene expression signatures, significantly higher than ARPE-19. In addition, in iPSC-RPE, genes relating to stem cell maintenance, retina development, and muscle contraction were significantly upregulated compared to ahRPE. We compared ahRPE to iPSC-RPE in a model of epithelial-mesenchymal transition (EMT) and observed an increased sensitivity of iPSC-RPE to producing contractile aggregates in vitro which resembles incident reports upon transplantation. P38 inhibition was capable of inhibiting iPSC-RPE-derived aggregates. In summary, we find that the transcriptomic signature of iPSC-RPE conveys an immature RPE state which may be ameliorated by targeting "immature" gene regulatory networks.

Management of submacular massive haemorrhage in age-related macular degeneration: comparison between subretinal transplant of human amniotic membrane and subretinal injection of tissue plasminogen activator

PURPOSE

Macular neovascularization (MNV) can complicate age-related macular degeneration (AMD) and lead to severe visual acuity reduction. Massive submacular haemorrhage (SMH) is a sight-threatening complication of MNV and a challenge in the management of complications related to MNV in AMD since the effects of anti-vascular endothelial growth factor treatment alone are insufficient. Here, we evaluate the different postoperative outcomes of patients affected by MNV complicated by SMH that underwent subretinal implant of human amniotic membrane (hAM) or subretinal injection of tissue plasminogen activator (tPA).

METHODS

This is a retrospective, consecutive, comparative, non-randomized interventional study. We included 44 eyes of 44 patients affected by AMD complicated by MNV and SMH. Twenty-two eyes underwent a pars plana vitrectomy (PPV), SMH and neovascular membrane removal, with a subretinal implant of hAM and silicone oil, and 22 eyes underwent PPV, subretinal injection of tPA, and 20% sulphur hexafluoride. The primary study outcome was visual acuity improvement. Secondary outcomes were postoperative complications, and MNV recurrence and optical coherence tomography (OCT)-Angiography parameters correlated with best-corrected visual acuity (BCVA).

RESULTS

Mean preoperative BCVA was 1.9 logarithm of the minimal angle of resolution (logMAR) in the amniotic membrane-group and 2 logMAR in the tPA-group. The mean final BCVA values were 1.25 and 1.4 logMAR, respectively, with a statistically significant difference. Optical coherence tomography (OCT)-Angiography scan was be used to evaluate the retinal vascularization in the treated eye.

CONCLUSION

Both techniques report similar VA improvements and postoperative complications. However, transplantation of hAM seems to have a significant benefit in inhibiting MNV recurrence.

Exploring the choroidal vascular labyrinth and its molecular and structural roles in health and disease

The choroid is a key player in maintaining ocular homeostasis and plays a role in a variety of chorioretinal diseases, many of which are poorly understood. Recent advances in the field of single-cell RNA sequencing have yielded valuable insights into the properties of choroidal endothelial cells (CECs). Here, we review the role of the choroid in various physiological and pathophysiological mechanisms, focusing on the role of CECs. We also discuss new insights regarding the phenotypic properties of CECs, CEC subpopulations, and the value of measuring transcriptomics in primary CEC cultures derived from post-mortem eyes. In addition, we discuss key phenotypic, structural, and functional differences that distinguish CECs from other endothelial cells such as retinal vascular endothelial cells. Understanding the specific clinical and molecular properties of the choroid will shed new light on the pathogenesis of the broad clinical range of chorioretinal diseases such as age-related macular degeneration, central serous chorioretinopathy and other diseases within the pachychoroid spectrum, uveitis, and diabetic choroidopathy. Although our knowledge is still relatively limited with respect to the clinical features and molecular pathways that underlie these chorioretinal diseases, we summarise new approaches and discuss future directions for gaining new insights into these sight-threatening diseases and highlight new therapeutic strategies such as pluripotent stem cell‒based technologies and gene therapy.

Innovative strategies for treating retinal diseases

OBJECTIVE

The aim of this comprehensive paper is to acquaint the readers with innovative approaches in the treatment of retinal diseases, which could in the coming years to get into clinical practice. Retinal prostheses, retinal pigment epithelial (RPE) transplantation, gene therapy and optogenetics will be described in this paper.

METHODOLOGY

Describing the basic characteristics and mechanisms of different types of therapy and subsequently literary minireview clarifying the current state of knowledge in the area.

RESULTS

Retinal prostheses, RPE transplantation, gene therapy and optogenetics offer yet unexplored possibilities and are considered as the future of treatment of retinal diseases where classical pharmacotherapy or surgical treatment are no longer sufficient. However, all these methods challenge not only in the innovative technical implementation itself, but also for the ethical, administrative and economic demands.

CONCLUSION

There will be certainly interesting development in the treatment of retinal diseases, but it is not possible to fully estimate which modality of treatment will be dominant in the future.

Silicone oil-induced displacement of subretinal hemorrhage in age-related macular degeneration

PURPOSE

To describe the use of silicone oil (SO) in combination with subretinal recombinant tissue plasminogen activator (rtPA) to achieve dislocation of large subretinal hemorrhage secondary to exudative age-related macular degeneration (AMD).

METHODS

A single-eye 81-year-old woman, known for exudative AMD, presented for a profound vision loss in her left eye since 7 days due to a massive subretinal hemorrhage. She promptly underwent standard three-port pars plana vitrectomy with subretinal injection of rtPA and SO tamponade.

RESULTS

The surgical technique showed favorable anatomical and functional outcomes, achieving a substantial peripheral displacement of blood and visual improvement.

CONCLUSION

This report favorably supports the use of SO in adjunction to subretinal rtPA in selected cases of subretinal hemorrhage secondary to wet AMD.

Development of Stem Cell Therapies for Retinal Degeneration

Degenerative retinal disease is the major cause of sight loss in the developed world and currently there is a lack of effective treatments. As the loss of vision is directly the result of the loss of retinal cells, effective cell replacement through stem-cell-based therapies may have the potential to treat a great number of retinal diseases whatever their underlying etiology. The eye is an ideal organ to develop cell therapies as it is immune privileged, and modern surgical techniques enable precise delivery of cells to the retina. Furthermore, a range of noninvasive diagnostic tests and high-resolution imaging techniques facilitate the evaluation of any therapeutic intervention. In this review, we evaluate the progress to date of current cell therapy strategies for retinal repair, focusing on transplantation of pluripotent stem-cell-derived retinal pigment epithelium (RPE) and photoreceptor cells.

Human Amniotic Membrane Plug to Restore Age-Related Macular Degeneration Photoreceptor Damage

PURPOSE

Age-related macular degeneration (AMD) is the leading cause of legal blindness in adults 65 years of age and older. Choroidal neovascularization (CNV) can complicate AMD and lead to severe visual acuity reduction. Despite the several treatments available, if the retinal pigment epithelium is damaged, we have to cope with the impossibility of restoring acceptable visual acuity using only medical treatments.

DESIGN

Prospective, consecutive, interventional study.

PARTICIPANTS

Eleven patients affected by AMD, 6 patients affected by CNV, and 5 patients affected by geographic atrophy.

METHODS

All patients underwent a pars plana vitrectomy with subretinal implantation of human amniotic membrane (hAM) to induce photoreceptor regeneration and partial visual acuity restoration.

MAIN OUTCOME MEASURES

Primary study outcome was visual acuity improvement. Secondary outcomes were multimodal imaging results.

RESULTS

Mean preoperative best-corrected visual acuity (BCVA) was 20/2000 (2 logarithm of the minimum angle of resolution [logMAR]), and all the patients showed a BCVA of counting fingers or less. Mean final BCVA was 20/400 (1.31 logMAR), ranging from 20/2000 to 20/100 (2-0.7 logMAR). OCT angiography was used to measure retinal vascularization in the treated eye compared with the fellow eye. A high correlation between BCVA and deep vascular density was evidenced. Adaptive optics findings, obtained over the retinal area where the highest functionality was observed, were evaluated using microperimetry. The images showed possible photoreceptor presence over the hAM membrane.

CONCLUSIONS

This work supports the feasibility and safety of the hAM to promote partial retinal function restoration 6 months after surgery with visual acuity improvement. The advanced diagnostics help to understand the interaction between the hAM and photoreceptors and suggest that photoreceptor regeneration may occur.