Presumed Silicone Oil Droplets After Intravitreal Pegcetacoplan Injections.

Importance: Recently, intravitreal pegcetacoplan became the first drug to gain US Food and Drug Administration approval for the treatment of geographic atrophy associated with nonexudative age-related macular degeneration, but the administration of this medication may be associated with unanticipated posttreatment complications. Objective: To assess the prevalence of presumed silicone oil droplets in the vitreous cavity after intravitreal injection of pegcetacoplan. Design, Setting, and Participants: This case series study involved a retrospective record review of all 55 patients treated with intravitreal pegcetacoplan, 0.1 mL in 150-mg/mL solution, between March 24 and June 5, 2023, at a single specialty retina practice. All injections were done using needles from the kit supplied by Apellis Pharmaceuticals on a 1-mL McKesson Luer lock syringe. Main Outcomes and Measures: The presence or absence of presumed silicone bubbles detected during dilated biomicroscopic fundus examination and/or on color fundus photographs, the presence or absence of symptoms, change in visual acuity, and/or increase in intraocular pressure. Results: A total of 62 intravitreal pegcetacoplan injections were given to 55 patients (mean [SD] age, 83.8 [7.8] years; 33 women [60%]) from March 24 to June 5, 2023. Of the 55 patients, 16 (29%; mean [SD] age, 83.8 [7.4] years; 9 women [56%]) had presumed intravitreal silicone droplets discovered 2 to 4 weeks after treatment, 3 of which were documented on color fundus photographs. Of the 16 patients, 14 (88%) were symptomatic for new floaters that they described as persistent, while 2 (13%) were asymptomatic. There were no signs of inflammation or infection, no increases in intraocular pressure, and no changes in visual acuity for all 16 patients. Conclusions and Relevance: A substantial percentage of patients had symptomatic floaters from presumed intravitreal silicone oil droplets after injections of pegcetacoplan using a McKesson 1-mL Luer lock syringe. These findings support consideration of informing patients of this potential adverse effect, avoiding use of the McKesson syringe, and considering use of silicone-free syringes for pegcetacoplan injections.

Deuterated docosahexaenoic acid protects against oxidative stress and geographic atrophy-like retinal degeneration in a mouse model with iron overload.

Oxidative stress plays a central role in age-related macular degeneration (AMD). Iron, a potent generator of hydroxyl radicals through the Fenton reaction, has been implicated in AMD. One easily oxidized molecule is docosahexaenoic acid (DHA), the most abundant polyunsaturated fatty acid in photoreceptor membranes. Oxidation of DHA produces toxic oxidation products including carboxyethylpyrrole (CEP) adducts, which are increased in the retinas of AMD patients. In this study, we hypothesized that deuterium substitution on the bis-allylic sites of DHA in photoreceptor membranes could prevent iron-induced retinal degeneration by inhibiting oxidative stress and lipid peroxidation. Mice were fed with either DHA deuterated at the oxidation-prone positions (D-DHA) or control natural DHA and then given an intravitreal injection of iron or control saline. Orally administered D-DHA caused a dose-dependent increase in D-DHA levels in the neural retina and retinal pigment epithelium (RPE) as measured by mass spectrometry. At 1 week after iron injection, D-DHA provided nearly complete protection against iron-induced retinal autofluorescence and retinal degeneration, as determined by in vivo imaging, electroretinography, and histology. Iron injection resulted in carboxyethylpyrrole conjugate immunoreactivity in photoreceptors and RPE in mice fed with natural DHA but not D-DHA. Quantitative PCR results were consistent with iron-induced oxidative stress, inflammation, and retinal cell death in mice fed with natural DHA but not D-DHA. Taken together, our findings suggest that DHA oxidation is central to the pathogenesis of iron-induced retinal degeneration. They also provide preclinical evidence that dosing with D-DHA could be a viable therapeutic strategy for retinal diseases involving oxidative stress.

Intraocular iron injection induces oxidative stress followed by elements of geographic atrophy and sympathetic ophthalmia.

Iron has been implicated in the pathogenesis of age-related retinal diseases, including age-related macular degeneration (AMD). Previous work showed that intravitreal (IVT) injection of iron induces acute photoreceptor death, lipid peroxidation, and autofluorescence (AF). Herein, we extend this work, finding surprising chronic features of the model: geographic atrophy and sympathetic ophthalmia. We provide new mechanistic insights derived from focal AF in the photoreceptors, quantification of bisretinoids, and localization of carboxyethyl pyrrole, an oxidized adduct of docosahexaenoic acid associated with AMD. In mice given IVT ferric ammonium citrate (FAC), RPE died in patches that slowly expanded at their borders, like human geographic atrophy. There was green AF in the photoreceptor ellipsoid, a mitochondria-rich region, 4 h after injection, followed later by gold AF in rod outer segments, RPE and subretinal myeloid cells. The green AF signature is consistent with flavin adenine dinucleotide, while measured increases in the bisretinoid all-trans-retinal dimer are consistent with the gold AF. FAC induced formation carboxyethyl pyrrole accumulation first in photoreceptors, then in RPE and myeloid cells. Quantitative PCR on neural retina and RPE indicated antioxidant upregulation and inflammation. Unexpectedly, reminiscent of sympathetic ophthalmia, autofluorescent myeloid cells containing abundant iron infiltrated the saline-injected fellow eyes only if the contralateral eye had received IVT FAC. These findings provide mechanistic insights into the potential toxicity caused by AMD-associated retinal iron accumulation. The mouse model will be useful for testing antioxidants, iron chelators, ferroptosis inhibitors, anti-inflammatory medications, and choroidal neovascularization inhibitors.

Enlargement rate of geographic atrophy before and after secondary CNV conversion with associated anti-VEGF treatment.

BACKGROUND: To study the enlargement rate of primary geographic atrophy (GA) before and after diagnosis of a secondary choroidal neovascularization (CNV) treated with anti-vascular endothelial growth factor (VEGF) therapy. METHODS: Five hundred twenty-two consecutive eyes with primary GA were screened for the development of a complicating secondary CNV. Geographic atrophy was measured on blue autofluorescence (BAF) by two readers and calculated into mean growth rate before and after CNV diagnosis. RESULTS: Ten eyes of six patients were included in the study (six study eyes with GA complicated by CNV, four GA only partner eyes). Follow-up was 1.42 ± 0.48 years before and 3.64 ± 2.73 years after CNV. There was no significant difference between mean growth rate before and after CNV (1.58 ± 0.99 vs. 1.39 ± 0.65 mm2/year; p = 0.44) or between study and partner eyes (p = 0.86). Over a mean time of 3.64 ± 2.73 years, a mean of 8.3 ± 2.8 anti-VEGF injections were given. No correlation between the amount of anti-VEGF injections and change in growth rate could be observed (r = 0.58; p = 0.23). CONCLUSION: In this pilot study, primary GA enlargement did not seem to be influenced by a secondary CNV. No association between the intensity of anti-VEGF treatment and changes in atrophy enlargement rates were found. Further studies with larger sample sizes are warranted.

Evolution of oxidative stress, inflammation and neovascularization in the choroid and retina in a subretinal lipid induced age-related macular degeneration model.

Oxidative stress, inflammation and neovascularization are the key pathological events that are implicated in human age-related macular degeneration (AMD). There are a limited number of animal models available for evaluating and developing new therapies. Most models represent late exudative or neovascular AMD (nAMD) but there is a relative paucity of models that mimic early events in AMD. The purpose of this study is to characterize the evolution of oxidative stress, inflammation, retinal degeneration and neovascularization in a rat model of AMD, created by subretinal injection of human lipid hydroperoxide (HpODE) that found in the sub-macular region in aged and AMD patients. Subretinal HpODE induced retinal pigment epithelium (RPE) and retinal degeneration resulting in loss of RPE cells, photoreceptors and retinal thinning. RPE degeneration and atrophy were detected by day 5, followed by neural tissue degeneration at day 12 with robust TUNEL positive cells. Western blot analysis confirmed an increase in pro-apoptotic Bak protein at day 12 in retinal tissues. Oxidative damage biomarkers (4-hydroxynonenal, malondialdehyde, 8-hydroxy-2'-deoxyguanosine, and nitrotyrosine) increased in retinal tissue from days 5-12. Müller glial activation was observed in the HpODE injected area at day 5 followed by its remodeling and migration in the outer retina by day 20. RT-qPCR analysis further indicated upregulation of pro-inflammatory genes (TNF-α, IL-1ß and IL-6) both in retinal and RPE/choroidal tissue as early as day 2 and persisted until day 12. Upregulation of oxidative stress markers such as NADPH oxidase (NOX and DOUX family) was detected early in retinal tissue by day 2 followed by its upregulation in choroidal tissue at day 5. Neovascularization was demonstrated from day 12 to day 20 post HpODE injection in choroidal tissue. The results from this study indicate that subretinal HpODE induces advanced AMD phenotypes comprising many aspects of both dry/early and late) and neovascular/late AMD as observed in humans. Within 3 weeks via oxidative damage, upregulation of reactive oxygen species and pro-inflammatory genes, pro-apoptotic Bak and pro-angiogenic VEGF upregulation occurs leading to CNV formation. This experimental model of subretinal HpODE is an appropriate model for the study of AMD and provides an important platform for translational and basic research in developing new therapies particularly for early/dry AMD where currently no viable therapies are available.

Association of macular disease with long-term use of pentosan polysulfate sodium: findings from a US cohort.

BACKGROUND/AIMS: A series at a single clinical centre recently demonstrated an association between the interstitial cystitis drug pentosan polysulfate sodium (PPS) and a vision-threatening pigmentary maculopathy. The aim of this study was to determine if an association exists between PPS use and macular disease in a large national cohort. METHODS: A retrospective, matched cohort study using data from a large US medical claims database from 2002 to 2016 was performed. A total of 3012 and 1604 PPS users were compared with 15 060 and 8017 matched controls at 5 and 7 years, respectively. The primary outcome measures included (1) any new diagnosis of a hereditary or secondary pigmentary maculopathy (atypical maculopathy outcome), and (2) any new diagnosis of dry age-related macular degeneration (AMD) or drusen in addition to the aforementioned diagnoses (atypical maculopathy+AMD outcome). RESULTS: At the 5-year and 7-year follow-up, 9 (0.3%) and 10 (0.6%) PPS patients progressed to the atypical maculopathy outcome compared with 32 (0.2%) and 25 (0.3%) control patients, respectively. 103 (3.4%) and 87 (5.4%) PPS patients developed the atypical maculopathy+AMD outcome compared with 440 (2.9%) and 328 (4.1%) control patients at 5 and 7 years, respectively. At 5 years, multivariate analysis showed no significant association (p>0.13). At 7 years, PPS users had significantly increased odds of having the atypical maculopathy+AMD outcome (OR=1.41, 95% CI 1.09 to 1.83, p=0.009). CONCLUSIONS: PPS exposure was associated with a new diagnosis of macular disease at the 7-year follow-up in a large national cohort.

Protective effect of RIPK1-inhibitory compound in in vivo models for retinal degenerative disease.

Receptor interacting protein kinase 1 (RIPK1) plays a key role in necroptosis, which is a type of programmed necrosis that is involved in ocular diseases, including glaucoma and dry age-related macular degeneration (AMD). We previously introduced RIPK1-inhibitory compound (RIC), which has biochemical characteristics and a mode of action that are distinct from those of the prototype RIPK1 inhibitor necrostatin-1. The intraperitoneal administration of RIC exerts a protective effect on retinal ganglion cells against a glaucomatous insult. In this study, we examined the protective effect of RIC on retinal pigment epithelium (RPE) against sodium iodate (SI) insult, which is associated with dry AMD pathogenesis. The eye drop administration of RIC that reached on the retina prevented RPE loss in SI-induced retinal degeneration. RIC consistently demonstrated retinal protection in the funduscopy and electroretinogram analyses in SI-injected rabbits and iodoacetic acid-treated mini-pigs. Moreover, the in vivo protective effects of RIC were superior to those of ACU-4429 and doxycycline, which are other medications investigated in clinical trials for the treatment of dry AMD, and RIC did not induce retinal toxicity following topical administration in rats. Collectively, RIC displayed excellent retinal penetration and prevented retinal degeneration in the pathogenesis of dry AMD with a high in vivo efficacy.

An Acute Injury Model for the Phenotypic Characteristics of Geographic Atrophy.

Purpose: Geographic atrophy (GA) is the late stage of non-neovascular age-related macular degeneration. A lack of animal models for GA has hampered treatment efforts. Presented herein is a rat model for GA using subretinal injection of sodium iodate (NaIO3). Methods: Rats were given subretinal injections of NaIO3 (5 µg/µL) using a pico-injector. Fundus photographs and spectral domain optical coherent tomography scans were collected at 1, 3, 7, 14, and 28 days after injection, at which time rats were euthanized and eyes were enucleated. Eyes were either cryopreserved or dissected into retinal and choroidal flatmounts. Fluorescence immunohistochemistry was performed for retinal glial fibrillary acidic protein (activated Müller cells and astrocytes) and vimentin (Müller cells), as well as peanut agglutin lectin (photoreceptors) labeling. RPE/choroids were labeled for RPE65 and CD34. Images were collected on Zeiss confocal microscopes. Results: Fundus photos, spectral domain optical coherent tomography, and RPE65 staining revealed well-demarcated areas with focal loss of RPE and photoreceptors in NaIO3-treated rats. At 1 day after injection, RPE cells appeared normal. By 3 days, there was patchy RPE and photoreceptor loss in the injected area. RPE and photoreceptors were completely degenerated in the injected area by 7 days. A large subretinal glial membrane occupied the degenerated area. Choriocapillaris was highly attenuated in the injected area at 14 and 28 days. Conclusions: The rat model reported herein mimics the photoreceptor cell loss, RPE atrophy, glial membrane formation, and choriocapillaris degeneration seen in GA. This model will be valuable for developing and testing drugs and progenitor cell regenerative therapies for GA.

Association of Anticholinergic Drug Use With Risk for Late Age-Related Macular Degeneration.

Importance: Amyloid-ß is a major component of retinal drusen, the primary lesions of age-related macular degeneration (AMD), and autopsy and animal models suggested that anticholinergic drug (ACD) use increased brain amyloid-ß deposition. Objective: To investigate the association between exposure to ACDs and late AMD (features of neovascular AMD or geographic atrophy of the retinal pigment epithelium in at least 1 eye). Design, Setting and Participants: A multicenter case-control study in 4 French ophthalmologic centers comprising 200 cases with late AMD and 200 controls enrolled from July 2016 to June 2017. Exposures: Exposure to at least 3 months of ACDs started before AMD diagnosis was recorded during a specific interview. A dose-effect association with cumulative exposure duration and Anticholinergic Burden Score was explored. The association between ACD exposure and AMD was assessed by multivariate logistic regression analysis adjusted for age, sex, smoking status, family history of AMD, alcohol consumption, and use of anticoagulant and anti-inflammatory drugs. Odds ratios (ORs) and 95% confidence intervals were estimated. Main Outcomes and Measures: Association between exposure to ACDs and late AMD. Results: Among case participants, the mean (SD) age was 74.8 (9.2) years, 129 (64.5%) were women, 192 (96%) were white, 65 (32.5%) had geographic atrophy, 135 (67.5%) had neovascular AMD, 116 (58%) had unilateral AMD, and 84 (42%) had bilateral AMD. Among control participants, the mean (SD) age was 75.5 (7.2) years, with 116 (58%) women and 187 (93.5%) white participants. Twenty-six cases (13%) and 10 controls (5%) were exposed to ACDs throughout life for at least 3 months before AMD onset. Risk of AMD was increased with ever exposure to ACDs (adjusted OR [aOR], 2.84; 95% CI, 1.33-6.06; P = .007), high Anticholinergic Burden Score (≥3) (aOR, 6.42; 95% CI, 1.38-29.92; P = .02), and longest cumulative exposure to ACD (≥15 years) (aOR, 5.88; 95% CI, 1.22-28.31; P = .03). Conclusions and Relevance: Risk of late AMD may be increased with at least 3 months' use of ACDs. A dose-effect association was suggested by a greater association with prolonged use and high Anticholinergic Burden Score. Further studies, in particular those with longitudinal design, are needed to confirm this association.

[Long-term results in neovascular age-related macular degeneration : Changes in visual acuity and geographic atrophy during long-standing anti-VEGF therapy]. / Langzeitergebnisse bei neovaskulärer altersabhängiger Makuladegeneration : Entwicklung des Visus und der geografischen Atrophie unter langjähriger VEGF-Inhibitionstherapie.

BACKGROUND: In neovascular age-related macular degeneration (nAMD) intravitreal injection of anti-vascular endothelial growth factor (VEGF) is the standard therapy. According to the results of the CATT study with reference to the potential relationship between ranibizumab injections and the occurrence of geographic atrophy (GA) this retrospective real life evaluation was performed. MATERIAL AND METHODS: Eyes with more than 28 intravitreal anti-VEGF injections (IVT) using bevacizumab, pegaptanib, ranibizumab or aflibercept were evaluated with respect to visual acuity and geographic atrophy using the RegionFinder of Heidelberg Engineering. For statistical analysis the Wilcoxon rank test was used (SPSS version 20, SPSS, Chicago, IL). RESULTS: In this study 56 eyes were evaluated with a median number of 41.5 (range 28-66) injections, which corresponds to an injection rate of 6.8 IVT per year. The median visual acuity at baseline was 0.4 logMAR ± 0.32 (range 0-1.2) and 0.6 logMAR ± 0.33 (range 0.1-1.7) at the end of the observation period. This decrease was statistically significant (p = 0.029). In 55.8 % of the eyes visual acuity was equal or better after a median of 6 years follow-up whereas 23.3 % revealed a visual acuity that was ≤ 0.3 logMAR. Of the eyes 30 % showed a clearly defined GA. The median GA at baseline was 0.45 mm(2) (range 0-6.24) and at the time of evaluation 4.36 mm(2) (range 0.95-24.71) corresponding to an annual growth of 0.49 mm(2)/year. CONCLUSION: In conjunction with the results of other long-term studies it can be assumed that despite regular monitoring and long-term treatment not all patients with nAMD can be protected against a final loss of visual acuity over the years; however, more than 50 % of the eyes could maintain a stable or improved visual acuity. With respect to GA this small collective showed growth rates that are comparable to those in slowly progressing dry AMD. Thus no evidence was found for accelerated increase of GA during IVT therapy.

Improved cell metabolism prolongs photoreceptor survival upon retinal-pigmented epithelium loss in the sodium iodate induced model of geographic atrophy.

Age-related macular degeneration (AMD) is characterized by malfunction and loss of retinal-pigmented epithelium (RPE) cells. Because the RPE transfers nutrients from the choriocapillaris to photoreceptor (PR), PRs are affected as well. Geographic atrophy (GA) is an advanced form of AMD characterized by severe vision impairment due to RPE loss over large areas. Currently there is no treatment to delay the degeneration of nutrient deprived PRs once RPE cells die. Here we show that cell-autonomous activation of the key regulator of cell metabolism, the kinase mammalian target of rapamycin complex 1 (mTORC1), delays PR death in the sodium iodate induced model of RPE atrophy. Consistent with this finding loss of mTORC1 in cones accelerates cone death as cones fail to balance demand with supply. Interestingly, promoting rod survival does not promote cone survival in this model of RPE atrophy as both, rods and cones suffer from a sick and dying RPE. The findings suggest that activation of metabolic genes downstream of mTORC1 can serve as a strategy to prolong PR survival when RPE cells malfunction or die.

Vision-threatening lesions developing with longer-term follow-up after treatment of neovascular age-related macular degeneration.

PURPOSE: To assess the development of vision-threatening lesions at least 3.5 years after initiating anti-vascular endothelial growth factor (VEGF) for choroidal neovascularization (CNV) in eyes with age-related macular degeneration (AMD). DESIGN: Retrospective cohort study. PARTICIPANTS: A total of 75 patients (81 eyes) with CNV secondary to AMD who received intravitreous anti-VEGF treatment and were followed for at least 3.5 years after initiating treatment. METHODS: Retrospective record review of patients initiating anti-VEGF treatment between November 2005 and June 2008 at a university-based institution for whom at least 3.5 years of follow-up was available at the same institution. MAIN OUTCOME MEASURES: Predominantly hemorrhagic lesions or geographic atrophy (GA). RESULTS: Among 75 patients (81 eyes; 59% were women; median age, 78 years), mean follow-up was 4.9 years and at least 6 years for 40%. Median visual acuity (VA) was 20/80 (interquartile range [IQR], 20/50-20/100) initially, 20/63 (IQR, 20/40-20/160) at 2 years, 20/80 (IQR, 20/40-20/200) at 3.5 years, and 20/63 (IQR 20/32-20/200) at 6 years. Six eyes (7%) had predominantly hemorrhagic lesions initially, whereas this developed in an additional 3 eyes (4%, 95% confidence interval [CI], 1% to 10%) in 3.5 years and in 1 additional eye (1%, 95% CI, 0.03% to 7%) at more than 3.5 years of follow-up. Initially, GA within or overlapping the boundary of the entire CNV was present in 4 eyes (5%) and outside this boundary in 8 eyes (10%). Geographic atrophy enlarged in each eye over time. The only eyes that developed GA outside the CNV boundary were those that had GA outside the lesion at baseline. Additional atrophy within the boundary of CNV defined at baseline, termed "atrophic disciform scars," developed in 5 eyes (6%), all within 4 years of treatment initiation. CONCLUSIONS: Longer-term follow-up of neovascular AMD managed with anti-VEGF therapy suggests that predominantly hemorrhagic lesions may develop within 3.5 years of initiating therapy and more than 3.5 years after initiating therapy. In contrast, new areas of GA beyond the boundaries of the CNV lesion as defined at initiation of anti-VEGF therapy seem unlikely to develop if there is no GA outside of the CNV lesion initially.

Risk factors for geographic atrophy after intravitreal ranibizumab injections for retinal angiomatous proliferation.

PURPOSE: To describe the risk factors for the development of geographic atrophy (GA) following intravitreal ranibizumab injection treatment for retinal angiomatous proliferation (RAP). DESIGN: Retrospective interventional series. METHODS: Forty-three eyes (38 South Korean patients) from patients being treated for naïve RAP with intravitreal ranibizumab injection were included in this study. All patients were treated with an initial series of 3 monthly loading injections, followed by further injections as required. Baseline ocular characteristics and lesion features assessed using fluorescein angiography (FA), indocyanine angiography (ICGA), and spectral-domain optical coherence tomography (SD OCT) were evaluated as potential risk factors for GA through 2 years of follow-up. RESULTS: At 2 years follow-up, GA had developed in 16 of 43 eyes (37.2%). The mean number of ranibizumab injections was 7.52 ± 2.11. Using multiple logistic regression, thinning of the subfoveal choroid at baseline (odds ratio [OR], 0.955; 95% confidence interval [CI], 0.929-0.982; P = .002), presence of reticular pseudodrusen (OR, 1.092; 95% CI, 1.017-1.485; P = .039), and presence of GA in the fellow eye at baseline (OR, 1.433; 95% CI, 1.061-1.935; P = .025) were identified as significant risk factors for GA development. CONCLUSIONS: GA developed in 37.2% of eyes with RAP during the 24 months following intravitreal ranibizumab injections. Subfoveal choroidal thinning at baseline, the presence of reticular pseudodrusen, and the presence of GA in the fellow eye at baseline were associated with increased risk of GA development after treatment.

Polyethylene glycol induced mouse model of retinal degeneration.

Age-related macular degeneration (AMD) is a leading cause of irreversible blindness. This study was done to characterize dry AMD-like changes in mouse retinal pigment epithelium (RPE) and retina after polyethylene glycol (PEG) treatment. We injected male C57BL/6 mice subretinally with PBS, 0.025, 0.25, 0.5 and 1.0 mg of PEG-400 and the animals were sacrificed on day 5. Eyes were harvested and processed for histological analysis. In all other experiments 0.5 mg PEG was injected and animals were sacrificed on days 1, 3, 5 or 14. Paraffin, 5 µm and plastic, 1 µm and 80 nm sections were used for further analysis. Subretinal injection of 0.5 mg PEG induced a 32% reduction of outer nuclear layer (ONL) thickness, 61% decrease of photoreceptor outer and inner segment length, 49% decrease of nuclear density in the ONL and 31% increase of RPE cell density by day 5 after injection. The maximum level of TUNEL positive nuclei in the ONL (6.8 + 1.99%) was detected at day 5 after PEG injection and co-localized with Casp3act. Histological signs of apoptosis were observed in the ONL by light or electron microscopy. Degeneration of RPE cells was found in PEG injected eyes. Gene expression data identified several genes reported to be involved in human AMD. C3, Cfi, Serping1, Mmp9, Htra1 and Lpl were up-regulated in PEG injected eyes compared to PBS controls. PEG leads to morphological and gene expression changes in RPE and retina consistent with dry AMD. This model will be useful to investigate dry AMD pathogenesis and treatment.