Synaptic dysfunction is a major driver of cognitive decline in Alzheimer's disease (AD), yet its extent and molecular basis in the retina remain poorly defined. We integrated postmortem retinal and matched brain histopathology with ultrastructural, proteomic, biochemical, and machine-learning analyses across cognitively normal, mild cognitive impairment, and AD cohorts. Retinal glutamatergic synapses exhibited early, progressive degeneration, marked by loss of presynaptic vesicular glutamate transporter 1 (VGLUT1) and synaptophysin and postsynaptic density protein 95 (PSD95) and N-methyl-D-aspartate receptor subunit 2A (NMDAR2A), along with ribbon synapse ultrastructural disruption. Synaptic deficits correlated with amyloid-β42 (Aβ42), pathogenic tau, oxidative stress, the Aβ-binding p75 neurotrophin receptor, and glial activation that paralleled disease progression. Proteomics revealed widespread synaptic remodeling accompanied by disease-associated microglia, astrocyte-mediated excitotoxicity, and pyroptotic pathways. The synapse-enriched deubiquitinase ubiquitin C-terminal hydrolase L1 (UCHL1) was dysregulated early, particularly in horizontal and bipolar interneurons, and strongly associated with synaptic loss and neuroinflammation. Mechanistically, fibrillar Aβ42 induced rapid UCHL1 and synaptic depletion in human and murine neurons before overt neurodegeneration. Machine-learning models identified retinal UCHL1 as the strongest predictor of Braak stage and cognitive impairment. These findings establish the retina as an early site of AD synaptopathy and position UCHL1 as a candidate biomarker and mechanistic mediator linking amyloid pathology, neuroinflammation, and synaptic vulnerability.

Research in corneal biology and pathology including disease modeling and drug testing largely depends on the availability of human ex vivo cultures. Because normal corneal epithelium can be cultured only for several passages, stable epithelial cell lines transformed by different agents or spontaneously have been developed. Telomerase immortalized diploid cell lines introduced more recently were shown to recapitulate traits of normal cells including the expression of some markers and stratification ability. At the same time, there are frequently used cell lines generated by transformation with viruses. The most popular lines were shown to be unstable, tetraploid, lacking important epithelial markers, having aberrant differentiation and deviating from normal cells by gene expression patterns. This perspective reviews properties of various corneal epithelial cell lines and cautions against the use of virally transformed, especially tumorigenic cell lines, as seriously deviating form normal cells. We also provide commercial sources of normal corneal cells and briefly discuss possible future use of limbal organoids.

Synaptic failure predicts cognitive decline in Alzheimer's disease (AD), yet its impact and molecular drivers in the human retina remain unclear. Leveraging the retina as an accessible central nervous system (CNS) proxy, we integrated spatially resolved histopathology of retinal cross-sections with ultrastructural, proteomic, and biochemical profiling across independent postmortem cohorts spanning normal cognition, mild cognitive impairment due to AD (MCI), and AD dementia. We uncover early, progressive degeneration of excitatory glutamatergic synapses, evidenced by losses of presynaptic vesicular glutamate transporter 1 (VGLUT1) and synaptophysin, and postsynaptic density protein 95 (PSD95) and N-methyl-D-aspartate receptor subunit 2A (NMDAR2A), accompanied by disruption of synaptic ultrastructure. Retinal synaptic loss tightly associates with local accumulation of amyloid-β 42 (Aβ42) and immature tau species, heightened oxidative stress, and upregulation of the Aβ-binding death receptor p75 neurotrophin receptor (p75NTR). Notably, the synapse-enriched deubiquitinase ubiquitin C-terminal hydrolase L1 (UCHL1) is profoundly dysregulated, correlates with synaptic integrity and cognition, and emerges as the strongest retinal predictor of Braak stage and cognitive status in multivariable machine-learning models. Together, these findings position retinal Aβ/p75NTR-mediated UCHL1 imbalance as a proteostasis-synapse mechanistic hub and candidate biomarker reflecting AD severity.

Women face a twofold higher lifetime risk of Alzheimer's disease (AD) than men, yet the mechanisms underlying female-biased vulnerability and sex-specific disease signatures across the retina-brain axis remain unknown. By integrating clinicopathological and proteomic datasets from paired retinal and brain tissues from 182 donors, we identified sex-divergent molecular and pathological features across the AD continuum. Despite comparable retinal and cerebral amyloid and tau burdens between sexes, females exhibited a more severe neuroinflammatory-neurodegenerative phenotype with intensified gliosis and tissue atrophy, whereas males displayed a dominant vasculopathy, marked by increased retinal vascular Aβ40 deposition, tight-junction disruption, and cerebral amyloid angiopathy. In females, this profile coincided with inflammation-associated estrogen receptor (ER)-α remodeling and reduced global and astrocytic-nuclear ER-β, which associated more strongly with cognitive decline than in males. These results indicate that comparable AD proteinopathy is associated with divergent downstream consequences across the retina-brain axis and identify astrocytic ERα/ERβ imbalance as a sex-linked glial mechanism associated with female vulnerability in AD.

Abstract Pathological tau isoforms, including hyperphosphorylated tau at serine 396 (pS396-tau) and tau oligomers (Oligo-tau), are elevated in the retinas of patients with mild cognitive impairment (MCI) due to Alzheimer’s disease (AD) and AD dementia. These patients exhibit significant retinal ganglion cell (RGC) loss, however the presence of tau isoforms in RGCs and their impact on RGC integrity, particularly in early AD, have not been studied. Here, we analyzed retinal superior temporal cross-sections from 25 MCI or AD patients and 16 age- and sex-matched cognitively normal controls. Using the RGC marker ribonucleic acid binding protein with multiple splicing (RBPMS) and Nissl staining, we found a 46–56% reduction in RBPMS+ RGCs and Nissl+ neurons in the ganglion cell layer (GCL) of MCI and AD retinas (P < 0.05–0.001). RGC loss was accompanied by soma hypertrophy (10–50% enlargement, P < 0.05–0.0001), nuclear displacement, apoptosis (30–50% increase, P < 0.05–0.01), and prominent expression of granulovacuolar degeneration (GVD) bodies and GVD-necroptotic markers. Both pS396-tau and Oligo-tau were identified in RGCs, including in hypertrophic cells. PS396-tau+ and Oligo-tau+ RGC counts were significantly increased by 2.1–3.5-fold in MCI and AD retinas versus control retinas (P < 0.05–0.0001). Tauopathy-laden RGCs strongly inter-correlated (r P =0.85, P < 0.0001) and retinal tauopathy associated with RGC reduction (r P =-0.40–(-0.64), P < 0.05–0.01). Their abundance correlated with brain pathology and cognitive deficits, with higher tauopathy-laden RGCs in patients with Braak stages (V–VI), clinical dementia ratings (CDR = 3), and mini-mental state examination (MMSE ≤ 26) scores. PS396-tau+ RGCs in the central and mid-periphery showed the closest associations with disease status, while Oligo-tau+ RGCs in the mid-periphery exhibited the strongest correlations with brain pathology (NFTs, Braak stages, ABC scores; r S =0.78–0.81, P < 0.001–0.0001) and cognitive decline (MMSE; r S =-0.79, P = 0.0019). Overall, these findings identify a link between pathogenic tau in RGCs and RGC degeneration in AD, involving apoptotic and GVD-necroptotic cell death pathways. Future research should validate these results in larger and more diverse cohorts and develop RGC tauopathy as a potential noninvasive biomarker for early detection and monitoring of AD progression.

Primary Central Nervous System Lymphoma is an aggressive central nervous system neoplasm with poor response to pharmacological treatment, partially due to insufficient drug delivery across blood-brain barrier. In this study, we developed a novel therapy for this lymphoma by combining a targeted nanopolymer treatment with an immune checkpoint inhibitor antibody (anti-PD-1). A N-(2-hydroxypropyl)methacrylamide copolymer-based nanoconjugate was designed to block tumor cell c-Myc oncogene expression by antisense oligonucleotide. Angiopep-2 peptide was conjugated to the copolymer to facilitate nanodrug crossing of the blood-brain barrier. Systemically administered polymeric nanodrug, alone or in combination with immune checkpoint inhibitor antibody anti-PD-1, was tested in syngeneic mouse model of A20 intracranial brain lymphoma. There was no significant survival difference between saline- and free anti-PD-1-treated groups. However, significant survival advantage vs. saline was observed upon treatment with nanodrug bearing Angiopep-2, H6 (6 histidines for endosome escape), and c-Myc antisense alone and especially when it was combined with anti-PD-1 antibody. Animal survival after combined treatment was also significantly increased vs. free anti-PD-1. Artificial Intelligence-assisted analysis of gene expression database after RNA-seq of tumors was used to find novel immune pathways, molecular targets and the most effective multifunctional drugs together with future drug prediction for brain lymphoma in vivo model. Spectral flow cytometry and RNA-seq analysis revealed a robust activation of tumor infiltrating T lymphocytes with enhanced interferon γ signaling and polarization to M1-type macrophages in treated tumors, which was confirmed by immunofluorescence staining. In summary, a new effective blood-brain barrier crossing nano immuno therapeutic system was developed that effectively blocked tumor c-Myc acting in combination with immune checkpoint inhibitor anti-PD-1 to treat primary brain lymphoma. The treatment improved survival of tumor-bearing animals through activation of both the adaptive and innate immune responses.

Glioblastomas (GBM) escape the immune system and are heterogenous making it difficult to target the tumor directly for treatment. However, tumor microenvironment is independent of glioma heterogeneity and might be a universal target. GBMs overexpressing laminin-411 are associated with poor patient survival. We synthesized a blood brain barrier (BBB) crossing drug delivery system that can selectively inhibit laminin-411 synthesis in vivo, upregulating innate immune system and improving survival. GBM cell lines CT-2A and GL261 with CRISPR/Cas9 depletion of laminin-411 or control wild-type were intracranially implanted in C57BL/6J mice, n = 8 per group. Depletion was validated by western blot. We used flow cytometry (FC) to verify molecular changes in tumor microenvironment after laminin-411 depletion and examined mouse survival. Additionally, wild-type GL261-implanted mice (n=8) were I.V. treated with nanoimmuno polymeric drug crossing BBB and specifically blocking laminin-411 synthesis using morpholino antisense. Mouse survival was determined, and tumors were assessed by RNA-seq, immune markers (FC), and immunohistochemistry. Animals with laminin-411 knockout GBMs showed significant tumor upregulation of innate immune system markers, CD3, CD8, as well as NK T cells, NK, IFNg+ NK cells, and M1 macrophages by FC analyses vs. control tumors. These mice had increased median survival, 47 vs. 34 days in CT-2A (p = 0.003) and over 50 vs. 26 days in GL261 (p = 0.001). Similarly, in vivo treatment of wild-type GBM GL261-bearing mice with nanoimmuno polymeric drug showed 32% greater survival (33 vs. 25 days, p = 0.0001) vs. PBS. Immunohistochemistry-validated RNA-seq showed increase in IFN-g, TNF-a, and M1 macrophage iNOS, and decrease of proliferation markers Ki-67 and c-Myc after treatment. For the first time, laminin-411 was studied as a targetable regulator of GBM immunity. Our nanoimmuno drug inhibiting laminin-411 can cross BBB and inhibit tumor growth.

Emerging evidence implicates bacterial infections, including Chlamydia pneumoniae (Cp), a gram-negative obligate intracellular bacterium responsible for community-acquired pneumonia, in Alzheimer's disease (AD) pathogenesis. However, the involvement of Cp in early and advanced AD in the retina is unknown. Here, we identified the existence and distribution of intracellular Cp inclusions and related NLRP3 inflammasome activation and neurodegeneration in postmortem retinas and brains from 95 human donors. Histological analysis in neuropathologically-confirmed MCI and AD patients compared with cognitively normal individuals (n=70), revealed 2.9-4.1-fold increases of Cp inclusions in AD retinas and brains, respectively, with no significant increases in MCI retinas or brains. Mass spectrometry-based proteomics in additional cohorts (n=30), revealed dysregulated brain and retinal bacterial infection-related proteins and inflammasome-associated pathways. Retinal Cp was strongly linked to Aβ42, caspase-1 and NLRP3-inflammasome activation components, as well as cleaved caspase-3+ apoptosis and cleaved gasdermin D pyroptotic cell death. Despite increased IBA1+ microgliosis in the AD retina, the Cp-associated microglial population was reduced by 62%, suggesting impaired microglial phagocytosis. Higher retinal Cp burden correlated with APOEε4 status, advanced Braak stage, and cognitive decline. Machine learning models revealed that retinal Cp or NLRP3, in combination with retinal Aβ42, effectively predicted AD diagnosis, Braak stage, and cognition. These findings suggest that Cp infection contributes to AD dementia but is unlikely to initiate AD pathological changes, whereas elevated retinal NLRP3 may serve as an early AD marker. These results underscore the need for future studies investigating Cp's role in AD dementia and testing early antibiotic or inflammasome-targeting therapies.

Purpose: Persistent epithelial alterations such as delayed wound healing are a key feature of diabetic corneal disease. Previously, we reported that epigenetic changes in the diabetic cornea led to the suppression of Wnt-5a, and that addition of Wnt-5a accelerated wound healing. In this study, we set to determine which Wnt receptor(s) mediated Wnt-5a induced stimulation of diabetic corneal epithelial wound healing. Methods: Human limbal epithelial cells (LECs) were isolated from postmortem diabetic and non-diabetic donor eyes for single-cell RNA sequencing (scRNA-seq) and DNA methylation analysis. These analyses were validated by qRT-PCR, western blot, or immunostaining of corneal tissue sections. Cultured primary LECs were transfected with small interfering RNA (siRNA) to specific Wnt receptors to evaluate their role in scratch wound healing in the presence or absence of 200 ng/mL Wnt-5a. Results: Single-cell RNA sequencing analysis revealed differential gene expression of Wnt receptors, ROR2, MCAM, FZD5, FZD6, and FZD7. DNA methylation arrays showed hypomethylation of ROR2 gene promoter in diabetic versus non-diabetic LECs by 41.3% (**P < 0.01) resulting in increased ROR2 protein expression. Non-diabetic cells transfected with siRNA to knockdown ROR2 but not FZD5, FZD6, FZD7, MCAM, and RYK showed significantly decreased wound healing by approximately 50% (*P < 0.05) versus control siRNA. In diabetic LECs, knockdown of ROR2 significantly inhibited wound healing by 40% (*P < 0.05) and of FZD5 partially blocked wound healing that could not be restored by the addition of Wnt-5a. Conclusions: Wnt-5a seems to mediate wound healing in diabetic LECs mainly through receptor tyrosine kinase like orphan receptor 2 with Frizzled-5 serving as a possible co-receptor with a smaller effect.

The therapeutic potential of exosomes (Exos), a subpopulation of extracellular vesicles (EVs) secreted by various cell types, has been broadly emphasized. Exos are endosome-derived membrane-bound vesicles 50–150 nm in size. Exos can be general or cell type-specific. Their contents enable them to function as multi-signaling and vectorized vehicles. Exos are important for maintaining cellular homeostasis. They are released into extracellular spaces, leading to uptake by neighboring or distant cells and delivering their contents to modulate cell signaling. Exos influence tissue responses to injury, infection, and disease by fusion with the target cells and transferring their cargo, including cytokines, growth and angiogenic factors, signaling molecules, lipids, DNA, mRNAs, and non-coding RNAs. They are implicated in various physiological and pathological conditions, including ocular surface events, such as corneal scarring, wound healing, and inflammation. Their biocompatibility, stability, low immunogenicity, and easy detectability in bodily fluids (blood, tears, saliva, and urine) make them promising tools for diagnosing and treating ocular diseases. The potential to engineer specific Exo cargos makes them outstanding therapeutic delivery vehicles. The objective of this review is to provide novel insights into the functions of Exo cargos and their applications as biomarkers and therapeutics, or targets in the cornea.

Prominent features of diabetic corneal disease are oxidative stress, neuropathy and epitheliopathy including delayed wound healing and dysfunction of limbal epithelial stem cells. We hypothesised that regulatory miRNAs altered in the diabetic cornea, such as miR-10b-5p, may be responsible for these abnormalities. We aimed to understand the molecular impact of miR-10b-5p increase in human diabetic vs non-diabetic limbal epithelial cells (LECs) enriched in limbal epithelial stem cells by identifying its target genes and proteins and testing it as a potential therapy for inhibiting oxidative stress in diabetic corneas. LECs were isolated from diabetic and non-diabetic human autopsy corneas. Telomerase-immortalised human corneal epithelial cells (HCECs), primary LECs and ex vivo organ-cultured corneas were transfected with 50 nmol/l hsa-miR-10b-5p mimic or miRNA inhibitor or siRNA against GCLM (glutamate-cysteine ligase modifier subunit) along with their respective controls using Lipofectamine RNAiMAX. Total RNA was extracted for transcriptomic analysis. Proteins were extracted, digested and quantified using LC-MS/MS proteomics. Oxidative stress was induced using 200 µmol/l hydrogen peroxide (H2O2) in transfected LECs and/or HCECs post starvation. Cell lysates at 0, 3, 6, 9 and 24 h time points were analysed on western blots. Reactive oxygen species in transfected HCECs were measured using the DCFDA/H2DCFDA–Cellular ROS Assay Kit. Glutathione (GSH) levels were quantified using the GSH-Glo assay from H2O2-treated LECs. Glutamate-cysteine ligase modifier subunit (GCLM) and lanthionine synthetase C-like protein 1 (LANCL1) protein expression levels were also analysed by immunostaining. Integrative proteomic and genomic analysis of miR-10b- vs miRNA mimic control-transfected primary LECs identified GCLM and LANCL1 as key miR-10b-5p targets (false discovery rate p<0.05), validated by western blot and immunostaining. miR-10b- and siRNA-GCLM-transfected LECs 3 h after H2O2 treatment showed a significant reduction in glutathione/glutathione disulfide (2GSH/GSSG) ratio and overall GSH levels. Further, miR-10b-5p-transfected HCECs produced higher ROS levels, peaking at 12.67 ± 0.22

Chlamydia pneumoniae (Cp), an obligate intracellular bacterium, has been implicated in Alzheimer's disease (AD), yet its role in retinal pathology remains unexplored. We analyzed postmortem tissues from 95 human donors and found 2.9-4.1-fold increases in Cp inclusions in AD retinas and brains, with no significant elevation in mild cognitive impairment (MCI). Proteomics revealed dysregulation of retinal and brain bacterial infection-related proteins and NLRP3 inflammasome pathways. NLRP3 expression was markedly elevated in MCI and AD retinas, and its activation was evident by increased N-terminal gasdermin D (NGSDMD) and mature interleukin-1β. Retinal Cp strongly correlated with Aβ42 and NLRP3 inflammasome components, which tightly linked to cleaved caspase-3-apoptotic and NGSDMD-pyroptotic cell death. Although retinal microgliosis was elevated in AD, Cp-associated microglia were reduced by 62%, suggesting impaired Cp phagocytosis. Higher retinal Cp burden correlated with APOEε4, Braak stage, and cognitive deficit. Machine learning identified retinal Cp or NLRP3 combined with Aβ42 as strong predictors of AD diagnosis, staging, and cognitive impairment. Our findings suggest that Cp infection contributes to AD dementia but not initiating pathology, whereas early NLRP3 activation may promote disease development, warranting studies on Cp's role in AD pathogenesis and early antibiotic or inflammasome-targeted therapies.

Primary central nervous system lymphoma (PCNSL) is a lethal cancer with poor survival, especially in its recurrent form. This is mainly due to low penetrance of therapeutic agents across the blood brain barrier (BBB). We created a novel nano immunodrug (nanodrug) that can cross the BBB and deliver anti-cancer agents directly to the tumor. The RNA therapeutics based on N-(2-hydroxypropyl)methacrylamide copolymer nanoplatform that was designed to block lymphoma’s cell c-Myc protein synthesis and to ensure brain tumor targeting and BBB crossing. Inhibiting of c-Myc protein synthesis played a dual role as anti-tumor proliferative factor and immune stimulator. Angiopep-2 peptide is conjugated to the nano platform to provide BBB crossing and brain lymphoma cell targeting via LRP-1 receptor. The nanodrug also contains H6 (6 histidines for endosome escape) to release into lymphoma cell cytoplasm. We tested the nanodrug in a A20 intracranial brain lymphoma mouse model alone, and in combination with anti-PD-1 antibody. Treatment with nanodrug resulted in a significant survival advantage compared to control. Survival was significantly enhanced when the nanodrug was co-injected with anti-PD-1. Spectral flow cytometry and RNA-seq analysis of treated tumors showed robust activation of tumor-infiltrating T lymphocytes with enhanced interferon γ signaling and polarization to M1-type macrophages. Artificial Intelligence-assisted analysis of gene expression data from RNA-seq revealed novel immune pathways, molecular targets, and suggested effective multifunctional drugs. Overall, we created a novel nano therapeutic drug delivery system that inhibits tumor c-Myc protein to treat PCNSL. When used in conjunction with anti-PD-1 checkpoint inhibitor, the treatment results in enhanced survival of tumor bearing animals by activating both adaptive and immune responses. NIH grants: R01 CA246716, R01 CA206220, R01 CA209921, R01 CA284247

This study investigates various pathological tau isoforms in the retina of individuals with early and advanced Alzheimer’s disease (AD), exploring their connection with disease status. Retinal cross-sections from predefined superior-temporal and inferior-temporal subregions and corresponding brains from neuropathologically confirmed AD patients with a clinical diagnosis of either mild cognitive impairment (MCI) or dementia (n = 45) were compared with retinas from age- and sex-matched individuals with normal cognition (n = 30) and non-AD dementia (n = 4). Retinal tau isoforms, including tau tangles, paired helical filament of tau (PHF-tau), oligomeric-tau (Oligo-tau), hyperphosphorylated-tau (p-tau), and citrullinated-tau (Cit-tau), were stereologically analyzed by immunohistochemistry and Nanostring GeoMx digital spatial profiling, and correlated with clinical and neuropathological outcomes. Our data indicated significant increases in various AD-related pretangle tau isoforms, especially p-tau (AT8, 2.9-fold, pS396-tau, 2.6-fold), Cit-tau at arginine residue 209 (CitR209-tau; 4.1-fold), and Oligo-tau (T22+, 9.2-fold), as well as pretangle and mature tau tangle forms like MC-1-positive (1.8-fold) and PHF-tau (2.3-fold), in AD compared to control retinas. MCI retinas also exhibited substantial increases in Oligo-tau (5.2-fold), CitR209-tau (3.5-fold), and pS396-tau (2.2-fold). Nanostring GeoMx analysis confirmed elevated retinal p-tau at epitopes: Ser214 (2.3-fold), Ser396 (2.6-fold), Ser404 (2.4-fold), and Thr231 (1.8-fold), particularly in MCI patients. Strong associations were found between retinal tau isoforms versus brain pathology and cognitive status: a) retinal Oligo-tau vs. Braak stage, neurofibrillary tangles (NFTs), and CDR cognitive scores (ρ = 0.63–0.71), b) retinal PHF-tau vs. neuropil threads (NTs) and ABC scores (ρ = 0.69–0.71), and c) retinal pS396-tau vs. NTs, NFTs, and ABC scores (ρ = 0.67–0.74). Notably, retinal Oligo-tau strongly correlated with retinal Aβ42 and arterial Aβ40 forms (r = 0.76–0.86). Overall, this study identifies and quantifies diverse retinal tau isoforms in MCI and AD patients, underscoring their link to brain pathology and cognition. These findings advocate for further exploration of retinal tauopathy biomarkers to facilitate AD detection and monitoring via noninvasive retinal imaging.

Importance:This study identifies and quantifies diverse pathological tau isoforms in the retina of both early and advanced-stage Alzheimer's disease (AD) and determines their relationship with disease status. Objective:A case-control study was conducted to investigate the accumulation of retinal neurofibrillary tangles (NFTs), paired helical filament (PHF)-tau, oligomeric tau (oligo-tau), hyperphosphorylated tau (p-tau), and citrullinated tau (Cit-tau) in relation to the respective brain pathology and cognitive dysfunction in mild cognitively impaired (MCI) and AD dementia patients versus normal cognition (NC) controls. Design setting and participants:Eyes and brains from donors diagnosed with AD, MCI (due to AD), and NC were collected (n=75 in total), along with clinical and neuropathological data. Brain and retinal cross-sections-in predefined superior-temporal and inferior-temporal (ST/IT) subregions-were subjected to histopathology analysis or Nanostring GeoMx digital spatial profiling. Main outcomes and measure:Retinal burden of NFTs (pretangles and mature tangles), PHF-tau, p-tau, oligo-tau, and Cit-tau was assessed in MCI and AD versus NC retinas. Pairwise correlations revealed associations between retinal and brain parameters and cognitive status. Results:Increased retinal NFTs (1.8-fold, p=0.0494), PHF-tau (2.3-fold, p<0.0001), oligo-tau (9.1-fold, p<0.0001), CitR 209 -tau (4.3-fold, p<0.0001), pSer202/Thr205-tau (AT8; 4.1-fold, p<0.0001), and pSer396-tau (2.8-fold, p=0.0015) were detected in AD patients. Retinas from MCI patients showed significant increases in NFTs (2.0-fold, p=0.0444), CitR 209 -tau (3.5-fold, p=0.0201), pSer396-tau (2.6-fold, p=0.0409), and, moreover, oligo-tau (5.8-fold, p=0.0045). Nanostring GeoMx quantification demonstrated upregulated retinal p-tau levels in MCI patients at phosphorylation sites of Ser214 (2.3-fold, p=0.0060), Ser396 (1.8-fold, p=0.0052), Ser404 (2.4-fold, p=0.0018), and Thr231 (3.3-fold, p=0.0028). Strong correlations were found between retinal tau forms to paired-brain pathology and cognitive status: a) retinal oligo-tau vs. Braak stage (r=0.60, P=0.0002), b) retinal PHF-tau vs. ABC average score (r=0.64, P=0.0043), c) retinal pSer396-tau vs. brain NFTs (r=0.68, P<0.0001), and d) retinal pSer202/Thr205-tau vs. MMSE scores (r= -0.77, P=0.0089). Conclusions and Relevance:This study reveals increases in immature and mature retinal tau isoforms in MCI and AD patients, highlighting their relationship with brain pathology and cognition. The data provide strong incentive to further explore retinal tauopathy markers that may be useful for early detection and monitoring of AD staging through noninvasive retinal imaging.