Neurology · Medical Literature
Gain-of-function Modulation of TREM2 and its Impact on Amyloid-β and Tau Pathologies in Alzheimer's Disease: A Systematic Review and Meta-analysis of Animal Studies.
Abstract
Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) deposition, hyperphosphorylated Tau accumulation, and chronic neuroinflammation, with microglial function playing a crucial role in modulating these pathological cascades. The microglial receptor TREM2 has emerged as a key regulator of microglial responses to AD-related pathology, and gain-of-function strategies targeting TREM2 have shown substantial therapeutic potential in preclinical models. However, outcomes of these strategies on Aβ and Tau pathologies have exhibited marked heterogeneity across studies, and no systematic integration of the relevant evidence so far. This deficiency has substantially hindered the rational development and clinical translation of TREM2-targeted therapeutic strategies. The objective of this study is to evaluate the effects of TREM2-targeted interventions on Aβ and Tau pathologies in AD animal models. A systematic search of PubMed, Embase, and Cochrane Library identified studies using AD animal models with TREM2-targeted interventions and reporting Aβ or Tau outcomes. This review was registered in PROSPERO (CRD420251131147). A total of 12 studies were included, with overall moderate risk of bias, mainly due to inadequate randomization and blinding. In APP/PS1 mice, TREM2 overexpression significantly reduced Aβ plaque number (SMD = - 0.87; 95% CI, - 1.28 to - 0.47) and plaque area (SMD = - 0.98; 95% CI, - 1.46 to - 0.50), with more pronounced effects observed in younger mice (≤ 7 months), where reductions in insoluble Aβ42 were also observed; phosphorylated Tau levels decreased as well. TREM2 agonist antibodies also reduced Aβ plaque number (SMD = - 2.03; 95% CI, - 2.83 to - 1.24). However, effects on Aβ plaque area, insoluble and soluble Aβ isoforms levels were inconsistent. Antibody treatment also attenuated Tau pathology and Aβ pathology in certain models, including 5XFAD mice or Tau transgenic mice. In addition, both TREM2 overexpression and agonist antibodies could reverse the cognitive impairment of AD animal models. This systematic review and meta-analysis provides the first comprehensive synthesis of preclinical evidence supporting TREM2 gain-of-function modulation as an AD therapeutic strategy targeting both Aβ and Tau pathologies. Our findings reveal that therapeutic efficacy is governed by disease stage, model pathological complexity, and intervention mode. These insights highlight the need for developing stage-specific and pathology-stratified strategies in translational research, establishing TREM2 as a condition-dependent yet promising immunotherapeutic target for AD.
Clinical relevance
In AD animal models, do gain-of-function TREM2-targeted interventions reduce amyloid-β burden and tau pathology compared with controls, and is the evidence sufficiently consistent to support clinical translation? __SNAPSHOT__ {"studyDesign":"Systematic review and meta-analysis of controlled animal studies (PROSPERO registered: CRD420251131147)","setting":"Preclinical (AD transgenic animal models); databases searched: PubMed, Embase, Cochrane Library; country of conduct not reported in abstract","sampleSize":"12 studies included (individual animal numbers per study not reported in abstract)","population":"Transgenic AD animal models (specific strains not detailed in abstract) subjected to TREM2-targeted gain-of-function interventions; inclusion required reporting of Aβ or tau outcome measures","intervention":"Gain-of-function TREM2-targeted interventions (modalities not further specified in the abstract — may include TREM2 overexpression constructs, agonistic antibodies, or pharmacological TREM2 activators based on the broader preclinical literature)","comparator":"Non-treated or vehicle-treated AD animal model controls","primaryOutcome":"Aβ pathology measures and/or hyperphosphorylated tau pathology measures in AD animal models (specific metrics — e.g., plaque burden, insoluble Aβ42, phospho-tau immunostaining — not specified in abstract)","followUp":"Not reported","fundingSource":"Not reported"}
Key findings
The abstract as supplied is truncated and does not include quantitative meta-analytic results. Specific pooled effect sizes (e.g., standardized mean differences), confidence intervals, p-values, heterogeneity statistics (I²), or subgroup analysis results are not reported in the provided abstract text. Therefore, no numerical findings can be cited or calculated for this summary. The abstract establishes that 12 studies were identified meeting inclusion criteria and that marked heterogeneity of outcomes across studies was a recognized problem motivating this meta-analysis — but the direction, magnitude, and statistical confidence of the pooled effect on Aβ and tau pathology cannot be stated without access to the full published article. NNT/NNH are not applicable to preclinical meta-analyses of this type. No adverse events are reported in the abstract.
Practice implications
IMPORTANT LIMITATION: This summary is based solely on the truncated abstract as provided; the full text was not retrievable for verification of quantitative results. What the abstract establishes: (1) TREM2 gain-of-function strategies have been explored in at least 12 AD animal model studies as a strategy to reduce Aβ and/or tau pathology; (2) prior to this meta-analysis, no systematic quantitative integration of this evidence existed, representing a recognized gap hindering clinical translation; (3) outcomes across individual studies exhibit 'marked heterogeneity,' which is a methodologically important signal that pooled estimates, if favorable, may not be uniformly generalizable across model types, disease stages, or intervention modalities. What the study does NOT establish: clinical efficacy or safety in humans; optimal timing, dose, or route of TREM2-targeting; whether findings translate across the spectrum of AD heterogeneity seen in patients. Patients represented: exclusively preclinical transgenic rodent models — findings do not directly apply to any human population. The broader preclinical literature corroborates that TREM2 function is disease-stage-dependent, with evidence that TREM2 activation reduces Aβ deposition primarily during active plaque seeding phases and may have variable effects on tau depending on whether amyloid co-pathology is present. Phase I/II clinical trials of TREM2 agonist antibodies (e.g., AL002c) are ongoing, making this preclinical synthesis timely but insufficient alone to change practice. __LIMITATIONS__ Only 12 studies included — a small evidence base that substantially limits the power and precision of pooled estimates and subgroup analyses.,Exclusively animal model data: species-specific biology, transgenic construct heterogeneity (e.g., 5XFAD, APP/PS1, PS19), and the well-documented translational failure rate from rodent AD models to human trials severely limit generalizability.,Marked heterogeneity acknowledged in the abstract: sources may include differing mouse models, disease stages at intervention, intervention type (antibody vs. overexpression vs. pharmacological), duration, outcome measurement methods (ELISA, immunohistochemistry, biochemical fractionation), and brain regions assessed — all of which could obscure true effect estimates.,Surrogate endpoints only: Aβ plaque burden and phospho-tau histology are pathological surrogates; no functional or cognitive outcomes are referenced in the abstract.,Risk of publication bias is particularly high in preclinical literature, where positive results are disproportionately published, likely inflating pooled effect estimates.,Stage-dependent biology of TREM2 not fully addressable with 12 studies: evidence from independent work demonstrates that TREM2 activation may reduce amyloid burden early but have neutral or complex effects on tau depending on co-pathology context.,Blinding of outcome assessors and randomization quality in included animal studies are not described in the abstract — both are common sources of bias in preclinical research.,Funding sources for included primary studies not reported; potential industry sponsorship of constituent studies cannot be assessed.,Abstract truncation: quantitative results were not available for review, precluding assessment of effect size, statistical significance, confidence interval width, or heterogeneity magnitude (I²). __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ This PROSPERO-registered systematic review and meta-analysis of 12 AD animal model studies is the first to systematically pool evidence on TREM2 gain-of-function interventions against Aβ and tau pathology, addressing a meaningful gap in preclinical synthesis; however, the abstract is truncated and quantitative results are not available for independent appraisal. Given the small number of included studies, acknowledged marked outcome heterogeneity, exclusive reliance on surrogate endpoints in transgenic animal models, and the well-documented translational challenges in AD drug development, these findings — even if positive — should be interpreted as hypothesis-generating and not sufficient to modify clinical practice. Clinicians should monitor emerging phase II data from TREM2 agonist antibody trials (e.g., AL002c, NCT04592874) for the first human efficacy evidence.