Cleavage-Resistant TREM2 Restores Macrophage Efferocytosis

Macrophages help resolve inflammation by engulfing apoptotic cells before they accumulate and contribute to tissue injury. In their 2026 Cell Reports Medicine study, Dong and colleagues address a specific obstacle to this process: inflammatory conditions can promote cleavage of the debris-sensing receptor TREM2, weakening the signaling macrophages need for efficient efferocytosis. The authors engineered a cleavage-resistant receptor and used lipid nanoparticles (LNPs) to deliver its mRNA to macrophages in mouse models of metabolic-dysfunction-associated steatohepatitis (MASH) and atherosclerosis.

Study Background and Research Question

TREM2 recognizes ligands that include aminophospholipids exposed on apoptotic cells. Following ligand engagement, its association with the signaling adaptor DAP12 supports intracellular signaling that promotes phagocytic activity. When macrophages clear dying cells effectively, they limit the opportunity for those cells to undergo secondary necrosis and intensify local inflammation. Conversely, impaired clearance can leave apoptotic material in tissues and sustain inflammatory responses.

A barrier to harnessing TREM2 is that inflammatory signals can increase activity of the sheddase ADAM17. ADAM17 cleaves TREM2 in its extracellular stalk region, releasing soluble TREM2 and leaving a truncated receptor fragment. This reduces the availability of intact receptor for signaling. The study’s central question was therefore whether a redesigned receptor could retain TREM2’s ligand-sensing and signaling functions while resisting cleavage, and whether mRNA delivery could generate functional receptor-expressing macrophages in diseased tissues.

Key Innovation from the Reference Study

The team designed a synthetic cleavage-resistant TREM2 receptor, termed CRT. Rather than simply increasing expression of native TREM2, CRT combines the TREM2 ligand-binding domain with the DAP12 signaling adaptor through an engineered stalk and transmembrane segment. The design is intended to maintain a productive connection between ligand recognition and intracellular signaling while reducing vulnerability to ADAM17-mediated shedding.

This receptor engineering is paired with a delivery strategy. The researchers used phosphatidylserine-functionalized LNPs to deliver CRT-encoding mRNA to macrophages. In principle, the approach enables macrophages to produce the engineered receptor in situ, rather than requiring administration of pre-engineered cells. The study thus links two interventions: preserving receptor function at the cell surface and directing mRNA delivery toward the cell population responsible for efferocytosis.

The work is notable because it targets a failure point in a protective pathway rather than treating inflammation only as a downstream outcome. Its findings support the idea that sustained TREM2 signaling can be therapeutically useful when receptor shedding is part of the inflammatory environment. The evidence does not establish that this strategy will work across all inflammatory diseases, but it provides a rationale for testing cleavage-resistant receptor designs in settings where defective apoptotic-cell clearance contributes to pathology.

Methods and Experimental Design Insights

The study combines receptor design, mRNA delivery, and disease-model evaluation. The reported approach first creates CRT as a receptor construct, then packages its mRNA in phosphatidylserine-functionalized LNPs for macrophage-directed delivery. The researchers assessed whether the engineered receptor resisted ADAM17-associated cleavage and amplified TREM2 signaling, and then investigated the consequences for efferocytosis and inflammation in mouse models of MASH and atherosclerosis.

This design makes it possible to distinguish a receptor-level effect from a delivery-level effect. Receptor function concerns whether CRT maintains signaling in the presence of ADAM17; delivery concerns whether the LNP system can introduce the mRNA into the intended macrophage population. Disease-model outcomes then test whether those molecular and cellular effects translate into reduced apoptotic-cell burden and inflammation. The article’s reported findings support each link in this proposed chain, although the summary available here does not specify dosing, administration schedules, or assay-level protocols.

Protocol Parameters

• Receptor construct: The reported CRT integrates the TREM2 ligand-binding domain with DAP12 through an engineered stalk and transmembrane segment; this is a design feature of the study, not a general receptor-construction protocol.
• mRNA delivery: The study used phosphatidylserine-functionalized LNPs carrying CRT mRNA for macrophage-directed delivery. Exact formulation and administration parameters should be taken from the full article before attempting replication.
• Biological evaluation: The reported disease settings were mouse models of MASH and atherosclerosis, with outcomes including efferocytosis, apoptotic-cell accumulation, and inflammation. These model choices do not establish efficacy in other diseases or in humans.
• Suggested experimental planning: For follow-up work, consider separating delivery controls from receptor-function controls and measuring receptor expression alongside efferocytosis. These are workflow recommendations, not protocol parameters reported in the study summary.

Core Findings and Why They Matter

First, CRT was reported to resist ADAM17-mediated shedding and to amplify TREM2-associated intracellular signaling, including under conditions in which ADAM17 is present. This addresses a limitation of strategies that aim only to increase native TREM2 abundance: added receptor may remain susceptible to the same proteolytic pressure that disrupts signaling in inflamed tissue.

Second, the LNP-mRNA approach generated CRT-expressing macrophages in situ. The resulting CRT macrophages showed enhanced efferocytosis and reduced the accumulation of apoptotic cells in the reported models. This links the engineered receptor’s signaling behavior to a relevant cellular function rather than relying on receptor expression alone as evidence of benefit.

Third, the study reports reduced inflammation in mouse models of both MASH and atherosclerosis. These findings suggest that improving macrophage clearance capacity can be beneficial in more than one peripheral inflammatory setting. The results are consistent with a model in which more effective apoptotic-cell removal limits persistent tissue inflammation, though the study does not imply that efferocytosis is the only driver of disease improvement.

Together, the findings establish a proof of concept for combining a proteolysis-resistant receptor with targeted mRNA delivery. They also sharpen the therapeutic question: in diseases where TREM2 function is compromised, can the receptor be made more durable while remaining responsive to relevant ligands? The present work provides encouraging preclinical evidence, not a clinical treatment recommendation.

Comparison with Existing Internal Articles

The internal article on ROS-degradable LNPs for tumor-selective mRNA delivery also discusses nanoparticle-based mRNA delivery, but its delivery logic and disease context differ from Dong et al.’s study. The TREM2 work uses phosphatidylserine-functionalized LNPs to target macrophages in inflammatory disease models; the ROS-responsive system is framed around tumor-selective delivery. The shared platform concept is useful for comparing design questions in mRNA delivery, but the formulations and results should not be treated as interchangeable.

A separate resource on fluorescent RNA probe synthesis and in situ hybridization concerns a different research task: producing labeled RNA for detection workflows. Such probes can support molecular analysis, but fluorescent probe synthesis is not the therapeutic mRNA-delivery method used to generate CRT macrophages in the reference study.

Limitations and Transferability

The reported evidence comes from mouse models, so it does not establish safety, delivery efficiency, or therapeutic benefit in people. Translation will depend on whether macrophage targeting is sufficiently selective in relevant human tissues, whether receptor expression persists for an appropriate duration, and whether the engineered receptor remains functional across different inflammatory environments. These questions require direct testing rather than extrapolation from the reported models.

The disease scope also matters. MASH and atherosclerosis provide evidence in two settings associated with inflammation and apoptotic-cell accumulation, but they do not represent all inflammatory disorders. The balance between enhanced clearance and other macrophage functions may vary by tissue and disease stage. Further work should clarify how broadly CRT’s effects transfer, how the delivery system behaves in vivo, and which measures best capture durable improvement. The study supports continued investigation of cleavage-resistant TREM2; it does not yet establish an optimal clinical formulation or dosing regimen.

Research Support Resources

For separate analytical workflows involving fluorescent RNA probes, researchers can use the HyperScribe™ T7 High Yield Cy5 RNA Labeling Kit (SKU K1062). This Cy5 RNA labeling kit uses RNA polymerase T7 transcription and Cy5-UTP incorporation to produce labeled transcripts, with applications such as in situ hybridization probe preparation and Northern blot hybridization probe generation. It supports probe-based analysis and should not be confused with the CRT mRNA delivery system evaluated in the study.