A novel role for PGE2 signalling in promoting aged neuromuscular junctions reinnervation and counteracting sarcopenia.

Project Information

RestorAGING

Grant agreement ID: 101109133

DOI

10.3030/101109133

EC signature date 2 May 2023

Start date 1 April 2024

End date 31 March 2027

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 288 859,20

Coordinated by

UNIVERSITA DEGLI STUDI DI PADOVA
Italy

Periodic Reporting for period 1 - RestorAGING (A novel role for PGE2 signalling in promoting aged neuromuscular junctions reinnervation and counteracting sarcopenia.)

Reporting period: 2024-04-01 to 2026-03-31

Summary of the context and overall objectives of the project

As people live longer, we are facing a rapid rise in the number of older adults living with muscle weakness and loss of muscle mass, a condition known as sarcopenia. Sarcopenia increases the risk of falls and fractures, loss of independence, hospitalisation and long‑term care, with substantial costs for healthcare systems and families and a heavy impact on elderly people's quality of life. Current sarcopenia management relies on exercise and lifestyle counselling, two extremely important but often insufficient strategies to counteract the worsening of muscle weakness. There is therefore a strong need for new, targeted therapies that can help maintain muscle strength and function in later life.
Recent research suggests that sarcopenia is not only a “muscle-related disease”, but also has a major nerve component. With ageing, some motor nerves that control muscle fibres degenerate, and the specialised connections between nerves and muscles, called neuromuscular junctions, become damaged. In healthy individuals, many of these connections can be repaired, but in older people the restoration of neuromuscular junctions is often incomplete, leading to long‑term muscle weakness. Preserving these nerve–muscle connections, or restoring them when they fail, is emerging as a promising strategy to slow down sarcopenia progression.
My project focuses on a signalling pathway centred on prostaglandin E2 (PGE2) and the enzyme 15‑prostaglandin dehydrogenase (15‑PGDH), which degrades PGE2. Previous work from my host laboratory showed that 15‑PGDH levels increase with age, lowering pro-regenerative PGE2 signalling and contributing to muscle wasting. Inhibiting 15‑PGDH with a small molecule can restore PGE2 to youthful levels and improve muscle strength in aged mice. Building on these findings, my fellowship investigates whether the 15‑PGDH/PGE2 pathway is a key driver of nerve–muscle disconnection in ageing, and whether its modulation could be developed into a treatment for sarcopenia and related neuromuscular conditions.
In my project, I aim to show whether muscle denervation (loss of nerve input) in mice triggers an increase in 15‑PGDH in muscle and to test whether its inhibition protects motor neurons and neuromuscular junctions in injured and aged mice, representing a viable therapeutic strategy. I further aim to translate these findings to humans by assessing whether an imbalance in the 15‑PGDH/PGE2 pathway is also present in sarcopenic patients. To achieve this, I will obtain in-vivo data and muscle biopsies from young, healthy aged and sarcopenic individuals. I will generate multi-omics data (single nuclei RNA-sequencing and spatial proteomics) to molecularly characterize young, aged and sarcopenic muscles and link this molecular signature, including 15-PGDH/PGE2 signalling axis, to their in-vivo morpho-functional features.
By linking basic mechanisms in mice to human data, and by generating large, openly shareable datasets, the project is expected to contribute to the development of new therapeutic strategies for sarcopenia. If successful, this work could support future clinical trials of 15 PGDH inhibitors or related compounds, help identify individuals at higher risk of rapid muscle decline, and ultimately contribute to healthier ageing, reduced disability and lower healthcare costs in ageing societies.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the first two years of the fellowship (outgoing phase), I have focused on understanding how the 15 PGDH/PGE2 pathway contributes to nerve–muscle disconnection and weakness in aged mice, and on generating the core datasets needed to translate these insights to humans.
I first established that loss of nerve input (denervation) is a trigger for the increase in 15 PGDH seen in mice muscles. By cutting the sciatic nerve in one leg of young mice and comparing the muscles to the intact contralateral leg, I showed that denervation leads to a strong and sustained rise in 15 PGDH expression and activity in skeletal muscle fibres. Using single nucleus RNA sequencing, I identified a distinct population of “denervated” myonuclei with high 15 PGDH and a stress response gene program. Through advanced imaging techniques, I confirmed local accumulation of 15 PGDH protein in denervated fibres. These findings provide mechanistic support for the idea that denervation itself drives the harmful increase in 15 PGDH during ageing.
I then tested whether inhibiting 15 PGDH could help restore neuromuscular connectivity and strength. I crushed the sciatic nerve of young mice, and allowed the nerve to regrow. During the regeneration phase, I treated animals with a specific 15 PGDH inhibitor or a vehicle (placebo) solution. I found that treated mice regained muscle strength more quickly than controls, via a better regeneration of motor axons and neuromuscular junctions. These results indicated that boosting PGE2 signalling can accelerate functional recovery after nerve injury. In aged mice, I applied the same treatment for one month and observed fewer denervated and structurally abnormal neuromuscular junctions, increased muscle mass and force and signs of improved motor neuron survival and pro survival signalling in the spinal cord. Together, these results show that pharmacological inhibition of 15 PGDH can partially reverse age related neuromuscular defects and increase strength in old animals.
In parallel, I have completed the experimental generation of the human datasets planned in the project. In vivo measurements of muscle morphology, electrophysiology and function were collected from young, aged and sarcopenic individuals. At the outgoing host, I processed their muscle biopsies to perform large scale single nucleus RNA sequencing and spatial proteomics imaging. I complemented the generation of these datasets with western blot and histological analyses, including measurements of 15 PGDH protein. I have also developed and tested the computational pipelines needed to process, integrate and explore these multi omics datasets, setting the stage to generate a macro to micro atlas of skeletal muscle ageing and sarcopenia and evaluate 15 PGDH as a biomarker and potential therapeutic target.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

My project has already generated several results that go beyond the existing state of the art in how we understand and potentially treat age related muscle weakness and sarcopenia.
I have shown that denervation is not only associated with ageing but is a direct driver of the increase in 15 PGDH. Using a combination of nerve injury models, high resolution imaging and single nucleus RNA sequencing, I provided mechanistic insight into how denervation and muscle wasting are linked at the molecular level. This clarifies a missing step in previous work, which had shown that 15 PGDH accumulates with age but had not identified what drives this change.
My work also demonstrates that pharmacological inhibition of 15 PGDH can restore neuromuscular connectivity and function in vivo both in young mice after nerve injury, and in old mice. This is one of the first demonstrations that a systemic intervention can simultaneously target both the muscle and the motor neuron sides of the neuromuscular system to counteract age related decline, thereby opening a new therapeutic avenue for sarcopenia and other denervation related conditions.
On the methodological side, the project is generating a very large and rich set of multi omics and imaging data from human skeletal muscle, which will form the basis for a publicly accessible “atlas” of muscle ageing and sarcopenia. This resource will provide the research community with cell type resolved and spatial information that can be re used to explore many questions beyond the original scope of the project, thereby increasing the long term scientific value of the data.
For these advances to be fully taken up and translated, several needs can be identified. Further preclinical research is required to refine dosing, timing and safety windows for 15 PGDH inhibition in different models of neuromuscular disease and ageing, and to understand potential off target effects or long term consequences. Larger, well designed clinical trials will be needed to evaluate efficacy and safety in humans, which in turn will require sustained investment and engagement with regulatory authorities. On the data side, continued support for open repositories, analysis tools and standardisation will be important to ensure that the human atlas and associated code can be widely used, combined with other datasets and integrated into future biomarker or drug development pipelines.