# Peripheral blood mononuclear cell number and paracrine function in responses to a 50‐km trail race: An exploratory study

## TL;DR

This study explores how a 50-km trail race affects blood cells that support blood vessel growth, finding that prolonged running temporarily boosts their function.

## Contribution

The study is the first to explore PBMC paracrine function and subtype changes during and after a 50-km ultramarathon.

## Key findings

- PBMC paracrine activity increased during the race, enhancing endothelial cell proliferation.
- CD31+ PBMCs increased after the race, while CD3+ and CD31+/CD3+ PBMCs decreased.
- Changes in PBMC subtypes suggest a protective role in response to prolonged exercise stress.

## Abstract

Peripheral blood mononuclear cells (PBMCs) represent a heterogeneous mix of cells with paracrine functions that may be altered following prolonged exercise. We determined the effect of ultramarathon running on PBMC paracrine function and PBMC subtype number. Recreational athletes participated in a 50 km ultramarathon. Blood was sampled from N = 7 at baseline, 10 km, 50 km, and 24 h post‐race. PBMCs were isolated and cultured, and conditioned media was used for a HUVEC‐based proliferation assay. CD31+, CD3+, and CD31+/CD3+ PBMCs were quantified at each time point. Proliferation increased from baseline to 50 km (p = 0.004) and was reduced from 50 km to 24 h post (p = 0.008). There was an increase in CD31+ PBMCs after 50 km (p = 0.014), returning to baseline at 24 h post‐race (p = 0.246). CD3+ PBMC and CD31+/CD3+ PBMC numbers were reduced after 50 km (p = 0.001 and p = 0.002, respectively), returning to baseline levels 24 h post‐race (p = 0.190 and p = 0.315, respectively). PBMC paracrine activity following a 50 km enhances endothelial cell proliferation. Alterations in PBMC subtypes after 50 km suggest a protective role of PBMCs in response to prolonged stresses of ultramarathon running.