INTRODUCTION
Allergic rhinitis (AR) is a non-infectious inflammatory disease of the
nasal mucosa which is mainly mediated by IgE and driven by Th2 cells
after exposure to allergens. The main clinical symptoms are sneezing, a
runny nose, nasal itching, and nasal congestion1. It
has been reported that 10–40% of adults worldwide suffer from AR, and
in developing countries, the situation is even worse, as the number of
cases of AR rapidly increased in recent decades, especially in
China2. The main treatment methods for AR are allergen
avoidance, drug therapy, and specific immunotherapy3.
However, drug therapy can only manage symptoms and cannot reverse or
alleviate the immune imbalance. Although specific immunotherapy can
desensitize patients to allergens and prevent the development of
lesions, it has a long treatment cycle, which tends to result in poor
patient compliance and unproductive
treatments4.
Therefore, it is urgent to find new directions for effective treatment.
Mesenchymal stem cells (MSCs) have the potential for self-renewal and
multi-directional differentiation5 and have
immunomodulatory functions6. Previous studies have
shown that transplantation of MSCs via the tail vein into an AR mouse
model can improve symptoms7, 8. Xenogeneic MSCs have
also been proven to exert similar therapeutic effects in AR
mice9. In addition, MSCs can also reduce the
immunological indicators and adjust the Th1/Th2 reaction balance in AR
patients10. The application of MSCs has resulted in
definite curative effects. However, MSCs have several disadvantages,
including vascular obstruction caused by the large
cells11, unpredictable differentiation in the
host12, and reported concerns regarding the cancer
progression13, 14.
It has also been proven that exosomes secreted by MSCs (MSCs-Exo) have
the same efficacy as MSCs; more importantly, transplantation with its
associated risks can be avoided15. Exosomes are
homogenous vesicles with a diameter of 30–150 nm secreted by a variety
of cells16. The vesicles contain different types of
proteins, nucleotides, and other substances. Cells can swallow the
vesicles through endocytosis so that the active substances in the
vesicles can function inside the cells17. MSCs-Exo can
mimic the functions of MSCs and exert similar immunomodulatory
effects18. Moreover, exosomes do not have a nuclear
structure and cannot be amplified in the host, and thus they are safer
in clinical application19. However, the clinical use
of MSCs-Exo to treat AR has never been investigated. In this paper, we
show that AR mice treated with MSCs-Exo by intranasal administration
showed a significant improvement in behavior and histology via MAPK
signaling.