# Granulocyte Colony Stimulating Factor (G‐CSF) and Olfactory Function—A Clinical Pilot Study

## TL;DR

This pilot study explores whether G-CSF, a growth factor, can improve olfactory function in patients and donors, finding some suggestive but not statistically significant results.

## Contribution

The study provides preliminary clinical evidence for G-CSF's potential in olfactory regeneration in humans.

## Key findings

- Threshold scores slightly improved after G-CSF in myeloma patients and donors, but not significantly.
- No improvement in olfactory identification was observed after G-CSF administration.
- Results suggest G-CSF may have potential for olfactory regeneration, but further studies are needed.

## Abstract

Although the olfactory epithelium, including its neuronal cell line, has inherent regenerative potential, therapeutic options remain limited. Promising effects of granulocyte colony stimulating factor (G‐CSF) on olfactory regeneration have been observed in both animal and human studies. In this study, we assessed olfaction before and after G‐CSF administration in myeloma patients who underwent autologous stem cell transplantation and in allogeneic stem cell donors.

A total of 40 subjects were included in this study (10 myeloma patients, 10 allogeneic stem cell donors, 20 controls who did not receive any G‐CSF). Olfactory function was psychophysically assessed using the threshold and extended identification domain of the Sniffin' Sticks test.

After G‐CSF administration, threshold scores were slightly enhanced in both myeloma patients (8.9 ± 3.6 vs. 9.3 ± 3.3) and allogeneic stem cell donors (10.2 ± 3.5 vs. 11.8 ± 2.9). However, this effect was not statistically significant. For olfactory identification, no improvement was observed.

Even though being not statistically significant, the findings of this study align with previous evidence and underline the potential of G‐CSF on olfactory regeneration. However, additional studies, including carefully designed animal trials, are required to comprehensively evaluate this promising therapeutic option.

Level of Evidence: 2.

Promising effects of granulocyte colony stimulating factor (G‐CSF) on olfactory regeneration have been observed in both animal and human studies. Even though being not statistically significant, our study underlines the potential of G‐CSF on olfactory regeneration. However, carefully designed animal trials are required to comprehensively evaluate this promising therapeutic option.