Autotransplantation of cryopreserved minor salivary glands: a new approach for management of radiation-induced xerostomia

Role of glial-cell-derived neurotrophic factor in salivary gland stem cell response to irradiation

BACKGROUND AND PURPOSE

Recently, stem cell therapy has been proposed to allow regeneration of radiation damaged salivary glands. It has been suggested that glial-cell-derived neurotrophic factor (GDNF) promotes survival of mice salivary gland stem cells (mSGSCs). The purpose of this study was to investigate the role of GDNF in the modulation of mSGSC response to irradiation and subsequent salivary gland regeneration.

METHODS

Salivary gland sphere derived cells of Gdnf hypermorphic (Gdnf^wt/hyper) and wild type mice (Gdnf^wt/wt) were irradiated (IR) with γ-rays at 0, 1, 2, 4 and 8Gy. mSGSC survival and stemness were assessed by calculating surviving fraction measured as post-IR sphere forming potential and population doublings. Flow cytometry was used to determine the CD24^hi/CD29^hi stem cell (SC) population. QPCR and immunofluorescence was used to detect GDNF expression.

RESULTS

The IR survival responses of mSGSCs were similar albeit resulted in larger spheres and an increased cell number in the Gdnf^wt/hyper compared to Gdnf^wt/wt group. Indeed, mSGSC of Gdnf^wt/hyper mice showed high sphere forming efficiency upon replating. Interestingly, GDNF expression co-localized with receptor tyrosine kinase (RET) and was upregulated after IR in vitro and in vivo, but normalized in vivo after mSGSC transplantation.

CONCLUSION

GDNF does not protect mSGSCs against irradiation but seems to promote mSGSCs proliferation through the GDNF-RET signaling pathway. Post-transplantation stimulation of GDNF/RET pathway may enhance the regenerative potential of mSGSCs.

Wetting the whistle: neurotropic factor improves salivary function

Xerostomia, or dry mouth, is a common side effect of head and neck radiotherapy, Sjögren syndrome, diabetes, old age, and numerous medications. In this issue of the JCI, Xiao and colleagues identified glial cell line-derived neurotrophic factor (GDNF) as a potential stimulus for salivary stem cell growth. Due to its ability to promote neuronal growth, differentiation, and survival, GDNF is currently being used in clinical trials as a treatment for Parkinson disease; therefore, the findings of Xiao and colleagues may initiate a potential treatment for the millions of patients who suffer from xerostomia each year.