Cytoprotective role of human dental pulp stem cell-conditioned medium in chemotherapy-induced alopecia

Background Chemotherapy-induced alopecia (CIA) is a distressing adverse effect of chemotherapy, with an estimated incidence of 65% and limited treatment options. Cyclophosphamide (CYP) is a common alopecia-inducing chemotherapy agent. Human dental pulp stem cells (DPSCs) secrete several paracrine factors that up-regulate hair growth. Conditioned medium (CM) collected from DPSCs (DPSC-CM) promotes hair growth; culturing mesenchymal stem cells under hypoxic conditions can enhance this effect. Methods The effect of DPSC-CM cultured under normoxic (N-) and hypoxic (H-) conditions against CYP-mediated cytotoxicity in keratinocytes was examined using cell viability assay, lactate dehydrogenase (LDH) cytotoxicity assay, and apoptosis detection. The damage-response pathway was determined in a well-established CIA mouse model by analyzing macroscopic effects, histology, and apoptosis. Reverse transcription-quantitative PCR and Caspase-3/7 activity assay were used to investigate the impact of DPSC-CM on the molecular damage-response pathways in CYP-treated mice. The effect of post-CIA DPSC-CM application on post-CIA hair regrowth was analyzed by macroscopic effects and microstructure observation of the hair surface. Furthermore, to investigate the safety of DPSC-CM as a viable treatment option, the effect of DPSC-CM on carcinoma cell lines was examined by cell viability assay and a subcutaneous tumor model. Results In the cell viability assay, DPSC-CM was observed to increase the number of keratinocytes over varying CYP concentrations. Furthermore, it reduced the LDH activity level and suppressed apoptosis in CYP-treated keratinocytes. DPSC-CM exhibited the cytoprotective role in vivo via the dystrophic anagen damage-response pathway. While both N-CM and H-CM downregulated the Caspase-3/7 activity level, H-CM downregulated Caspase-3 mRNA expression. The proportion of post-CIA H-CM-treated mice with > 90% normal hair was nearly twice that of vehicle- or N-CM-treated mice between days 50 and 59 post-depilation, suggesting that post-CIA H-CM application may accelerate hair regrowth and improve hair quality. Furthermore, DPSC-CM suppressed proliferation in vitro in certain carcinoma cell lines and did not promote the squamous cell carcinoma (SCC-VII) tumor growth rate in mice. Conclusions The potentiality of DPSC-CM and H-CM as a promising cytoprotective agent and hair regrowth stimulant, respectively, for CIA needs in-depth exploration.