Role of increased vascular permeability in chemotherapy‐induced alopecia: In vivo imaging of the hair follicular microenvironment in mice

Abstract

Chemotherapy‐induced alopecia is one of the most difficult adverse events of cancer treatment for patients. However, it is still unknown why anticancer drugs cause hair loss. We aimed to clarify the mechanism of chemotherapy‐induced alopecia in mice using an in vivo imaging technique with a two‐photon microscope, which enables observation of the deep reaction in the living body in real time. In this study, ICR mice were injected intraperitoneally with cyclophosphamide (120 µg/g). Changes in the hair bulb morphology, subcutaneous vessel permeability, and vessel density were evaluated by two‐photon microscopy and conventional methods. In order to determine whether there is a causal relationship between vascular permeability and hair loss, we combined cyclophosphamide (50 µg/g) with subcutaneous histamine. We found that the hair bulbs became smaller, blood vessels around the hair follicle decreased in diameter, and vascular permeability was confirmed by two‐photon microscopy and conventional examination at 24 h after cyclophosphamide injection. Apoptosis occurred in vascular endothelial cells around the hair follicle. Additionally, hair loss was exacerbated by temporarily enhancing vascular permeability with histamine. In conclusion, cyclophosphamide caused a decrease in vascular density and an increase in vascular permeability, therefore increased vascular permeability might be one of the causes of chemotherapy‐induced alopecia.

Efficacy of cooling therapy and α‐lipoic acid derivative against chemotherapy‐induced alopecia in an animal model

“…CYP has been reported to have a high sensitivity to vascular endothelial cells and to induce apoptosis of vascular endothelial cells 24 . Previously, we have also reported that the pathological condition of increased vascular permeability is potentially due to the induction of apoptosis in those vascular endothelial cells 15 . We demonstrated that the suppression of this pathological condition may promote hair recovery, and that the effectiveness of these treatments may be due to the regulation of this pathological condition.…”

“…While an adult mouse model was used in this study, it has been reported that by aligning the growth phase through hair removal, the growth phase shifts from mature anagen to catagen by the 15th day, and enters the mature anagen phase again after the 30th day 16,17 . In a previous study, we also reported that changes occurred in the perifollicular area 24 h after anticancer drug administration 15 . Therefore, in this study, the 10th day, 24 h after administration of CYP was evaluated as early phase, the 16th day as middle phase, and the 37th day as late phase.…”

“…This was due to CYPs being widely used in breast cancer treatment in practice and causing high rates of CIA. Moreover, CYP has been shown to induce follicular apoptosis and CIA in mice, including in our previous study 15,16 . Cyclophosphamide (030–12,953, FUJIFILM Wako Pure Chemical Corporation, Osaka, Japan) was used as the anticancer agent to induce CIA.…”

“…Therefore, we defined the period until the 15th day as the early phase, the period from the 16th day to the 29th day as the middle phase, and the period after the 30th day as the late phase. Alopecia was induced by intraperitoneal administration of 120 μg/g of CYP dissolved in PBS 15,16 …”

“…We excised approximately 2 × 3 cm of skin from the mice under general anesthesia, and the skin on the lateral side was set to enable observation using an upright two‐photon excitation fluorescence microscopy system (A1RMP, Nikon Corporation) from the inside by inverting it while still attached to the body. We injected 3.75 mg of TRITC‐conjugated 70‐kDa dextran (D‐1819, Life Technologies Corporation) and 1.25 mg of FITC‐conjugated 150‐kDa dextran (FD150S‐1G, Sigma‐Aldrich) that were dissolved in 50 μl PBS into the mice eyeball and conducted observations 15 . We randomly imaged and evaluated three locations from each mouse to reduce selection bias.…”