Evaluation of radiation-induced hair follicle apoptosis in mice and the preventive effects of fibroblast growth factor-1

Hair Growth Regulation by Fibroblast Growth Factor 12 (FGF12)

The fibroblast growth factor (FGF) family has various biological functions, including cell growth, tissue regeneration, embryonic development, metabolism, and angiogenesis. In the case of hair growth, several members of the FGF family, such as FGF1 and FGF2, are involved in hair growth, while FGF5 has the opposite effect. In this study, the regulation of the hair growth cycle by FGF12 was investigated. To observe its effect, the expression of FGF12 was downregulated in mice and outer root sheath (ORS) by siRNA transfection, while FGF12 overexpression was carried out using FGF12 adenovirus. For the results, FGF12 was primarily expressed in ORS cells with a high expression during the anagen phase of hair follicles. Knockdown of FGF12 delayed telogen-to-anagen transition in mice and decreased the hair length in vibrissae hair follicles. It also inhibited the proliferation and migration of ORS cells. On the contrary, FGF12 overexpression increased the migration of ORS cells. FGF12-overexpressed ORS cells induced the telogen-to-anagen transition in the animal model. In addition, FGF12 overexpression regulated the expression of PDGF-CC, MDK, and HB-EGF, and treatment of these factors exhibited hair growth promotion. Altogether, FGF12 promoted hair growth by inducing the anagen phase of hair follicles, suggesting the potential for hair loss therapy.

High-Sulfated Hyaluronic Acid Ameliorates Radiation-Induced Intestinal Damage Without Blood Anticoagulation

Purpose

Many growth factors, such as fibroblast growth factors (FGFs), are useful for the treatment or prevention of radiation damage after radiation therapy. Although heparin can be supplemented to increase the therapeutic effects of FGFs, it possesses strong anticoagulant effects, which limit its potential for clinical use. Therefore, chemically sulfated hyaluronic acid (HA) was developed as a safe alternative to heparin. This study examined the involvement of sulfated HA in radioprotective and anticoagulant effects.

Methods and Materials

FGF1 was administered intraperitoneally to BALB/c mice with sulfated HA 24 hours before or after total body irradiation with γ-rays. Several radioprotective effects were examined in the jejunum. The blood coagulation time in the presence of sulfated HA was measured using murine whole blood.

Results

FGF1 with high-sulfated HA (HA-HS) exhibited almost the same level of in vitro mitogenic activity as heparin, whereas FGF1 with HA or low-sulfated HA exhibited almost no mitogenic activity. Furthermore, HA-HS had high binding capability with FGF1. FGF1 with HA-HS significantly promoted crypt survival to the same level as heparin after total body irradiation and reduced radiation-induced apoptosis in crypt cells. Moreover, pretreatment of HA-HS without FGF1 also increased crypt survival and reduced apoptosis. Crypt survival with FGF1 in the presence of HA depended on the extent of sulfation of HA. Moreover, the blood anticoagulant effects of sulfated HA were weaker than those of heparin. As sulfated HA did not promote the reactivity of antithrombin III to thrombin, it did not increase anticoagulative effects to the same extent as heparin.

Conclusions

This study suggested that HA-HS promotes the radioprotective effects of FGF1 without anticoagulant effects. HA-HS has great potential for practical use to promote tissue regeneration after radiation damage.

Effects of Adipose-Derived Stem Cells and Platelet-Rich Plasma for Prevention of Alopecia and Other Skin Complications of Radiotherapy

BACKGROUND

Radiotherapy (RT) involves the use of ionizing radiation in treating malignancies and benign disorders. However, RT damages target and healthy surrounding tissues in a dose-dependent manner. This effectively reduces patient compliance and quality of life, thereby warranting the prevention of RT-induced adverse effects on skin. Adipose-derived stem cells (ASCs) are used to treat RT-induced damage and platelet-rich plasma (PRP) provides a scaffold that potentiates the effects of ASCs. Thus, the aim of this study was to determine the mechanism employed by ASCs and PRP in protecting against RT-induced adverse effects.

METHODS

We have established an immunodeficient mouse transplantation model using which human hair follicular units were implanted. When the follicular units were macroscopically and microscopically mature and anagenic, we administered localized RT. Subsequently, the mice were randomly divided into 4 groups based on the subcutaneous injection of the following to the irradiated transplantation site: saline, PRP, ASCs, and a combination of ASCs and PRP. Next, we used macroscopic and microscopic analyses to determine the protective effects of the injected solutions on skin and hair follicles.

RESULTS

Adipose-derived stem cells reduced RT-induced adverse effects, such as impaired wound healing, alopecia, skin atrophy, and fibrosis by suppressing inflammation, dystrophy, degeneration, connective tissue synthesis, and apoptosis and increasing cellular proliferation, differentiation, and signaling. Moreover, these effects were augmented by PRP.

CONCLUSIONS

Thus, co-administering ASCs with PRP in mice prevented RT-induced adverse effects and can be tested for use in clinical practice.

Rational Design of Nanomaterials for Various Radiation-Induced Diseases Prevention and Treatment

Radiation treatments often unfavorably damage neighboring healthy organs and cause a series of radiation sequelae, such as radiation-induced hematopoietic system diseases, radiation-induced gastrointestinal diseases, radiation-induced lung diseases, and radiation-induced skin diseases. Recently, emerging nanomaterials have exhibited good superiority for these radiation-induced disease treatments. Given this background, the rational design principle of nanomaterials, which helps to optimize the therapeutic efficiency, has been an increasing need. Consequently, it is of great significance to perform a systematic summarization of the advances in this field, which can trigger the development of new high-performance nanoradioprotectors with drug efficiency maximization. Herein, this review highlights the advances and perspectives in the rational design of nanomaterials for preventing and treating various common radiation-induced diseases. Furthermore, the sources, clinical symptoms, and pathogenesis/injury mechanisms of these radiation-induced diseases will also be introduced. Furthermore, current challenges and directions for future efforts in this field are also discussed.

Extracellular vesicles released from irradiated neonatal mouse cheek tissue increased cell survival after radiation

Alopecia is one of the common symptoms after high-dose radiation exposure. In our experiments, neonatal mice that received 7 Gy X-ray exhibited defects in overall hair growth, except for their cheeks. This phenomenon might suggest that some substances were secreted and prevented hair follicle loss in the infant tissues around their cheeks after radiation damage. In this study, we focused on exosome-like vesicles (ELV) secreted from cheek skin tissues and back skin tissues, as control, and examined their radiation protective effects on mouse fibroblast cell lines. We observed that ELV from irradiated cheek skin showed protective effects from radiation. Our results suggest that ELV from radiation-exposed cheek skin tissue is one of the secreted factors that prevent hair follicle loss after high-dose radiation.

Altered FGF expression profile in human scalp-derived fibroblasts upon WNT activation: implication of their role to provide folliculogenetic microenvironment

Background

Hair follicle (HF) formation and growth are sustained by epithelial-mesenchymal interaction via growth factors and cytokines. Pivotal roles of FGFs on HF regeneration and neogenesis have been reported mainly in rodent models. FGF expression is regulated by upstream pathways, represented by canonical WNT signaling; however, how FGFs influence on human folliculogenesis remains elusive. The aim of this study is to assess if human scalp-derived fibroblasts (sFBs) are able to modulate their FGF expression profile in response to WNT activation and to evaluate the influence of WNT-activated or suppressed FGFs on folliculogenesis.

Methods

Dermal papilla cells (DPCs), dermal sheath cells (DSCs), and sFBs were isolated from the human scalp and cultured independently. The gene expression profile of FGFs in DPCs, DSCs, and sFBs and the influence of WNT activator, CHIR99021, on FGF expression pattern in sFBs were evaluated by reverse transcription polymerase chain reaction, which were confirmed at protein level by western blotting analysis. The changes in the expression of DPC or keratinocyte (KC) biomarkers under the presence of FGF7 or 9 were examined in both single and co-culture assay of DPCs and/or KCs. The influence of FGF 7 and FGF 9 on hair morphogenesis and growth was analyzed in vivo using mouse chamber assay.

Results

In single culture, sFBs were distinguished from DPCs and DSCs by relatively high expression of FGF5 and FGF18, potential inducers of hair cycle retardation or catagen phase. In WNT-activated state, sFBs downregulated FGF7 while upregulating FGF9, a positive regulator of HF morphogenesis, FGF16 and FGF20 belonging to the same FGF subfamily. In addition, CHIR99021, a WNT activator, dose-dependently modulated FGF7 and 9 expression to be folliculogenic. Altered expressions of FGF7 and FGF9 by CHIR99021 were confirmed at protein level. Supplementation of FGF9 to cultured DPCs resulted in upregulation of representative DP biomarkers and this tendency was sustained, when DPCs were co-cultured with KCs. In mouse chamber assay, FGF9 increased both the number and the diameter of newly formed HFs, while FGF7 decreased HF diameter.

Conclusion

The results implied that sFBs support HF formation by modulating regional FGF expression profile responding to WNT activation.

Accelerated senescence in skin in a murine model of radiation-induced multi-organ injury

Accidental high-dose radiation exposures can lead to multi-organ injuries, including radiation dermatitis. The types of cellular damage leading to radiation dermatitis are not completely understood. To identify the cellular mechanisms that underlie radiation-induced skin injury in vivo, we evaluated the time-course of cellular effects of radiation (14, 16 or 17 Gy X-rays; 0.5 Gy/min) in the skin of C57BL/6 mice. Irradiation of 14 Gy induced mild inflammation, observed histologically, but no visible hair loss or erythema. However, 16 or 17 Gy radiation induced dry desquamation, erythema and mild ulceration, detectable within 14 days post-irradiation. Histological evaluation revealed inflammation with mast cell infiltration within 14 days. Fibrosis occurred 80 days following 17 Gy irradiation, with collagen deposition, admixed with neutrophilic dermatitis, and necrotic debris. We found that in cultures of normal human keratinocytes, exposure to 17.9 Gy irradiation caused the upregulation of p21/waf1, a marker of senescence. Using western blot analysis of 17.9 Gy-irradiated mice skin samples, we also detected a marker of accelerated senescence (p21/waf1) 7 days post-irradiation, and a marker of cellular apoptosis (activated caspase-3) at 30 days, both preceding histological evidence of inflammatory infiltrates. Immunohistochemistry revealed reduced epithelial stem cells from hair follicles 14-30 days post-irradiation. Furthermore, p21/waf1 expression was increased in the region of the hair follicle stem cells at 14 days post 17 Gy irradiation. These data indicate that radiation induces accelerated cellular senescence in the region of the stem cell population of the skin.

FGF18 signaling in the hair cycle resting phase determines radioresistance of hair follicles by arresting hair cycling

Purpose

Telogen (resting phase) hair follicles (HFs) are more radioresistant than their anagen (growth phase) counterparts. Fibroblast growth factor (FGF) 18 is strongly expressed in telogen HFs to maintain the telogen phase, whereas several other FGFs exert radioprotective effects; however, the role of FGF18 in the radioresistance of HFs remains unknown. This study focused on clarifying the role of FGF18 in the radioresistance of telogen HFs and its potential as a radioprotector.

Methods and materials

BALB/c mice with telogen or plucking-induced anagen HFs were exposed to total body irradiation with γ-rays at 4 to 12 Gy after intraperitoneal treatment with FGF18 or an FGF receptor inhibitor. A time course analysis was performed histologically and hair growth was observed 14 or 15 days after depilation. Skin specimens were analyzed by DNA microarrays and Western blotting.

Results

Telogen irradiation at 6 Gy resulted in transient cell growth arrest, leading to successful hair growth, whereas anagen irradiation failed to promote hair growth. Telogen irradiation did not induce apoptosis in HFs or reduce HF stem cells, whereas anagen irradiation induced apoptosis and reduced stem cell numbers. The Inhibition of FGF receptor signaling during the telogen phase promoted HF cell proliferation; however, hair failed to grow after irradiation. In contrast, recombinant FGF18 induced transient cell growth arrest after anagen irradiation with enhanced DNA repair, leading to the inhibition of apoptosis, maintenance of HF stem cells, and successful hair growth. Moreover, FGF18 reduced the expression levels of genes promoting G2/M transition as well as the protein expression levels of cyclin B1 and cdc2 in skin, and induced G2/M arrest in the keratinocyte cell line HaCaT.

Conclusions

These results suggest that FGF18 signaling mediates radioresistance in telogen HFs by arresting the cell cycle, and that FGF18 has potential as a radioprotector for radiation-induced alopecia.

Epidermis-dermis junction as a novel location for bone marrow-derived cells to reside in response to ionizing radiation

Bone marrow-derived cells (BMDCs) can migrate into the various organs in the mice irradiated by ionizing radiation (IR). However, it may not be the case in the skin. While IR is used for bone marrow (BM) transplantation, studying with the epidermal sheets demonstrated that the BMDC recruitment is extraordinarily rare in epidermis in the mouse. Herein, using the chimera mice with BM from green fluorescent protein (GFP) transgenic mice, we simply examined if BMDCs migrate into any layers in the total skin, as opposed to the epidermal sheets, in response to IR. Interestingly, we identified the presence of GFP-positive (GFP(+)) cells in the epidermis-dermis junction in the total skin sections although the epidermal cell sheets failed to have any GFP cells. To examine a possibility that the cells in the junction could be mechanically dissociated during separating epidermal sheets, we then salvaged such dissociated cells and examined its characteristics. Surprisingly, some GFP(+) cells were found in the salvaged cells, indicating that these cells could be derived from BM. In addition, such BMDCs were also associated with inflammation in the junction. In conclusion, BMDCs can migrate to and reside in the epidermis-dermis junction after IR.

A kinome-targeted RNAi-based screen links FGF signaling to H2AX phosphorylation in response to radiation

A general radioprotective effect by fibroblast growth factor (FGF) has been extensively described since the early 1990s; however, the molecular mechanisms involved remain largely unknown. Radiation-induced DNA double-strand breaks (DSBs) lead to a complex set of responses in eukaryotic cells. One of the earliest consequences is phosphorylation of histone H2AX to form nuclear foci of the phosphorylated form of H2AX (γH2AX) in the chromatin adjacent to sites of DSBs and to initiate the recruitment of DNA-repair molecules. Upon a DSB event, a rapid signaling network is activated to coordinate DNA repair with the induction of cell-cycle checkpoints. To date, three kinases (ATM, ATR, and DNA-PK) have been shown to phosphorylate histone H2AX in response to irradiation. Here, we report a kinome-targeted small interfering RNA (siRNA) screen to characterize human kinases involved in H2AX phosphorylation. By analyzing γH2AX foci at a single-nucleus level, we identified 46 kinases involved either directly or indirectly in H2AX phosphorylation in response to irradiation in human keratinocytes. Furthermore, we demonstrate that in response to irradiation, the FGFR4 signaling cascade promotes JNK1 activation and direct H2AX phosphorylation leading, in turn, to more efficient DNA repair. This can explain, at least partially, the radioprotective effect of FGF.

Cellular internalization of fibroblast growth factor-12 exerts radioprotective effects on intestinal radiation damage independently of FGFR signaling

PURPOSE

Several fibroblast growth factors (FGFs) were shown to inhibit radiation-induced tissue damage through FGF receptor (FGFR) signaling; however, this signaling was also found to be involved in the pathogenesis of several malignant tumors. In contrast, FGF12 cannot activate any FGFRs. Instead, FGF12 can be internalized readily into cells using 2 cell-penetrating peptide domains (CPP-M, CPP-C). Therefore, this study focused on clarifying the role of FGF12 internalization in protection against radiation-induced intestinal injury.

METHODS AND MATERIALS

Each FGF or peptide was administered intraperitoneally to BALB/c mice in the absence of heparin 24 hours before or after total body irradiation with γ rays at 9 to 12 Gy. Several radioprotective effects were examined in the jejunum.

RESULTS

Administration of FGF12 after radiation exposure was as effective as pretreatment in significantly promoting intestinal regeneration, proliferation of crypt cells, and epithelial differentiation. Two domains, comprising amino acid residues 80 to 109 and 140 to 169 of FGF12B, were identified as being responsible for the radioprotective activity, so that deletion of both domains from FGF12B resulted in a reduction in activity. Interestingly, these regions included the CPP-M and CPP-C domains, respectively; however, CPP-C by itself did not show an antiapoptotic effect. In addition, FGF1, prototypic FGF, possesses a domain corresponding to CPP-M, whereas it lacks CPP-C, so the fusion of FGF1 with CPP-C (FGF1/CPP-C) enhanced cellular internalization and increased radioprotective activity. However, FGF1/CPP-C reduced in vitro mitogenic activity through FGFRs compared with FGF1, implying that FGFR signaling might not be essential for promoting the radioprotective effect of FGF1/CPP-C. In addition, internalized FGF12 suppressed the activation of p38α after irradiation, resulting in reduced radiation-induced apoptosis.

CONCLUSIONS

These findings indicate that FGF12 can protect the intestine against radiation-induced injury through its internalization, independently of FGFRs, suggesting that cellular uptake of FGF12 is an alternative signaling pathway useful for cancer radiation therapy.

Damage of hair follicle stem cells and alteration of keratin expression in external radiation-induced acute alopecia

Alopecia is known as a symptom of acute radiation, yet little is known concerning the mechanism of this phenomenon and the alteration of hair protein profiles. To examine this, 6-week-old male C57/BL6 mice were exposed to 6 Gy of X-ray irradiation, which caused acute alopecia. Their hair and skin were collected, and hair proteins were analyzed with liquid chromatography/electrospray-ionization mass spectrometry and immunohistochemistry. No change was observed in the composition of major hair keratins, such as Krt81, Krt83 and Krt86. However, cytokeratin Krt15 and CD34, which are known as hair follicle stem cell markers, were decreased in alopecic mice. Cytokeratin Krt5, which is known as a marker for basal and undifferentiated keratinocytes, was increased in the epidermis of alopecic mice. These findings suggest that radiation damages hair stem cells and the differentiation of keratinocytes in the epidermis. For the evaluation of radiation exposure, chromosomal aberration is considered to be the gold standard, yet our results suggest that Krt5 may be a novel biological marker for acute radiation symptoms.

Effects of topical application of EGCG on testosterone-induced hair loss in a mouse model

We investigated the effect of topical epigallocatechin-3-gallate (EGCG) on testosterone (T)-induced hair loss in mice. Marked hair loss was observed at the T-injected site, and topical EGCG significantly reduced the hair loss (P < 0.05). TUNEL staining showed apoptosis of follicular epithelial cells in the T-injected groups where topical EGCG was found to significantly diminish T-induced apoptosis (P < 0.05). Topical EGCG down-regulated the T-induced expression of androgen receptor but did not down-regulate 17β-hydroxysteroid dehydrogenase (HSD) and three β-HSD expression. Analysis using liquid chromatography tandem mass spectrometry (LC-MS/MS) on serum and tissue samples revealed no significant difference in T and dihydrotestosterone concentrations between the T-injected and T + EGCG groups. Thus, we found that T injection in a mouse model induces hair loss by apoptosis of the hair follicles rather than through the androgen metabolic pathway and also saw that T-induced apoptosis of hair follicles was reduced by topical EGCG.

Fibroblast growth factor-12 (FGF12) translocation into intestinal epithelial cells is dependent on a novel cell-penetrating peptide domain: involvement of internalization in the in vivo role of exogenous FGF12

The extracellular effect of fibroblast growth factor-12 (FGF12) remains unknown because FGF12 cannot activate any fibroblast growth factor receptors (FGFRs), and FGF12 is not currently thought to be released from cells. We reported previously that FGF12 plays an intracellular role in the inhibition of radiation-induced apoptosis. In this study, we demonstrated that recombinant FGF12 was able to be internalized into the cytoplasm of a rat intestinal epithelial cell line, IEC6, and this process was dependent on two novel cell-penetrating peptide (CPP) domains (CPP-M and CPP-C). In particular, CPP-C, composed of ∼10 amino acids, was identified as a specific domain of FGF12 and its subfamily in the C-terminal region (residues 140-149), although CPP-M was a common domain in the internal region of the FGF family. The absence of CPP-C from FGF12 or a mutation (E142L) in the CPP-C domain drastically reduced the internalization of FGF12 into cells. Therefore, CPP-C played an essential role in the internalization of FGF12. In addition, CPP-C was able to deliver other polypeptides into cells as a CPP because an FGF1/CPP-C chimeric protein was internalized into IEC6 cells more efficiently than wild-type FGF1. Finally, intraperitoneally added FGF12 inhibited radiation-induced apoptosis in the intestinal epithelial cells of BALB/c mice, and deletion of the CPP-C domain decreased the inhibition of the apoptosis. These findings suggest that exogenous FGF12 can play a role in tissues by translocating into cells through the plasma membrane, and the availability of this novel CPP provides a new tool for the intracellular delivery of bioactive molecules.

Fluorine-induced apoptosis and lipid peroxidation in human hair follicles in vitro

Fluoride is an essential trace element for human body; however, exposure to high amounts of fluoride has been documented to be correlated with an increasing risk of hair loss. To date, little is known about the mechanism(s) of how fluoride affects hair follicles. Here, we demonstrated that middle (1.0 mmol/L) and high (10.0 mmol/L) concentrations of sodium fluoride (NaF) significantly inhibited hair follicle elongation in vitro, but low NaF (0.1 mmol/L) showed little influence. Moreover, treatment with high levels of NaF resulted in a marked increase in terminal dUTP nick end labeling-positive cells in the outer layer of the outer root sheath, the dermal sheath, and the lower bulb matrix surrounding dermal papilla. Furthermore, the enhanced apoptosis was coupled with an increased oxidative stress manifested as higher malondialdehyde content. Additionally, the presence of selenium considerably antagonized the effects of middle NaF on hair follicles, with regard to either the suppression of hair growth or the induction of oxidative stress and apoptosis. In conclusion, exposure to high levels of fluoride compromises hair follicle growth and accelerate cell apoptosis in vitro. The toxicity of fluoride can be reduced by selenium, at least partially via the suppression of intracellular oxidative stress.

Post treatment with an FGF chimeric growth factor enhances epithelial cell proliferation to improve recovery from radiation-induced intestinal damage

PURPOSE

A fibroblast growth factor (FGF) 1-FGF2 chimera (FGFC) was created previously and showed greater structural stability than FGF1. This chimera was capable of stimulating epithelial cell proliferation much more strongly than FGF1 or FGF2 even without heparin. Therefore FGFC was expected to have greater biologic activity in vivo. This study evaluated and compared the protective activity of FGFC and FGF1 against radiation-induced intestinal injuries.

METHODS AND MATERIALS

We administered FGFC and FGF1 intraperitoneally to BALB/c mice 24 h before or after total-body irradiation (TBI). The numbers of surviving crypts were determined 3.5 days after TBI with gamma rays at doses ranging from 8 to 12 Gy.

RESULTS

The effect of FGFC was equal to or slightly superior to FGF1 with heparin. However, FGFC was significantly more effective in promoting crypt survival than FGF1 (p < 0.01) when 10 μg of each FGF was administered without heparin before irradiation. In addition, FGFC was significantly more effective at promoting crypt survival (p < 0.05) than FGF1 even when administered without heparin at 24 h after TBI at 10, 11, or 12 Gy. We found that FGFC post treatment significantly promoted 5-bromo-2'-deoxyuridine incorporation into crypts and increased crypt depth, resulting in more epithelial differentiation. However, the number of apoptotic cells in FGFC-treated mice decreased to almost the same level as that in FGF1-treated mice.

CONCLUSIONS

These findings suggest that FGFC strongly enhanced radioprotection with the induction of epithelial proliferation without exogenous heparin after irradiation and is useful in clinical applications for both the prevention and post treatment of radiation injuries.