Therapeutic role of human hepatocyte growth factor (HGF) in treating hair loss

Desmodesmus pannonicus Water Extract Inhibits Melanin Synthesis and Promotes Wound Healing

This study investigated the multifaceted benefits of Desmodesmus pannonicus water extract across various cell lines, including murine B16F1 melanoma cells, human keratinocyte HaCaT cells, and human follicle dermal papilla cells (HFDPCs), to assess its potential in skin health improvement. Initially, the antioxidant capacity of the extract was evaluated using the ABTS assay, revealing significant radical scavenging activity, indicating strong antioxidative properties. Subsequently, D. pannonicus extract showed notable inhibition of α-MSH-enhanced melanin production in B16F1 cells without cell toxicity by suppressing tyrosinase expression. Furthermore, the extract significantly promoted cell migration and enhanced wound healing in HaCaT cells, accompanied by an upregulation of VEGF and MMP mRNA levels, which are crucial for the wound healing process. In addition, we investigated the effect of D. pannonicus extract on hair growth-related genes in HFDPCs. Despite a slight reduction in VEGF mRNA levels, an increase in CTGF and HGF1 mRNA levels was observed, alongside a significant down-regulation of TGFβ1, highlighting the extract's potential to promote hair growth and exhibit antiandrogenic effects. Collectively, these findings demonstrated the therapeutic potential of D. pannonicus extract in treating hyperpigmentation, enhancing wound healing, and promoting hair growth, making it a promising candidate for future dermatological applications.

Profound Properties of Protein-Rich, Platelet-Rich Plasma Matrices as Novel, Multi-Purpose Biological Platforms in Tissue Repair, Regeneration, and Wound Healing

Autologous platelet-rich plasma (PRP) preparations are prepared at the point of care. Centrifugation cellular density separation sequesters a fresh unit of blood into three main fractions: a platelet-poor plasma (PPP) fraction, a stratum rich in platelets (platelet concentrate), and variable leukocyte bioformulation and erythrocyte fractions. The employment of autologous platelet concentrates facilitates the biological potential to accelerate and support numerous cellular activities that can lead to tissue repair, tissue regeneration, wound healing, and, ultimately, functional and structural repair. Normally, after PRP preparation, the PPP fraction is discarded. One of the less well-known but equally important features of PPP is that particular growth factors (GFs) are not abundantly present in PRP, as they reside outside of the platelet alpha granules. Precisely, insulin-like growth factor-1 (IGF-1) and hepatocyte growth factor (HGF) are mainly present in the PPP fraction. In addition to their roles as angiogenesis activators, these plasma-based GFs are also known to inhibit inflammation and fibrosis, and they promote keratinocyte migration and support tissue repair and wound healing. Additionally, PPP is known for the presence of exosomes and other macrovesicles, exerting cell-cell communication and cell signaling. Newly developed ultrafiltration technologies incorporate PPP processing methods by eliminating, in a fast and efficient manner, plasma water, cytokines, molecules, and plasma proteins with a molecular mass (weight) less than the pore size of the fibers. Consequently, a viable and viscous protein concentrate of functional total proteins, like fibrinogen, albumin, and alpha-2-macroglobulin is created. Consolidating a small volume of high platelet concentrate with a small volume of highly concentrated protein-rich PPP creates a protein-rich, platelet-rich plasma (PR-PRP) biological preparation. After the activation of proteins, mainly fibrinogen, the PR-PRP matrix retains and facilitates interactions between invading resident cells, like macrophages, fibroblast, and mesenchymal stem cells (MSCs), as well as the embedded concentrated PRP cells and molecules. The administered PR-PRP biologic will ultimately undergo fibrinolysis, leading to a sustained release of concentrated cells and molecules that have been retained in the PR-PRP matrix until the matrix is dissolved. We will discuss the unique biological and tissue reparative and regenerative properties of the PR-PRP matrix.

Can Plant Extracts Help Prevent Hair Loss or Promote Hair Growth? A Review Comparing Their Therapeutic Efficacies, Phytochemical Components, and Modulatory Targets

This narrative review aims to examine the therapeutic potential and mechanism of action of plant extracts in preventing and treating alopecia (baldness). We searched and selected research papers on plant extracts related to hair loss, hair growth, or hair regrowth, and comprehensively compared the therapeutic efficacies, phytochemical components, and modulatory targets of plant extracts. These studies showed that various plant extracts increased the survival and proliferation of dermal papilla cells in vitro, enhanced cell proliferation and hair growth in hair follicles ex vivo, and promoted hair growth or regrowth in animal models in vivo. The hair growth-promoting efficacy of several plant extracts was verified in clinical trials. Some phenolic compounds, terpenes and terpenoids, sulfur-containing compounds, and fatty acids were identified as active compounds contained in plant extracts. The pharmacological effects of plant extracts and their active compounds were associated with the promotion of cell survival, cell proliferation, or cell cycle progression, and the upregulation of several growth factors, such as IGF-1, VEGF, HGF, and KGF (FGF-7), leading to the induction and extension of the anagen phase in the hair cycle. Those effects were also associated with the alleviation of oxidative stress, inflammatory response, cellular senescence, or apoptosis, and the downregulation of male hormones and their receptors, preventing the entry into the telogen phase in the hair cycle. Several active plant extracts and phytochemicals stimulated the signaling pathways mediated by protein kinase B (PKB, also called AKT), extracellular signal-regulated kinases (ERK), Wingless and Int-1 (WNT), or sonic hedgehog (SHH), while suppressing other cell signaling pathways mediated by transforming growth factor (TGF)-β or bone morphogenetic protein (BMP). Thus, well-selected plant extracts and their active compounds can have beneficial effects on hair health. It is proposed that the discovery of phytochemicals targeting the aforementioned cellular events and cell signaling pathways will facilitate the development of new targeted therapies for alopecia.

Promotion of hair growth by a conditioned medium from human umbilical cord mesenchymal stem cells cultivated in a 3D scaffold of gelatin sponge

BACKGROUND

This study aims to investigate the effects of a conditioned medium (CM) from human umbilical cord mesenchymal stem cells (HuMSCs) cultivated in gelatin sponge (GS-HuMSCs-CM) on hair growth in a mouse model.

METHODS

CM was collected from the HuMSCs cultivated in a monolayer or in a gelatin sponge. Vascular endothelial growth factor (VEGF), insulin-like growth factor-1 (IGF-1), keratinocyte growth factor (KGF), and hepatocyte growth factor (HGF) levels in CMs were measured by enzyme-linked immunosorbent assays (ELISAs). A hair loss model by a C57 BL/6J mouse was prepared. The effects of GS-HuMSCs-CM and HuMSCs on hair regrowth in mice were investigated by intradermal injection in the depilated back skin with normal saline (NS) as the control. The time for hair regrowth and full covering in depilated areas was observed, and the hair growth was evaluated histologically and by grossly measuring hair length and diameter.

RESULTS

Compared with monolayer cultured cells, the three-dimensional (3D) culture of HuMSCs in gelatin sponge drastically increased VEGF, IGF-1, KGF, and HGF production. GS-HuMSCs-CM and HuMSCs injection both promoted hair regeneration in mice, while GS-HuMSCs-CM presented more enhanced effects in hair length, hair diameter, and growth rate. GS-HuMSCs-CM significantly promoted angiogenesis in injected skin areas, which might also contribute to faster hair regrowth.

CONCLUSION

GS-HuMSCs-CM exerted significant effects on inducing hair growth and promoted skin angiogenesis in C57BL/6J mice.

Imprinted Dlk1-Gtl2 cluster miRNAs are potential epigenetic regulators of lamb fur quality

BACKGROUND

Tan and Hu sheep are well-known local breeds in China, producing lamb fur with unique ornamental and practical values highly appreciated by consumers worldwide. Fur quality is optimal at one month of age and gradually declines with time. Despite active research on its genetic mechanism using transcriptomic and whole genome bisulfite sequencing analysis, the main effective gene locus has not been found, and its regulatory mechanism is still unclear, which limits the breeding and improvement of fur traits.

RESULTS

Scapular skin samples from newborn (1-month old) and adult (24-month old) Tan sheep were utilized for small ribonucleic acid (RNA) sequencing Principal Component Analysis (PCA) showed that the newborn and adult groups were completely separated. Differential expression analysis of micro-RNAs (miRNAs) identified 32 up-regulated miRNAs and 48 down-regulated miRNAs in the newborn groups. All up-regulated miRNAs were located in the imprinted. Dlk1-Gtl2 locus on chromosome 18, whereas all down-regulated miRNAs were distributed across the sheep chromosomes, without a clear pattern of positional consistency. Further, by systematically analyzing the target genes and signaling pathways of all 32 up-regulated miRNAs, we found that the PI3K-AKT signaling pathway has the potential to be targeted and regulated by most of the miRNAs in the Dlk1-Gtl2 region. In addition, we also re-analyzed miRNA sequencing data from public databases on Hu lambs (full sibling Hu lambs with high- and low-quality fur characteristics). Again, it was found that most of the up-regulated miRNAs in lambs with high-quality fur were also located in the Dlk1-Gtl2 region, whereas this patter was not present for down-regulated miRNAs.

CONCLUSION

Sequencing of miRNAs in conjunction with public databases was employed to identify miRNAs within the imprinted Dlk1-Gtl2 region on chromosome 18, suggesting their potential roles as epigenetic regulators of fur traits. Small RNAs located at the Dlk1-Gtl2 locus were identified as having the potential to systematically regulate the PI3K-AKT signaling pathway, thereby indicating the relevance of the Dlk1-Gtl2/PI3K-AKT axis in the context of fur traits. Selection of parental specific expressed imprinted genes in the process of conserving and exploiting lamb fur traits should be emphasized.

Cell Therapy for Androgenetic Alopecia: Elixir or Trick?

Androgenetic alopecia is the most common cause of hair loss aggravated by increased life pressure, tension, and anxiety. Although androgenetic alopecia (AGA) does not significantly effect physical health, it can have serious negative impact on the mental health and quality of life of the patient. Currently, the effect of medical treatment for AGA is not idealistic, stem cell-based regenerative medicine has shown potential for hair regrowth and follicle repair, but the long-term effect and mechanism of stem cell therapy is not quite explicit. In this review, we summarize the methods, efficacy, mechanism, and clinical progress of stem cell therapies for AGA by now, hope it will present a more comprehensive view in this topic.

Stem cell secretome as a mechanism for restoring hair loss due to stress, particularly alopecia areata: narrative review

Background

Living organisms are continuously exposed to multiple internal and external stimuli which may influence their emotional, psychological, and physical behaviors. Stress can modify brain structures, reduces functional memory and results in many diseases such as skin disorders like acne, psoriasis, telogen effluvium, and alopecia areata. In this review, we aim to discuss the effect of secretome on treating alopecia, especially alopecia areata. We will shed the light on the mechanism of action of the secretome in the recovery of hair loss and this by reviewing all reported in vitro and in vivo literature.

Main body

Hair loss has been widely known to be enhanced by stressful events. Alopecia areata is one of the skin disorders which can be highly induced by neurogenic stress especially if the patient has a predisposed genetic background. This condition is an autoimmune disease where stress in this case activates the immune response to attack the body itself leading to hair cycle destruction. The currently available treatments include medicines, laser therapy, phototherapy, and alternative medicine therapies with little or no satisfactory results. Regenerative medicine is a new era in medicine showing promising results in treating many medical conditions including Alopecia. The therapeutic effects of stem cells are due to their paracrine and trophic effects which are due to their secretions (secretome).

Conclusion

Stem cells should be more used as an alternative to conventional  therapies due to their positive outcomes. More clinical trials on humans should be done to maximize the dose needed and type of stem cells that must be used to treat alopecia areata.

Effect of Coffee Berry Extract on Anti-Aging for Skin and Hair—In Vitro Approach

The aging process encompasses gradual and continuous changes at the cellular level that slowly accumulate with age. The signs of aging include many physiological changes in both skin and hair such as fine lines, wrinkles, age spots, hair thinning and hair loss. The aim of the current study was to investigate the anti-aging potential of coffee berry extract (CBE) on human dermal fibroblast (HDF) and hair follicle dermal papilla (HFDP) cells. Coffee berry was extracted by 50% ethanol and determined for chemical constituents by HPLC technique. Cytotoxicity of the extract was examined on both cells by MTT assay. Then, HDF cells were used to evaluate antioxidant properties by using superoxide dismutase activity (SOD) and nitric oxide inhibition as well as anti-collagenase inhibition assays. The effectiveness of anti-hair loss properties was investigated in HFDP cells by considering cell proliferation, 5α-reductase inhibition (5AR), and growth factor expression. The results showed that caffeine and chlorogenic acid were identified as major constituents in CBE. CBE had lower toxicity and cell proliferation than caffeine and chlorogenic acid on both cells. CBE showed SOD and nitric oxide inhibition activities that were higher than those of caffeine but lower than those of chlorogenic acid. Interestingly, CBE had the highest significant anti-collagenase activity, and its 5AR inhibition activity was comparable to that of chlorogenic acid, which was higher than caffeine. CBE also stimulated hair-related gene expression, especially insulin-like growth factor 1 (IGF-1), keratinocyte growth factor (KGF) and vascular endothelial growth factor (VEGF). The results confirmed that CBE provided anti-aging activity on both skin and hair cells and could be beneficial for applications in cosmeceuticals.

Hair-growth promoting effect and anti-inflammatory mechanism of Ginkgo biloba polysaccharides

The aim of this study was to optimize the separation and purification technology of water-soluble Ginkgo biloba leaves polysaccharides (WGBP), analyze its composition characteristics, observe its hair-growth promoting effect in alopecia areata mice, clarify the polysaccharide fraction with bioactive activities, and explore its anti-inflammation mechanism. We isolated acidic polysaccharides (WGBP-A2) and purified a RG-I type polysaccharide (WGBP-A2b) with a molecular weight of 44 kDa. Results showed that WGBP-A2 could significantly increase the contents of VEGF and HGF in the skin tissue of alopecia areata mice, decrease the contents of Inflammatory factors in the serum. On a cellular level, the expressions of p-p65 and p-IκBα, TNF-α and IL-1β in HUVECs treated with WGBP-A2b were down-regulated. The bioinformatic analysis showed that the inflammation signaling pathway was significantly changed. Its specific mechanism may be related to its regulating the expression of p-p65 p-IκBα, TNF-α and IL-1β proteins in the inflammation signaling pathway.

Dermal Adipose Tissue Secretes HGF to Promote Human Hair Growth and Pigmentation

Hair follicles (HFs) are immersed within dermal white adipose tissue (dWAT), yet human adipocyte‒HF communication remains unexplored. Therefore, we investigated how perifollicular adipocytes affect the physiology of human anagen scalp HFs. Quantitative immunohistomorphometry, X-ray microcomputed tomography, and transmission electron microscopy showed that the number and size of perifollicular adipocytes declined during anagen‒catagen transition, whereas fluorescence-lifetime imaging revealed increased lipid oxidation in adipocytes surrounding the bulge and/or sub-bulge region. Ex vivo, dWAT tendentially promoted hair shaft production, and significantly stimulated hair matrix keratinocyte proliferation and HF pigmentation. Both dWAT pericytes and PREF1/DLK1⁺ adipocyte progenitors secreted HGF during human HF‒dWAT co-culture, for which the c-Met receptor was expressed in the hair matrix and dermal papilla. These effects were reproduced using recombinant HGF and abrogated by an HGF-neutralizing antibody. Laser-capture microdissection‒based microarray analysis of the hair matrix showed that dWAT-derived HGF upregulated keratin (K) genes (K27, K73, K75, K84, K86) and TCHH. Mechanistically, HGF stimulated Wnt/β-catenin activity in the human hair matrix (increased AXIN2, LEF1) by upregulating WNT6 and WNT10B, and inhibiting SFRP1 in the dermal papilla. Our study demonstrates that dWAT regulates human hair growth and pigmentation through HGF secretion, and thus identifies dWAT and HGF as important novel molecular and cellular targets for therapeutic intervention in human hair growth and pigmentation disorders.

Prevascularization-free Primary Subcutaneous Transplantation of Xenogeneic Islets Coencapsulated With Hepatocyte Growth Factor

Subcutaneous pouch is a potential site for islet transplantation. However, insufficient oxygen supply remains challenging. Pretreatment of neovascularization using basic fibroblast growth factor can solve this, but it needs 2× operations. We developed a device that contains rat islets in chitosan gel packed in a bag made of highly biocompatible ethylene vinyl alcohol copolymer porous membrane. This study investigated whether coencapsulation of hepatocyte growth factor (HGF) with islets in the device enables novel method of prevascularization-free primary subcutaneous transplantation.

METHODS

In vitro experiments examined slow release of HGF from the chitosan gel and islet-protection effect of HGF against hypoxia. In the latter, rat islets with/without HGF (200 ng/mL) was cultured in 1% oxygen. In in vivo experiment, fabricated device with/without HGF (10 μg/device) containing rat islets was primarily transplanted to streptozotocin-induced diabetic mice subcutaneously.

RESULTS

In vitro experiments showed sustained release of HGF for 28 d and alleviating effect of HGF on cell death and glucose-responsive insulin release after hypoxic culture. Islet + HGF mice, but not islet-alone mice, showed decreased nonfasting blood glucose and regained body weight after transplantation. In intraperitoneal glucose tolerance test, islet + HGF mice exhibited decreased fasting blood glucose (200 ± 55 mg/dL) and good blood glucose disappearance rate (K value) (0.817 ± 0.101) comparing to normal mice (123 ± 28 mg/dL and 1.074 ± 0.374, respectively). However, in islet-alone mice, fasting blood glucose was high (365 ± 172 mg/dL) and K value was indeterminable. Serum insulin in islet + HGF mice (1.58 ± 0.94 μg/L) was close to normal mice (1.66 ± 0.55 μg/L), whereas those in islet-alone mice (0.279 ± 0.076 μg/L) and diabetic mice (0.165 ± 0.079 μg/L) were low. Immunohistochemical examination showed intact insulin- and glucagon-positive islets in retrieved devices with HGF, but no intact islet was found in the device without HGF.

CONCLUSIONS

HGF could enhance islet survival in hypoxia and enhance in vivo function of encapsulated islets after primary subcutaneous transplantation.

Characterization and functional analysis of SIAH1 during skin and hair follicle development in the angora rabbit (Oryctolagus cuniculus)

BACKGROUND

Seven in absentia homolog 1 (SIAH1) is an E3 ubiquitin ligase containing a RING-finger domain and a key regulator of normal development. Skin and hair follicle development is a complex and special process of morphogenesis involving multiple signaling pathways. SIAH1 is enriched in the Wnt signaling pathway and potentially related to hair follicle cycle and skin development. This study aims to provide evidence for the role of SIAH1 in skin and hair development.

RESULTS

Full-length cloning and analysis of SIAH1 was conducted to better understand its function. Phylogenetically, the sequence of SIAH1 in the rabbit shares the greatest homology with Home sapiens, Pongo abelii and Mus mulatta. Based on the rabbit hair follicle synchronization model, we found that the expression level of SIAH1 in the regressive period of the rabbit hair cycle is significantly lower than in the active growth and rest periods. In addition, the mRNA expression levels of skin and hair follicle development-related genes changed significantly when SIAH1 was overexpressed and silenced. After SIAH1 overexpression, the expression levels of WNT2, LEF1 and FGF2 decreased, and those of SFRP2 and DKK1 increased (P < 0.05). After interference of SIAH1, the expression levels of WNT2, LEF1 and FGF2 increased (P < 0.05), and SFRP2 and DKK1 decreased.

CONCLUSIONS

SIAH1 can affect skin and hair follicle development and exert an inhibitory effect. These results could provide foundamental insights into the role of SIAH1 as a target gene in rabbit skin and hair follicle development.

Systematic large-scale meta-analysis identifies miRNA-429/200a/b and miRNA-141/200c clusters as biomarkers for necrotizing enterocolitis in newborn

Necrotizing enterocolitis (NEC) is a critical neonatal disease with a high mortality. The possibility that miRNAs may play an important role in NEC has raised great attention. Hence, the present study identified biomarkers that affected NEC in newborn progression through miRNA and gene expression profile analysis. miRNA chip GSE68054 and gene chip GSE46619 of NEC in newborn were analyzed to screen out differentially expressed miRNA and differentially expressed genes (DEGs). Next, target genes of differentially expressed miRNA were predicted, and differentially expressed miRNA-DEG regulatory network was constructed to select key miRNAs. After gene ontology and kyoto encyclopedia of genes and genomes enrichment analysis on target genes of key miRNAs, the target genes enriched in pathways were extracted to establish differentially expressed miRNA-DEG-disease gene network for gene interaction analysis. Targetting relationship between miRNAs and target genes was verified. A total of 15 miRNAs were differentially expressed in NEC in newborn, amongst which miR-429/200a/b and miR-141/200c clusters were poorly expressed and might play a significant role in NEC in newborn. Besides, target genes of miR-429/200a/b and miR-141/200c clusters were enriched in 11 signaling pathways. Vascular endothelial growth factor (VEGFA), E-selectin (SELE), kinase insert domain receptor (KDR), fms-related tyrosine kinase 1 (FLT1), and hepatocyte growth factor (HGF) were highly expressed in NEC in newborn, which were negatively regulated by miR-429/200a/b and miR-141/200c clusters and shared close association with disease genes. miR-429/200a/b and miR-141/200c clusters are poorly expressed while their target genes (VEGFA, SELE, KDR, FLT1, and HGF) are highly expressed in NEC in newborn, which might be identified as important biomarkers for this disease.

Comparative transcriptomic analysis of human mesenchymal stem cells derived from dental pulp and adipose tissues

Objective: Mesenchymal stem cells (MSCs) have been isolated from various human tissues. Although they share cardinal stem cell features of self-renewal and multi-potency, they also seem to possess distinct characteristics depending on the tissue types they originated from. When developing stem cell-based therapies, MSCs with the most desirable characteristics should be chosen. However, our knowledge on tissue type-specific characteristics of MSCs is limited. Here, we comparatively studied the gene expression profiles of MSCs from different tissue types, and predicted target diseases suitable for each type of MSCs. Methods: We harvested MSCs from human dental pulp and adipose tissue specimens and subjected them to gene expression microarray analysis. Characteristic gene expression signatures of the MSCs from each tissue type were identified using gene-annotation enrichment analysis. Results: Dental pulp-derived MSCs exhibited gene expression signatures of neuronal growth, while adipose tissue-derived MSCs exhibited signatures of angiogenesis and hair growth. MSCs from each tissue type expressed a discrete set of genes encoding secretory peptides, which may function as paracrine factors. Conclusions: MSCs derived from different tissue types demonstrated distinct gene expression signatures, which are suggestive of target diseases in clinical applications of the MSCs and stem cell-conditioned media. By expanding the analysis to MSCs from a wide range of tissue types, and by employing multiple omics approaches, a catalogue of MSCs and therapeutic targets can be generated.

Mechanical stretch induces hair regeneration through the alternative activation of macrophages

Tissues and cells in organism are continuously exposed to complex mechanical cues from the environment. Mechanical stimulations affect cell proliferation, differentiation, and migration, as well as determining tissue homeostasis and repair. By using a specially designed skin-stretching device, we discover that hair stem cells proliferate in response to stretch and hair regeneration occurs only when applying proper strain for an appropriate duration. A counterbalance between WNT and BMP-2 and the subsequent two-step mechanism are identified through molecular and genetic analyses. Macrophages are first recruited by chemokines produced by stretch and polarized to M2 phenotype. Growth factors such as HGF and IGF-1, released by M2 macrophages, then activate stem cells and facilitate hair regeneration. A hierarchical control system is revealed, from mechanical and chemical signals to cell behaviors and tissue responses, elucidating avenues of regenerative medicine and disease control by demonstrating the potential to manipulate cellular processes through simple mechanical stimulation.

Morpho-regulation in diverse chicken feather formation: Integrating branching modules and sex hormone-dependent morpho-regulatory modules

Many animals can change the size, shape, texture and color of their regenerated coats in response to different ages, sexes, or seasonal environmental changes. Here, we propose that the feather core branching morphogenesis module can be regulated by sex hormones or other environmental factors to change feather forms, textures or colors, thus generating a large spectrum of complexity for adaptation. We use sexual dimorphisms of the chicken to explore the role of hormones. A long-standing question is whether the sex-dependent feather morphologies are autonomously controlled by the male or female cell types, or extrinsically controlled and reversible. We have recently identified core feather branching molecular modules which control the anterior-posterior (bone morphogenetic orotein [BMP], Wnt gradient), medio-lateral (Retinoic signaling, Gremlin), and proximo-distal (Sprouty, BMP) patterning of feathers. We hypothesize that morpho-regulation, through quantitative modulation of existing parameters, can act on core branching modules to topologically tune the dimension of each parameter during morphogenesis and regeneration. Here, we explore the involvement of hormones in generating sexual dimorphisms using exogenously delivered hormones. Our strategy is to mimic male androgen levels by applying exogenous dihydrotestosterone and aromatase inhibitors to adult females and to mimic female estradiol levels by injecting exogenous estradiol to adult males. We also examine differentially expressed genes in the feathers of wildtype male and female chickens to identify potential downstream modifiers of feather morphogenesis. The data show male and female feather morphology and their color patterns can be modified extrinsically through molting and resetting the stem cell niche during regeneration.