Progenitor-derived endothelin controls dermal sheath contraction for hair follicle regression.

Substantial follicle remodelling during the regression phase of the hair growth cycle is coordinated by the contraction of the dermal sheath smooth muscle, but how dermal-sheath-generated forces are regulated is unclear. Here, we identify spatiotemporally controlled endothelin signalling-a potent vasoconstriction-regulating pathway-as the key activating mechanism of dermal sheath contraction. Pharmacological blocking or genetic ablation of both endothelin receptors, ETA and ETB, impedes dermal sheath contraction and halts follicle regression. Epithelial progenitors at the club hair-epithelial strand bottleneck produce the endothelin ligand ET-1, which is required for follicle regression. ET signalling in dermal sheath cells and downstream contraction is dynamically regulated by cytoplasmic Ca2+ levels through cell membrane and sarcoplasmic reticulum calcium channels. Together, these findings illuminate an epithelial-mesenchymal interaction paradigm in which progenitors-destined to undergo programmed cell death-control the contraction of the surrounding sheath smooth muscle to orchestrate homeostatic tissue regression and reorganization for the next stem cell activation and regeneration cycle.

BMP-AKT-GSK3ß Signaling Restores Hair Follicle Stem Cells Decrease Associated with Loss of Sfrp1.

Wnt signaling plays a pivotal role in regulating activation, proliferation, stem cell renewal, and differentiation of hair follicle stem cells (HFSCs). Secreted frizzled-related protein 1 (Sfrp1), a Wnt antagonist is upregulated in the HFSCs; however, its role in the HFSCs regulation is still obscure. Here, we show that Sfrp1 loss showed a depletion of HFSCs, enhanced HFSC proliferation, and faster hair follicle cycle at PD21-PD28; HFSC markers, such as Lgr5 and Axin2, were decreased in both the Sfrp1+/- and Sfrp1-/- HFSCs. In addition, the second hair follicle cycle was also faster compared with WT. Importantly, Sfrp1-/- showed a restoration of HFSC by second telogen (PD49), whereas Sfrp1+/- did not show restoration with still having a decreased HFSC. In fact, restoration of HFSCs was due to a pronounced downregulation of ß-catenin activity mediated through a cross-talk of BMP-AKT-GSK3ß signaling in Sfrp1-/- compared with Sfrp1+/-, where downregulation was less pronounced. In cultured keratinocytes, Sfrp1 loss resulted in enhanced proliferation and clonogenicity, which were reversed by treating with either BMPR1A or GSK3ß inhibitor thereby confirming BMP-AKT-GSK3ß signaling involved in ß-catenin regulation in both the Sfrp1+/- and Sfrp1-/- mice. Our study reveals a novel function of Sfrp1 by unraveling an in vivo molecular mechanism that regulates the HFSCs pool mediated through a hitherto unknown cross-talk of BMP-AKT-GSK3ß signaling that maintains stem cell pool balance, which in turn maintains skin tissue homeostasis.

Understanding the binding affinities between SFRP1CRD, SFRP1Netrin, Wnt5B and frizzled receptors 2, 3 and 7 using MD simulations.

cWnt-signalling plays a crucial role in stem cell maintenance and tissue homeostasis. Secreted frizzled-related proteins(SFRP), Wnt inhibitors consist of the N-terminal cysteine rich domain(CRD) and the C-terminal netrin(NTR) domain. SFRP1 binds to the Wnt ligands and frizzled receptors(FZ) either through its SFRP1CRD or through its SFRP1Netrin domains; however, very little is known on these binding affinities. Here, we attempted to understand the interactions and binding affinities of SFRP1-Wnt5B, SFRP1-FZ(2, 3 & 7) and Wnt5B-FZ(2, 3 & 7) that are mainly expressed in murine hair follicle stem cells. SFRP1CRD, SFRP1Netrin, Wnt5B and FZ(2, 3 & 7) structures were built using homology modelling, followed by their molecular dynamics simulations. SFRP1CRD showed lower fluctuation when in complex with FZ2, FZ3 and FZ7 and Wnt5B as compared to SFRP1Netrin using RMSF and RMSD. However, free energy showed SFRP1Netrin was energetically more stable than SFRP1CRD. SFRP1Netrin formed more number of interactions with FZ as compared to SFRP1CRD. Importantly, SFRP1Netrin favoured binding to the FZ receptors(FZ3 > FZ7 > FZ2) as compared to Wnt5B ligand. Conversely, the SFRP1CRD showed more affinity towards the Wnt5B ligand as compared to FZ receptors. Wnt5B showed the best binding affinity with FZ3 followed by SFRP1CRD and SFRP1Netrin. Therefore, SFRP1Netrin can bind to the FZ3 with higher binding affinity and may inhibit non-canonical Wnt-signalling pathway. Our study provides the comprehensive information on the binding affinities among the Wnt5B, SFRP1CRD/Netrin and FZ(2, 3 & 7). Thus, this information might also help in designing novel strategies to inhibit aberrant Wnt-signalling.Communicated by Ramaswamy H. Sarma.

EMT imparts cancer stemness and plasticity: new perspectives and therapeutic potential.

Epithelial-to-mesenchymal transition (EMT) is a fundamental cellular phenomenon that plays an intrinsic role in development, tissue repair, and cancer progression. EMT is tightly regulated by transcription factors that alter gene expression to promote epithelial to mesenchymal phenotype. EMT is also regulated by a diverse array of cytokines and growth factors whose activities are deregulated during malignancy. EMT enables tumor cells to exist in various intermediate states along the epithelial-mesenchymal phenotypic axis that transit from cancer stem cells (CSCs) to circulating tumor cells (CTCs). Recent studies have revealed the importance of CSCs in tumor promotion, invasion and metastasis. The relapsed tumors encompass CSCs which are resistant to radiotherapy and chemotherapy. In this review, we have summarized our current understanding of the molecular mechanisms that regulate EMT induced CSC phenotype. We have highlighted studies implicating the function of TGF-�, Wnt, and Notch regulated non-coding RNAs in driving EMT promoting CSC self-renewal. Finally, we discuss how the EMT and CSCs cause drug resistance with the hope to overcome such resistance as a possible approach for cancer treatment.

Publisher Correction: Secretory phospholipase A2-IIA overexpressing mice exhibit cyclic alopecia mediated through aberrant hair shaft differentiation and impaired wound healing response.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

SFRP1 in Skin Tumor Initiation and Cancer Stem Cell Regulation with Potential Implications in Epithelial Cancers.

Wnt signaling is involved in the regulation of cancer stem cells (CSCs); however, the molecular mechanism involved is still obscure. SFRP1, a Wnt inhibitor, is downregulated in various human cancers; however, its role in tumor initiation and CSC regulation remains unexplored. Here, we used a skin carcinogenesis model, which showed early tumor initiation in Sfrp1-/- (Sfrp1 knockout) mice and increased tumorigenic potential of Sfrp1-/- CSCs. Expression profiling on Sfrp1-/- CSCs showed upregulation of genes involved in epithelial to mesenchymal transition, stemness, proliferation, and metastasis. Further, SOX-2 and SFRP1 expression was validated in human skin cutaneous squamous cell carcinoma, head and neck squamous cell carcinoma, and breast cancer. The data showed downregulation of SFRP1 and upregulation of SOX-2, establishing their inverse correlation. Importantly, we broadly uncover an inverse correlation of SFRP1 and SOX-2 in epithelial cancers that may be used as a potential prognostic marker in the management of cancer.

Context-dependent effect of sPLA2-IIA induced proliferation on murine hair follicle stem cells and human epithelial cancer.

BACKGROUND: Tissue stem cells (SCs) and cancer cells proliferation is regulated by many common signalling mechanisms. These mechanisms temporally balance proliferation and differentiation events during normal tissue homeostasis and repair. However, the effect of these aberrant signalling mechanisms on the ultimate fate of SCs and cancer cells remains obscure. METHODS: To evaluate the functional effects of Secretory Phospholipase A2-IIA (sPLA2-IIA) induced abnormal signalling on normal SCs and cancer cells, we have used K14-sPLA2-IIA transgenic mice hair follicle stem cells (HFSCs), DMBA/TPA induced mouse skin tumour tissues, human oral squamous cell carcinoma (OSCC) and skin squamous cell carcinoma (SCC) derived cell lines. FINDINGS: Our study demonstrates that sPLA2-IIA induces rapid proliferation of HFSCs, thereby altering the proliferation dynamics leading to a complete loss of the slow cycling H2BGFP positive HFSCs. Interestingly, in vivo reversion study by JNK inhibition exhibited a significant delay in post depilation hair growth, confirming that sPLA2-IIA promotes HFSCs proliferation through JNK/c-Jun signalling. In a different cellular context, we showed increased expression of sPLA2-IIA in human OSCC and mouse skin cancer tissues. Importantly, a xenograft of sPLA2-IIA knockdown cells of OSCC and SCC cell lines showed a concomitant reduction of tumour volume in NOD-SCID mice and decreased JNK/c-Jun signalling. INTERPRETATION: This study unravels how an increased proliferation induced by a common proliferation inducer (sPLA2-IIA) alters the fate of normal SCs and cancer cells distinctively through common JNK/c-Jun signalling. Thus, sPLA2-IIA can be a potential target for various diseases including cancer. FUND: This work was partly supported by the Indian Council of Medical Research (ICMR-3097) and ACTREC (42) grants.

Secretory phospholipase A2-IIA overexpressing mice exhibit cyclic alopecia mediated through aberrant hair shaft differentiation and impaired wound healing response.

Secretory phospholipase A2 Group-IIA (sPLA2-IIA) is involved in lipid catabolism and growth promoting activity. sPLA2-IIA is deregulated in many pathological conditions including various cancers. Here, we have studied the role of sPLA2-IIA in the development of cyclic alopecia and wound healing response in relation to complete loss of hair follicle stem cells (HFSCs). Our data showed that overexpression of sPLA2-IIA in homozygous mice results in hyperproliferation and terminal epidermal differentiation followed by hair follicle cycle being halted at anagen like stage. In addition, sPLA2-IIA induced hyperproliferation leads to compl pathological conditions including various cancers. Here ete exhaustion of hair follicle stem cell pool at PD28 (Postnatal day). Importantly, sPLA2-IIA overexpression affects the hair shaft differentiation leading to development of cyclic alopecia. Molecular investigation study showed aberrant expression of Sox21, Msx2 and signalling modulators necessary for proper differentiation of inner root sheath (IRS) and hair shaft formation. Further, full-thickness skin wounding on dorsal skin of K14-sPLA2-IIA homozygous mice displayed impaired initial healing response. Our results showed the involvement of sPLA2-IIA in regulation of matrix cells differentiation, hair shaft formation and complete loss of HFSCs mediated impaired wound healing response. These novel functions of sPLA2-IIA may have clinical implications in alopecia, cancer development and ageing.