Repurposing DPP4 Inhibition to Improve Hair Follicle Activation and Regeneration.

Skin injury and several diseases elicit fibrosis and induce hair follicle (HF) growth arrest and loss. The resulting alopecia and disfiguration represent a severe burden for patients, both physically and psychologically. Reduction of profibrotic factors such as dipeptidyl peptidase 4 (DPP4) might be a strategy to tackle this issue. We show DPP4 overrepresentation in settings with HF growth arrest (telogen), HF loss, and nonregenerative wound areas in mouse skin and human scalp. Topical DPP4 inhibition with Food and Drug Administration/European Medicines Agency-approved sitagliptin on preclinical models of murine HF activation/regeneration results in accelerated anagen progress, whereas treatment of wounds with sitagliptin results in reduced expression of fibrosis markers, increased induction of anagen around wounds, and HF regeneration in the wound center. These effects are associated with higher expression of Wnt target Lef1, known to be required for HF anagen/HF-activation and regeneration. Sitagliptin treatment decreases profibrotic signaling in the skin, induces a differentiation trajectory of HF cells, and activates Wnt targets related to HF activation/growth but not those supporting fibrosis. Taken together, our study shows a role for DPP4 in HF biology and shows how DPP4 inhibition, currently used as oral medication to treat diabetes, could be repurposed into a topical treatment agent to potentially reverse HF loss in alopecia and after injury.

Cell Population Dynamics in Wound-Induced Hair Follicle Neogenesis Model.

Hair follicle (HF) regeneration can be achieved in the center of large full-thickness wounds on mouse backs (wound-induced HF neogenesis model, WIHN). Investigations with this model have allowed for the identification of some of the factors limiting the extent of fibrosis, which creates a permissive environment for the reposition of HF. For WIHN, specific subpopulations of cells rather than cell types are permissive to this process. Detailed information on the cellular composition in WIHN is not available. Here, we provide a description of changes in cell numbers of fibroblasts, HF dermal papilla, endothelial cells, keratinocytes (interfollicular epidermis, HF-infundibulum, HF-isthmus, HF-bulge (basal and suprabasal), HF-hair germ) and immune cells (macrophages, monocytes, dendritic cells, T cells (CD4+, CD8+, CD4+/CD8+, regulatory T cells) and neutrophils) based on flow cytometric analysis. We compared unwounded skin with large wounds (1.5 × 1.5 cm) at different time points after wounding. We found that non-immune dermal cells have the largest share in the skin at all time points studied, and that the number of epidermal cells started increasing nine days after wounding, which precede isthmus cells and bulge cells, mirroring the development of hair follicles. Monocytes and neutrophils represent most myeloid cells in wounds and remain in wounds even beyond the inflammatory phase of wound healing. Macrophages can be identified as inflammatory and alternative cells and are also found in wounds even in the late remodeling phase of wound healing. Lastly, we provide information about T cells in large wounds. Most T cells in the wounds were CD8+ at all time points and expressed γδTCR, which was previously thought to be expressed mainly on CD4+. We also report the existence of double positive CD4/CD8. Our study provides a guide in terms of time points suitable for the further study of cell subpopulations aiming to dissect the cellular heterogeneity in WIHN. Our results might set the base for the comparison of WIHN between control mice and animals manipulated to influence HF neogenesis and the full understanding of the responsible actors allowing for HF regeneration.

[Alopecia areata universalis under treatment with sitagliptin : Possible immunological effect of dipeptidyl peptidase-4 inhibitors?] / Alopecia areata universalis nach Sitagliptin-Einnahme : Mögliche immunologische Wirkung von Dipeptidylpeptidase-4-Inhibitoren?

A 64-year old man developed alopecia universalis after one month of treatment with metformin and sitagliptin, a dipeptidyl peptidase­4 (DPP-4) inhibitor. Diabetes treatment was changed to another genericum of sitagliptin and dapagliflozin. Following our recommendation, sitagliptin was interrupted and monotherapy with dapagliflozin was continued. After 6 weeks, sitagliptin was reassumed due to unsatisfactory diabetes control. Alopecia did not improve. We suspect a connection between DPP­4 inhibition and development of alopecia due to its immunological potential. We assume that the treatment interruption might have been too short to induce regrowth of hair. DPP­4 may result in both inhibition and activation of the immune system.

Autologous, Non-Invasively Available Mesenchymal Stem Cells from the Outer Root Sheath of Hair Follicle Are Obtainable by Migration from Plucked Hair Follicles and Expandable in Scalable Amounts.

BACKGROUND: Regenerative therapies based on autologous mesenchymal stem cells (MSC) as well as stem cells in general are still facing an unmet need for non-invasive sampling, availability, and scalability. The only known adult source of autologous MSCs permanently available with no pain, discomfort, or infection risk is the outer root sheath of the hair follicle (ORS). METHODS: This study presents a non-invasively-based method for isolating and expanding MSCs from the ORS (MSCORS) by means of cell migration and expansion in air-liquid culture. RESULTS: The method yielded 5 million cells of pure MSCORS cultured in 35 days, thereby superseding prior art methods of culturing MSCs from hair follicles. MSCORS features corresponded to the International Society for Cell Therapy characterization panel for MSCs: adherence to plastic, proliferation, colony forming, expression of MSC-markers, and adipo-, osteo-, and chondro-differentiation capacity. Additionally, MSCORS displayed facilitated random-oriented migration and high proliferation, pronounced marker expression, extended endothelial and smooth muscle differentiation capacity, as well as a paracrine immunomodulatory effect on monocytes. MSCORS matched or even exceeded control adipose-derived MSCs in most of the assessed qualities. CONCLUSIONS: MSCORS qualify for a variety of autologous regenerative treatments of chronic disorders and prophylactic cryopreservation for purposes of acute treatments in personalized medicine.

Phagocytosis of Wnt inhibitor SFRP4 by late wound macrophages drives chronic Wnt activity for fibrotic skin healing.

Human and murine skin wounding commonly results in fibrotic scarring, but the murine wounding model wound-induced hair neogenesis (WIHN) can frequently result in a regenerative repair response. Here, we show in single-cell RNA sequencing comparisons of semi-regenerative and fibrotic WIHN wounds, increased expression of phagocytic/lysosomal genes in macrophages associated with predominance of fibrotic myofibroblasts in fibrotic wounds. Investigation revealed that macrophages in the late wound drive fibrosis by phagocytizing dermal Wnt inhibitor SFRP4 to establish persistent Wnt activity. In accordance, phagocytosis abrogation resulted in transient Wnt activity and a more regenerative healing. Phagocytosis of SFRP4 was integrin-mediated and dependent on the interaction of SFRP4 with the EDA splice variant of fibronectin. In the human skin condition hidradenitis suppurativa, phagocytosis of SFRP4 by macrophages correlated with fibrotic wound repair. These results reveal that macrophages can modulate a key signaling pathway via phagocytosis to alter the skin wound healing fate.

Glycosaminoglycan-based hydrogels capture inflammatory chemokines and rescue defective wound healing in mice.

Excessive production of inflammatory chemokines can cause chronic inflammation and thus impair cutaneous wound healing. Capturing chemokine signals using wound dressing materials may offer powerful new treatment modalities for chronic wounds. Here, a modular hydrogel based on end-functionalized star-shaped polyethylene glycol (starPEG) and derivatives of the glycosaminoglycan (GAG) heparin was customized for maximal chemokine sequestration. The material is shown to effectively scavenge the inflammatory chemokines MCP-1 (monocyte chemoattractant protein-1), IL-8 (interleukin-8), and MIP-1α (macrophage inflammatory protein-1α) and MIP-1ß (macrophage inflammatory protein-1ß) in wound fluids from patients suffering from chronic venous leg ulcers and to reduce the migratory activity of human monocytes and polymorphonuclear neutrophils. In an in vivo model of delayed wound healing (db/db mice), starPEG-GAG hydrogels outperformed the standard-of-care product Promogran with respect to reduction of inflammation, as well as increased granulation tissue formation, vascularization, and wound closure.

Dermal Fibroblasts Promote Alternative Macrophage Activation Improving Impaired Wound Healing.

Tight control of inflammation is required for tissue repair and wound healing and depends on alternative polarization of macrophages as checkpoint for inflammatory resolution. Its perturbations lead to impaired regeneration. Administration of cells/cell factors capable of reversing inflammation and rescuing alternative polarization could be promising for treating inflammatory diseases. We show that human dermal fibroblasts (dFb) are ideal candidates for such a task by demonstrating a new function of these cells, which is modulating macrophage polarization. Coculture of dFb with human monocytes in vitro or injection of dFb into mice with thioglycollate-induced peritonitis favors alternative macrophage activation and reduces inflammation by releasing tumor necrosis factor-inducible gene 6 protein and Cox-2 products. Silencing these factors in dFb abolishes the reported effects, demonstrating their importance for immunomodulation. Importantly, in a model of delayed wound healing due to prolonged inflammation (db/db mice), administration of dFb improves defective tissue repair with augmentation of alternative macrophage polarization and inflammation resolution. Human dFb are low immunogenic cells, easy to obtain, and can be expanded extensively in vitro conserving their immunomodulatory capacity; this, together with our findings, suggests that dFb might represent an alternative for cell-based therapies of conditions characterized by excessive inflammation and delayed tissue repair.

MicroRNA-23a mediates post-transcriptional regulation of CXCL12 in bone marrow stromal cells.

The chemokine CXCL12 regulates the interaction between hematopoietic stem and progenitor cells and bone marrow stromal cells. Although its relevance in the bone marrow niche is well recognized, the regulation of CXCL12 by microRNA is not completely understood. We transfected a library of 486 microRNA in the bone marrow stromal cell line SCP-1 and studied the expression of CXCL12. Twenty-seven microRNA were shown to downregulate expression of CXCL12. Eight microRNA (miR-23a, 130b, 135, 200b, 200c, 216, 222, and 602) interacted directly with the 3'UTR of CXCL12. Next, we determined that only miR-23a is predicted to bind to the 3'UTR and is strongly expressed in primary bone marrow stromal cells. Modulation of miR-23a changes the migratory potential of hematopoietic progenitor cells in co-culture experiments. We discovered that TGFB1 mediates its inhibitory effect on CXCL12 levels by upregulation of miR-23a. This process was partly reversed by miR-23a molecules. Finally, we determined an inverse expression of CXCL12 and miR-23a in stromal cells from patients with myelodys-plastic syndrome indicating that the interaction has a pathophysiological role. Here, we show for the first time that CXCL12-targeting miR23a regulates the functional properties of the hematopoietic niche.

Mesenchymal stromal cells from patients with myelodyplastic syndrome display distinct functional alterations that are modulated by lenalidomide.

The contribution of the bone marrow microenvironment in myelodysplastic syndrome is controversial. We therefore analyzed the functional properties of primary mesenchymal stromal cells from patients with myelodysplastic syndrome in the presence or absence of lenalidomide. Compared to healthy controls, clonality and growth were reduced across all disease stages. Furthermore, differentiation defects and particular expression of adhesion and cell surface molecules (e.g. CD166, CD29, CD146) were detected. Interestingly, the levels of stromal derived factor 1-alpha in patients' cells culture supernatants were almost 2-fold lower (P<0.01) than those in controls and this was paralleled by a reduced induction of migration of CD34(+) hematopoietic cells. Co-cultures of mesenchymal stromal cells from patients with CD34(+) cells from healthy donors resulted in reduced numbers of cobblestone area-forming cells and fewer colony-forming units. Exposure of stromal cells from patients and controls to lenalidomide led to a further reduction of stromal derived factor 1-alpha secretion and cobblestone area formation, respectively. Moreover, lenalidomide pretreatment of mesenchymal stromal cells from patients with low but not high-risk myelodysplastic syndrome was able to rescue impaired erythroid and myeloid colony formation of early hematopoietic progenitors. In conclusion, our analyses support the notion that the stromal microenvironment is involved in the pathophysiology of myelodysplastic syndrome thus representing a potential target for therapeutic interventions.

Impact of lenalidomide on the functional properties of human mesenchymal stromal cells.

OBJECTIVE: Lenalidomide (LEN) has emerged as a promising therapeutic option for the management of various hematologic malignancies. Although its direct mechanisms of action on malignant cells have been studied intensively, its effects on the stromal compartment of bone marrow have not yet been analyzed systematically. Therefore, we investigated whether LEN alters the functional capacity of mesenchymal stromal cells (MSCs) as the main cellular component of the bone marrow microenvironment. In addition to their growth and differentiation characteristics, we focused on the ability of MSC to modulate T-cell function and support hematopoietic stem cells (HSCs). MATERIALS AND METHODS: Bone marrow-derived MSCs were exposed to LEN (10 µM), and differences in proliferation, phenotype, inhibition of T-cell proliferation, and differentiation capacity were analyzed. A Boyden chamber assay was used to test the migratory potential of HSC toward the conditioned medium of LEN-treated or untreated MSCs, and the stromal cell-derived factor-1 (SDF-1) concentrations in these supernatants were determined by enzyme-linked immunosorbent assay. RESULTS: Treatment of MSCs with LEN did not affect their growth rate, proliferation, osteogenic and adipogenic differentiation potential, or capacity to inhibit T-cell proliferation. However, LEN treatment increased the average of mean fluorescence intensity of CD29 and CD73 by 15 and 22%, respectively. Interestingly, LEN reduced SDF-1 by MSCs by 32% compared to that of control cells. As a functional consequence, the serum-free supernatant of LEN-treated MSCs had a significantly lower potential to induce the directed migration of CD34(+) HSCs. CONCLUSION: LEN can modulate the expression of cell surface molecules and the chemokine secretion of MSCs in vitro. These effects might contribute to the clinical effects of the compound in vivo for patients with hematological malignancies.