Intradermal adipocytes mediate fibroblast recruitment during skin wound healing

Myofibroblast proliferation and heterogeneity are supported by macrophages during skin repair

During tissue repair, myofibroblasts produce extracellular matrix (ECM) molecules for tissue resilience and strength. Altered ECM deposition can lead to tissue dysfunction and disease. Identification of distinct myofibroblast subsets is necessary to develop treatments for these disorders. We analyzed profibrotic cells during mouse skin wound healing, fibrosis, and aging and identified distinct subpopulations of myofibroblasts, including adipocyte precursors (APs). Multiple mouse models and transplantation assays demonstrate that proliferation of APs but not other myofibroblasts is activated by CD301b-expressing macrophages through insulin-like growth factor 1 and platelet-derived growth factor C. With age, wound bed APs and differential gene expression between myofibroblast subsets are reduced. Our findings identify multiple fibrotic cell populations and suggest that the environment dictates functional myofibroblast heterogeneity, which is driven by fibroblast-immune interactions after wounding.

Visfatin Promotes Wound Healing through the Activation of ERK1/2 and JNK1/2 Pathway

Visfatin, a member of the adipokine family, plays an important role in many metabolic and stress responses. The mechanisms underlying the direct therapeutic effects of visfatin on wound healing have not been reported yet. In this study, we examined the effects of visfatin on wound healing in vitro and in vivo. Visfatin enhanced the proliferation and migration of human dermal fibroblasts (HDFs) and keratinocytes the expression of wound healing-related vascular endothelial growth factor (VEGF) in vitro and in vivo. Treatment of HDFs with visfatin induced activation of both extracellular signal-regulated kinases 1 and 2 (ERK1/2) and c-Jun N-terminal kinases 1 and 2 (JNK1/2) in a time-dependent manner. Inhibition of ERK1/2 and JNK1/2 led to a significant decrease in visfatin-induced proliferation and migration of HDFs. Importantly, blocking VEGF with its neutralizing antibodies suppressed the visfatin-induced proliferation and migration of HDFs and human keratinocytes, indicating that visfatin induces the proliferation and migration of HDFs and human keratinocytes via increased VEGF expression. Moreover, visfatin effectively improved wound repair in vivo, which was comparable to the wound healing activity of epidermal growth factor (EGF). Taken together, we demonstrate that visfatin promotes the proliferation and migration of HDFs and human keratinocytes by inducing VEGF expression and can be used as a potential novel therapeutic agent for wound healing.

Pitx2 maintains mitochondrial function during regeneration to prevent myocardial fat deposition

Loss of the paired-like homeodomain transcription factor 2 (Pitx2) in cardiomyocytes predisposes mice to atrial fibrillation and compromises neonatal regenerative capacity. In addition, Pitx2 gain-of-function protects mature cardiomyocytes from ischemic injury and promotes heart repair. Here, we characterized the long-term myocardial phenotype following myocardial infarction (MI) in Pitx2 conditional-knockout (Pitx2 CKO) mice. We found adipose-like tissue in Pitx2 CKO hearts 60 days after MI induced surgically at postnatal day 2 but not at day 8. Molecular and cellular analyses showed the onset of adipogenic signaling in mutant hearts after MI. Lineage tracing experiments showed a non-cardiomyocyte origin of the de novo adipose-like tissue. Interestingly, we found that Pitx2 promotes mitochondrial function through its gene regulatory network, and that the knockdown of a key mitochondrial Pitx2 target gene, Cox7c, also leads to the accumulation of myocardial fat tissue. Single-nuclei RNA-seq revealed that Pitx2-deficient hearts were oxidatively stressed. Our findings reveal a role for Pitx2 in maintaining proper cardiac cellular composition during heart regeneration via the maintenance of proper mitochondrial structure and function.

Hydrogel from Acellular Porcine Adipose Tissue Accelerates Wound Healing by Inducing Intradermal Adipocyte Regeneration

As an important component of the skin, intradermal adipocytes are closely associated with skin homeostasis and wound healing. Although studies have focused on the role of fibroblasts, keratinocytes, and inflammatory cells in wound healing, the role of adipocytes has not been fully investigated. Here, we verified whether the induction of adipocyte regeneration in a wound bed can effectively promote wound healing, finding that the hydrogel from acellular porcine adipose tissue in combination with adipose-derived stem cells can induce in situ adipogenesis in the wound microenvironment. The newly regenerated adipocytes enhanced fibroblast migration, accelerated wound closing, and enhanced wound epithelialization. More importantly, newly formed intact skin structure was observed after treating the wound with adipose-derived stem cell-loaded hydrogel from acellular porcine adipose tissue. These results show that hydrogel from acellular porcine adipose tissue might substantially improve re-epithelialization, angiogenesis, and skin-appendage regeneration, making it a promising therapeutic biomaterial for skin wound healing.

Adipocyte hypertrophy and lipid dynamics underlie mammary gland remodeling after lactation

Adipocytes undergo pronounced changes in size and behavior to support diverse tissue functions, but the mechanisms that control these changes are not well understood. Mammary gland-associated white adipose tissue (mgWAT) regresses in support of milk fat production during lactation and expands during the subsequent involution of milk-producing epithelial cells, providing one of the most marked physiological examples of adipose growth. We examined cellular mechanisms and functional implications of adipocyte and lipid dynamics in the mouse mammary gland (MG). Using in vivo analysis of adipocyte precursors and genetic tracing of mature adipocytes, we find mature adipocyte hypertrophy to be a primary mechanism of mgWAT expansion during involution. Lipid tracking and lipidomics demonstrate that adipocytes fill with epithelial-derived milk lipid. Furthermore, ablation of mgWAT during involution reveals an essential role for adipocytes in milk trafficking from, and proper restructuring of, the mammary epithelium. This work advances our understanding of MG remodeling and tissue-specific roles for adipocytes.

Skin Cell Heterogeneity in Development, Wound Healing, and Cancer

Skin architecture and function depend on diverse populations of epidermal cells and dermal fibroblasts. Reciprocal communication between the epidermis and dermis plays a key role in skin development, homeostasis and repair. While several stem cell populations have been identified in the epidermis with distinct locations and functions, it is now recognised that there is additional heterogeneity within the mesenchymal cells of the dermis. Here, we discuss recent insights into how these distinct cell populations are maintained and coordinated during development, homeostasis, and wound healing. We highlight the importance of the local environment, or niche, in cellular plasticity. We also discuss new mechanisms that have been identified as influencing wound repair and cancer progression.

Development of a biodegradable antifibrotic local drug delivery system for glaucoma microstents

To prevent implant failure due to fibrosis is a major objective in glaucoma research. The present study investigated the antifibrotic effects of paclitaxel (PTX), caffeic acid phenethyl ester (CAPE), and pirfenidone (PFD) coated microstent test specimens in a rat model. Test specimens based on a biodegradable blend of poly(4-hydroxybutyrate) biopolymer and atactic poly(3-hydroxybutyrate) (at.P(3HB)) were manufactured, equipped with local drug delivery (LDD) coatings, and implanted in the subcutaneous white fat depot. Postoperatively, test specimens were explanted and analyzed for residual drug content. Fat depots including the test specimens were histologically analyzed. In vitro drug release studies revealed an initial burst for LDD devices. In vivo, slow drug release of PTX was found, whereas it already completed 1 week postoperatively for CAPE and PFD LDD devices. Histological examinations revealed a massive cell infiltration in the periphery of the test specimens. Compact fibrotic capsules around the LDD devices were detectable at 4–36 weeks and least pronounced around PFD-coated specimens. Capsules stained positive for extracellular matrix (ECM) components. The presented model offers possibilities to investigate release kinetics and the antifibrotic potential of drugs in vivo as well as the identification of more effective agents for a novel generation of drug-eluting glaucoma microstents.

Mesothelial Stem Cells and Stromal Vascular Fraction for Skin Rejuvenation

The use of stem cells in regenerative medicine and specifically facial rejuvenation is thought provoking and controversial. Today there is increased emphasis on tissue engineering and regenerative medicine, which translates into a need for a reliable source of stem cells in addition to biomaterial scaffolds and cytokine growth factors. Adipose tissue is currently recognized as an accessible and abundant source for adult stem cells. Cellular therapies and tissue engineering are still in their infancy, and additional basic science and preclinical studies are needed before cosmetic and reconstructive surgical applications can be routinely undertaken and satisfactory levels of patient safety achieved.

PPARγ Controls Ectopic Adipogenesis and Cross-Talks with Myogenesis During Skeletal Muscle Regeneration

Skeletal muscle is a regenerative tissue which can repair damaged myofibers through the activation of tissue-resident muscle stem cells (MuSCs). Many muscle diseases with impaired regeneration cause excessive adipose tissue accumulation in muscle, alter the myogenic fate of MuSCs, and deregulate the cross-talk between MuSCs and fibro/adipogenic progenitors (FAPs), a bi-potent cell population which supports myogenesis and controls intra-muscular fibrosis and adipocyte formation. In order to better characterize the interaction between adipogenesis and myogenesis, we studied muscle regeneration and MuSC function in whole body Pparg null mice generated by epiblast-specific Cre/lox deletion (Pparg^Δ/Δ). We demonstrate that deletion of PPARγ completely abolishes ectopic muscle adipogenesis during regeneration and impairs MuSC expansion and myogenesis after injury. Ex vivo assays revealed that perturbed myogenesis in Pparg^Δ/Δ mice does not primarily result from intrinsic defects of MuSCs or from perturbed myogenic support from FAPs. The immune transition from a pro- to anti-inflammatory MuSC niche during regeneration is perturbed in Pparg^Δ/Δ mice and suggests that PPARγ signaling in macrophages can interact with ectopic adipogenesis and influence muscle regeneration. Altogether, our study demonstrates that a PPARγ-dependent adipogenic response regulates muscle fat infiltration during regeneration and that PPARγ is required for MuSC function and efficient muscle repair.

Foxn1 in Skin Development, Homeostasis and Wound Healing

Intensive research effort has focused on cellular and molecular mechanisms that regulate skin biology, including the phenomenon of scar-free skin healing during foetal life. Transcription factors are the key molecules that tune gene expression and either promote or suppress gene transcription. The epidermis is the source of transcription factors that regulate many functions of epidermal cells such as proliferation, differentiation, apoptosis, and migration. Furthermore, the activation of epidermal transcription factors also causes changes in the dermal compartment of the skin. This review focuses on the transcription factor Foxn1 and its role in skin biology. The regulatory function of Foxn1 in the skin relates to physiological (development and homeostasis) and pathological (skin wound healing) conditions. In particular, the pivotal role of Foxn1 in skin development and the acquisition of the adult skin phenotype, which coincides with losing the ability of scar-free healing, is discussed. Thus, genetic manipulations with Foxn1 expression, specifically those introducing conditional Foxn1 silencing in a Foxn1+/+ organism or its knock-in in a Foxn1−/− model, may provide future perspectives for regenerative medicine.

Engineering Pro-Regenerative Hydrogels for Scarless Wound Healing

Skin and skin appendages protect the body from harmful environment and prevent internal organs from dehydration. Superficial epidermal wounds usually heal without scarring, however, deep dermal wound healing commonly ends up with nonfunctioning scar formation with substantial loss of skin appendage. Wound healing is one of the most complex dynamic biological processes, during which a cascade of biomolecules combine with stem cell influx and matrix synthesis and synergistically contribute to wound healing at all levels. Although many approaches have been investigated to restore complete skin, the clinically effective therapy is still unavailable and the regeneration of perfect skin still remains a significant challenge. The complete mechanism behind scarless skin regeneration still requires further investigation. Fortunately, recent advancement in regenerative medicine empowers us more than ever to restore tissue in a regenerative manner. Many studies have elucidated and reviewed the contribution of stem cells and growth factors to scarless wound healing. This article focuses on recent advances in scarless wound healing, especially strategies to engineer pro-regenerative scaffolds to restore damaged skin in a regenerative manner.

[Effect of human adipose-derived stem cells on pressure ulcer healing in mouse]

Objective

To investigate the effect of human adipose-derived stem cells (hADSCs) on pressure ulcers in mouse.

Methods

The subcutaneous adipose tissue from voluntary donation was harvested. Then the hADSCs were isolated and cultured by mechanical isolation combined with typeⅠcollagenase digestion. The 3rd generation cells were identified by osteogenic, adipogenic, chondrogenic differentiations and flow cytometry. The platelet rich plasma (PRP) from peripheral blood donated by healthy volunteers was prepared by centrifugation. The pressure ulcer model was established in 45 C57BL/6 mice by two magnets pressurized the back skin, and randomly divided into 3 groups ( n=15). The wounds were injected with 100 μL of hADSCs (1×10 ⁶ cells) transfected with a green fluorescent protein (GFP)-carrying virus, 100 μL human PRP, and 100 μL PBS in hADSCs group, PRP group, and control group, respectively. The wound healing was observed after injection. The wound healing rate was calculated on the 5th, 9th, and 13th days. On the 5th, 11th, and 21st day, the specimens were stained with HE staing, Masson staining, and CD31 and S100 immunohistochemical staining to observe the vascular and nerve regeneration of the wound. In hADSCs group, fluorescence tracer method was used to observe the colonization and survival of the cells on the 11th day.

Results

The cultured cells were identified as hADSCs by induced differentiation and flow cytometry. The platelet counting was significantly higher in PRP group than in normal peripheral blood group ( t=5.781, P=0.029). General observation showed that the wound healing in hADSCs group was superior to those in PRP group and control group after injection. On the 5th, 9th, and 13th days, the wound healing rate in hADSCs group was significantly higher than those in PRP group and control group ( P<0.05). Histological observation showed that compared with PRP group and control group, inflammatory cell infiltration and inflammatory reaction were significantly reduced in hADSCs group, collagen deposition was significantly increased, and skin appendage regeneration was seen on the 21st day; at each time point, the expression of collagen was significantly higher in hADSCs group than in PRP group and control group ( P<0.05). Immunohistochemical staining showed that the number of neovascularization and the percentage of S100-positive cells in hADSCs group were significantly better than those in PRP group and control group on the 5th, 9th, and 13th days ( P<0.05). Fluorescent tracer method showed that the hADSCs could colonize the wound and survive during 11 days after injection.

Conclusion

Local transplantation of hADSCs can accelerate healing of pressure ulcer wounds in mice and improve healing quality by promoting revascularization and nerve regeneration.

ADM Scaffolds Generate a Pro-regenerative Microenvironment During Full-Thickness Cutaneous Wound Healing Through M2 Macrophage Polarization via Lamtor1

Adult mammalian skin has a defective regenerative capacity following full-thickness cutaneous injury; this defect overshadows the complete physiological functions of the skin. Immune-mediated skin reconstruction driven by biological scaffolds is a recently developed innovative repair strategy to support regenerative wound healing. However, to date, little is known about how biological scaffolds orchestrate the immune response to promote regeneration. Here, using acellular dermal matrix (ADM) scaffolds, we discovered that the default pro-inflammatory response was altered in response to a pro-regenerative response characterized by specific M2 polarization. M2 macrophages subsequently produced a series of wound healing factors, including matrix metalloproteinases (Mmps), and growth factors which promoted cell proliferation, stabilized angiogenesis, and remodeled the extracellular matrix. Our investigations further revealed that the M2 polarization of macrophages arose from an ADM scaffold-derived amino acid sufficiency signal by collagen degradation via macrophage phagocytosis, which activated the acid-sensing pathway (v-ATPase, Lamtor1, and mTORC1). Lamtor1, the acid-sensing pathway-associated lysosomal adaptor protein was critical for inducing M2 polarization, while with the presence of extracellular interleukin 4 (IL4). Our results suggest that ADM scaffolds generate a pro-regenerative microenvironment during full-thickness cutaneous wound healing through M2 macrophage polarization via Lamtor1.

Mesenchymal Stromal Cells and Cutaneous Wound Healing: A Comprehensive Review of the Background, Role, and Therapeutic Potential

Cutaneous wound repair is a highly coordinated cascade of cellular responses to injury which restores the epidermal integrity and its barrier functions. Even under optimal healing conditions, normal wound repair of adult human skin is imperfect and delayed healing and scarring are frequent occurrences. Dysregulated wound healing is a major concern for global healthcare, and, given the rise in diabetic and aging populations, this medicoeconomic disease burden will continue to rise. Therapies to reliably improve nonhealing wounds and reduce scarring are currently unavailable. Mesenchymal stromal cells (MSCs) have emerged as a powerful technique to improve skin wound healing. Their differentiation potential, ease of harvest, low immunogenicity, and integral role in native wound healing physiology make MSCs an attractive therapeutic remedy. MSCs promote cell migration, angiogenesis, epithelialization, and granulation tissue formation, which result in accelerated wound closure. MSCs encourage a regenerative, rather than fibrotic, wound healing microenvironment. Recent translational research efforts using modern bioengineering approaches have made progress in creating novel techniques for stromal cell delivery into healing wounds. This paper discusses experimental applications of various stromal cells to promote wound healing and discusses the novel methods used to increase MSC delivery and efficacy.

Dermal white adipose tissue undergoes major morphological changes during the spontaneous and induced murine hair follicle cycling: a reappraisal

In murine skin, dermal white adipose tissue (DWAT) undergoes major changes in thickness in synchrony with the hair cycle (HC); however, the underlying mechanisms remain unclear. We sought to elucidate whether increased DWAT thickness during anagen is mediated by adipocyte hypertrophy or adipogenesis, and whether lipolysis or apoptosis can explain the decreased DWAT thickness during catagen. In addition, we compared HC-associated DWAT changes between spontaneous and depilation-induced hair follicle (HF) cycling to distinguish between spontaneous and HF trauma-induced events. We show that HC-dependent DWAT remodelling is not an artefact caused by fluctuations in HF down-growth, and that dermal adipocyte (DA) proliferation and hypertrophy are HC-dependent, while classical DA apoptosis is absent. However, none of these changes plausibly accounts for HC-dependent oscillations in DWAT thickness. Contrary to previous studies, in vivo BODIPY uptake suggests that increased DWAT thickness during anagen occurs via hypertrophy rather than hyperplasia. From immunohistomorphometry, DWAT thickness likely undergoes thinning during catagen by lipolysis. Hence, we postulate that progressive, lipogenesis-driven DA hypertrophy followed by dynamic switches between lipogenesis and lipolysis underlie DWAT fluctuations in the spontaneous HC, and dismiss apoptosis as a mechanism of DWAT reduction. Moreover, the depilation-induced HC displays increased DWAT thickness, area, and DA number, but decreased DA volume/area compared to the spontaneous HC. Thus, DWAT shows additional, novel HF wounding-related responses during the induced HC. This systematic reappraisal provides important pointers for subsequent functional and mechanistic studies, and introduces the depilation-induced murine HC as a model for dissecting HF-DWAT interactions under conditions of wounding/stress.

Liposome-Encapsulated Baicalein Suppressed Lipogenesis and Extracellular Matrix Formation in Hs68 Human Dermal Fibroblasts

The dermis of human skin contains large numbers of fibroblasts that are responsible for the production of the extracellular matrix (ECM) that supporting skin integrity, elasticity and wound healing. Previously, an in vivo study demonstrated that dermal fibroblasts siting in the lower dermis are capable to convert into skin adipose layer and hence fibroblast lipogenesis may vary the structure and elasticity of dermis. In the present study, Hs68 human dermal fibroblasts were utilized as an in vitro model to study the lipogenesis via using adipogenic differentiation medium (ADM). Baicalein, isolated from Scutellaria baicalensis, is one of the flavonoids to inhibit adipocyte differentiation due to high antioxidant activity in vitro. In order to develop a suitable formulation for baicalein (a poorly water-soluble drug), soybean phosphatidylcholine (SPC) was used to prepare baicalein-loaded liposomes to enhance drug bioavailability. Our results demonstrated that liposome-encapsulated baicalein protected cell viability and increased cellular uptake efficiency of Hs68 fibroblasts. Lipid accumulation, triglyceride synthesis and gene expressions of lipogenesis enzymes (FABP4 and LPL) were significantly increased in ADM-stimulated Hs68 fibroblasts but subsequently suppressed by liposome-encapsulated baicalein. In addition, ADM-induced TNF-α expression and related inflammatory factors was down-regulated by liposome-encapsulated baicalein. Through ADM-induced lipogenesis, the protein expression of elastin, type I and type III collagens increased remarkably, whereas liposome-encapsulated baicalein can down-regulate ADM-induced ECM protein synthesis. Taken together, we found that liposome-encapsulated baicalein can inhibit ADM-induced lipid accumulation and ECM formation in Hs68 fibroblasts through the suppression of lipogenesis enzymes and inflammatory responses. Liposome-encapsulated baicalein may have the potential to improve wound healing and restore skin structure after skin injury.

Emerging nonmetabolic functions of skin fat

Although the major white adipose depots evolved primarily to store energy, secrete hormones and thermo-insulate the body, multiple secondary depots developed additional specialized and unconventional functions. Unlike any other fat tissue, dermal white adipose tissue (dWAT) evolved a large repertoire of novel features that are central to skin physiology, which we discuss in this Review. dWAT exists in close proximity to hair follicles, the principal appendages of the skin that periodically grow new hairs. Responding to multiple hair-derived signals, dWAT becomes closely connected to cycling hair follicles and periodically cycles itself. At the onset of new hair growth, hair follicles secrete activators of adipogenesis, while at the end of hair growth, a reduction in the secretion of activators or potentially, an increase in the secretion of inhibitors of adipogenesis, results in fat lipolysis. Hair-driven cycles of dWAT remodelling are uncoupled from size changes in other adipose depots that are controlled instead by systemic metabolic demands. Rich in growth factors, dWAT reciprocally signals to hair follicles, altering the activation state of their stem cells and modulating the pace of hair regrowth. dWAT cells also facilitate skin repair following injury and infection. In response to wounding, adipose progenitors secrete repair-inducing activators, while bacteria-sensing adipocytes produce antimicrobial peptides, thus aiding innate immune responses in the skin.

Fat Body Cells Are Motile and Actively Migrate to Wounds to Drive Repair and Prevent Infection

Adipocytes have many functions in various tissues beyond energy storage, including regulating metabolism, growth, and immunity. However, little is known about their role in wound healing. Here we use live imaging of fat body cells, the equivalent of vertebrate adipocytes in Drosophila, to investigate their potential behaviors and functions following skin wounding. We find that pupal fat body cells are not immotile, as previously presumed, but actively migrate to wounds using an unusual adhesion-independent, actomyosin-driven, peristaltic mode of motility. Once at the wound, fat body cells collaborate with hemocytes, Drosophila macrophages, to clear the wound of cell debris; they also tightly seal the epithelial wound gap and locally release antimicrobial peptides to fight wound infection. Thus, fat body cells are motile cells, enabling them to migrate to wounds to undertake several local functions needed to drive wound repair and prevent infections.

The Effects of Adipose-Derived Stem Cell-Differentiated Adipocytes on Skin Burn Wound Healing in Rats

Both adipose-derived stem cells (ADSCs) and fat grafting promote burn wound healing, but whether adipogen-derived cells using various inducers such as 3-isobutyl-1-methylxanthine (IBMX) and insulin affect wound healing is unknown. Herein, ADSC-differentiated adipogenic lineages were used in rat burn wounds to evaluate wound healing potential. ADSCs were cultivated using six different adipogenic differentiation conditions (IBMX ± insulin, IBMX for 5 days, high and low Dulbecco's modified Eagle's medium) and in vitro morphological changes and cell proliferations during adipogenic differentiation were recorded. Intermediate burn wounds were inflicted in 15 Wistar male rats. Afterwards, the rats were divided into five groups for subcutaneous injections under the wounds: control; ADSCs; differentiated adipocytes (-IBMX+INSULIN and +IBMX[D1-5]+INSULIN) and fat prepared by Coleman technique. Macroscopic changes and histology were documented for 3 weeks. Repeated measures analysis of variance was performed to analyze cell growth and wound healing with a statistical level set of P < .05. Induction cocktails significantly reduced proliferation and induced lipid droplet accumulation. Conditioning without insulin induced the least lipid accumulation, while discontinuing IBMX generated larger adipocytes (P < .001). Adipogenic differentiated ADSCs had similar wound healing abilities with ADSC and fat injections, but differentiated adipocytes (+IBMX[D1-5]+INSULIN) and fat grafting accelerated the early healing process relative to ADSC (P < .001). Reduced fibrosis and mild inflammatory infiltration limited to superficial dermis were observed in +IBMX(D1-5)+INSULIN and fat injection groups, while those reactions were mild to moderate in ADSC group. Differentiated adipocytes achieve similar wound healing results compared with ADSC and fat injections, but differentiated adipocytes (+IBMX[D1-5]+INSULIN) and fat grafting accelerate early healing relative to ADSC.

Anatomical, Physiological, and Functional Diversity of Adipose Tissue

Adipose tissue depots can exist in close association with other organs, where they assume diverse, often non-traditional functions. In stem cell-rich skin, bone marrow, and mammary glands, adipocytes signal to and modulate organ regeneration and remodeling. Skin adipocytes and their progenitors signal to hair follicles, promoting epithelial stem cell quiescence and activation, respectively. Hair follicles signal back to adipocyte progenitors, inducing their expansion and regeneration, as in skin scars. In mammary glands and heart, adipocytes supply lipids to neighboring cells for nutritional and metabolic functions, respectively. Adipose depots adjacent to skeletal structures function to absorb mechanical shock. Adipose tissue near the surface of skin and intestine senses and responds to bacterial invasion, contributing to the body's innate immune barrier. As the recognition of diverse adipose depot functions increases, novel therapeutic approaches centered on tissue-specific adipocytes are likely to emerge for a range of cancers and regenerative, infectious, and autoimmune disorders.

Fibroblast heterogeneity: implications for human disease

Fibroblasts synthesize the extracellular matrix of connective tissue and play an essential role in maintaining the structural integrity of most tissues. Researchers have long suspected that fibroblasts exhibit functional specialization according to their organ of origin, body site, and spatial location. In recent years, a number of approaches have revealed the existence of fibroblast subtypes in mice. Here, we discuss fibroblast heterogeneity with a focus on the mammalian dermis, which has proven an accessible and tractable system for the dissection of these relationships. We begin by considering differences in fibroblast identity according to anatomical site of origin. Subsequently, we discuss new results relating to the existence of multiple fibroblast subtypes within the mouse dermis. We consider the developmental origin of fibroblasts and how this influences heterogeneity and lineage restriction. We discuss the mechanisms by which fibroblast heterogeneity arises, including intrinsic specification by transcriptional regulatory networks and epigenetic factors in combination with extrinsic effects of the spatial context within tissue. Finally, we discuss how fibroblast heterogeneity may provide insights into pathological states including wound healing, fibrotic diseases, and aging. Our evolving understanding suggests that ex vivo expansion or in vivo inhibition of specific fibroblast subtypes may have important therapeutic applications.

Dermal fibroblast in cutaneous development and healing

The skin is the largest organ of the body and is composed of two layers: the overlying epidermis and the underlying dermis. The dermal fibroblasts originate from distinct locations of the embryo and contain the positional identity and patterning information in the skin. The dermal fibroblast progenitors differentiate into various cell types that are fated to perform specific functions such as hair follicle initiation and scar formation during wound healing. Recent studies have revealed the heterogeneity and plasticity of dermal fibroblasts within skin, which has implications for skin disease and tissue engineering. The objective of this review is to frame our current understanding and provide new insights on the origin and differentiation of dermal fibroblasts and their function during cutaneous development and healing. WIREs Dev Biol 2018, 7:e307. doi: 10.1002/wdev.307 This article is categorized under: Birth Defects > Organ Anomalies Signaling Pathways > Cell Fate Signaling Adult Stem Cells, Tissue Renewal, and Regeneration > Regeneration Nervous System Development > Vertebrates: Regional Development.

Pro-Regenerative Hydrogel Restores Scarless Skin during Cutaneous Wound Healing

The transformation of fibrotic healing process to regenerative one has great potential to fully restore wounded skin. The M2 macrophage phenotype promotes constructive tissue remodeling and instructs tissue repair in a regenerative manner. It is hypothesized that hydrogels that can establish robustness of endogenous cells to regulate M2 phenotype will promote constructive dermal remodeling. Toward this end, a series of dextran-based bioabsorbable hydrogels are developed and self-crosslinkable dextran-isocyanatoethyl methacrylate-ethylamine (DexIEME) is identified as the potential scaffold. The initial screening study revealed that DexIEME has superior biocompatibility in varying concentrations. Although DexIEME brings about low proinflammatory responses, it promotes M2 macrophage phenotype. Then the optimized hydrogel formulation is tested for acute skin injuries using both murine and porcine models. Preliminary data demonstrated that the innovative DexIEME hydrogel promotes complete skin regeneration with hair regrowth on pre-existing scars, while untreated scars remain intact. Preclinical studies further demonstrated that the DexIEME hydrogel regenerated perfect skin during deep porcine wound healing. Overall, the approach to investigate immune-modulated hydrogels yields pro-regenerative DexIEME hydrogel, which may lead to greater clinical success in treating deep dermal injury and attenuating scar formation.

Ozone oil promotes wound healing by increasing the migration of fibroblasts via PI3K/Akt/mTOR signaling pathway

Skin injury affects millions of people via the uncontrolled inflammation and infection. Many cellular components including fibroblasts and signaling pathways such as transforming growth factor-β (TGF-β) were activated to facilitate the wound healing to repair injured tissues. C57BL/6 female mice were divided into control and ozone oil treated groups. Excisional wounds were made on the dorsal skin and the fibroblasts were isolated from granulation tissues. The skin injured mouse model revealed that ozone oil could significantly decrease the wound area and accelerate wound healing compared with control group. QPCR and Western blotting assays showed that ozone oil up-regulated collagen I, α-SMA, and TGF-β1 mRNA and protein levels in fibroblasts. Wound healing assay demonstrated that ozone oil could increase the migration of fibroblasts. Western blotting assay demonstrated that ozone oil increased the epithelial–mesenchymal transition (EMT) process in fibroblasts via up-regulating fibronectin, vimentin, N-cadherin, MMP-2, MMP-9, insulin-like growth factor binding protein (IGFBP)-3, IGFBP5, and IGFBP6, and decreasing epithelial protein E-cadherin and cellular senescence marker p16 expression. Mechanistically, Western blotting assay revealed that ozone oil increased the phosphorylation of PI3K, Akt, and mTOR to regulate the EMT process, while inhibition of PI3K reversed this effect of ozone oil. At last, the results from Cytometric Bead Array (CBA) demonstrated ozone oil significantly decreased the inflammation in fibroblasts. Our results demonstrated that ozone oil facilitated the wound healing via increasing fibroblast migration and EMT process via PI3K/Akt/mTOR signaling pathway in vivo and in vitro. The cellular and molecular mechanisms we found here may provide new therapeutic targets for the treatment of skin injury.

The roles of dermal white adipose tissue loss in scleroderma skin fibrosis

PURPOSE OF REVIEW

Dermal white adipose tissue (DWAT) is distinct from subcutaneous white adipose tissue and is lost in scleroderma skin fibrosis. The roles of DWAT loss in scleroderma skin fibrosis have not been well understood, and here we discuss recent findings that begin to provide insight into the multiple mechanisms involved.

RECENT FINDINGS

The DWAT loss in part reflects the direct contribution of DWAT cells to the fibrotic tissue, with the reprogramming of adipocytes to myofibroblasts. The DWAT contains reparative adipose-derived stromal cells and expresses antifibrotic cytokines such as adiponectin, and the loss of these skin-protective mechanisms with DWAT loss further contributes to skin fibrosis and injury.

SUMMARY

Potentially, halting or reversing the transdifferentiation of adipocytes to myofibroblasts along with improving survival of reparative adipose-derived stromal cells (ADSCs) and expression of antifibrotic cytokines may be effective therapeutic avenues.

Current and Future Perspectives of Stem Cell Therapy in Dermatology

Stem cells are undifferentiated cells capable of generating, sustaining, and replacing terminally differentiated cells and tissues. They can be isolated from embryonic as well as almost all adult tissues including skin, but are also generated through genetic reprogramming of differentiated cells. Preclinical and clinical research has recently tremendously improved stem cell therapy, being a promising treatment option for various diseases in which current medical therapies fail to cure, prevent progression or relieve symptoms. With the main goal of regeneration or sustained genetic correction of damaged tissue, advanced tissue-engineering techniques are especially applicable for many dermatological diseases including wound healing, genodermatoses (like the severe blistering disorder epidermolysis bullosa) and chronic (auto-)inflammatory diseases. This review summarizes general aspects as well as current and future perspectives of stem cell therapy in dermatology.

Interfacial Adipose Tissue in Systemic Sclerosis

Purpose of Review

This review provides a summary of recent insights into the role of the local white adipose tissue (WAT) in systemic sclerosis.

Recent Findings

Adipocytes located in an interfacial WAT area adjacent to fibrotic lesions have an intermediate phenotype and special properties implicated in fibrotic pathology in systemic sclerosis (SSc). The important role of these cells is recognized in different pathologies, such as wound healing, psoriasis, breast cancer, and prostate cancer. Additionally, both immature and mature adipocytes are involved in the appearance of fibroblast-like cells but exhibit different phenotypes and synthetic properties.

Summary

Adipocytes from interfacial WAT adjacent to the fibrotic area in SSc are phenotypically different from bulk adipocytes and are involved in pathogenesis of SSc. Immature and mature adipocytes from this WAT layer differentiate into various types of fibroblast-like cells, making the local ratio of immature to mature adipocytes in interfacial WAT of particular importance in SSc pathogenesis.

Delayed Hair Follicle Morphogenesis and Hair Follicle Dystrophy in a Lipoatrophy Mouse Model of Pparg Total Deletion

PPARγ regulates multiple aspects of skin physiology, including sebocyte differentiation, keratinocyte proliferation, epithelial stem cell survival, adipocyte biology, and inflammatory skin responses. However, the effects of its global deletion, namely of nonredundant key functions of PPARγ signaling in mammalian skin, are yet unknown because of embryonic lethality. Here, we describe the skin and hair phenotype of a whole-body PPARγ-null mouse (Pparg^Δ/Δ), obtained by preserving PPARγ expression in the placenta. Pparg^Δ/Δ mice exhibited total lipoatrophy and complete absence of sebaceous glands. Right after birth, hair follicle (HF) morphogenesis was transiently delayed, along with reduced expression of HF differentiation markers and of transcriptional regulators necessary for HF development. Later, adult Pparg^Δ/Δ mice developed scarring alopecia and severe perifollicular inflammation. Skin analyses in other models of lipodystrophy, AZIP^tg/+ and Adipoq-Cre^tg/+Pparg^fl/fl mice, coupled with skin graft experiments, showed that the early defects observed in hair morphogenesis were caused by the absence of adipose tissue. In contrast, the late alteration of HF cycle and appearance of inflammation were observed only in Pparg^Δ/Δ mice and likely were due to the lack sebaceous glands. Our findings underscore the increasing appreciation for the importance of adipose tissue-mediated signals in HF development and function.

Revisiting ovarian cancer microenvironment: a friend or a foe?

Development of ovarian cancer involves the co-evolution of neoplastic cells together with the adjacent microenvironment. Steps of malignant progression including primary tumor outgrowth, therapeutic resistance, and distant metastasis are not determined solely by genetic alterations in ovarian cancer cells, but considerably shaped by the fitness advantage conferred by benign components in the ovarian stroma. As the dynamic cancer topography varies drastically during disease progression, heterologous cell types within the tumor microenvironment (TME) can actively determine the pathological track of ovarian cancer. Resembling many other solid tumor types, ovarian malignancy is nurtured by a TME whose dark side may have been overlooked, rather than overestimated. Further, harnessing breakthrough and targeting cures in human ovarian cancer requires insightful understanding of the merits and drawbacks of current treatment modalities, which mainly target transformed cells. Thus, designing novel and precise strategies that both eliminate cancer cells and manipulate the TME is increasingly recognized as a rational avenue to improve therapeutic outcome and prevent disease deterioration of ovarian cancer patients.

Growth Factor-Reinforced ECM Fabricated from Chemically Hypoxic MSC Sheet with Improved In Vivo Wound Repair Activity

MSC treatment can promote cutaneous wound repair through multiple mechanisms, and paracrine mediators secreted by MSC are responsible for most of its therapeutic benefits. Recently, MSC sheet composed of live MSCs and their secreted ECMs was reported to promote wound healing; however, whether its ECM alone could accelerate wound closure remained unknown. In this study, Nc-ECM and Cc-ECM were prepared from nonconditioned and CoCl₂-conditioned MSC sheets, respectively, and their wound healing properties were evaluated in a mouse model of full-thickness skin defect. Our results showed that Nc-ECM can significantly promote wound repair through early adipocyte recruitment, rapid reepithelialization, enhanced granulation tissue growth, and augmented angiogenesis. Moreover, conditioning of MSC sheet with CoCl₂ dramatically enriched its ECM with collagen I, collagen III, TGF-β1, VEGF, and bFGF via activation of HIF-1α and hence remarkably improved its ECM's in vivo wound healing potency. All the Cc-ECM-treated wounds completely healed on day 7, while Nc-ECM-treated wounds healed about 85.0% ± 8.6%, and no-treatment wounds only healed 69.8% ± 9.6% (p < 0.05). Therefore, we believe that such growth factor-reinforced ECM fabricated from chemically hypoxic MSC sheet has the potential for clinical translation and will lead to a MSC-derived, cost-effective, bankable biomaterial for wound management.

Conditional knock out of N-WASP in keratinocytes causes skin barrier defects and atopic dermatitis-like inflammation

Neural-Wiskott Aldrich Syndrome Protein (N-WASP) is expressed ubiquitously and regulates actin cytoskeleton remodeling. In order to characterize the role of N-WASP in epidermal homeostasis and cutaneous biology, we generated conditional N-WASP knockout mouse using CK14-cre (cytokeratin 14) to ablate expression of N-WASP in keratinocytes. N-WASP^K14KO (N-WASP^fl/fl; CK14-Cre) mice were born following Mendelian genetics suggesting that N-WASP expression in keratinocytes is not essential during embryogenesis. N-WASP^K14KO mice exhibited stunted growth, alopecia, dry and wrinkled skin. The dry skin in N-WASP^K14KO mice is probably due to increased transepidermal water loss (TEWL) caused by barrier function defects as revealed by dye penetration assay. N-WASP^K14KO mice developed spontaneous inflammation in the neck and face 10 weeks after birth. Histological staining revealed thickening of the epidermis, abnormal cornified layer and extensive infiltration of immune cells (mast cells, eosinophils and T-lymphocytes) in N-WASP^K14KO mice skin compared to control mice. N-WASP^K14KO mice had higher serum levels of IL-1α, TNF-α, IL-6 and IL-17 compared to control mice. Thus our results suggest that conditional N-WASP knockout in keratinocytes leads to compromised skin barrier, higher infiltration of immune cells and hyperproliferation of keratinocytes due to increased production of cytokines highlighting the importance of N-WASP in maintaining the skin homeostasis.

Cell-based cytotoxicity assays for engineered nanomaterials safety screening: exposure of adipose derived stromal cells to titanium dioxide nanoparticles

BACKGROUND

Increasing production of nanomaterials requires fast and proper assessment of its potential toxicity. Therefore, there is a need to develop new assays that can be performed in vitro, be cost effective, and allow faster screening of engineered nanomaterials (ENMs).

RESULTS

Herein, we report that titanium dioxide (TiO2) nanoparticles (NPs) can induce damage to adipose derived stromal cells (ADSCs) at concentrations which are rated as safe by standard assays such as measuring proliferation, reactive oxygen species (ROS), and lactate dehydrogenase (LDH) levels. Specifically, we demonstrated that low concentrations of TiO2 NPs, at which cellular LDH, ROS, or proliferation profiles were not affected, induced changes in the ADSCs secretory function and differentiation capability. These two functions are essential for ADSCs in wound healing, energy expenditure, and metabolism with serious health implications in vivo.

CONCLUSIONS

We demonstrated that cytotoxicity assays based on specialized cell functions exhibit greater sensitivity and reveal damage induced by ENMs that was not otherwise detected by traditional ROS, LDH, and proliferation assays. For proper toxicological assessment of ENMs standard ROS, LDH, and proliferation assays should be combined with assays that investigate cellular functions relevant to the specific cell type.

Adiponectin is an endogenous anti-fibrotic mediator and therapeutic target

Skin fibrosis in systemic sclerosis (SSc) is accompanied by attrition of dermal white adipose tissue (dWAT) and reduced levels of circulating adiponectin. Since adiponectin has potent regulatory effects on fibroblasts, we sought to assess adiponectin signaling in SSc skin biopsies, and evaluate fibrosis in mice with adiponectin gain- and loss-of-function mutations. Furthermore, we investigated the effects and mechanism of action of agonist peptides targeting adiponectin receptors in vitro and in vivo. We found that adiponectin pathway activity was significantly reduced in a subset of SSc skin biopsies. Mice lacking adiponectin mounted an exaggerated dermal fibrotic response, while transgenic mice with constitutively elevated adiponectin showed selective dWAT expansion and protection from skin and peritoneal fibrosis. Adiponectin receptor agonists abrogated ex vivo fibrotic responses in explanted normal and SSc fibroblasts and in 3D human skin equivalents, in part by attenuating focal adhesion complex assembly, and prevented and reversed experimentally-induced organ fibrosis in mice. These results implicate aberrant adiponectin pathway activity in skin fibrosis, identifying a novel function for this pleiotropic adipokine in regulation of tissue remodeling. Restoring adiponectin signaling in SSc patients therefore might represent an innovative pharmacological strategy for intractable organ fibrosis.

The Effect of Antiseptics on Adipose-Derived Stem Cells

BACKGROUND

Although chemical antiseptics are the most basic measure to control wound infection and frequently come into contact with subcutaneous adipose tissue, no studies have evaluated their toxicity on adipose tissue and its cell fractions. In the present study, the effects of five different antiseptics on adipose-derived stem cells were evaluated.

METHODS

Human adipose-derived stem cells were harvested from healthy donors. Adipose-derived stem cell viability was measured after treatment with different concentrations of antiseptics over 5 days. Furthermore, the effect on the proliferation, adipogenic differentiation, and apoptosis/necrosis of adipose-derived stem cells was analyzed. Finally, the mRNA expression of the stem cell markers CD29, CD34, CD73, CD90, and CD105 was detected.

RESULTS

Octenisept and Betaisodona significantly reduced cell proliferation and differentiation and led to considerable adipose-derived stem cell necrosis. Octenisept decreased stem cell viability at the lowest concentrations tested, and all stem cell markers were down-regulated by Octeniseptr and Betaisodona. Lavasept and Prontosan both led to reduced stem cell viability, proliferation, and differentiation, and increased apoptosis/necrosis, although the effects were less pronounced compared with Octenisept and Betaisodona. Adipose-derived stem cells survived treatment with mafenide acetate even at high concentrations, and mafenide acetate showed minimal negative effects on their proliferation, adipogenic differentiation, cell death, and stem cell marker expression.

CONCLUSIONS

Mafenide acetate may be regarded as a feasible antiseptic for the treatment of wounds with exposed adipose tissue because of its low adipose-derived stem cell toxicity. Lavasept and Prontosan are possible alternatives to mafenide acetate. Octenisept and Betaisodona, by contrast, may be used only in highly diluted solutions.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Activation of Parathyroid Hormone 2 Receptor Induces Decorin Expression and Promotes Wound Repair

In this study, we report that TIP39, a parathyroid hormone ligand family member that was recently identified to be expressed in the skin, can induce decorin expression and enhance wound repair. Topical treatment of mice with TIP39 accelerated wound repair, whereas TIP39-deficient mice had delayed repair that was associated with formation of abnormal collagen bundles. To study the potential mechanism responsible for the action of TIP39 in the dermis, fibroblasts were cultured in three-dimensional collagen gels, a process that results in enhanced decorin expression unless activated to differentiate to adipocytes, whereupon these cells reduce expression of several proteoglycans, including decorin. Small interfering RNA-mediated silencing of parathyroid hormone 2 receptor (PTH2R), the receptor for TIP39, suppressed the expression of extracellular matrix-related genes, including decorin, collagens, fibronectin, and matrix metalloproteases. Skin wounds in TIP39^-/- mice had decreased decorin expression, and addition of TIP39 to cultured fibroblasts induced decorin and increased phosphorylation and nuclear translocation of CREB. Fibroblasts differentiated to adipocytes and treated with TIP39 also showed increased decorin and production of chondroitin sulfate. Furthermore, the skin of PTH2R^-/- mice showed abnormal extracellular matrix structure, decreased decorin expression, and skin hardness. Thus, the TIP39-PTH2R system appears to be a previously unrecognized mechanism for regulation of extracellular matrix formation and wound repair.

An overview of the therapeutic potential of regenerative medicine in cutaneous wound healing

The global burden of disease associated with wounds is an increasingly significant public health concern. Current treatments are often expensive, time-consuming and limited in their efficacy in chronic wounds. The challenge of overcoming current barriers associated with wound care requires innovative management techniques. Regenerative medicine is an emerging field of research that focuses on the repair, replacement or regeneration of cells, tissues or organs to restore impaired function. This article provides an overview of the pathophysiology of wound healing and reviews the latest evidence on the application of the principal components of regenerative medicine (growth factors, stem cell transplantation, biomaterials and tissue engineering) as therapeutic targets. Improved knowledge and understanding of the pathophysiology of wound healing has pointed to new therapeutic targets. Regenerative medicine has the potential to underpin the design of specific target therapies in acute and chronic wound healing. This personalised approach could eventually reduce the burden of disease associated with wound healing. Further evidence is required in the form of large animal studies and clinical trials to assess long-term efficacy and safety of these new treatments.

Mesenchymal Stem Cells from Adipose Tissue in Clinical Applications for Dermatological Indications and Skin Aging

Operating at multiple levels of control, mesenchymal stem cells from adipose tissue (ADSCs) communicate with organ systems to adjust immune response, provide signals for differentiation, migration, enzymatic reactions, and to equilibrate the regenerative demands of balanced tissue homeostasis. The identification of the mechanisms by which ADSCs accomplish these functions for dermatological rejuvenation and wound healing has great potential to identify novel targets for the treatment of disorders and combat aging. Herein, we review new insights into the role of adipose-derived stem cells in the maintenance of dermal and epidermal homeostasis, and recent advances in clinical applications of ADSCs related to dermatology.

The Role of Adipocytes in Tissue Regeneration and Stem Cell Niches

Classically, white adipose tissue (WAT) was considered an inert component of connective tissue but is now appreciated as a major regulator of metabolic physiology and endocrine homeostasis. Recent work defining how WAT develops and expands in vivo emphasizes the importance of specific locations of WAT or depots in metabolic regulation. Interestingly, mature white adipocytes are integrated into several tissues. A new perspective regarding the in vivo regulation and function of WAT in these tissues has highlighted an essential role of adipocytes in tissue homeostasis and regeneration. Finally, there has been significant progress in understanding how mature adipocytes regulate the pathology of several diseases. In this review, we discuss these novel roles of WAT in the homeostasis and regeneration of epithelial, muscle, and immune tissues and how they contribute to the pathology of several disorders.

[Very high frequency ultrasound: New therapeutic method in aesthetic medicine and dermatology]

Very high frequency ultrasound (VHF-US) is new therapy method with a broad application spectrum in dermatology and aesthetic medicine. In this method, ultrasound waves with frequencies over 10 MHz, which were for a long time only used in ultrasound diagnostics, are applied for therapeutic purposes. Such US waves demonstrate specific biophysical efficiencies which warrant their application for the treatment of the skin efflorescences, chronic wounds and hypertrophic scars as well as in anti-aging and skin improvement procedures in aesthetic medicine. VHF-US can be applied not only for stand-alone treatments, but also as a supportive pre- and posttreatment method in combination with laser, radiofrequency currents, injection lipolysis, etc. as well as in aesthetic plastic surgery.

Skin aging: are adipocytes the next target?

Dermal white adipose tissue (dWAT) is increasingly appreciated as a special fat depot. The adipocytes in this depot exert a variety of unique effects on their surrounding cells and can undergo massive phenotypic changes. Significant modulation of dWAT content can be observed both in intrinsically and extrinsically aged skin. Specifically, skin that has been chronically photo-damaged displays a reduction of the dWAT volume, caused by the replacement of adipocytes by fibrotic structures. This is likely to be caused by the recently uncovered process described as "adipocyte-myofibroblast transition" (AMT). In addition, contributions of dermal adipocytes to the skin aging processes are also indirectly supported by spatial correlations between the prevalence of hypertrophic scarring and the appearance of signs of skin aging in different ethnic groups. These observations could elevate dermal adipocytes to prime targets in strategies aimed at counteracting skin aging.

Microfluidic single-cell transcriptional analysis rationally identifies novel surface marker profiles to enhance cell-based therapies

Current progenitor cell therapies have only modest efficacy, which has limited their clinical adoption. This may be the result of a cellular heterogeneity that decreases the number of functional progenitors delivered to diseased tissue, and prevents correction of underlying pathologic cell population disruptions. Here, we develop a high-resolution method of identifying phenotypically distinct progenitor cell subpopulations via single-cell transcriptional analysis and advanced bioinformatics. When combined with high-throughput cell surface marker screening, this approach facilitates the rational selection of surface markers for prospective isolation of cell subpopulations with desired transcriptional profiles. We establish the usefulness of this platform in costly and highly morbid diabetic wounds by identifying a subpopulation of progenitor cells that is dysfunctional in the diabetic state, and normalizes diabetic wound healing rates following allogeneic application. We believe this work presents a logical framework for the development of targeted cell therapies that can be customized to any clinical application.

Unrecognized progenitor cell perturbations underlying a disease state may limit the efficacy of cell therapies. Here, the authors use high-throughput, single-cell transcriptional analysis to identify disease-specific cellular alterations and prospectively isolate restorative cell subpopulations.

CD301b+ Macrophages Are Essential for Effective Skin Wound Healing

Regeneration of skin's barrier function after injury requires temporally coordinated cellular interactions between multiple cell types. Macrophages are essential inflammatory cells in skin wound regeneration. These cells switch their phenotype from inflammatory in the early regenerative stages to anti-inflammatory in the midstages of healing to coordinate skin repair. However, little is known about how different subsets of anti-inflammatory macrophages contribute to skin wound healing. Here, we characterize midstage macrophages (CD45(+)/CD11b(+)/F4-80(+)) and identify two major populations: CD206(+)/CD301b(+) and CD206(+)/CD301b(-). The numbers of CD206(+)/CD301b(+) macrophages increased concomitantly with repair, when the anti-inflammatory phenotype switch occurs in midstage healing. Using diphtheria toxin-mediated depletion models in mice, we show that selective depletion of midstage CD301b-expressing macrophages phenocopied wound healing defects observed in mice where multiple myeloid lineages are depleted. Additionally, when FACS-isolated subpopulations of myeloid cells were transplanted into 3-day wounds of syngeneic mice, only CD206(+)/CD301b(+) macrophages significantly increased proliferation and fibroblast repopulation. These data show that the CD301b-expressing subpopulation of macrophages is critical for activation of reparative processes during the midstage of cutaneous repair.