Landscape of mast cell populations across organs in mice and humans.

Mast cells (MCs) are tissue-resident immune cells that exhibit homeostatic and neuron-associated functions. Here, we combined whole-tissue imaging and single-cell RNA sequencing datasets to generate a pan-organ analysis of MCs in mice and humans at steady state. In mice, we identify two mutually exclusive MC populations, MrgprB2+ connective tissue-type MCs and MrgprB2neg mucosal-type MCs, with specific transcriptomic core signatures. While MrgprB2+ MCs develop in utero independently of the bone marrow, MrgprB2neg MCs develop after birth and are renewed by bone marrow progenitors. In humans, we unbiasedly identify seven MC subsets (MC1-7) distributed across 12 organs with different transcriptomic core signatures. MC1 are preferentially enriched in the bladder, MC2 in the lungs, and MC4, MC6, and MC7 in the skin. Conversely, MC3 and MC5 are shared by most organs but not skin. This comprehensive analysis offers valuable insights into the natural diversity of MC subtypes in both mice and humans.

Synthetic Nanoclay Gels Do Not Cause Skin Irritation in Healthy Human Volunteers.

Synthetic clays are promising biomaterials for delivery of therapeutic molecules in regenerative medicine. However, before their use can be translated into clinical applications, their safety must be assessed in human volunteers. The aim of this study was to test the hypothesis that a synthetic nanoclay (LAPONITE) does not cause irritation to the human skin. To achieve this, a nanoclay gel at two different concentrations (1.5 and 3% w/v) was applied on the forearm of healthy volunteers for 24 h. 1% sodium lauryl sulfate (SLS) and 3% (w/v) polyacrylic acid were used as the positive and negative controls, respectively. The compromise in the skin barrier function was measured by trans-epidermal water loss (TEWL), erythema by spectroscopic measurements, and skin inflammatory biomarkers (IL-1α and IL-1RA) by the enzyme-linked immunosorbent assay. We found that the nanoclay caused no prolonged increase in TEWL, erythema, or induction of inflammatory cytokines. This was in contrast to 1% SLS, a known irritant, which induced significant increases in both skin erythema and TEWL. We conclude that the nanoclay is not an irritant and is thus suitable for therapeutic interventions at the skin surface.

A pulsed current electric field alters protein expression creating a wound healing phenotype in human skin cells.

Aim: Pulsed current (PC) electric field (EF) devices promote healing in chronic wounds but the underpinning mechanisms are largely unknown. The gap between clinical evidence and mechanistic understanding limits device uptake in clinics. Materials & methods: Migration, proliferation and gene/protein expression profiles were investigated in the presence/absence of PCEF, in skin: keratinocytes (NHK); dermal fibroblasts (HDF); dermal microvascular endothelial cells (HDMEC) and macrophages (THP-1). Results: While PCEF had little effect on migration or proliferation, it significantly altered the expression of 31 genes and the secretion of 7 pro-angiogenic and pro-regenerative growth factors using ELISAs. Conclusion: PCEF significantly altered skin cell genomes/proteomes which provides some evidence of how PCEF devices promote healing of chronic wounds.

The influence of incontinence pads moisture at the loaded skin interface.

AIM: Prolonged mechanical loading on soft tissues adjacent to bony prominences can lead to pressure ulcers. The presence of moisture at the skin interface will lower the tolerance to load. Absorbent pads manage moisture in individuals with incontinence, although their role in maintaining skin health is unknown. The present study investigated the effects of moist incontinence pads on skin physiology after periods of mechanical loading. MATERIAL AND METHODS: Twelve healthy participants were recruited to evaluate a single incontinence pad design under three moisture conditions: 0% (dry), 50% and 100% fluid capacity. For each pad condition, pressure (9 kPa) or pressure in combination with shear (3 N) was applied to the sacrum, followed by a period of off-loading. Measures included trans-epidermal water loss (TEWL) and inflammatory biomarkers sampled at the skin interface. RESULTS: Results revealed no change in TEWL in the loaded dry pad condition. By contrast, when the pads contained moisture, significant increases in TEWL were observed. These increases were reversed during off-loading. Inflammatory biomarkers, specifically IL-1α/total protein ratio, were up-regulated during dry pad loading, which recovered during off-loading. Loaded moist pads caused a significant increase in biomarkers, which remained elevated throughout the test period. CONCLUSION: The study revealed a marked compromise to stratum corneum integrity when the skin was exposed to moist incontinence pads in combination with mechanical loads. These physiological changes were largely reversed during off-loading. Incontinence pads provided some protection in the dry state, although more research is required to determine optimal clinical guidance for their use.

Tenascin-X increases the stiffness of collagen gels without affecting fibrillogenesis.

Tenascin-X is an extracellular matrix protein whose absence leads to an Ehlers-Danlos Syndrome in humans, mainly characterised by connective tissue defects including the disorganisation of fibrillar networks, a reduced collagen deposition, and modifications in the mechanical properties of dense tissues. Here we tested the effect of tenascin-X on in vitro collagen fibril formation. We observed that the main parameters of fibrillogenesis were unchanged, and that the diameter of fibrils was not significantly different when they were formed in the presence of tenascin-X. Interestingly, mechanical analysis of collagen gels showed an increased compressive resistance of the gels containing tenascin-X, indicating that this protein might be directly involved in determining the mechanical properties of collagen-rich tissues in vivo.