Silicone Breast Implant Surface Texture Impacts Gene Expression in Periprosthetic Fibrous Capsules.

BACKGROUND: Silicone breast implants with smooth outer shells are associated with higher rates of capsular contracture, whereas textured implants have been linked to the development of breast implant-associated anaplastic large cell lymphoma. By assessing the gene expression profile of fibrous capsules formed in response to smooth and textured implants, insight into the development of breast implant-associated abnormalities can be gained. METHODS: Miniature smooth or textured silicone implants were surgically inserted into female rats ( n = 10) and harvested for the surrounding capsules at postoperative week 6. RNA sequencing and quantitative polymerase chain reaction were performed to identify genes differentially expressed between smooth and textured capsules. For clinical correlation, the expression of candidate genes was assayed in implant capsules harvested from human patients with and without capsular contracture. RESULTS: Of 18,555 differentially expressed transcripts identified, three candidate genes were selected: matrix metalloproteinase-3 ( MMP3 ), troponin-T3 ( TNNT3 ), and neuregulin-1 ( NRG1 ). In textured capsules, relative gene expression and immunostaining of MMP3 and TNNT3 was up-regulated, whereas NRG1 was down-regulated compared to smooth capsules [mean relative fold change, 8.79 ( P = 0.0059), 4.81 ( P = 0.0056), and 0.40 ( P < 0.0001), respectively]. Immunostaining of human specimens with capsular contracture revealed similar gene expression patterns to those of animal-derived smooth capsules. CONCLUSIONS: An expression pattern of low MMP3 /low TNNT3 /high NRG1 is specifically associated with smooth implant capsules and human implant capsules with capsular contracture. The authors' clinically relevant breast implant rat model provides a strong foundation to further explore the molecular genetics of implant texture and its effect on breast implant-associated abnormalities. CLINICAL RELEVANCE STATEMENT: The authors have demonstrated that there are distinct gene expression profiles in response to smooth versus textured breast implants. Since surface texture may be linked to implant-related pathology, further molecular analysis of periprosthetic capsules may yield strategies to mitigate implant-related complications.

Mesenchymal Stromal Cells Isolated from Irradiated Human Skin Have Diminished Capacity for Proliferation, Differentiation, Colony Formation, and Paracrine Stimulation.

Ionizing radiation, commonly used in the treatment of solid tumors, has unintended but deleterious effects on overlying skin and is associated with chronic nonhealing wounds. Skin-derived mesenchymal stromal cells (SMSCs) are a pluripotent population of cells that are critically involved in skin homeostasis and wound healing. The aim of this study was to isolate and functionally characterize SMSCs from human skin that was previously irradiated as part of neoadjuvant or adjuvant cancer therapy. To this end, SMSCs were isolated from paired irradiated and nonirradiated human skin samples. Irradiated SMSCs expressed characteristic SMSC markers at lower levels, had disorganized cytoskeletal structure, and had disordered morphology. Functionally, these cells had diminished proliferative capacity and substantial defects in colony-forming capacity and differentiation in vitro. These changes were associated with significant differential expression of genes known to be involved in skin physiology and wound healing. Conditioned media obtained from irradiated SMSCs affected fibroblast but not endothelial cell proliferation and migration. These results suggest that in situ damage to SMSCs during neoadjuvant or adjuvant radiation may play a critical role in the pathogenesis of slow or nonhealing radiation wounds. Stem Cells Translational Medicine 2019;8:925&934.

Renal dysfunction aggravated impaired cutaneous wound healing in diabetic mice.

Renal dysfunction has been associated with poor outcomes of wound healing in the diabetic population. The purpose of this study was to create an excisional wound healing model in diabetic mice with renal dysfunction to investigate the combined effects of diabetes and nephropathy on cutaneous ulcers. Renal impairment was introduced in diabetic db/db mice through unilateral nephrectomy and electrocoagulation of the contralateral kidney. Renal function was subsequently monitored with assays of blood urea nitrogen and spot urinary protein/creatinine ratio. After 8 weeks, splinted, full-thickness excisional wounds were created on the dorsal skin and harvested on postoperative days 7 and 14 for further evaluation of wound healing. Renal injury promoted the increase of blood urea nitrogen 3 weeks after initial operation, which was maintained at double the control level throughout the study, concomitantly leading to a significant increase of spot urinary protein excretion. Diabetic mice with renal injury displayed notably impaired wound healing processes, concurrent with reductions in cellular proliferation and angiogenesis, as well as increases in M1 polarized macrophages, infiltrated neutrophils, oxidative stress, and cellular apoptosis. Furthermore, quantitative polymerase chain reaction (qPCR) results displayed corresponding changes of related genes (TNF-α, IL-1ß, SOD2) in the wounds of renal injured db/db mice. Renal manipulation in this study accelerated the progress of renal impairment, which was demonstrated to aggravate impaired cutaneous wound healing in diabetic mice.

Residual sodium dodecyl sulfate in decellularized muscle matrices leads to fibroblast activation in vitro and foreign body response in vivo.

Detergents such as sodium dodecyl sulfate (SDS) are commonly used to extract cells from tissues in a process called "decellularization". Residual SDS is difficult to completely remove and may lead to an undesirable host response towards an implanted biomaterial. In this study, we developed a modification for SDS cell extraction from muscle equally efficient to previous methods but leading to significantly less residual SDS remnants in the matrices. Muscle-derived matrices were prepared via 2 SDS-based decellularization methods, which led to removal of either 81.4% or 98.4% of the SDS. In vitro, matrices were seeded with thp1 macrophages and primary human foreskin fibroblasts. By Day 2, both matrices demonstrated similar macrophage polarization; however, fibroblasts cultured on matrices with greater residual SDS expressed higher levels of mRNA associated with fibroblast activation: α-smooth muscle actin and connective tissue growth factor. In vivo, Collagen I gels spiked with increasing concentrations of SDS displayed a corresponding decrease in cell infiltration when implanted subcutaneously in rats after 4 days. Finally, as a model for muscle regeneration, matrices produced by each method were implanted in rat latissimus dorsi defects. At POD 30 greater levels of IL-1ß mRNA were present in defects treated with matrices containing higher levels of SDS, indicating a more severe inflammatory response. Although matrices containing higher levels of residual SDS became encapsulated by POD 30 and showed evidence of a foreign body response, matrices with the lower levels of SDS integrated into the defect area with lower levels of inflammatory and fibrosis-related gene expression.

Thermal injury model in the rabbit ear with quantifiable burn progression and hypertrophic scar.

Hypertrophic scar is a major clinical outcome of deep-partial thickness to full thickness thermal burn injury. Appropriate animal models are a limitation to burn research due to the lack of, or access to, animal models which address the endpoint of hypertrophic scar. Lower species, such as rodents, heal mainly by contracture, which limits the duration of study. Higher species, such as pigs, heal more similarly to humans, but are associated with high cost, long duration for scar development, challenges in quantifying scar hypertrophy, and poor manageability. Here, we present a quantifiable deep-partial thickness burn model in the rabbit ear. Burns were created using a dry-heated brass rod for 10 and 20 seconds at 90 °C. At the time of eschar excision on day 3, excisional wounds were made on the contralateral ear for comparison. Burn wound progression, in which the wound size expands over time is a major distinction between excisional and thermal injuries, was quantified at 1 hour and 3 days after the injuries using calibrated photographs and histology and the size of the wounds was found to be unchanged from the initial wound size at 1 hour, but 10% in the 20 seconds burn wounds at 3 days. A quantifiable hypertrophic scar, measured by histology as the scar elevation index, was present in both 20 seconds burn wounds and excisional wounds at day 35. ImageJ measurements revealed that the 20 seconds burn wound scars were 22% larger than the excisional wound scars and the 20 seconds burn scar area measurements from histology were 26% greater than in the excisional wound scar. The ability to measure both burn progression and scar hypertrophy over a 35-day time frame suits this model to screening early intervention burn wound therapeutics or scar treatments in a burn-specific scar model.

Sodium channel Nax is a regulator in epithelial sodium homeostasis.

The mechanisms by which the epidermis responds to disturbances in barrier function and restores homeostasis are unknown. With a perturbation of the epidermal barrier, water is lost, resulting in an increase in extracellular sodium concentration. We demonstrate that the sodium channel Nax functions as a sodium sensor. With increased extracellular sodium, Nax up-regulates prostasin, which results in activation of the sodium channel ENaC, resulting in increased sodium flux and increased downstream mRNA synthesis of inflammatory mediators. Nax is present in multiple epithelial tissues, and up-regulation of its downstream genes is found in hypertrophic scars. In animal models, blocking Nax expression results in improvement in scarring and atopic dermatitis-like symptoms, both of which are pathological conditions characterized by perturbations in barrier function. These findings support an important role for Nax in maintaining epithelial homeostasis.