Microbubble-enhanced ultrasound for gene transfer into living skin equivalents

Disorganisation of basement membrane zone architecture impairs melanocyte residence in vitiligo

The basement membrane zone is the interface between the epidermis and dermis, and it is disrupted in several skin conditions. Here, we report the results of a comprehensive investigation into the structural and molecular factors of the basement membrane zone in vitiligo, a dermatological disorder characterised by depigmented patches on the skin. Using electron microscopy and immunofluorescence staining, we confirmed abnormal basement membrane zone morphology and disrupted basement membrane zone architecture in human vitiliginous skin. Furthermore, we identified elevated expression of matrix metalloproteinase 2 (MMP2) in human dermal fibroblasts as a key factor responsible for basement membrane zone matrix degradation. In our in vitro and ex vivo models, overexpression of MMP2 in fibroblasts led to basement membrane zone disruption and melanocyte disappearance. Importantly, we reveal that the loss of melanocytes in vitiligo is primarily linked to their weakened adhesion to the basement membrane, mediated by binding between integrin β1 and laminin and discoidin domain receptor 1 and collagen IV. Finally, inhibition of matrix metalloproteinase 2 expression reversed depigmentation in a mouse model of vitiligo. In conclusion, our research shows the importance of basement membrane zone integrity in melanocyte residence and offers new avenues for therapeutic interventions to address this challenging skin condition. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Highly concentrated trehalose induces prohealing senescence-like state in fibroblasts via CDKN1A/p21

Trehalose is the nonreducing disaccharide of glucose, evolutionarily conserved in invertebrates. The living skin equivalent (LSE) is an organotypic coculture containing keratinocytes cultivated on fibroblast-populated dermal substitutes. We demonstrated that human primary fibroblasts treated with highly concentrated trehalose promote significantly extensive spread of the epidermal layer of LSE without any deleterious effects. The RNA-seq analysis of trehalose-treated 2D and 3D fibroblasts at early time points revealed the involvement of the CDKN1A pathway, the knockdown of which significantly suppressed the upregulation of DPT, ANGPT2, VEGFA, EREG, and FGF2. The trehalose-treated fibroblasts were positive for senescence-associated β-galactosidase. Finally, transplantation of the dermal substitute with trehalose-treated fibroblasts accelerated wound closure and increased capillary formation significantly in the experimental mouse wounds in vivo, which was canceled by the CDKN1A knockdown. These data indicate that high-concentration trehalose can induce the senescence-like state in fibroblasts via CDKN1A/p21, which may be therapeutically useful for optimal wound repair.

Ultrasound-assisted ocular drug delivery: A review of current evidence

Efficient ocular drug delivery is a challenging clinical problem with various therapeutic options but no clearly preferred methodology. Given the ubiquity of ultrasound as a diagnostic technique, the safety profile of ultrasound in an ocular context, and the prospect of custom-made ultrasound-sensitive contrast agents, ultrasound presents an attractive ocular drug delivery modality. In this review, we evaluate our present understanding of ultrasound as it relates to ocular drug delivery and significant knowledge gaps in the field. In doing so, we hope to call attention to a potentially novel drug delivery pathway that could be manipulated to treat or cure ocular diseases.

Accelerated human epidermal turnover driven by increased hyaluronan production

BACKGROUND

Hyaluronan (HA) is an essential component of extracellular matrix in the skin, but its functions in the epidermis remain elusive.

OBJECTIVE

We examined the interaction of increased HA production mediated by 1-ethyl-β-N-acetylglucosaminide (β-NAG2), a newly developed highly selective inducer of HA production which is intracellularly converted to UDP-N-acetylglucosamine, a substrate of HA, with epidermal proliferation and differentiation.

METHODS

The amount, molecular size and epidermal tissue distribution of HA and expression of CD44, a cell surface receptor for HA, were analyzed in β-NAG2-treated organ cultured human skin, reconstructed human skin equivalents or cultured human skin keratinocytes. The relationship between HA and epidermal proliferation or differentiation was examined.

RESULTS

β-NAG2 significantly increased HA production in the epidermis of skin explants or skin equivalents without affecting molecular size of HA (>2000 kDa) or CD44 mRNA expression. Histochemical experiments revealed that β-NAG2 enhances HA signals in the basal to granular layers of the epidermis of skin equivalents, accompanying increased epidermal stratification. Immunohistochemical experiments demonstrated that signals of Ki67, transglutaminase 1 and filaggrin are increased in β-NAG2-treated skin equivalents, and these observations were confirmed by the data showing that mRNA expression of PCNA, transglutaminase 1 (TGM1) and filaggrin (FLG) is significantly up-regulated by β-NAG2 in skin equivalents. Importantly, blockade of HA production by inhibiting conversion of β-NAG2 to UDP-NAG abolished β-NAG2-mediated up-regulation of PCNA, TGM1 and FLG mRNA expression in cultured keratinocytes.

CONCLUSION

These results suggest that increased epidermal HA production plays a key role in epidermal morphogenesis and homeostasis by accelerating keratinocyte proliferation and differentiation.

Protective role of Galectin-7 for skin barrier impairment in atopic dermatitis

Background

Atopic dermatitis (AD) patients have a barrier disorder in association with Th2 dominant skin inflammation. Galectin‐7 (Gal‐7), a soluble unglycosylated lectin, is highly expressed in the stratum corneum of AD patients. However, the biological significance of increased Gal‐7 expression in AD skin lesions remains unclear.

Objective

We aimed to investigate the production mechanism and functional role of Gal‐7 in AD patients and IL‐4/IL‐13–stimulated epidermal keratinocytes.

Methods

We assessed the Gal‐7 expression levels in skin lesions and sera from AD patients. Gal‐7 levels were also measured in monolayered normal human epidermal keratinocytes (NHEKs) and 3‐dimensional (3D)–reconstructed epidermis in the presence or absence of IL‐4/IL‐13 with or without Stat3, Stat6 or Gal‐7 gene silencing.

Results

Gal‐7 was highly expressed in the stratum corneum or intercellular space of AD lesional epidermis as assessed by the stratum corneum proteome analysis and immunohistochemistry. A positive correlation was noted between serum Gal‐7 level and transepidermal water loss in patients with AD. These clinical findings were corroborated by our in vitro data, which showed that IL‐4/IL‐13 facilitated the extracellular release of endogenous Gal‐7 in both monolayered NHEKs and 3D‐reconstructed epidermis. This machinery was caused by IL‐4/IL‐13–induced cell damage and inhibited by knockdown of Stat6 but not Stat3 in NHEKs. Moreover, we performed Gal‐7 knockdown experiment on 3D‐reconstructed epidermis and the result suggested that endogenous Gal‐7 serves as a protector from IL‐4/IL‐13–induced disruption of cell‐to‐cell adhesion and/or cell‐to‐extracellular matrix adhesion.

Conclusion and Clinical Relevance

Our study unveils the characteristic of Gal‐7 and its possible role as an alarmin that reflects the IL‐4/IL‐13–induced skin barrier impairment in AD.

House dust mite allergens induce interleukin 33 (IL-33) synthesis and release from keratinocytes via ATP-mediated extracellular signaling

In atopic diseases, the epithelium releases cytokines and chemokines that initiate skin inflammation. Atopic dermatitis (AD) is characterized by a disrupted epidermal barrier and is triggered or exacerbated by environmental stimuli such as house dust mite (HDM) allergens. The proinflammatory cytokine interleukin 33 (IL-33) plays an important role in the pathogenesis of AD, but how IL-33 production in keratinocytes is elicited by HDM is unknown. To that end, here we stimulated monolayer-cultured human keratinocytes and human living skin equivalents with Dermatophagoides pteronyssinus HDM extract to investigate its effects on IL-33 production from keratinocytes. The HDM extract induced intracellular expression of IL-33 and modulated its processing and maturation, triggering rapid IL-33 release from keratinocytes. Group 1 HDM allergen but not group 2 HDM allergen elicited IL-33 production. An ATP assay of keratinocyte culture supernatants revealed an acute and transient accumulation of extracellular ATP immediately after the HDM extract stimulation. Using the broad-spectrum P2 antagonist suramin, the specific purinergic receptor P2Y2 (P2RY2) antagonist AR-C118925XX, and P2RY2-specific siRNA, we discovered that the HDM extract-induced IL-33 expression was mainly dependent on extracellular ATP/P2Y2 signaling mediated by transactivation of epidermal growth factor receptor, followed by activation of the ERK kinase signaling pathway. Moreover, HDM extract-induced release of 25-kDa IL-33 from the keratinocytes depended on an extracellular ATP/P2 signaling-mediated intracellular Ca²⁺ increase. Our study demonstrates the new mechanism controlling the induction and maturation of keratinocyte-produced IL-33 by HDM allergens, an innate immune process that might play a role in AD development or severity.

Decreased expression of suprabasin induces aberrant differentiation and apoptosis of epidermal keratinocytes: Possible role for atopic dermatitis

BACKGROUND

Suprabasin (SBSN), a secreted protein, is expressed in various epithelial tissues. The role of SBSN in epidermal differentiation and atopic dermatitis (AD) pathology remains largely unknown.

OBJECTIVE

To evaluate the effects of SBSN on epidermal keratinocytes and its role in AD.

METHODS

We examined the SBSN expression levels in the stratum corneum and the epidermis by proteome analysis and immunohistochemistry, respectively. The serum SBSN concentration was measured by ELISA. These values were compared between AD and healthy control. Morphological changes in the epidermis were investigated in SBSN-knockdown three-dimensional human living skin equivalent (LSE) model with or without IL-4/IL-13.

RESULTS

Epidermal SBSN expression was decreased in AD lesional skin compared to healthy skin, as assessed by the stratum corneum proteome analysis and immunohistochemistry. The SBSN serum levels were significantly lower in AD patients than in normal subjects (P<0.05). The SBSN-deficient LSE exhibited compact stratum corneum, immature stratum granulosum, and increased keratinocyte apoptosis. Th2 cytokines, IL-4 and IL-13, did not affect SBSN expression in LSE. There were no differentiation-associated makers that were affected by the SBSN knockdown. SBSN deficiency-induced apoptosis of keratinocytes was exaggerated by IL-4/IL-13, and accordingly, the addition of recombinant SBSN induced significant keratinocyte proliferation (P<0.05).

CONCLUSION

Our data demonstrated that SBSN regulates normal epidermal barrier. Th2 cytokines unaffect SBSN expression in keratinocytes, but promote SBSN deficiency-induced apoptosis. It is suggested that SBSN has an anti-apoptotic activity, and its deficiency is involved in the pathogenesis of AD.

Heparinoid suppresses Der p-induced IL-1β production by inhibiting ERK and p38 MAPK pathways in keratinocytes

Epidermal keratinocytes initiate skin inflammation by activating immune cells. The skin barrier is disrupted in atopic dermatitis (AD) and epidermal keratinocytes can be exposed to environmental stimuli, such as house dust mite (HDM) allergens. We showed previously that HDM allergens activate the NLRP3 inflammasome of keratinocytes, thereby releasing pro-inflammatory cytokines. Heparinoid is an effective moisturizer for atopic dry skin. However, a recent report showed that heparinoid treatment can improve inflammation of lichen planus. Therefore, we hypothesized that it acts on epidermal keratinocytes not only as a moisturizer, but also as a suppressant of the triggers of skin inflammation. We found that HDM allergen-induced interleukin (IL)-1β release from keratinocytes was inhibited significantly by heparinoid pretreatment without affecting cell viability. However, heparinoid did not affect caspase-1 release, suggesting that heparinoid did not affect HDM allergen-induced inflammasome activation. Heparinoid treatment not only decreased intracellular levels of pro-IL-1β, but also suppressed IL-1β messenger RNA (mRNA) expression in keratinocytes. Among the intracellular signalling pathways, the activation of extracellular signal-regulated kinase and p38 pathways, which are required for IL-1β expression in keratinocytes, was inhibited by heparinoid treatment. The inhibitory effect of heparinoid on IL-1β mRNA expression was also confirmed with living skin equivalents. Our results demonstrated that heparinoid suppresses the initiation of keratinocyte-mediated skin inflammation.

Basic Fibroblast Growth Factor Influences Epidermal Homeostasis of Living Skin Equivalents through Affecting Fibroblast Phenotypes and Functions

AIMS

To elucidate the possible mechanisms of how basic fibroblast growth factor (bFGF) influences epidermal homeostasis in a living skin equivalent (LSE) model.

METHODS

Several wound healing-related growth factors were analyzed at protein and mRNA levels for dermal fibroblasts of induced alpha-smooth muscle actin (α-SMA)-positive or α-SMA-negative phenotypes. During culturing an LSE model by seeding normal human keratinocytes on a fibroblast-populated type I collagen gel, bFGF or neutralizing antibody for keratinocyte growth factor (KGF) was added to investigate its effects on fibroblast phenotypes and, subsequently, epidermal homeostasis by histology and immunohistochemistry.

RESULTS

The α-SMA-positive phenotype of fibroblasts induced by transforming growth factor beta-1 (TGF-β1) markedly suppressed the expression of KGF and hepatocyte growth factor (HGF), and slightly upregulated vascular endothelial growth factor (VEGF) and TGF-β1 at mRNA and protein levels, compared with α-SMA-negative fibroblasts treated with bFGF. α-SMA expression of fibroblasts at the epidermal-mesenchymal junction of the LSEs was suppressed by the addition of bFGF, and a better-differentiated epidermis was presented. The abrogation of KGF from fibroblasts by the addition of the KGF neutralizing antibody disenabled the LSE culturing system to develop an epidermis.

CONCLUSIONS

bFGF, through affecting the phenotypes and functions of fibroblasts, especially KGF expression, influenced epidermal homeostasis in an LSE model.

Epidermal keratinocytes sense dsRNA via the NLRP3 inflammasome, mediating interleukin (IL)-1β and IL-18 release

Skin epidermis, in addition to its barrier function, is able to actively sense harmful pathogens using pattern recognition receptors. In immune cells, the nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing 3 (NLRP3) inflammasome can mediate innate immunity against viral infection via a mechanism involving viral dsRNA recognition. Epidermal keratinocytes express NLRP3 inflammasome, which can sense contact sensitizers and mite allergens, leading to pro-interleukin (IL)-1β and pro-IL-18 cleavage into their active forms. Skin often faces viral infection. However, it is unknown whether viral dsRNA can be detected by the keratinocyte NLRP3 inflammasome. We transfected polyinosinic:polycytidylic acid (poly I:C), a synthetic viral dsRNA analogue, into cultured primary human keratinocytes at the aid of Lipofectamine 2000, and found that transfected poly I:C activated caspase-1 and induced caspase-1-dependent release of IL-1β and IL-18, which were suppressed on transfection with NLRP3 siRNA. The activation of keratinocyte NLRP3 inflammasome by transfected poly I:C was dependent on dsRNA-induced protein kinase (PKR) activation, and priming with type I interferons upregulated NLRP3 inflammasome activation through promoting PKR activation in poly I:C-transfected keratinocytes. In conclusion, the NLRP3 inflammasome can act as a sensor of dsRNA in epidermal keratinocytes, which may be important in both skin innate immune defense against viral infection and skin inflammation.

Fabrication of ultrasound-responsive microbubbles via coaxial electrohydrodynamic atomization for triggered release of tPA

A single-step fabrication method, coaxial electrohydrodynamic atomization (CEHDA), was developed to synthesize drug-loaded microbubbles (MBs) for combination treatment of ischemic stroke. The bioactivity of therapeutic agent (tPA, tissue plasminogen activator) after preparation was evaluated, showing that CEHDA could be very promising method for producing MBs with therapeutic functions. The bubble performance and tPA release profiles were also examined by exposing the bubbles to 2MHz ultrasound of various intensities. The results showed that the mean diameter of tPA-loaded MBs was found to fluctuate about its original diameter when exposed to ultrasound and higher intensity ultrasound was more effective in triggering the burst of CEHDA MBs. High ultrasound-triggered bubble disintegration effectiveness in a short period (first 5min) fits well with the requirement of short ultrasound exposure time for human brain. Moreover, a numerical model was also applied to investigate the stability of the fabricated MBs in the bloodstream. It was found that MB dissolution time increased with initial radius, decreased with initial surface tension and increased with initial shell resistance but it was barely affected by the average excessive bloodstream pressure.

Targeted gene delivery to the synovial pannus in antigen-induced arthritis by ultrasound-targeted microbubble destruction in vivo

The purpose of this study was to optimize an ultrasound-targeted microbubble destruction (UTMD) technique to improve the in vivo transfection efficiency of the gene encoding enhanced green fluorescent protein (EGFP) in the synovial pannus in an antigen-induced arthritis rabbit model. A mixture of microbubbles and plasmids was locally injected into the knee joints of an antigen-induced arthritis (AIA) rabbits. The plasmid concentrations and ultrasound conditions were varied in the experiments. We also tested local articular and intravenous injections. The rabbits were divided into five groups: (1) ultrasound+microbubbles+plasmid; (2) ultrasound+plasmid; (3) microbubble+plasmid; (4) plasmid only; (5) untreated controls. EGFP expression was observed by fluorescent microscope and immunohistochemical staining in the synovial pannus of each group. The optimal plasmid dosage and ultrasound parameter were determined based on the results of EGFP expression and the present and absent of tissue damage under light microscopy. The irradiation procedure was performed to observe the duration of the EGFP expression in the synovial pannus and other tissues and organs, as well as the damage to the normal cells. The optimal condition was determined to be a 1-MHz ultrasound pulse applied for 5 min with a power output of 2 W/cm(2) and a 20% duty cycle along with 300 μg of plasmid. Under these conditions, the synovial pannus showed significant EGFP expression without significant damage to the surrounding normal tissue. The EGFP expression induced by the local intra-articular injection was significantly more increased than that induced by the intravenous injection. The EGFP expression in the synovial pannus of the ultrasound+microbubbles+plasmid group was significantly higher than that of the other four groups (P<0.05). The expression peaked on day 5, remained detectable on day 40 and disappeared on day 60. No EGFP expression was detected in the other tissues and organs. The UTMD technique can significantly enhance the in vivo gene transfection efficiency without significant tissue damage in the synovial pannus of an AIA model. Thus, this could become a safe and effective non-viral gene transfection procedure for arthritis therapy.

Vesicular LL-37 contributes to inflammation of the lesional skin of palmoplantar pustulosis

“Pustulosis palmaris et plantaris”, or palmoplantar pustulosis (PPP), is a chronic pustular dermatitis characterized by intraepidermal palmoplantar pustules. Although early stage vesicles (preceding the pustular phase) formed in the acrosyringium contain the antimicrobial peptides cathelicidin (hCAP-18/LL-37) and dermcidin, the details of hCAP-18/LL-37 expression in such vesicles remain unclear. The principal aim of the present study was to clarify the manner of hCAP-18/LL-37 expression in PPP vesicles and to determine whether this material contributed to subsequent inflammation of lesional skin. PPP vesicle fluid (PPP-VF) induced the expression of mRNAs encoding IL-17C, IL-8, IL-1α, and IL-1β in living skin equivalents, but the level of only IL-8 mRNA decreased significantly upon stimulation of PPP vesicle with depletion of endogenous hCAP-18/LL-37 by affinity chromatography (dep-PPP-VF). Semi-quantitative dot-blot analysis revealed higher concentrations of hCAP-18/LL-37 in PPP-VF compared to healthy sweat (2.87±0.93 µM vs. 0.09±0.09 µM). This concentration of hCAP-18/LL-37 in PPP-VF could upregulate expression of IL-17C, IL-8, IL-1α, and IL-1β at both the mRNA and protein levels. Recombinant hCAP-18 was incubated with dep-PPP-VF. Proteinase 3, which converts hCAP-18 to the active form (LL-37), was present in PPP-VF. Histopathological and immunohistochemical examination revealed that early stage vesicles contained many mononuclear cells but no polymorphonuclear cells, and the mononuclear cells were CD68-positive. The epidermis surrounding the vesicle expresses monocyte chemotactic chemokine, CCL2. In conclusion, PPP-VF contains the proteinase required for LL-37 processing and also may directly upregulate IL-8 in lesional keratinocytes, in turn contributing to the subsequent inflammation of PPP lesional skin.

Effective gene transfer into central nervous system following ultrasound-microbubbles-induced opening of the blood-brain barrier

To investigate whether ultrasound-targeted microbubble destruction (UTMD) could transfer gene into central nervous system (CNS) following blood-brain barrier disruption (BBBD), DNA-loaded microbubbles were infused into the mice intravenously following ultrasonic exposure. Opening of the BBB, changes of mRNA and expression of enhanced green fluorescent protein (EGFP), and safety evaluation were measured. By UTMD, EGFP were substantially expressed in the cytoplasm of the neurons at the sonicated area with minor erythrocytes extravasation and the mRNA and expression of EGFP were markedly enhanced by about 15-fold and 10-fold, respectively, than that with US alone (p < 0.01). No EGFP was detected in the mice treated with DNA-loaded microbubbles or plasmid alone. The gene expression reached a climax at 48 h, gradually reduced to a much lower level thereafter. These results demonstrated UTMD could effectively enhance exogenous gene delivery and expression in CNS following BBBD, and this technique may provide a new method for CNS gene therapy.

Explorations of high-intensity therapeutic ultrasound and microbubble-mediated gene delivery in mouse liver

Ultrasound (US) combined with microbubbles (MBs) is a promising technology for non-viral gene delivery. Significant enhancements of gene expression have been obtained in our previous studies. To optimize and prepare for application to larger animal models, the luciferase reporter gene transfer efficacy of lipid-based Definity MBs of various concentrations, pressure amplitudes and a novel unfocused high-intensity therapeutic US (HITU) system were explored. Luciferase expression exhibited a dependence on MB dose over the range of 0-25 vol%, and a strong dependence on acoustic peak negative pressure at over the range of 0-3.2 MPa. Gene expression reached an apparent plateau at MB concentration ≥2.5 vol% or at negative pressures >1.8 MPa. Maximum gene expression in treated animals was 700-fold greater than in negative controls. Pulse train US exposure protocols produced an upward trend of gene expression with increasing quiescent time. The hyperbolic correlation of gene expression and transaminase levels suggested that an optimum gene delivery effect can be achieved by maximizing acoustic cavitation-induced enhancement of DNA uptake and minimizing unproductive tissue damage. This study validated the new HITU system equipped with an unfocused transducer with a larger footprint capable of scanning large tissue areas to effectively enhance gene transfer efficiencies.

Ultrasound-mediated gene delivery

IMPORTANCE OF THE FIELD

The use of ultrasound with microbubbles raises the possibility of an efficient and safe gene delivery.

AREAS COVERED IN THIS REVIEW

This review summarizes the current state of the art of gene delivery by sonoporation under the following topics. First, the basic ultrasound parameters and the characteristics of microbubble in biological systems are discussed. Second, the extensions of sonoporation to other fields of gene delivery such as viral and non-viral vector are briefly reviewed. Finally, recent applications in an animal model for various diseases are introduced.

WHAT THE READER WILL GAIN

Information and comments on gene delivery by sonoporation or enhanced cell membrane permeability by means of ultrasound.

TAKE HOME MESSAGE

Ultrasound-mediated gene delivery combined with microbubble agents provides significant safety advantages over other methods of local gene delivery.

Overview of drug delivery and alternative methods to electroporation

This chapter provides an overview of the application of electroporation to areas other than gene delivery. These areas include the delivery of drugs and vaccines to tissues and tumors as well as into and through the skin. Achievements and limitations of electroporation in these areas are presented. Alternative physical methods for gene and drug delivery besides electroporation are described. The advantages and drawbacks of electroporation, compared with these methods, are also discussed.

Preparation of microbubble suspensions by co-axial electrohydrodynamic atomization

In this paper we report a novel method, based on co-axial electrohydrodynamic jetting, for the preparation of microbubble suspensions containing bubbles <10 microm in size and having a narrow size distribution. No selective filtration is necessary and the suspensions are produced directly by the process. To demonstrate the method, glycerol was used as the liquid medium, flowing in the outer needle of the co-axial twin needle arrangement and undergoing electrohydrodynamic atomization in the stable cone-jet mode while air flowed through the inner needle at the same time. At zero applied voltage a hollow stream of liquid flowed from the outer needle. When the applied voltage was increased, eventually the hollow stream became a stable cone-jet and emitted a microthread of bubbles, which were collected in a container of glycerol to obtain microbubble suspensions. The size of the microbubbles was measured via optical microscopy and laser diffractometry. Several microbubble suspensions were prepared and characterised and the size distribution was found to be critically dependent on the ratio (n) of flow rates of liquid/air and, in particular the flow rate of the air. At n=1.5, with the flow rate of air set at approximately 1.7 microl/s, a microbubble suspension containing bubbles in the size range 2-8 microm was obtained.

New skin-equivalent model from de-epithelialized amnion membrane

The presence of pre-existing basement membrane (BM) components improves the morphogenesis of epidermis and BM in constructing a human living skin-equivalent (LSE). De-epithelialized amniotic membrane (AM) retains key BM components. We have therefore investigated the usefulness of AM for constructing LSE. De-epithelialized AM was overlaid on type I collagen gel embedded with fibroblasts. Normal human keratinocytes (NHKs) were then seeded onto the epithelial side of the AM to construct an AM-LSE. A conventional LSE was constructed by seeding NHKs on a fibroblast-populated type I collagen gel. When the keratinocytes reached confluence, the LSE was lifted to the air-liquid interface and cultured for up to 3 weeks. Samples were harvested at various times and investigated morphologically, immunohistochemically, and ultrastructurally. In AM-LSE, the epidermis was better stratified, with more compact, polarized, columnar basal cells, and the expression of differentiation and proliferation markers was more similar to that of normal human skin than was that of LSE without AM. A more continuous BM and better-developed hemidesmosomes were found in AM-LSE. The epidermis of AM-LSE outgrew much faster than that of LSE without AM. When transplanted onto nude mice, both LSEs took well; however, the AM-LSE graft showed better morphogenesis of the epidermis, BM, and hemidesmosomes. The better epidermal morphology and better-developed BM in AM-LSE in vitro and in vivo indicates its superiority over LSE without AM for clinical applications.

Transfection effect of microbubbles on cells in superposed ultrasound waves and behavior of cavitation bubble

The combination of ultrasound and ultrasound contrast agents (UCAs) is able to induce transient membrane permeability leading to direct delivery of exogenous molecules into cells. Cavitation bubbles are believed to be involved in the membrane permeability; however, the detailed mechanism is still unknown. In the present study, the effects of ultrasound and the UCAs, Optison on transfection in vitro for different medium heights and the related dynamic behaviors of cavitation bubbles were investigated. Cultured CHO-E cells mixed with reporter genes (luciferase or beta-gal plasmid DNA) and UCAs were exposed to 1 MHz ultrasound in 24-well plates. Ultrasound was applied from the bottom of the well and reflected at the free surface of the medium, resulting in the superposition of ultrasound waves within the well. Cells cultured on the bottom of 24-well plates were located near the first node (displacement node) of the incident ultrasound downstream. Transfection activity was a function determined with the height of the medium (wave traveling distance), as well as the concentration of UCAs and the exposure time was also determined with the concentration of UCAs and the exposure duration. Survival fraction was determined by MTT assay, also changes with these values in the reverse pattern compared with luciferase activity. With shallow medium height, high transfection efficacy and high survival fraction were obtained at a low concentration of UCAs. In addition, capillary waves and subsequent atomized particles became significant as the medium height decreased. These phenomena suggested cavitation bubbles were being generated in the medium. To determine the effect of UCAs on bubble generation, we repeated the experiments using crushed heat-treated Optison solution instead of the standard microbubble preparation. The transfection ratio and survival fraction showed no additional benefit when ultrasound was used. These results suggested that cavitation bubbles created by the collapse of UCAs were a key factor for transfection, and their intensities were enhanced by the interaction of the superpose ultrasound with the decreasing the height of the medium. Hypothesizing that free cavitation bubbles were generated from cavitation nuclei created by fragmented UCA shells, we carried out numerical analysis of a free spherical bubble motion in the field of ultrasound. Analyzing the interaction of the shock wave generated by a cavitation bubble and a cell membrane, we estimated the shock wave propagation distance that would induce cell membrane damage from the center of the cavitation bubble.