Structural and molecular characteristics of weight-bearing volar skin can be reconstituted by micro skin tissue column grafting.

For patients with lower limb amputations, prostheses are immensely helpful for mobility and the ability to perform job-related or recreational activities. However, the skin covering the amputation stump is typically transposed from adjacent areas of the leg and lacks the weight-bearing capacity that is only found in the specialized skin covering the palms and soles (a.k.a. volar skin). As a result, the skin tissue in direct contact with the prosthesis frequently breaks down, leading to the development of painful sores and other complications that limit, and often preclude, the use of prostheses. Transplanting volar skin onto amputation stumps could be a solution to these problems, but traditional skin transplantation techniques cause substantial morbidity at the donor site, such as pain and scarring, which are especially problematic for volar skin given the critical functional importance of the volar skin areas. We previously developed the technology to collect and engraft full-thickness skin tissue while avoiding long-term donor site morbidity, by harvesting the skin in the form of small (~0.5 mm diameter) cores that we termed "micro skin tissue columns" (MSTCs), so that each donor wound is small enough to heal quickly and without clinically appreciable scarring or other long-term abnormalities. The goal of this study was to establish whether a similar approach could be used to confer the structural and molecular characteristics of volar skin ectopically to other skin areas. In a human-to-mouse xenograft model, we show the long-term persistence of various human plantar MSTC-derived cell types in the murine recipient. Then in an autologous porcine model, we harvested MSTCs from the bottom of the foot and transplanted them onto excision wounds on the animals' trunks. The healing processes at both the donor and graft sites were monitored over 8 weeks, and tissue samples were taken to verify volar-specific characteristics by histology and immunohistochemistry. The volar donor sites were well-tolerated, healed rapidly, and showed no signs of scarring or any other long-term defects. The graft sites were able to maintain volar-specific histologic features and expression of characteristics protein markers, up to the 8-week duration of this study. These results suggest that MSTC grafting could be a practical approach to obtain autologous donor volar skin tissue, confer volar skin characteristics ectopically to nonvolar skin areas, improve the load-bearing capacity of amputation stump skin, and ultimately enhance mobility and quality-of-life for lower limb amputees.

Increased susceptibility to ischemia causes exacerbated response to microinjuries in the cirrhotic liver.

Fractional laser ablation is a technique developed in dermatology to induce remodeling of skin scars by creating a dense pattern of microinjuries. Despite remarkable clinical results, this technique has yet to be tested for scars in other tissues. As a first step toward determining the suitability of this technique, we aimed to (1) characterize the response to microinjuries in the healthy and cirrhotic liver, and (2) determine the underlying cause for any differences in response. Healthy and cirrhotic rats were treated with a fractional laser then euthanized from 0 h up to 14 days after treatment. Differential expression was assessed using RNAseq with a difference-in-differences model. Spatial maps of tissue oxygenation were acquired with hyperspectral imaging and disruptions in blood supply were assessed with tomato lectin perfusion. Healthy rats showed little damage beyond the initial microinjury and healed completely by 7 days without scarring. In cirrhotic rats, hepatocytes surrounding microinjury sites died 4-6 h after ablation, resulting in enlarged and heterogeneous zones of cell death. Hepatocytes near blood vessels were spared, particularly near the highly vascularized septa. Gene sets related to ischemia and angiogenesis were enriched at 4 h. Laser-treated regions had reduced oxygen saturation and broadly disrupted perfusion of nodule microvasculature, which matched the zones of cell death. Our results demonstrate that the cirrhotic liver has an exacerbated response to microinjuries and increased susceptibility to ischemia from microvascular damage, likely related to the vascular derangements that occur during cirrhosis development. Modifications to the fractional laser tool, such as using a femtosecond laser or reducing the spot size, may be able to prevent large disruptions of perfusion and enable further development of a laser-induced microinjury treatment for cirrhosis.

A practical device to produce consistent, controlled cryoinjury on the skin.

It has long been known that sensitivity to cold-induced damage can vary greatly between different cell types, with lethal temperatures reportedly ranging from -2 °C for canine osteocytes, to -70 °C for mammary adenocarcinomas. This suggests that, for certain applications, "therapeutic windows" may exist wherein the cryosurgery temperature could be controlled to specifically target more cold-sensitive cell types, while sparing less sensitive cells. However, this potential selectivity has not been developed into practical clinical treatments, in part because of a lack of available investigative tools that can provide consistent, reproducible cooling within the desired temperature range. Here we describe an experimental cryosurgery tool that allows user control over the three key cryosurgery parameters - temperature, pressure, and duration. The tool is composed of inexpensive components that are generally accessible in most laboratory settings, and could be a practical investigative tool for developing and optimizing novel topical cryosurgery approaches.

Local vasoregulative interventions impact drug concentrations in the skin after topical laser-assisted delivery.

INTRODUCTION: The ability of ablative fractional lasers (AFL) to enhance topical drug uptake is well established. After AFL delivery, however, drug clearance by local vasculature is poorly understood. Modifications in vascular clearance may enhance AFL-assisted drug concentrations and prolong drug dwell time in the skin. Aiming to assess the role and modifiability of vascular clearance after AFL-assisted delivery, this study examined the impact of vasoregulative interventions on AFL-assisted 5-fluorouracil (5-FU) concentrations in in vivo skin. METHODS: 5-FU uptake was assessed in intact and AFL-exposed skin in a live pig model. After fractional CO2 laser exposure (15 mJ/microbeam, 5% density), vasoregulative intervention using topical brimonidine cream, epinephrine solution, or pulsed dye laser (PDL) was performed in designated treatment areas, followed by a single 5% 5-FU cream application. At 0, 1, 4, 48, and 72 h, 5-FU concentrations were measured in 500 and 1500 µm skin layers by mass spectrometry (n = 6). A supplemental assessment of blood flow following AFL ± vasoregulation was performed using optical coherence tomography (OCT) in a human volunteer. RESULTS: Compared to intact skin, AFL facilitated a prompt peak in 5-FU delivery that remained elevated up to 4 hours (1500 µm: 1.5 vs. 31.8 ng/ml [1 hour, p = 0.002]; 5.3 vs. 14.5 ng/ml [4 hours, p = 0.039]). However, AFL's impact was transient, with 5-FU concentrations comparable to intact skin at later time points. Overall, vasoregulative intervention with brimonidine or PDL led to significantly higher peak 5-FU concentrations, prolonging the drug's dwell time in the skin versus AFL delivery alone. As such, brimonidine and PDL led to twofold higher 5-FU concentrations than AFL alone in both skin layers by 1 hour (e.g., 500 µm: 107 ng/ml [brimonidine]; 96.9 ng/ml [PDL], 46.6 ng/ml [AFL alone], p ≤ 0.024), and remained significantly elevated at 4 hours (p ≤ 0.024). A similar pattern was observed for epinephrine, although trends remained nonsignificant (p ≥ 0.09). Prolonged 5-FU delivery was provided by PDL, resulting in sustained drug deposition compared to AFL alone at both 48 and 72 hours in the superficial skin layer (p ≤ 0.024). Supporting drug delivery findings, OCT revealed that increases in local blood flow after AFL were mitigated in test areas also exposed to PDL, brimonidine, or epinephrine, with PDL providing the greatest, sustained reduction in flow over 48 hours. CONCLUSION: Vasoregulative intervention in conjunction with AFL-assisted delivery enhances and prolongs 5-FU deposition in in vivo skin.

Photobiomodulation Response From 660 nm is Different and More Durable Than That From 980 nm.

BACKGROUND AND OBJECTIVES: Photobiomodulation (PBM) therapy uses light at various wavelengths to stimulate wound healing, grow hair, relieve pain, and more-but there is no consensus about optimal wavelengths or dosimetry. PBM therapy works through putative, wavelength-dependent mechanisms including direct stimulation of mitochondrial respiration, and/or activation of transmembrane signaling channels by changes in water activity. A common wavelength used in the visible red spectrum is ~660 nm, whereas recently ~980 nm is being explored and both have been proposed to work via different mechanisms. We aimed to gain more insight into identifying treatment parameters and the putative mechanisms involved. STUDY DESIGN/MATERIALS AND METHODS: Fluence-response curves were measured in cultured keratinocytes and fibroblasts exposed to 660 or 980 nm from LED sources. Metabolic activity was assessed using the MTT assay for reductases. ATP production, a major event triggered by PBM therapy, was assessed using a luminescence assay. To measure the role of mitochondria, we used an ELISA to measure COX-1 and SDH-A protein levels. The respective contributions of cytochrome c oxidase and ATP synthase to the PBM effects were gauged using specific inhibitors. RESULTS: Keratinocytes and fibroblasts responded differently to exposures at 660 nm (red) and 980 nm (NIR). Although 980 nm required much lower fluence for cell stimulation, the resulting increase in ATP levels was short-term, whereas 660 nm stimulation elevated ATP levels for at least 24 hours. COX-1 protein levels were increased following 660 nm treatment but were unaffected by 980 nm. In fibroblasts, SDH-A levels were affected by both wavelengths, whereas in keratinocytes only 660 nm light impacted SDH-A levels. Inhibition of ATP synthase nearly completely abolished the effects of both wavelengths on ATP synthesis. Interestingly, inhibiting cytochrome c oxidase did not prevent the rise in ATP levels in response to PBM treatment. CONCLUSION: To the best of our knowledge, this is the first demonstration of differing kinetics in response to PBM therapy at red versus NIR wavelength. We also found cell-type-specific differences in PBM therapy response to the two wavelengths studied. These findings confirm that different response pathways are involved after 660 and 980 nm exposures and suggest that 660 nm causes a more durable response. © 2021 Wiley Periodicals LLC.

Construction and validation of UV-C decontamination cabinets for filtering facepiece respirators.

We present evidence-based design principles for three different UV-C based decontamination systems for N95 filtering facepiece respirators (FFRs) within the context of the SARS-CoV-2 outbreak of 2019-2020. The approaches used here were created with consideration for the needs of low- and middle-income countries (LMICs) and other under-resourced facilities. As such, a particular emphasis is placed on providing cost-effective solutions that can be implemented in short order using generally available components and subsystems. We discuss three optical designs for decontamination chambers, describe experiments verifying design parameters, validate the efficacy of the decontamination for two commonly used N95 FFRs (3M, #1860 and Gerson #1730), and run mechanical and filtration tests that support FFR reuse for at least five decontamination cycles.

Injectable slurry for selective destruction of neck adipose tissue in New Zealand obese mouse model.

PURPOSE: Increased neck circumference is a major risk factor for obstructive sleep apnea (OSA). New data suggest that increased adipose tissue in the neck may be a contributory cause of OSA. The aim of this study was to investigate safety and efficacy of a recently developed injectable ice slurry in selective reduction of neck adipose tissue in a mouse model. METHODS: We used the New Zealand obese mice that have increased volume of anterior neck fat, and are commonly used in OSA studies. MRI imaging was used to measure changes in fat tissue volume. RESULTS: Thirty animals were used in this study. Volumetric measurements in MRI images showed thatchanges in anterior neck adipose tissue volume from baseline in treated mice was significantly different in comparison with the control group (-1.09/kg ± 0.33/kg vs 0.68/kg ± 0.37/kg; p < 0.01 by two-tailed Student's t test). Histological analysis of samples from the treated area of the neck did not show scarring or damage to the surrounding tissues. CONCLUSIONS: Injection of ice slurry safely, effectively, and selectively reduces upper airway fat in New Zealand obese mice without scarring or damage to surrounding tissue. Our results suggest that slurry injection may be a novel and minimally invasive method of removing neck adipose tissue. This intervention should be further investigated to determine its suitability for treatment of OSA.

MIiSR: Molecular Interactions in Super-Resolution Imaging Enables the Analysis of Protein Interactions, Dynamics and Formation of Multi-protein Structures.

Our current understanding of the molecular mechanisms which regulate cellular processes such as vesicular trafficking has been enabled by conventional biochemical and microscopy techniques. However, these methods often obscure the heterogeneity of the cellular environment, thus precluding a quantitative assessment of the molecular interactions regulating these processes. Herein, we present Molecular Interactions in Super Resolution (MIiSR) software which provides quantitative analysis tools for use with super-resolution images. MIiSR combines multiple tools for analyzing intermolecular interactions, molecular clustering and image segmentation. These tools enable quantification, in the native environment of the cell, of molecular interactions and the formation of higher-order molecular complexes. The capabilities and limitations of these analytical tools are demonstrated using both modeled data and examples derived from the vesicular trafficking system, thereby providing an established and validated experimental workflow capable of quantitatively assessing molecular interactions and molecular complex formation within the heterogeneous environment of the cell.

Micro-fractional, directional skin tightening: A porcine model.

BACKGROUND AND OBJECTIVE: Skin changes are among the most visible signs of aging. Fractional ablative lasers improve skin quality by making small skin wounds that heal rapidly without scarring. While they improve skin texture and discoloration, there is minimal effect on skin laxity. This study was performed to assess skin shrinkage performed by removing multiple small full-thickness skin columns with coring needles combined with wound closure. MATERIALS AND METHODS: In 5 swine 116 squares (3 cm(2) ) were demarcated for treatment and control sites. In treatment sites 10% of the skin was removed by full-thickness skin coring needles (19 gauge) and afterwards closed and compressed with an elastic adhesive dressing. This procedure was compared to puncturing the skin with standard hypodermic needles (without tissue removal) and subsequent closure with compressive dressing. Area and shape of sites were measured before and 28 days after treatment. RESULTS: Test and control sites healed within a week without scarring. Coring with wound closure caused significant shrinkage after 28 days. The treated skin area was reduced by 9% (P < 0.0001) and the direction of shrinkage was influenced by the direction of wound closure. Coring without wound closure and puncturing the skin without tissue removal produced an insignificant 3% decrease in area. CONCLUSION: Significant minimally invasive skin tightening in a preferred direction can be achieved by removing skin with coring needles followed by wound closure. The direction of shrinkage is influenced by the direction of micro-hole closure, irrespective of the skin tension lines. This approach may allow reshaping the skin in a desired direction without scarring.

Pretreatment with ablative fractional laser changes kinetics and biodistribution of topical 5-aminolevulinic acid (ALA) and methyl aminolevulinate (MAL).

BACKGROUND AND OBJECTIVES: 5-Aminolevulinic acid (ALA) and methyl aminolevulinate (MAL) are porphyrin precursors used topically for photodynamic therapy (PDT). Previous studies have established that ablative fractional laser (AFXL) increases topical drug uptake. We evaluated kinetics and biodistribution of ALA- and MAL-induced porphyrins on intact and disrupted skin due to AFXL. MATERIALS AND METHODS: Two Yorkshire swine were exposed to CO2 AFXL (10.6 µm, 1,850 µm ablation depth) and subsequent topical application of ALA and MAL cream formulations (20%, weight/weight). Porphyrin fluorescence was quantified by digital fluorescence photography (30, 90, and 180 minutes) and fluorescence microscopy at specific skin depths (180 minutes). RESULTS: Porphyrins gradually formed over time, differently on intact and AFXL-disrupted skin. On intact skin (no AFXL), fluorescence photography showed that MAL initially induced higher fluorescence than ALA (t = 30 minutes MAL 21.1 vs. ALA 7.7 au, t = 90 minutes MAL 39.0 vs. ALA 26.6 (P < 0.009)) but reached similar intensities for long-term applications (t = 180 minutes MAL 56.6 vs. ALA 52 au, P = ns). AFXL considerably enhanced porphyrin fluorescence from both photosensitizers (P < 0.05). On AFXL-exposed skin, MAL expressed higher fluorescence than ALA for short-term application (t = 30 minutes, AFXL-MAL 26.4 vs. AFXL-ALA 14.1 au, P < 0.001), whereas ALA over time overcame MAL and induced the highest fluorescence intensities obtained (t = 180 minutes, AFXL-MAL 98.6 vs. AFXL-ALA 112.0 au, P < 0.001). In deep skin layers, fluorescence microscopy showed higher fluorescence in hair follicle epithelium for ALA than MAL (t = 180 minutes, 1.8 mm, AFXL-MAL 35.3 vs. AFXL-ALA 46.7 au, P < 0.05). CONCLUSIONS: AFXL changes kinetics and biodistribution of ALA and MAL. It appears that AFXL-ALA favors targeting deep structures.

The Yucatan miniature swine as a model for post-inflammatory hyperpigmentation.

Post-inflammatory hyperpigmentation (PIH) is a hypermelanosis that often occurs secondary to skin irritation or injury, especially in darker skin tones, for which there is currently a lack of effective treatment options. Few preclinical models are available to study PIH. Here, we show that the Yucatan miniature pig consistently develops PIH after skin injuries. Skin wounds were produced on Yucatan pigs by needle punches, full-thickness excisions, or burns. Wound sites were monitored and photographed regularly. Tissue samples were collected after 24 weeks and processed for histology/immunohistochemistry. Skin pigmentation and histologic changes were quantified by computer-assisted image analyses. All injury methods resulted in hyperpigmentation. Melanin content at the histologic level was quantified in the larger (burn and excision) wounds, showing a significant increase compared to uninjured skin. Increased melanin was found for both epidermal and dermal regions. Dermal melanin deposits were primarily clustered around the papillary vasculature, and were associated not with melanocytes but with leukocytes. The Yucatan miniature pig model recapitulates key clinical and histologic features of PIH in humans, including skin hyperpigmentation at both gross and histologic levels, and persistence of dermal melanin subsequent to injury. This model could be used to further our understanding of the etiology of PIH, and for new therapy development.

Analysis of culture and RNA isolation methods for precision-cut liver slices from cirrhotic rats.

Precision-cut liver slices (PCLS) are increasingly used as a model to investigate anti-fibrotic therapies. However, many studies use PCLS from healthy animals treated with pro-fibrotic stimuli in culture, which reflects only the early stages of fibrosis. The effects of different culture conditions on PCLS from cirrhotic animals has not been well characterized and there is no consensus on optimal methods. In this study, we report a method for the collection and culture of cirrhotic PCLS and compare the effect of common culture conditions on viability, function, and gene expression. Additionally, we compared three methods of RNA isolation and identified a protocol with high yield and purity. We observed significantly increased albumin production when cultured with insulin-transferrin-selenium and dexamethasone, and when incubated on a rocking platform. Culturing with insulin-transferrin-selenium and dexamethasone maintained gene expression closer to the levels in fresh slices. However, despite stable viability and function up to 4 days, we found significant changes in expression of key genes by day 2. Interestingly, we also observed that cirrhotic PCLS maintain viability in culture longer than slices from healthy animals. Due to the influence of matrix stiffness on fibrosis and hepatocellular function, it is important to evaluate prospective anti-fibrotic therapies in a platform that preserves tissue biomechanics. PCLS from cirrhotic animals represent a promising tool for the development of treatments for chronic liver disease.

Plantar Skin Exhibits Altered Physiology, Constitutive Activation of Wound-Associated Phenotypes, and Inherently Delayed Healing.

Wound research has typically been performed without regard for where the wounds are located on the body, despite well-known heterogeneities in physical and biological properties between different skin areas. The skin covering the palms and soles is highly specialized, and plantar ulcers are one of the most challenging and costly wound types to manage. Using primarily the porcine model, we show that plantar skin is molecularly and functionally more distinct from nonplantar skin than previously recognized, with unique gene and protein expression profiles, broad alterations in cellular functions, constitutive activation of many wound-associated phenotypes, and inherently delayed healing. This unusual physiology is likely to play a significant but underappreciated role in the pathogenesis of plantar ulcers as well as the last 25+ years of futility in therapy development efforts. By revealing this critical yet unrecognized pitfall, we hope to contribute to the development of more effective therapies for these devastating nonhealing wounds.

The case for considering volar skin in a "separate status" for wound healing.

Foot ulcers, particularly in the diabetic setting, are a major medical and socioeconomic challenge. While the effects of diabetes and its various sequelae have been extensively studied, in the wound field it is commonly assumed that the wound healing process is essentially identical between different skin types, despite the many well-known specializations in palmoplantar skin, most of which are presumed to be evolutionary adaptations for weightbearing. This article will examine how these specializations could alter the wound healing trajectory and contribute to the pathology of foot ulcers.

Antimicrobial blue light as a biofilm management therapy at the skin-implant interface in an ex vivo percutaneous osseointegrated implant model.

Biofilm contamination is often present at the skin-implant interface of transfemoral osseointegrated implants leading to frequent infection, irritation, and discomfort. New biofilm management regimens are needed as the current standard of washing the site with soap and water is inadequate to manage infection rates. We investigated the potential of antimicrobial blue light, which has reduced risk of resistance development and broad antimicrobial mechanisms. Our lab developed an antimicrobial blue light (aBL) device uniquely designed for an ex vivo system based on an established ovine osseointegrated (OI) implant model with Staphylococcus aureus ATCC 6538 biofilms as initial inocula. Samples were irradiated with aBL or washed for three consecutive days after which they were quantified. Colony-forming unit (CFU) counts were compared with a control group (bacterial inocula without treatment). After 1 day, aBL administered as a single 6 h dose or two 1 h doses spaced 6 h apart both reduced the CFU count by 1.63 log10 ± 0.02 CFU. Over 3 days of treatment, a positive aBL trend was observed with a maximum reduction of ~2.7 log10 CFU following 6 h of treatment, indicating a relation between multiple days of irradiation and greater CFU reductions. aBL was more effective at reducing the biofilm burden at the skin-implant interface compared with the wash group, demonstrating the potential of aBL as a biofilm management option.

Boot camp: Training and dressing regimens for modeling plantar wounds in the swine.

Foot ulceration annually affects millions of patients and accounts for billions of dollars in medical expenses in the US alone. Many previous studies have investigated co-morbidities associated with impaired healing, such as microbial infection, compromised circulation, and diabetes. By comparison, little is known about how wound healing proceeds in plantar skin, despite its many unique specializations related to its load-bearing function. One of the main challenges in modeling plantar wounds is the difficulty in maintaining wound dressings, as animals generally have a low tolerance to wearing bandages on their feet. With assistance from the MGH Center for Comparative Medicine, we developed a positive reinforcement-based behavioral training regimen that successfully induced tolerance for plantar dressings in swine, which is a critical first step towards enabling in vivo study of the wound healing process in this highly specialized skin area. This training program will be described in detail in this manuscript.

Comparison of Staphylococcus aureus tolerance between antimicrobial blue light, levofloxacin, and rifampin.

Background: Bacterial biofilms readily develop on all medical implants, including percutaneous osseointegrated (OI) implants. With the growing rate of antibiotic resistance, exploring alternative options for managing biofilm-related infections is necessary. Antimicrobial blue light (aBL) is a unique therapy that can potentially manage biofilm-related infections at the skin-implant interface of OI implants. Antibiotics are known to have antimicrobial efficacy disparities between the planktonic and biofilm bacterial phenotypes, but it is unknown if this characteristic also pertains to aBL. In response, we developed experiments to explore this aspect of aBL therapy. Methods: We determined minimum bactericidal concentrations (MBCs) and antibiofilm efficacies for aBL, levofloxacin, and rifampin against Staphylococcus aureus ATCC 6538 planktonic and biofilm bacteria. Using student t-tests (p < 0.05), we compared the efficacy profiles between the planktonic and biofilm states for the three independent treatments and a levofloxacin + rifampin combination. Additionally, we compared antimicrobial efficacy patterns for levofloxacin and aBL against biofilms as dosages increased. Results: aBL had the most significant efficacy disparity between the planktonic and biofilm phenotypes (a 2.5 log10 unit difference). However, further testing against biofilms revealed that aBL had a positive correlation between increasing efficacy and exposure time, while levofloxacin encountered a plateau. While aBL efficacy was affected the most by the biofilm phenotype, its antimicrobial efficacy did not reach a maximum. Discussion/conclusion: We determined that phenotype is an important characteristic to consider when determining aBL parameters for treating OI implant infections. Future research would benefit from expanding these findings against clinical S. aureus isolates and other bacterial strains, as well as the safety of long aBL exposures on human cells.

An antimicrobial blue light device to manage infection at the skin-implant interface of percutaneous osseointegrated implants.

Antimicrobial blue light (aBL) is an attractive option for managing biofilm burden at the skin-implant interface of percutaneous osseointegrated (OI) implants. However, marketed aBL devices have both structural and optical limitations that prevent them from being used in an OI implant environment. They must be handheld, preventing even irradiation of the entire skin-implant interface, and the devices do not offer sufficient optical power outputs required to kill biofilms. We present the developmental process of a unique aBL device that overcomes these limitations. Four prototypes are detailed, each being a progressive improvement from the previous iteration as we move from proof-of-concept to in vivo application. Design features focused on a cooling system, LED orientation, modularity, and "sheep-proofing". The final prototype was tested in an in vivo OI implant sheep model, demonstrating that it was structurally and optically adequate to address biofilm burdens at the skin-implant of percutaneous OI implants. The device made it possible to test aBL in the unique OI implant environment and compare its efficacy to clinical antibiotics-data which had not before been achievable. It has provided insight into whether or not continued pursual of light therapy research for OI implants, and other percutaneous devices, is worthwhile. However, the device has drawbacks concerning the cooling system, complexity, and size if it is to be translated to human clinical trials. Overall, we successfully developed a device to test aBL therapy for patients with OI implants and helped progress understanding in the field of infection management strategies.

Amyloid and Alzheimer's disease: inside and out.

Alzheimer's disease (AD) is poised to become the most serious healthcare issue of our generation. The leading theory of AD pathophysiology is the Amyloid Cascade Hypothesis, and clinical trials are now proceeding based on this hypothesis. Here, we review the original evidence for the Amyloid Hypothesis, which was originally focused on the extracellular deposition of beta amyloid peptides (Aß) in large fibrillar aggregates, as well as how this theory has been extended in recent years to focus on highly toxic small soluble amyloid oligomers. We will also examine emerging evidence that Aß may actually begin to accumulate intracellularly in lysosomes, and the role for intracellular Aß and lysosomal dysfunction may play in AD pathophysiology. Finally, we will review the clinical implications of these findings.

Fractional laser-assisted delivery of methyl aminolevulinate: Impact of laser channel depth and incubation time.

BACKGROUND AND OBJECTIVES: Pretreatment of skin with ablative fractional lasers (AFXL) enhances the uptake of topical photosensitizers used in photodynamic therapy (PDT). Distribution of photosensitizer into skin layers may depend on depth of laser channels and incubation time. This study evaluates whether depth of intradermal laser channels and incubation time may affect AFXL-assisted delivery of methyl aminolevulinate (MAL). MATERIALS AND METHODS: Yorkshire swine were treated with CO2 AFXL at energy levels of 37, 190, and 380 mJ/laser channel and subsequent application of MAL cream (Metvix) for 30, 60, 120, and 180 minutes incubation time. Fluorescence photography and fluorescence microscopy quantified MAL-induced porphyrin fluorescence (PpIX) at the skin surface and at five specific skin depths (120, 500, 1,000, 1,500, and 1,800 µm). RESULTS: Laser channels penetrated into superficial (∼300 µm), mid (∼1,400 µm), and deep dermis/upper subcutaneous fat layer (∼2,100 µm). Similar fluorescence intensities were induced at the skin surface and throughout skin layers independent of laser channel depth (180 minutes; P < 0.19). AFXL accelerated PpIX fluorescence from skin surface to deep dermis. After laser exposure and 60 minutes MAL incubation, surface fluorescence was significantly higher compared to intact, not laser-exposed skin at 180 minutes (AFXL-MAL 60 minutes vs. MAL 180 minutes, 69.16 a.u. vs. 23.49 a.u.; P < 0.01). Through all skin layers (120-1,800 µm), laser exposure and 120 minutes MAL incubation induced significantly higher fluorescence intensities in HF and dermis than non-laser exposed sites at 180 minutes (1,800 µm, AFXL-MAL 120 minutes vs. MAL 180 minutes, HF 14.76 a.u. vs. 6.69 a.u. and dermis 6.98 a.u. vs. 5.87 a.u.; P < 0.01). CONCLUSIONS: AFXL pretreatment accelerates PpIX accumulation, but intradermal depth of laser channels does not affect porphyrin accumulation. Further studies are required to examine these findings in clinical trials.