Serine Protease-Mediated Cutaneous Inflammation: Characterization of an Ex Vivo Skin Model for the Assessment of Dexamethasone-Loaded Core Multishell-Nanocarriers

Abstract

Standard experimental set-ups for the assessment of skin penetration are typically performed on skin explants with an intact skin barrier or after a partial mechanical or chemical perturbation of the stratum corneum, but they do not take into account biochemical changes. Among the various pathological alterations in inflamed skin, aberrant serine protease (SP) activity directly affects the biochemical environment in the superficial compartments, which interact with topically applied formulations. It further impacts the skin barrier structure and is a key regulator of inflammatory mediators. Herein, we used short-term cultures of ex vivo human skin treated with trypsin and plasmin as inflammatory stimuli to assess the penetration and biological effects of the anti-inflammatory drug dexamethasone (DXM), encapsulated in core multishell-nanocarriers (CMS-NC), when compared to a standard cream formulation. Despite a high interindividual variability, the combined pretreatment of the skin resulted in an average 2.5-fold increase of the transepidermal water loss and swelling of the epidermis, as assessed by optical coherence tomography, as well as in a moderate increase of a broad spectrum of proinflammatory mediators of clinical relevance. The topical application of DXM-loaded CMS-NC or DXM standard cream revealed an increased penetration into SP-treated skin when compared to untreated control skin with an intact barrier. Both formulations, however, delivered sufficient amounts of DXM to effectively suppress the production of interleukin-6 (IL-6), interleukin-8 (IL-8) and Thymic Stromal Lymphopoietin (TSLP). In conclusion, we suggest that the herein presented ex vivo inflammatory skin model is functional and could improve the selection of promising drug delivery strategies for anti-inflammatory compounds at early stages of development.

Topical Delivery of Rapamycin by Means of Microenvironment-Sensitive Core-Multi-Shell Nanocarriers: Assessment of Anti-Inflammatory Activity in an ex vivo Skin/T Cell Co-Culture Model

“… 41 , 42 For this reason, trypsin, a member of the SP family, was employed in the ex vivo skin model to reproduce some of the key features of inflammatory skin. 37 Here, to further characterize the effects of topically applied SP in the ex vivo skin model, we investigated the proteolytic effects of low concentrations (3 µg/cm 2 ) of SP towards skin barrier proteins. CDSN is part of corneodesmosomes and its degradation by skin proteases is central in the process of physiological desquamation.…”

Improved Skin Permeability after Topical Treatment with Serine Protease: Probing the Penetration of Rapamycin by Scanning Transmission X-ray Microscopy

“…Similar to previous work, this pretreatment was performed to model the enzymatic activity, cytokine environment, and barrier alteration typical of inflamed skin. 38 , 39 The samples were treated with a cotton swab for removing the formulation still sticking to the skin surface and subsequently prepared for STXM studies by fixation in 2.5% glutaraldehyde and 1% cacodylate buffer. Finally, they were embedded in EPON resin (Serva, Heidelberg, Germany) and cut into 200–300 nm slices with an area of typically 500 μm × 500 μm using an ultramicrotome, similar to previous work.…”

“…Trypsin applied in moderate concentrations capable of triggering inflammatory processes has been used as a stimulus in cell cultures to mimic enhanced serine protease activity, typically found in inflammatory skin diseases, such as atopic dermatitis. 38 , 39 It is also known that trypsin-like serine proteases in the SC are associated with desquamation. 40 These proteases are found to be more active in the outer SC than in the inner part of this skin layer.…”

“… 43 , 44 Recent work also highlights the increased drug penetration in serine protease pretreated ex vivo skin models with respect to the penetration of dexamethasone-loaded core-multishell nanocarriers. 39 …”

Automated Solvent‐Free Polymerization of Hyperbranched Polyglycerol with Tailored Molecular Weight by Online Torque Detection

“…Here, stimuli‐sensitive groups or cleaving points could be incorporated to degrade the polymer backbone or more complex architectures like PG based: micelles, hydrogels, nano capsules, or core–shell structures, in a controlled way, and transport and release the encapsulated therapeutic cargo at the target site. [ 15–19 ] Furthermore, PG was used as multivalent scaffold for applications like virus‐binding inhibition [ 20,21 ] and anti‐inflammatory therapy. [ 22 ] In the cosmetic industry PG was also applied as ingredient or used as precursor for surfactants and emulsifiers.…”