Bioengineering the microanatomy of human skin.

Mathilde Roger,Steven Bradbury,Teresa Dicolandrea,Nicola Fullard,Pamela Ritchie,Nicole Darling,Robert Isfort,Arto Määttä,Iakowos Karakesisoglou,Thomas Von Zglinicki,Charles Bascom,Steven O'Reilly,Ewa Markiewicz,Stefan Przyborski,Glyn Nelson,Lydia Costello

doi:10.1111/joa.12942

Abstract

Recreating the structure of human tissues in the laboratory is valuable for fundamental research, testing interventions, and reducing the use of animals. Critical to the use of such technology is the ability to produce tissue models that accurately reproduce the microanatomy of the native tissue. Current artificial cell‐based skin systems lack thorough characterisation, are not representative of human skin, and can show variation. In this study, we have developed a novel full thickness model of human skin comprised of epidermal and dermal compartments. Using an inert porous scaffold, we created a dermal construct using human fibroblasts that secrete their own extracellular matrix proteins, which avoids the use of animal‐derived materials. The dermal construct acts as a foundation upon which epidermal keratinocytes were seeded and differentiated into a stratified keratinised epithelium. In‐depth morphological analyses of the model demonstrated very close similarities with native human skin. Extensive immunostaining and electron microscopy analysis revealed ultrastructural details such as keratohyalin granules and lamellar bodies within the stratum granulosum, specialised junctional complexes, and the presence of a basal lamina. These features reflect the functional characteristics and barrier properties of the skin equivalent. Robustness and reproducibility of in vitro models are important attributes in experimental practice, and we demonstrate the consistency of the skin construct between different users. In summary, a new model of full thickness human skin has been developed that possesses microanatomical features reminiscent of native tissue. This skin model platform will be of significant interest to scientists researching the structure and function of human skin.

Highlights

The skin is the largest organ of the human body, accounting for approximately 16% of the total body weight
From day 14, the organisation was similar to the epidermis of human skin
Electron-dense hemidesmosome-like junctional complexes were observed on the basolateral surface of the basal keratinocytes at the interface with the collagen-coated membrane, and they were evenly distributed along the entire length of the membrane

Summary

Introduction

The skin is the largest organ of the human body, accounting for approximately 16% of the total body weight. The basal layer rests upon a basement membrane at the dermoepidermal junction It consists of mitotically active columnar cells which proliferate, migrate superficially, and sequentially differentiate to form the stratified epidermis. The basal layer is characterised by the expression of keratin 14, and the daughter keratinocytes undergo a characteristic basal-to-suprabasal switch from keratin 5/14 to keratin 1/10 as they move up the strata As these cells move towards the surface and differentiate into the spinous layer, they lose their ability to divide, become larger, and establish robust intercellular connections. Keratinocytes are terminally differentiated into corneocytes, which make up the stratum corneum During this transition, cells lose their nuclei and major organelles, lipids are released into the intercellular space and the cornified envelope replaces the cell membrane. The barrier function of the skin is mainly attributed to the stratum corneum, which is a 10- to 20-lmthick layer composed of terminally differentiated, flattened corneocytes separated by layers of densely packed lipids (Menon et al 2012)

Methods

Results

Conclusion