Biomaterials for Skin Repair and Regeneration

Elena Garcia-Gareta

• Publisher: Woodhead Publishing
• Year: 2019
• Print ISBN:
  9780081025468
• eBook ISBN:
  9780081025475
• Topic: Technology & Engineering
• Subtopic: Biotechnology in Medicine
• Index: Technology & Engineering

Biomaterials for Skin Repair and Regeneration examines a range of materials and technologies used for regenerating or repairing skin. With a strong focus on biomaterials and scaffolds, the book also examines the testing and evaluation pathway for human clinical trials. Beginning by introducing the fundamentals on skin tissue, the book goes on to describe contemporary technology used in skin repair as well as currently available biomaterials suitable for skin tissue repair and regeneration. Skin tissue engineering and the ideal requirements to take into account when developing skin biomaterials are discussed, followed by information on the individual materials used for skin repair and regeneration. As evaluation of biomaterials in animal models is mandatory before proceeding into human clinical trials, the book also examines the different animal models available. With a strong focus on materials, engineering, and application, this book is a valuable resource for materials scientists, skin biologists, and bioengineers with an interest in tissue engineering, regeneration, and repair of skin. - Provides an understanding of basic skin biology - Comprehensively examines a variety of biomaterial approaches - Looks at animal models for the evaluation of biomaterial-based skin constructs

Part One

Introduction

Outline

1. Skin biology

2. Skin repair technology

3. Skin tissue engineering

1

Skin biology

Magdalena Plotczyk, and Claire A. Higgins Department of Bioengineering, Imperial College London, London, United Kingdom

Abstract

The skin protects us from physical damage, bacterial invasion, and chemical hazards; guards against dehydration; and regulates our body temperature. In the case of injury, it is essential that the human body trigger a dynamic and complex wound healing response, which when successful leads to a full skin repair. Yet, human skin does not regenerate, meaning it cannot fully regain properties of uninjured skin. The development of advanced biomaterials presents new approaches to support skin repair and steer healing toward regeneration. In this chapter, we will cover the structure and function of various skin components, the mechanism of wound healing and its variable outcomes dependent on body site differences and developmental stages, as well as insight into how biomaterials can be used to target the skin and rewire the repair process.

Keywords

Extracellular matrix; Regeneration; Scar formation; Skin repair; Wound healing

1.1. Skin function

Indeed, one might say of modern man that he has an epidermis rather than a soul.

James Joyce [84].

The skin is a very important organ that not only covers and protects the internal organs, but also provides a unique personality trait to an individual. The color, age, and health of the integument, all play a role in social interactions and one's perception of self. Biologically, skin is one of the most complex structures and the body's largest organ. It encompasses a surface area of 1.5–2.0 m² and accounts for 16% of a person's total body weight (in comparison, bones make up around 15%) [1]. The skin forms a first-line protective barrier between the body and external environment. It regulates body temperature and prevents excessive loss of fluids via evaporation [2]. A variety of nerve endings located in the skin transmit pain, temperature, itch, and touch information to the central nervous system, allowing humans to interact with one other and their surrounding environment [3]. The complex skin structure is divided into three main anatomic and functional layers: epidermis on the surface forming the interface with the external environment, a middle dermal layer, and a deep fat layer also referred to as hypodermis or dermal white adipose tissue (Fig. 1.1(a)).

1.2. Skin layers

Pathologies that affect the integrity and functions of the skin are particularly detrimental to human health. Recent developments in the field of biomaterials bring hope for certain aspects of skin repair after injuries. However, to understand and control the mode of action of biomaterials, a detailed knowledge of skin architecture and the wound healing process is first required. In the sections below, we describe the main layers of the skin and their structural components.

1.2.1. Epidermis

Epidermis is the superficial skin layer formed by stratified squamous epithelium (Fig. 1.1(a)). Epidermal thickness ranges from 0.05 mm on eyelids to 1.55 mm on palms and soles (palmoplantar regions). It is divided into four sublayers across nearly all body sites: stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. In palmoplantar skin, the epidermis has an additional layer known as the stratum lucidum, which is located between the stratum granulosum and stratum corneum. The epidermis is comprised of multiple cell types, including keratinocytes, melanocytes, Langerhans cells, and Merkel cells (Fig. 1.1(a)).

Figure 1.1 Skin layers.(a) Epidermal layers populated with a range of cell populations. (b) The organization of skin layers (epidermis, dermis, hypodermis) and appendages; hair follicles with associated arrector pili muscle and sebaceous gland.

1.2.1.1. Keratinocytes

Approximately 90%–95% of cells in epidermis are keratinocytes, which arise from the superficial ectoderm during the first weeks of embryonic development [4]. In human skin, the epidermis is continuously shed and replaced by newly differentiated cells every 28 days. Due to this fast turnover, suprabasal keratinocytes in the epidermis are only transient. Therefore, in order to induce a long-term effect, instead of suprabasal cells, basal stem cells should be targeted by biomaterial-based approaches. These cells residing in stratum basale of the epidermis self-renew or differentiate to ensure maintenance of a constant number of cells in each layer. Extracellular matrix (ECM) proteins, including laminins, are deposited by cells residing in the basal layer to form the basement membrane, a thin acellular layer separating the epidermis from the dermis [5]. The interactions between laminins and their receptors, integrins, provide an anchor between epithelial cells and the membrane. Epidermal stratification (layering) has been proposed to result from weakening of the attachment between proliferating basal cells, their neighbors, and the basement membrane [6]. As a result, a cell is pushed out of the basal layer up into the stratum spinosum in a process referred to as delamination. Once epidermal cells leave the basal layer, they initiate differentiation as they migrate up through epidermal layers and produce diverse keratins along the way in a process known as keratinization. Keratins are the major structural proteins of the epidermis, which assemble into bundles of intermediate filaments that attach to desmosomes, intercellular structures responsible for cell-to-cell adhesion (Fig. 1.1(a)). The expression of distinct types of keratins (K5 and K14 in the basal layer, K1 and K10 in the suprabasal layers) is often used to ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• Introduction to biomaterials for skin repair and regeneration
• Part One. Introduction
• Part Two. Biomaterials for skin scaffolds
• Part Three. In vivo evaluation of new biomaterials for skin scaffolds
• Index