Stem Cell Cosmeceuticals

Introduction

Regenerative medicine is typically defined as a process of replacing or regenerating human cells, tissues and organs in order to restore or re-establish normal function. Regeneration of damaged tissues and organs can be achieved by stimulating and nursing the body's own repair mechanism to heal itself or by growing tissues and organs in the laboratory and safely implanting them. This technology can solve the problem of the shortage of organs available for donation, and the problem of organ transplantation rejection.

Use of stem cells is one of the most rapidly expanding fields of regenerative medicine, including regenerative medicine targeting skin regeneration. Skin regeneration has become the focus of the dermatological field as an aging population overexposed to sun, noninvasive treatment and topical products seeks treatment for reversal of wrinkles and the appearance of photo-aged skin ( ).

Aging of the skin, and in general, is influenced by both intrinsic and extrinsic factors. Intrinsic factors such as physiological, endocrine agents and genetic makeup are also better known as chronological aging. Extrinsic factors include environmental influences, such as air pollution, exposure to sun and ultraviolet (UV) rays, smoking, chemical exposure and poor nutrition ( ); skin aging that is a result of extrinsic factors is referred to as photoaging. Photoaging causes a decrease in epidermal thickness, degradation of collagen and deposition of altered elastic tissue, which shows as wrinkles, and yellow skin de-coloration ( ). In addition, photoaging leads to the production of free radicals, which in turn activate matrix metalloproteinases (MMPs), whose role is to degrade the extracellular matrix (ECM).

Clinically, youthful skin is characterized by smooth, unwrinkled appearance and even pigmentation, redness and radiance. In contrast, aged skin is thin, finely wrinkled with deep facial expression lines. Histologically, aged skin is characterized by thinned epidermis and dermis with flattening of the rete pegs at the dermo-epidermal junction, depolarization of keratinocytes and loss of collagen production in dermis.

The goal of stem cell based cosmeceutical products is to mitigate some of the effects of extrinsic factors while harnessing the potential of intrinsic ones.

Effective stem cell based cosmetics and cosmeceuticals must be able to preserve these growth factors while maintaining their effectiveness and allowing them to penetrate through the stratum corneum. They should also provide for visible improvement in skin appearance in a reasonably short time and without impacting the skin barrier ( ).

Some examples of stem cells uses in skin regeneration and rejuvenation include topical products that contain biologically active secretions of human adult or embryonic stem cells.

Types of stem cells and their source

Stem cells have the limitless ability to divide and proliferate in order to build, repair or regenerate tissue. Stem cells are distinguished from other cell types by two important abilities. The first ability is self-renewal – the ability to renew themselves even after long periods of inactivity. The second is potency, which is the cell's ability to differentiate into specific cells when induced by certain physiologic or experimental conditions. Each time a stem cell divides, it has the potential to either remain a stem cell or to become some specialized type of differentiated cell.

There are several types of stem cells based on their origin. The two main stem cell types are embryonic stem cells (hESCs) and adult stem cells (or somatic stem cells). Other types, such as induced pluripotent stem cells (iPSCs), are produced in the lab by reprogramming adult cells to express hESC characteristics.

Human embryonic stem cells are isolated from the inner cell mass of blastocysts of pre-implantation-stage embryos. These cells have the greatest capacity of becoming any cell type under the right growing conditions. Because the cells have the potential to form so many different adult tissues they are also called pluripotent (‘pluri’ = many, ‘potent’ = potentials) stem cells.

Adult or somatic or tissue-specific stem cells are specialized cells found in tissues of adults, children and fetuses. They are thought to exist in most of the body's tissues and organs. These cells are typically committed to becoming a cell from their tissue of origin, but they still have the broad ability to become any one of these cells. Stem cells of the bone marrow, for example, can give rise to any of the red or white cells of the blood system. Stem cells in the brain can form all the neurons and support cells of the brain, but cannot form nonbrain tissues. Unlike embryonic stem cells, researchers have not been able to grow adult stem cells indefinitely in the lab.

Different organs have different regeneration abilities and stem cell content. For example, colon stem cells regularly divide to repair and replace dead or damaged tissues. In other organs, however, such as the pancreas and the heart, stem cells only divide under special conditions.