PSP® production and safety

TECHNOLOGY / PSP® - a new skin nutrient

PSP® is obtained in a biotechnology derived process following stringent manufacturing procedures. A cell bank was established starting with a single skin biopsy of fetal skin tissue. The cell bank is stored frozen in liquid nitrogen and can be kept for many years, thereby providing a sustained supply of cells for PSP® production over decades.

The single skin tissue biopsy was obtained under informed consent in compliance with legal end ethical rules of the University Hospital of Lausanne in Switzerland. The skin sample was taken at the period of scarless wound healing. The biopsy was then transferred into a biotechnology facility for establishing a cell bank using standard cell culture techniques. The cell bank is composed of several hundred ampoules containing each several millions of cultured skin cells.

The cell bank testing included viral safety evaluation and characterization of cell substrates. It was performed in accordance with the requirements of Good Laboratory Practices for production of biotechnological/biological products. Besides the assessment of donor eligibility and serology testing at time of biopsy and after 3 months, this included a stringent testing for endogenous and adventitious agents in order to characterize the cell banks. Briefly, the cell banks were tested for human viruses, retroviruses, adventitious viral contaminants, sterility, mycoplasma as well as identity (Figure 1). The cell banks were shown to be free of viruses or viral adventitious agents, mycoplasma, bacteria or fungi.

Figure 1: Schematic overview of cell bank testing. PSP® (Processed Skin Cell Proteins) is obtained after cell lysis of cultured skin cells originating from this cell bank.

In order to produce PSP®, frozen cells from one or several ampoules of the Working Cell Bank are thawed, transferred into appropriate cell culture vessels and then expanded under standard cell culture condition respecting stringent manufacturing procedures. Thereby, cells from one Working Cell Bank ampoule are multiplied to yield several billion cells (Figure 2). These cells are then harvested, carefully washed and prepared for cell disruption. Cell disruption or lysis is realized by several freeze-thaw cycles and allows obtaining a mixture comprising skin cell proteins, called PSP® or ‘Processed Skin Cell Proteins’. Freeze-thawing is a relatively gentle process [22] and allows the production of a naturally balanced mixture of skin cell proteins present in the cells at the moment of cell disruption.

Figure 2: Schematic representation of PSP® production process by cell expansion in appropriate culture vessels (e.g. Cell Culture Flasks) starting with cells from one Working Cell Bank ampoule.

This process allows obtaining several billion cells, which are harvested and then freeze-thawed to finally obtain PSP®.

Dermatotoxicity studies showed that PSP® is well tolerated for external application in humans. A cumulative irritancy patch test during 21 days with 25 subjects and a repeated insult patch test with 200 subjects revealed that PSP® up to 0.5% is neither a contact irritant nor a contact allergen.

• PSP® production and safety