The neurotrophic potential of human platelet lysate substitution for fetal bovine serum in glial induction culture medium

Highlights

• Human platelet lysate, a xeno-free alternative to FBS, was used to create a glial induction culture medium (M-PLT).

• ASC in M-PLT express established glial markers (GFAP and S100) and secrete 2.4-fold more GDNF than SV cells.

• ASC and SV in M-PLT secrete ∼4.7-fold more GDNF than cells in control growth media containing FBS.

• M-PLT is rich in BDNF and can directly stimulate neurotrophic activity.

• Priming of ASC with M-PLT is advantageous for clinical neuronal regeneration applications.

Introduction

The primary role of the nervous system glial cells is to modulate neuronal cell functions. Glial cells are a heterogeneous population, including Schwann cells, that secrete neuronal growth (neurotrophic) factors, such as nerve growth factor (βNGF), glial cell-derived neurotrophic factor (GDNF), brain-derived growth factor (BDNF), and others, which can promote the survival and regeneration of neurons [1]. Another cell type, adipose derived stem cells (ASC), has also been shown to secrete neurotrophic factors including βNGF and BDNF [2]. Priming ASC by an in vitro exposure to a medium supplemented with fetal bovine serum (FBS) and a mixture of glial growth factors can promote a Schwann cell-like phenotype. This transition from ASC to a Schwann cell-like phenotype enhances the secretion of neurotrophic factors and, thereby, their neuroregenerative activity [3,4]. This neurotrophic activity of ASC suggests a therapeutic potential for neuronal regeneration.

However, these studies cannot be translated to clinical use because stimulating the secretion of neurotrophic factors of ASC relies on the addition of FBS. Developing a xeno-free culture system that stimulates the neurotrophic activity of human ASC will be beneficial. Human platelet lysate has been widely used by our institution and our group as a suitable substitute for FBS for the expansion of stromovascular (SV, the non-expanded cells derived from adipose tissue) and ASC [5,6]. The objective of this study was to modify an existing protocol for induction of Schwann cell-like differentiation of ASC [3] where FBS was replaced with human platelet lysate to assess the effect on the neurotrophic potential of ASC.

We compared the effects of FBS-containing (M-FBS) and xeno-free, platelet lysate enriched, induction media (M-PLT) on the expression of glial markers and the secretion of neurotrophic factors GDNF, BDNF, and βNGF. Cells in FBS-containing growth medium with no additional glial growth factors were used as controls (M-Ctrl). Adherent SV cells were also differentiated under the same three conditions, as SV cells have also been shown to accelerate peripheral nerve regeneration in animal models [7,8].