Optimization of pre-transplantation conditions to enhance the efficacy of mesenchymal stem cells

Abstract

Mesenchymal stem cells (MSCs) are considered a potential tool for cell based regenerative therapy due to their immunomodulatory property, differentiation potentials, trophic activity as well as large donor pool. Poor engraftment and short term survival of transplanted MSCs are recognized as major limitations which were linked to early cellular ageing, loss of chemokine markers during ex vivo expansion, and hyper-immunogenicity to xeno-contaminated MSCs. These problems can be minimized by ex vivo expansion of MSCs in hypoxic culture condition using well defined or xeno-free media i.e., media supplemented with growth factors, human serum or platelet lysate. In addition to ex vivo expansion in hypoxic culture condition using well defined media, this review article describes the potentials of transient adaptation of expanded MSCs in autologous serum supplemented medium prior to transplantation for long term regenerative benefits. Such transient adaptation in autologous serum supplemented medium may help to increase chemokine receptor expression and tissue specific differentiation of ex vivo expanded MSCs, thus would provide long term regenerative benefits.

Keywords: Mesenchymal stem cell; allogeneic.; autologous; chemokine receptors; hyper-immunogenicity; xenogenic.

Figure 1

Steps to produce clinical grade MSCs for long term regenerative benefits. Isolation and expansion of MSCs in platelet lysate or pooled allogeneic AB-serum supplemented medium followed by adaptation in autologous serum (patients' own serum) supplemented medium. Hypoxic (2-5% oxygen) culture condition will be favourable for both the initial isolation and expansion later for adaptation , , , , .

Figure 2

Immune response to transplanted xeno-contaminated MSCs. N-glycolylneuraminic acid (Neu5Gc) in FBS contaminates MSCs during ex vivo expansion. Anti-Neu5Gc antibody present in human serum may bind to the xeno-contaminated MSCs following transplantation. As a result, natural killer (NK) cells may bind to the antibody coated cells through Fc-gamma receptors (FcγR) and cause lysis by antibody dependent cell mediated cytotoxicity (ADCC). Anti-Neu5Gc antibody may also activate complement-dependent cytotoxicity (CDC) and cause lysis through membrane attack complex.

Figure 3

Effect of culture media supplement on in vitro or ex vivo expansion of MSCs, and their suitability for clinical applications. FBS, allogeneic serum (pooled AB-serum), platelet lysate and autologous serum supplemented media support isolation and expansion of MSCs. Presence of xenoantigen in FBS make its use controversial. Although xeno-free media do not support isolation, they support further expansion of MSCs isolated in any serum supplemented media. MSCs expanded in xeno-free media and media supplemented with platelet lysate, pooled allogeneic AB-serum or autologous serum are considered appropriate for regenerative therapy as they are free from any xeno-contamination. Abbreviations are: MSC, Mesenchymal stem cells; FBS, fetal bovine serum. [↓= decrease; ↑= increase; ↓↑= regular/unchanged; ×=absent; √ = present; ?= controversial; NA= data not available]

Figure 4

Possible effects of adaptation of expanded MSCs in autologous serum supplemented media on engraftment and regenerative eficiency. A) Cytokines and other soluble factors present in the freshly prepared autologous serum may increase chemokine receptor (CCR) expression on MSCs. Microvesicles present in the serum may deliver chemokine receptors that might enhance chemotactic properties of incubated MSCs. Expression of chemokine receptors may facilitate tissue specific migration and further regenerative benefits. B) In addition, mRNA or miRNA packed in microvesicle may be delivered to MSCs during incubation that could aid in tissue specific differentiation. Upon transplantation, these tissue specific differentiated cells may produce microvesicles similar to the cells within the injured tissues. This may help tissue specific migration of circulatory progenitors or MSCs and enhance regenerative outcomes.