Platelet lysate as a substitute for animal serum for the ex-vivo expansion of mesenchymal stem/stromal cells: present and future

Abstract

The use of fetal bovine serum (FBS) as a cell culture supplement is discouraged by regulatory authorities to limit the risk of zoonoses and xenogeneic immune reactions in the transplanted host. Additionally, FBS production came under scrutiny due to animal welfare concerns. Platelet derivatives have been proposed as FBS substitutes for the ex-vivo expansion of mesenchymal stem/stromal cells (MSCs) since platelet-derived growth factors can promote MSC ex-vivo expansion. Platelet-derived growth factors are present in platelet lysate (PL) obtained after repeated freezing–thawing cycles of the platelet-rich plasma or by applying physiological stimuli such as thrombin or CaCl2.PL-expanded MSCs have been used already in the clinic, taking advantage of their faster proliferation compared with FBS-expanded preparations. Should PL be applied to other biopharmaceutical products, its demand is likely to increase dramatically. The use of fresh platelet units for the production of PL raises concerns due to limited availability of platelet donors. Expired units might represent an alternative, but further data are needed to define safety, including pathogen reduction, and functionality of the obtained PL. In addition, relevant questions concerning the definition of PL release criteria, including concentration ranges of specific growth factors in PL batches for various clinical indications, also need to be addressed. We are still far from a common definition of PL and standardized PL manufacture due to our limited knowledge of the mechanisms that mediate PL-promoting cell growth. Here, we concisely discuss aspects of PL as MSC culture supplement as a preliminary step towards an agreed definition of the required characteristics of PL for the requirements of manufacturers and users.

Comparison of human platelet lysate alternatives using expired and freshly isolated platelet concentrates for adipose-derived stromal cell expansion

“…Currently, the recommended shelf-life of PCs is 5 days, whereafter the expired PCs are routinely discarded. Expired PCs are therefore readily available and represent an attractive alternative for ASC expansion when compared to fresh PCs, which may be more expensive and difficult to obtain (19,37,38).…”

“…It has been suggested by Astori et al that certain release criteria should be considered prior to using pHPL (19). These criteria include the quality, composition, endotoxin levels and viral and bacterial safety of the pHPL product.…”

“…One PC unit is comprised of four buffy coat (BC) units (the white blood cell and platelet fraction obtained following centrifugation), and is resuspended in either one unit of platelet-rich plasma or another additive solution (22,23). Expired PCs, which are usually discarded by blood banks after 4 or 5 days, can also be used to manufacture HPL, although there are very few reports on the use of expired PC products for the expansion of ASCs (19,24). In this study, we have investigated the effects that different pHPL alternatives (fresh versus expired BCs resuspended in either platelet-rich plasma or an additive solution), produced using quality controlled manufacturing protocols, have on ASC proliferation, morphology and immunophenotype.…”

“…It has therefore been suggested that the choice of human alternative should be determined on the basis of the proposed downstream application of the ASCs (8,(15)(16)(17). Human platelet lysate (HPL) has been used in the past few years as an alternative to FBS for GMP-compliant ASC expansion and is being used in several clinical trials (3,15,18,19). Both autologous (recipient-derived) and allogeneic (donor-derived) HPL have been investigated for ASC expansion with favourable outcomes (20,21).…”

Fetal bovine serum (FBS): Past – present – future

“…Since the number of reports on successful applications of hPL is steadily increasing, paralleled by an increase in the description of hPL preparation methods, there is clearly a need to reach international consensus on the production, quality, and safety criteria of hPL (Astori et al, 2016;Burnouf et al, 2016). So far, the promotion of cell proliferation, the differentiation behavior of stem cells, and the cellular metabolic activity, which are documented in many published studies, are commonly agreed parameters to prove the superiority of hPL over FBS.…”