Secretory phospholipase A (sPLA) group of enzymes have been shown to hydrolyze phospholipids, among which sPLA Group V (GV) and Group X (GX) exhibit high selectivity towards phosphatidylcholine-rich cellular plasma membranes. The enzymes have recently emerged as key regulators in lipid droplets formation and it is hypothesized that sPLA-GV and GX enhanced cell proliferation and lipid droplet accumulation in colon cancer cells (HT29). In this study, cell viability and lipid droplet accumulation were assessed by Resazurin assay and Oil-Red-O staining. Interestingly, both sPLA-GV and GX enzymes reduced intracellular lipid droplet accumulation and did not significantly affect cell proliferation in HT29 cells. Incubation with varespladib, a pan-inhibitor of sPLA-Group IIA/V/X, further suppressed lipid droplets accumulation in sPLA-GV but have no effects in sPLA-GX-treated cells. Further studies using catalytically inactive sPLA enzymes showed that the enzymes intrinsic catalytic activity is required for the net reduction of lipid accumulation. Meanwhile, inhibition of intracellular phospholipases (iPLA-γ and cPLA-α) unexpectedly enhanced lipid droplet accumulation in both sPLA-GV and GX-treated cells. The findings suggested an interconnected relationship between extracellular and intracellular phospholipases in lipid cycling. Previous studies indicated that sPLA enzymes are linked to cancer development due to their ability to induce release of arachidonic acid and eicosanoids as well as the stimulation of lipid droplet formation. This study showed that the two enzymes work in a distinct manner and they neither confer proliferative advantage nor enhanced the net lipid droplet accumulation in HT29 cells.
Platelet-rich plasma (PRP) is a well-established biological product used in
the tissue engineering field to promote wound healing and tissue regeneration. PRP can
form platelet gel with the addition of thrombin and/or calcium salts. Nonetheless, PRP
is more commonly combined with biomaterial and cells for various tissue engineering
applications. Over the years, PRP has been used in the dermatology field for hair
follicle regeneration and wound healing, in the orthopaedic field for bone, muscle,
tendon, and ligament repair, and in dentistry for many dental procedures, including
dental implants. Despite the long historical use of PRP in the clinic, the PRP isolation
technique is still continuously changing, evolving, and improving to increase the
therapeutic effect of PRP. Nowadays, PRP is not only used as a biomaterial but it also
can be used to replace foetal bovine serum and human serum in primary cell culture,
especially for cell therapy purposes. PRP derivatives such as platelet lysate, platelet.derived growth factors, and platelet-derived extracellular vesicles also are precious
functional materials used clinically in the tissue engineering field. In this book chapter,
we review the different subclasses of PRP, including its derivatives, its research, and
clinical applications, and underline the challenges of PRP in clinical translations.
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