Abstract
Platelet lysates (PL) contain a selection of proteins and growth factors (GFs) that are known to mediate cell activity. Many of these biomolecules have been identified as chemoattractants with the capacity to induce cell migration. In order to effectively deliver and retain these biomolecules to the site of injury, a scaffold containing PL could be an option. We use poly(ethylene glycol) (PEG) hydrogels consisting of 90 vol % PL to investigate their migratory potential on human mesenchymal stem cells (hMSCs). Cells exposed to these hydrogels were tracked, resulting in cell trajectories and detailed migratory parameters (velocity, Euclidean distance, directness, and forward migration index). Volumetric swelling ratios, hydrogel mechanical properties, and the release kinetics of proteins and GFs from hydrogels were also assessed. Furthermore, hMSC spheroids were encapsulated within the hydrogels to qualitatively assess cell invasion by means of sprouting and disintegration of the spheroid. Cell spheroids encapsulated within the PL-PEG gels exhibited initial outgrowths and eventually colonized the 3D matrix successfully. Results from this study confirmed that hMSCs exhibit directional migration toward the PL-loaded hydrogel with increased velocity and directness, compared to the controls. Overall, the incorporation of PL renders the PEG hydrogel bioactive. This study demonstrates the capacity of PL-loaded hydrogel constructs to attract stem cells for endogenous tissue engineering purposes.
Highlights
The advancement of regenerative treatments into viable clinical applications is largely limited by the expensive and time-consuming processes of cell isolation and expansion.[1]
The present study demonstrated that biomolecules released from the platelet lysates (PL)-loaded poly(ethylene glycol) (PEG) hydrogel scaffolds are capable of inducing directional migration of human mesenchymal stem cells (hMSCs)
While it remains unclear which growth factors (GFs) contributed to the cell migration, platelet-derived GFs (PDGFs)-BB in particular is a likely candidate due to the high amounts released from the hydrogel and its previously known chemotactic capacity
Summary
The advancement of regenerative treatments into viable clinical applications is largely limited by the expensive and time-consuming processes of cell isolation and expansion.[1]. While PL has been widely studied to replace fetal bovine serum (FBS) for cell culture,[7,8] the myriad of GFs within PL has purpose to promote endogenous regeneration as well.[4,9] Among these GFs, platelet-derived GFs (PDGFs) and vascular endothelial GFs (VEGFs) are important regulators of chemotaxis and angiogenesis during wound healing.[10−12] stromal cell-derived factor-1 (SDF-1α/CXCL12) has widely been recognized as a potent inducer of stem cell migration.[10,13−15] While the use of platelet-derived products has shown some positive clinical outcomes, the poor characterization, low mechanical competence, and burst release of bioactive molecules from plateletderived biomaterials have limited their clinical translation.[5,16]
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