The role of platelets in skeletal muscle regeneration

Scully, David

September 2019

Thesis or dissertation

© 2019 David Scully. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.

Overview: Biomaterials such as autologous platelet-based applications have gained intense research interest. However, the mechanisms driving platelet‐mediated skeletal myogenesis remain to be established. Therefore, the aim of this thesis was to optimise and determine the role of platelet releasate for skeletal myogenesis in vitro, ex vivo and in vivo.

Methods: Skeletal and cardiac myoblast proliferation and differentiation in response to platelet releasate was assessed by means of proliferation assays, immunohistochemistry and gene expression. We expanded these in vitro findings on murine single muscle fibre stem cells ex vivo using protein expression profiles for key myogenic regulatory factors. Most importantly, we validated these findings on an in vivo model of acute muscle injury via cardiotoxin. Finally, platelet secretomes were studied with their effect on the skeletal muscle function of a murine model of thrombospondin-1 deficiency - a potent angiostatic and pro-inflammatory factor.

Results: Preparation of platelet releasate with TRAP6 and collagen had a more pronounced effect on myoblast proliferation versus thrombin and sonication (p<0.05). Additionally, platelet concentration positively correlated with myoblast and cardiomyocyte proliferation. Platelet releasate increased skeletal myoblast and muscle stem cell proliferation and differentiation in a dose‐dependent manner, which was mitigated by VEGFR and PDGFR inhibition. This inhibition ablated MyoD expression on proliferating muscle stem cells, compromising their commitment to differentiation (p<0.001). Platelet releasate was detrimental for myoblast fusion in a temporal manner. Most importantly, platelet releasate accelerates skeletal muscle regeneration in vivo after acute injury, and may reduce cellular senescence. Furthermore, we report for the first time that depletion of thrombospondin-1 from platelet releasate promotes more potent myoblast proliferation and skeletal muscle regeneration as compared to wild-type.

Conclusion: This study provides novel mechanistic insights on the role of platelet releasate in skeletal myogenesis and set the physiological basis for exploiting platelets as biomaterials in regenerative medicine.

Hull York Medical School, The University of Hull and The University of York
Matsakas, Antonios
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