The exercise-induced biochemical milieu enhances collagen content and tensile strength of engineered ligaments.
Exercise stimulates a dramatic change in the concentration of circulating hormones, such as growth hormone (GH), but the biological functions of this response are unclear. Pharmacological GH administration stimulates collagen synthesis; however, whether the post-exercise systemic milieu has a similar action is unknown. We aimed to determine whether the collagen content and tensile strength of tissue-engineered ligaments is enhanced by serum obtained post-exercise. Primary cells from a human anterior cruciate ligament (ACL) were used to engineer ligament constructs in vitro. Blood obtained from 12 healthy young men 15 min after resistance exercise contained GH concentrations that were ∼7-fold greater than resting serum (P < 0.001), whereas IGF-1 was not elevated at this time point (P = 0.21 vs. rest). Ligament constructs were treated for 7 days with medium supplemented with serum obtained at rest (RestTx) or 15 min post-exercise (ExTx), before tensile testing and collagen content analysis. Compared with RestTx, ExTx enhanced collagen content (+19%; 181 ± 33 vs. 215 ± 40 μg per construct P = 0.001) and ligament mechanical properties - maximal tensile load (+17%, P = 0.03 vs. RestTx) and ultimate tensile strength (+10%, P = 0.15 vs. RestTx). In a separate set of engineered ligaments, recombinant IGF-1, but not GH, enhanced collagen content and mechanics. Bioassays in 2D culture revealed that acute treatment with post-exercise serum activated mTORC1 and ERK1/2. In conclusion, the post-exercise biochemical milieu, but not recombinant GH, enhances collagen content and tensile strength of engineered ligaments, in association with mTORC1 and ERK1/2 activation.
Department of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA, 95616, USA.
Daniel W D
DW
West
Department of Biomedical Engineering, University of California Davis, One Shields Ave, Davis, CA, 95616, USA.
Ann
A
Lee-Barthel
Department of Biomedical Engineering, University of California Davis, One Shields Ave, Davis, CA, 95616, USA.
Todd
T
McIntyre
Department of Neurobiology, Physiology and Behaviour, University of California Davis, One Shields Ave, Davis, CA, 95616, USA.
Baubak
B
Shamim
Department of Orthopaedic Surgery, University of California Davis, One Shields Ave, Davis, CA, 95616, USA.
Cassandra A
CA
Lee
Department of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA, 95616, USA.|Department of Biomedical Engineering, University of California Davis, One Shields Ave, Davis, CA, 95616, USA.|Department of Neurobiology, Physiology and Behaviour, University of California Davis, One Shields Ave, Davis, CA, 95616, USA.
Keith
K
Baar
D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008022:Ligaments / Q000378:metabolism* / Q000502:physiology*; D020935:MAP Kinase Signaling System; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D013718:Tensile Strength; D023822:Tissue Engineering
D003094:Collagen; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes; D019869:Phosphatidylinositol 3-Kinases; D051899:Smad2 Protein; D051900:Smad3 Protein; D058570:TOR Serine-Threonine Kinases; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human