LoPresti, Samuel
(2019)
AGED MUSCLE ECM RECAPITULATES ALTERED HOST RESPONSE OBSERVED IN AGED MUSCLE INJURY.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
This is the latest version of this item.
Abstract
Extracellular matrix acts as the supporting structure of a tissue and dynamically changes in a reciprocal relationship with cells of that tissue. ECM changes with aging and disease and can affect the responses of cells in these altered states. ECM can be used as a model for aged microenvironments to more fully understand their effect on cellular function. The formation of advanced glycation end-products (AGEs) is a modification that occurs with age and causes aberrant inflammatory responses. Skeletal muscle strength and healing potential are known to decrease with aging. The immune response, which is integral to muscle regeneration, is also dysfunctional with age. Macrophage polarization has been shown to be necessary for appropriate skeletal muscle healing. This study used decellularized skeletal muscle ECM from young and aged mice to determine microenvironmental effects on macrophage phenotype both in vitro and in vivo using an abdominal wall injury reconstruction model.
The first objective of this work was to characterize muscle ECM from young and aged mice and to observe its effect on macrophage phenotype and function. Results showed the young and aged muscle were able to be effectively and similarly decellularized using previously established methods. The major change in biochemical composition was a decrease in hydroxyproline content and collagen immunohistochemical staining with aging. Bone marrow-derived macrophages treated with muscle ECM showed increases in iNOS immunolabeling and nitric oxide production with aged muscle ECM indicative of a shift to a pro-inflammatory phenotype.
The second objective of this work was to characterize the macrophage response to artificially glycated ECM. Young muscle ECM was artificially glycated with low and high concentrations of glucose, ribose or fructose. The macrophage response to glycated muscle ECM showed an increased nitric oxide production compared to young ECM. ECM glycation caused a pro-inflammatory phenotype from bone marrow-derived macrophages.
The third objective of this work was to characterize the in vivo host response to young, aged and glycated muscle ECM implanted into an abdominal muscle injury. The host response to aged and glycated ECM was characterized by reduced infiltration of host cells including F4/80+ macrophages and delayed or prevented activation of macrophage polarization markers iNOS and arginase-1. Glycation led to increased collagen staining and reduced fast:slow muscle fiber type ratio by 90 days. In vivo results suggest that aged ECM delays inflammatory cascades while glycated ECM inhibits macrophage activation overall.
Aging and glycation of the skeletal muscle ECM microenvironment had direct effects on the macrophage response in vitro and in vivo. These results suggest that the deficiencies observed in aged muscle regeneration could be due to changes in the extracellular matrix. This provides evidence for a cell-extrinsic mechanism of aging which is separate from known changes in stem cell function and population with age.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
24 January 2019 |
| Date Type: |
Publication |
| Defense Date: |
22 October 2018 |
| Approval Date: |
24 January 2019 |
| Submission Date: |
30 November 2018 |
| Access Restriction: |
1 year -- Restrict access to University of Pittsburgh for a period of 1 year. |
| Number of Pages: |
306 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Bioengineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
extracellular matrix, biomaterial, aging, macrophage polarization, glycation, muscle regeneration |
| Date Deposited: |
24 Jan 2020 06:00 |
| Last Modified: |
24 Jan 2020 06:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/35692 |
Available Versions of this Item
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AGED MUSCLE ECM RECAPITULATES ALTERED HOST RESPONSE OBSERVED IN AGED MUSCLE INJURY. (deposited 24 Jan 2020 06:00)
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