Title page for ETD etd-0503104-172949

Document Type thesis

Author Name Ahlfors, Jan-Eric Wilhelm

URN etd-0503104-172949

Title A Comparative Analysis of the Biomechanics and Biochemistry of Cell-Derived and Cell-Remodeled Matrices: Implications for Wound Healing and Regenerative Medicine

Degree MS

Department Biomedical Engineering

Advisors
Prof. Kristen Billiar, Advisor
Prof. Daniel Gibson, Co-Advisor
Prof. George Pins, Committee Member

Keywords
tension
failure strain
mechanics
fibroblasts
regenerative medicine
serum-free
UTS
proteoglycans
thickness
glycosaminoglycans
extensibility
collagen
wound-healing model
cell-remodeled matrix
cell-derived matrix
fibroblast-populated
collagen gel
biomechanical characterization
fibrin gel
strength
chemically-defined medium
growth factors
tissue growth
tissue regeneration
total protein content
human
tissue formation
biochemical characterization

Date of Presentation/Defense 2004-04-24

Availability unrestricted

Abstract
The purpose of this research was to study the synthesis and remodeling of extracellular matrix (ECM) by fibroblasts with special emphasis on the culture environment (media composition and initial ECM composition) and the resulting mechanical integrity of the ECM. This was investigated by culturing fibroblasts for 3 weeks in a variety of culture conditions consisting of collagen gels, fibrin gels, or media permissive to the self-production of ECM (Cell-Derived Matrix), and quantifying the mechanics of the resulting ECM. The mechanical characteristics were related to the biochemistry of the resulting ECM, notably in terms of collagen accumulation and collagen fibril diameters. The ultimate tensile strength (UTS) of the collagen gels and fibrin gels at the end of the 3-week period was 168.5 ± 43.1 kPa and 133.2 ± 10.6 kPa, respectively. The ultimate tensile strength of the cell-derived matrices was 223.2 ± 9 kPa, and up to 697.1 ± 36.1 kPa when cultured in a chemically-defined medium that was developed for the rapid growth of matrix in a more defined environment. Normalizing the strength to collagen density resulted in a UTS / Collagen Density in these groups of 6.4 ± 1.9 kPa/mg/cm3, 25.9 ± 2.4 kPa/mg/cm3, 14.5 ± 1.1 kPa/mg/cm3, and 40.0 ± 1.9 kPa/mg/cm3, respectively. Cells were synthetically more active when they produced their own matrix than when they were placed within gels. The resulting matrix was also significantly stronger when it was self-produced than when the cells rearranged the matrix within gels that corresponded to a significantly larger fraction of non-acid and pepsin extractable collagen. These studies indicate that cell-derived matrices have potential both as in vitro wound healing models and as soft connective tissue substitutes.

Files
Ahlfors.pdf

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Document Type	thesis
Author Name	Ahlfors, Jan-Eric Wilhelm
URN	etd-0503104-172949
Title	A Comparative Analysis of the Biomechanics and Biochemistry of Cell-Derived and Cell-Remodeled Matrices: Implications for Wound Healing and Regenerative Medicine
Degree	MS
Department	Biomedical Engineering
Advisors	Prof. Kristen Billiar, Advisor Prof. Daniel Gibson, Co-Advisor Prof. George Pins, Committee Member
Keywords	tension failure strain mechanics fibroblasts regenerative medicine serum-free UTS proteoglycans thickness glycosaminoglycans extensibility collagen wound-healing model cell-remodeled matrix cell-derived matrix fibroblast-populated collagen gel biomechanical characterization fibrin gel strength chemically-defined medium growth factors tissue growth tissue regeneration total protein content human tissue formation biochemical characterization
Date of Presentation/Defense	2004-04-24
Availability	unrestricted
Abstract The purpose of this research was to study the synthesis and remodeling of extracellular matrix (ECM) by fibroblasts with special emphasis on the culture environment (media composition and initial ECM composition) and the resulting mechanical integrity of the ECM. This was investigated by culturing fibroblasts for 3 weeks in a variety of culture conditions consisting of collagen gels, fibrin gels, or media permissive to the self-production of ECM (Cell-Derived Matrix), and quantifying the mechanics of the resulting ECM. The mechanical characteristics were related to the biochemistry of the resulting ECM, notably in terms of collagen accumulation and collagen fibril diameters. The ultimate tensile strength (UTS) of the collagen gels and fibrin gels at the end of the 3-week period was 168.5 ± 43.1 kPa and 133.2 ± 10.6 kPa, respectively. The ultimate tensile strength of the cell-derived matrices was 223.2 ± 9 kPa, and up to 697.1 ± 36.1 kPa when cultured in a chemically-defined medium that was developed for the rapid growth of matrix in a more defined environment. Normalizing the strength to collagen density resulted in a UTS / Collagen Density in these groups of 6.4 ± 1.9 kPa/mg/cm3, 25.9 ± 2.4 kPa/mg/cm3, 14.5 ± 1.1 kPa/mg/cm3, and 40.0 ± 1.9 kPa/mg/cm3, respectively. Cells were synthetically more active when they produced their own matrix than when they were placed within gels. The resulting matrix was also significantly stronger when it was self-produced than when the cells rearranged the matrix within gels that corresponded to a significantly larger fraction of non-acid and pepsin extractable collagen. These studies indicate that cell-derived matrices have potential both as in vitro wound healing models and as soft connective tissue substitutes.
Files	Ahlfors.pdf