Author ORCID Identifier
0000-0002-8199-8006
Defense Date
2024
Document Type
Thesis
Degree Name
Doctor of Philosophy
Department
Physiology and Biophysics
First Advisor
Barbara D. Boyan, Ph.D.
Second Advisor
Henry J. Donahue, Ph.D.
Third Advisor
Zhao Lin, B.D.S., M.S., M.M.Sc., Ph.D.
Fourth Advisor
Montserrat Samso, Ph.D.
Fifth Advisor
Zvi Schwartz, D.M.D., Ph.D.
Abstract
Extracellular vesicles, of which there are many types, are a promising new cell-free, membrane-bound therapeutic in the field of regenerative medicine. Specific to the field of bone regeneration and repair are matrix vesicles, which are nano-sized extracellular vesicles released by mineralization-competent cells that become anchored in the extracellular matrix. Matrix vesicles are sites of initial calcium phosphate crystal deposition in the mineralization of the extracellular matrix during endochondral ossification and primary bone formation. They are involved in cellular signaling via small, non-coding microRNA in the growth plate, suggesting that they may play a similar role in bone. Previous research indicates that chondrocyte-derived matrix vesicles are enriched with microRNA and other cell signaling molecules, including lipids, proteins, and enzymes, that contribute to their ability to influence proliferation and differentiation of target cells; however, the role and mechanism of action of osteoblast-derived matrix vesicles remains to be elucidated. With this information, the biological functions in bone development and regeneration that matrix vesicles provide may translate into novel therapeutic potential for orthopedic pathologies, including critical size bone defects and fracture non-unions.
We hypothesize that matrix vesicles produced by osteoblast-lineage cells, as a specialized subset of extracellular vesicle, use their microRNA cargo to regulate osteoblast differentiation and bone regeneration. First, we determined the differences in physical and chemical characteristics between osteoblast-derived matrix vesicles and another class of extracellular vesicle, the exosome, in three different cellular models of osteoblast-lineage cells. Matrix vesicles and exosomes exhibited distinct size, protein, and microRNA enrichment that suggests they are different classes of extracellular vesicles. They also differed between cell types similarly to how matrix vesicles from chondrocytes at different maturation levels of the growth plate also differ from one another.
Next, we evaluated the role of matrix vesicles and exosomes in osteogenesis by determining their regulation of osteoblastic differentiation, osteoclast activation, and phenotypic commitment of macrophages. Matrix vesicles decreased osteoblastic differentiation in MG63 and MC3T3-E1 cells, whereas exosome-treated osteoblasts exhibited increases in some osteoblastic differentiation markers. Matrix vesicles and exosomes both decreased markers of osteoclast activation; only matrix vesicles exerted an effect on primary macrophages, promoting a pro-inflammatory phenotype. Each of these results suggest that matrix vesicles and exosomes play different roles in bone.
Then, we evaluated the mechanism of matrix vesicle uptake by osteoblast-like cells. Inhibiting different mechanisms of endocytosis, we found that both caveolae- and clathrin-mediated endocytosis are involved in the uptake of matrix vesicles in MG63 cells. This demonstrates the complex interaction between matrix vesicles and osteoblasts to exert their effect.
Finally, we established the effectiveness of a microRNA delivery system as the first step toward a matrix vesicle-derived therapeutic. Using carbohydrate-inspired nanoparticles, microRNA was effectively delivered into a primary articular chondrocyte model of osteoarthritis to mitigate the inflammatory environment.
Taken together, we identified the expansive characteristics of matrix vesicles demonstrating that they are a distinct class of extracellular vesicles, the role and mechanism of action they play in the coordinated effort to maintain bone homeostasis, and the viability to derive therapeutics from their microRNA cargo.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
1-20-2026