Publication Date



Open access

Degree Type


Degree Name

Master of Science (MS)


Biomedical Engineering (Engineering)

Date of Defense


First Committee Member

Fotios Andreopoulos - Committee Member

Second Committee Member

Herman S. Cheung - Mentor

Third Committee Member

Charles C.-Y. Huang - Outside Committee Member


Articular cartilage lines the surfaces of load bearing joints and has limited capabilities for self-repair due to its alymphatic and avascular structure. Attempts at making repairs to this tissue has resulted in substandard materials and/or causing further injury to the patient making this tissue a prime candidate for tissue engineering studies incorporating adult stem cells. These studies have given rise to some answers and many more questions including a search for alternative stem cell sources and what biochemical changes the cells undergo during the differentiation of these stem cells into chondrocytes, the cells which make up articular cartilage. Recently, periodontal dental ligament stem cells (PDLs) have come to the forefront as a practical alternative to other adult stem cells as well as the involvement of the mitogen-activated protein kinases (MAPKs) in stem cell differentiation via mechanical stimulation. During dynamic unconfined compression, levels of p42/44 MAPK increased by 50% (p<0.05). Additionally, the expression of the chondrogenic differentiation factor SRY (sex determining region Y)-box 9 (SOX-9) increased by 3-fold (p<0.05) as well as the chondrocyte marker aggrecan by over 2-fold after 4h of dynamic unconfined compression. Addition of the p42/44 phosphorylation inhibitor PD98059, along with compression, yielded no change in SOX-9 or aggrecan expression levels from basal levels in uncompressed controls. Inhibition of p38 MAPK or JNK phosphorylation during unconfined compression had no effect on the elevated expression of SOX-9 and aggrecan as compared to compressed cells without the addition of an inhibitor. It is therefore the overall findings of this study that PDLs possess the ability to differentiate into chondrocytes by mechanical compression and this differentiation is mediated by the p42/44 MAPK cascade.


TGF-beta; SOX9; Aggrecan; Mesenchymal Stem Cells; Periodontal Dental Ligament Cells; MAPK; Mitogen Activated Protien Kinases