1. Reprogramming Approaches for Musculoskeletal regeneration and Disease modeling.

The discovery of induced pluripotency by Yamanaka and colleagues has revolutionized the field of regenerative medicine. Induced pluripotent stem cells (iPSC), generated by introduction of a few defined factors in a somatic cell, provide an ideal patient-specific source for disease modeling, drug discovery and cellular therapies. Our research is geared towards applying reprogramming approaches towards musculoskeletal regeneration especially cartilage regeneration that remains an unmet medical need. We have recently optimized a quick and efficient differentiation methodology to generate chondrocytes from human iPSCs (Lee 2015, FASEBJ). The human iPSC-derived chondrocytes are now being utilized to address the molecular mechanism of cartilage aging and regeneration, including novel factors that differentiate young and old cartilage. In addition, these reprogramming and differentiation tools are being used for modeling pediatric growth disorders and for drug screening using small molecule libraries. Finally, we are optimizing scaffolds for engineering autologous cartilage tissue (Smeriglio 2015a, Tissue Eng Part A) from iPSC generated from human patient samples and testing its potential for repairing cartilage defects in animal models of focal cartilage repair.  

 

2. Understanding normal cartilage and bone development and the aberrant sarcomas.

We utilize in vitro stem cell differentiation as well as mouse models to study the development of cartilage and bone. We are particularly interested in understanding the role of the extracellular matrix in regulating stem cell self-renewal and differentiation in these tissues. Understanding the acquisition and maintenance of the 'differentiated' state can provide important clues regarding the 'de-differentiation' associated with cancers such as osteosarcoma. Additionally, by understanding the processes that give rise to these tissues in development, we can better identify lineage-specifying factors for 'differentiation' therapy for cancer cells.

 

 

 

3. Epigenetic regulation in development and disease.

DNA methylation is an epigenetic mark associated with long-term gene silencing during early development and lineage specification. Studies by our group and others have uncovered novel DNA repair based DNA demethylation pathways (Bhutani 2010, Nature). This, coupled with the discovery of a 'sixth base' in DNA, hydroxy-methylcytosine (5hmC) have increased the interest in the role of DNA methylation and demethylation dynamics (Bhutani 2011, Cell). The role and effect of 5hmC on 5mC turnover and gene expression is poorly understood. We are exploring the role of these novel DNA demethylation regulators in cartilage development, regeneration and disease.

Our recent studies (Taylor 2014, A&R) (Taylor 2015, A&R), have demonstrated that chondrocytes form patients with osteoarthritis(OA) have significantly elevated 5hmC levels, especially on the gene bodies of catabolic genes that lead to cartilage degradation. We are currently investigating the precise effect of 5hmC on gene expression and the individual roles of TET1, 2 and 3 on the onset and development of Osteoarthritis. Besides providing a fundamental understanding of OA pathogenesis, these studies can potentially lead to new therapeutic strategies to target this age-associated disease that affects 60% of the elderly US population.

 

 

Our optimized process for regenerating 97% pure chondrocytes. (Lee 2015).

Our optimized process for regenerating 97% pure chondrocytes. (Lee 2015).

hiPSC-derived chondrocytes express canonical chondrocyte markers such as Sox9 and Col2a1. (Lee 2015)

hiPSC-derived chondrocytes express canonical chondrocyte markers such as Sox9 and Col2a1. (Lee 2015)

By understanding difference between the ECM of young and old cartilage, we can engineer better scaffolds (Smeriglio 2015a).

By understanding difference between the ECM of young and old cartilage, we can engineer better scaffolds (Smeriglio 2015a).

 
Cartilage makes up the vast portion of the early embryo (stained in blue here) and is responsible for laying the template for early bone development. 

Cartilage makes up the vast portion of the early embryo (stained in blue here) and is responsible for laying the template for early bone development. 

 
 
Taylor 2014.  Elevation of 5hmC levels in chondrocytes extracted from osteoarthritic cartilage vs. normal cartilage.

Taylor 2014.  Elevation of 5hmC levels in chondrocytes extracted from osteoarthritic cartilage vs. normal cartilage.