Purified stem cell group shows greater levels of Type II collagen

By Gina Brockenbrough
1^st on the web (May 29, 2009)

MIAMI — Subpopulations of human mesenchymal stem cells (MSCs) may have varying potential for chondrogenic expression, according to a study presented here.

To determine if a purified subpopulation of MSCs would lead to a more uniform differentiation of cells into chondrocytes, Charles C. Secretan, MD, and his colleagues investigated the CD44 cell surface receptor which is believed to play a role in cartilage matrix generation and homoeostasis.

They reported their findings at the 8th World Congress of the International Cartilage Repair Society, here.

After culturing and isolating MSCs, the investigators used flow cytometry to detect the surface antigens in the population. They then created the following three groups of cells using a fluorescence-activated cell sorter:

• a CD44-positive population;
• a CD44-negative population; and,
• a mixed or native population.

They used real-time polymerase chain reaction to quantify and compare the Type I collagen, Type II collagen and aggrecan content in the stem cell-derived chondrocytes in each group.

The investigators discovered significantly greater Type II collagen expression in the CD44-positive population compared to the mixed and CD44-negative groups. The CD44-positive group also showed significantly greater aggrecan expression than the mixed population.

However, the investigators found no significant difference in the aggrecan expression between the CD44-positive and negative groups. All of the groups showed high levels of Type I collagen, Secretan said.

“Human MSC populations isolated from the bone marrow [are] heterogeneous,” he said during his presentation. “There does appear to be subpopulations in human mesenchymal stem cells with functional and differential capabilities, and a CD44 purified mesenchymal stem cell population did show an enhanced ability to produce more Type II collagen and aggrecan [compared to a mixed population].”

Reference:

• Secretan CC, Bater J, Bagnall KN, et al. Isolation of a subpopulation of human mesenchymal stem cells with enhanced chondrogenic potential. #9.2.5. Presented at the 8th World Congress of the International Cartilage Repair Society. May 23-26, 2009. Miami.