Autologous Stem Cell therapies for human injury and disease are gaining momentum. Understanding the properties of Stem Cell Colonies that have potential for these therapies is key to optimizing treatments. This study provides knowledge on the properties and their impact on future therapies for anterior cruciate ligament (hACL) and medial collateral ligament (hMCL) of the knee joint.
Jianying Zhang, Tiffany Pan, Hee-Jeong Im, Freddie H Fu and James HC Wang. Differential properties of human ACL and MCL stem cells may be responsible for their differential healing capacity. Differential properties of human ACL and MCL stem cells may be responsible for their differential healing capacity. BMC Medicine 2011, 9:68doi:10.1186/1741-7015-9-68.
Background: The human anterior cruciate ligament (hACL) and medial collateral ligament (hMCL) of the knee joint are frequently injured, especially in athletic settings. It has been known that, while injuries to the MCL typically heal with conservative treatment, ACL injuries usually do not heal. As adult stem cells repair injured tissues through proliferation and differentiation, we hypothesized that the hACL and hMCL contain stem cells exhibiting unique properties that could be responsible for the differential healing capacity of the two ligaments.
Methods: To test the above hypothesis, we derived ligament stem cells from normal hACL and hMCL samples from the same adult donors using tissue culture techniques and characterized their properties using immunocytochemistry, RT-PCR, and flow cytometry.
Images:The expression of stem cell markers in hACL-SCs and hMCL-SCs. At passage 5, hACL-SCs had already become highly elongated in confluent culture, a typical fibroblast phenotype (A). In contrast, even at passage 13, confluent hMCL-SCs remained cobblestone-like (B). Moreover, hACL-SCs no longer expressed nucleostemin (C) or SSEA-4 (E) at passages > 5, whereas hMCL-SCs expressed both stem cell markers at passage 13 (D, F). Note, however, that hMCL-SCs at this high passage exhibited a lesser degree of nucleostemin expression compared to the cells at passage 1 (see Figure 3). The results shown here were obtained from a male donor of 27 years oldTo test the above hypothesis, we derived ligament stem cells from normal hACL and hMCL samples from the same adult donors using tissue culture techniques and characterized their properties using immunocytochemistry, RT-PCR, and flow cytometry.
Results: We found that both hACL stem cells (hACL-SCs) and hMCL stem cells (hMCL-SCs) formed colonies in culture and expressed stem cell markers nucleostemin and stage-specific embryonic antigen-4 (SSEA-4). Moreover, both hACL-SCs and hMCL-SCs expressed CD surface markers for mesenchymal stem cells, including CD44 and CD90, but not those markers for vascular cells, CD31, CD34, CD45, and CD146. However, hACL-SCs differed from hMCL-SCs in that the size and number of hACL-SC colonies in culture were much smaller and grew more slowly than hMCL-SC colonies. Moreover, fewer hACL-SCs in cell colonies expressed stem cell markers STRO-1 and octamer-binding transcription factor-4 (Oct-4) than hMCL-SCs. Finally, hACL-SCs had less multi-differentiation potential than hMCL-SCs, evidenced by differing extents of adipogenesis, chondrogenesis, and osteogenesis in the respective induction media.
Conclusions: This study shows for the first time that hACL-SCs are intrinsically different from hMCL-SCs. We suggest that the differences in their properties contribute to the known disparity in healing capabilities between the two ligaments.
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