| Biologic and clinical interest in human mesenchymal stem cells (hMSCs) has risen dramatically over the last two decades. In orthopaedics, there is a great interest in developing therapies to improve bone healing by using a patient's own hMSCs to form new bone. hMSCs can be isolated from different skeletal sites; however they may differ in their capability to form new bone in vivo. Therefore, it is important to develop methodology which will allow for prediction of hMSCs' osteoblastic potential. This methodology includes testing of isolated hMSCs for the expression of a unique set of bone formation biomarkers prior to their surgical application. To identify the best skeletal site for hMSC isolation and their bone formation properties, we have tested bone specimens derived from patients undergoing orthopaedic surgeries at the UTMC. These studies were performed under institutional IRB protocol and Informed Consent from participating patients. Bone marrow specimens were isolated from iliac crest bone marrow aspirates, fatty marrow, cartilage, and cortical and trabecular bone from distal femur and proximal tibia. After expansion, the phenotype of hMSC isolates were tested by assessing a bona fide marker of osteoblastic phenotype, enzymatic activity of alkaline phosphatase, and correlating these findings to the relative expression of bone-associated genes and candidate ex vivo bone biomarkers. In our limited sample size, we observed differences amongst five cultures of primary cells from different sources when tested for alkaline phosphatase activity and gene expression. Our results suggest that hMSCs within bone marrow aspirates may already possess a potential to differentiate into an osteoblasts, in contrast to hMSCs from other tissues. When comparing biomarkers for bone formation, hMSCs derived from marrow aspirates demonstrate an overall greater change in gene expression after osteogenic induction than hMSCs derived from other sites. Further, extracellular matrix-associated genes in marrow aspirate samples at day 0 such as, decorin and carboxypeptidase E, demonstrate a predictive correlation to hMSC's osteogenic induction ability. Taken together, these preliminary results demonstrate the iliac crest marrow may be the best site to obtain hMSCs and testing for these candidate biomarkers may provide a clinician with insight into the osteogenic potential of their hMSCs to aid in surgical planning. |
