Stem Cell Trafficking to Sites of Injury by Parathyroid Hormone (PTH)

Open Access
Author:
Specht, Shane Richard
Graduate Program:
Anatomy
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 02, 2013
Committee Members:
  • Christopher Niyibizi, Thesis Advisor
  • Patricia Mc Laughlin, Thesis Advisor
  • Henry Joseph Donahue, Thesis Advisor
Keywords:
  • mesenchymal stem cells
  • MSC
  • parathyroid hormone
  • PTH
Abstract:
Diseases of bone, such as osteoporosis and osteogenesis imperfecta, cause weaker, more porous, and more brittle bones. Stem cell therapy has been suggested as one alternative approach that can be applied to treat these diseases. This approach however, would require distribution of the stem cells to the entire skeleton, which at present is not an easy task. The present project focused on developing methods to enhance trafficking of mesenchymal stem cells (MSCs) to the skeleton using mouse models of injury. MSCs are the precursor cells to bone, cartilage, and many other tissues. MSCs are found in extremely small amounts around the body, but mostly in the bone marrow. The goal of this project was to determine if trafficking and engraftment of intravenously injected MSCs in mouse models of injury could be enhanced by parathyroid hormone (PTH) administration. Mesenchymal stem cells were harvested from donor mice and were either labeled with PKH 26 to fluoresce red or harvested from mice engineered to express red fluorescent protein (RFP). The donor, red fluorescing cells were then injected into mice with marrow-ablated femurs to simulate an injury model following PTH administration. Donor cells trafficking and engraftment were assessed by histology, FACS analysis, and Real-Time PCR. By using PKH 26 to track the donor cells using FACS analysis, the results showed that there was a trend that PTH enhanced trafficking of donor MSCs in femurs of recipient mice at 48hr following cell injection, although no significant difference was detected. At day 7, all mice showed higher cell engraftment in femurs and tibia and no differences were noted between groups. These data suggested that PTH may be important for immediate trafficking but at later points injury appeared to be the determining factor in donor cell engraftment. When RFP cells were used followed by histological analysis 48 hours after the injection of donor MSCs, there appeared to be more donor cells in tissue sections made from femur and tibia of recipient mice than in the control mice that did not receive PTH. At day 7, there appeared to be a greater number of donor MSCs found in both femur and tibia of both the PTH and control groups. To confirm the histological findings, Real-Time PCR was used. The results showed that at 48hr following donor cell transplantation, mice treated with PTH had a higher engraftment of donor cells in femurs and tibia than in mice that did not receive PTH. Although the data showed more donor cells in PTH treated mice, there was a fluctuation in engraftment of donor cells between individual mice, resulting in no significant difference. Although the data was not significant, there was a trend indicating that either PTH or injury enhanced trafficking of MSCs.