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Vertebral Bone Marrow for Immunomodulation in Hand Transplantation
Nance Yuan, BA, Mario V. Lemas, PhD, Jeffrey Bitzan, MT, Janice D. Sproul, MAS, WP Andrew Lee, MD, Gerald Brandacher, MD, Damon S. Cooney, MD, PhD.
Johns Hopkins School of Medicine, Baltimore, MD, USA.
BACKGROUND:
Hand transplantation is a life-transforming option for select patients, but strategies to reduce the requirement for high-dose immunosuppression are greatly needed. In our clinical trials of hand transplantation, peri-operative infusion of cadaveric donor vertebral body bone marrow (VBBM) has shown promising immunomodulatory effects, allowing maintenance of allografts on low-dose tacrolimus monotherapy as opposed to the usual three-drug regimen. However, the mechanisms behind VBBM’s effects are still unknown. Detailed characterization of the cell populations and cell subtypes in VBBM has not yet been done.
METHODS:
As prepared in our clinical trials, bone marrow was harvested from cadaveric donor vertebral bodies, cryopreserved, then thawed. A portion of the bone marrow was ground with an alternative device for comparison. VBBM samples were stained with monoclonal anti-human antibodies to detect lymphocyte, mesenchymal stem cell (MSC), and hematopoietic progenitor cell populations and subtypes. Antibodies included those for human CD3, CD4, CD8, CD45RA, CD34, CD25, and Foxp3, among others, such as markers for Th1, Th2, and Th17 cells. MSCs were detected using a commercially available kit to identify cells that were CD34-/11b-/19-/45-/HLA-DR- and CD73+CD105+CD90+. For comparison, conventional iliac-crest bone marrow aspirates were also obtained from consenting donors.
RESULTS:
When compared to conventional bone marrow (BM) aspirates, preliminary data from VBBM showed similar percentages of overall CD3+ lymphocytes. However, VBBM demonstrated greater proportion of CD3+CD4+ cells, whereas conventional BM had greater percentage of CD3+CD8+ cells. CD3+CD8+CD45RA+ (naïve T cells) made up a greater percentage of the CD3+CD8+ fraction in VBBM samples. VBBM also showed greater percentage of CD3+CD3+CD25+ cells. Both types of bone marrow revealed small but detectable populations of MSCs. We will present further similarities and differences between VBBM and BM and will also compare the products from alternative bone-marrow processing techniques.
CONCLUSIONS:
We do the first in-depth immunophenotypical characterization of VBBM, which has shown beneficial immunomodulatory effects in our hand transplantation clinical trials. Further studies will continue to increase understanding of the unique properties and cell populations within VBBM. Our study lays the groundwork for functional characterization to identify how VBBM exerts its effects. This will eventually reveal possibilities for refining VBBM to enhance its promising effects.
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