Michael Pfaff

Publications (2)6.09 Total impact

• Article: Initial immune reaction and angiogenesis in bone healing.

  Katharina Schmidt-Bleek, Hanna Schell, Jasmin Lienau, Norma Schulz, Paula Hoff, Michael Pfaff, Gregor Schmidt, Claudia Martin, Carsten Perka, Frank Buttgereit, Hans-Dieter Volk, Georg Duda
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  ABSTRACT: During hematoma formation following injury, an inflammatory reaction ensues as an initial step in the healing process. As granulation tissue matures, revascularization is a prerequisite for successful healing. The hypothesis of this study was that scarless tissue reconstitution in the regenerative bone healing process is dependent on a balanced immune reaction that initiates revasculatory steps. To test this hypothesis, cellular composition and expression profiles of a bone hematoma (regenerative, scarless) was compared with a muscle soft tissue hematoma (healing with a scar) in a sheep model. Upregulation of regulatory T helper cells and anti-inflammatory cytokine expression (IL-10) coincided with an upregulation of angiogenic factors (HIF1α and HIF1α regulated genes) in the regenerative bone hematoma but not in the soft tissue hematoma. These results indicate that the timely termination of inflammation and early onset of revascularization are interdependent and essential for a regenerative healing process. Prolonged pro-inflammatory signaling occurring in a delayed bone-healing model supports the finding that timely termination of inflammation furthers the regenerative process. Differing cellular compositions are due to different cell sources invading the hematoma, determining the ensuing cytokine expression profile and thus paving the path for regenerative healing in bone or the formation of scar tissue in muscle injury. Copyright © 2012 John Wiley & Sons, Ltd.
  Journal of Tissue Engineering and Regenerative Medicine 04/2012; · 3.28 Impact Factor
• Article: Cellular composition of the initial fracture hematoma compared to a muscle hematoma: a study in sheep.

  Katharina Schmidt-Bleek, Hanna Schell, Paula Kolar, Michael Pfaff, Carsten Perka, Frank Buttgereit, Georg Duda, Jasmin Lienau
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  ABSTRACT: Bone fracture leads to a cycle of inflammation, cellular migration, and proliferation to restore tissue integrity. Immune cells at the site of injury are involved especially in the early phase of the healing process, but little is known about the cells present in the initial fracture hematoma. The hypothesis of this study was that the cellular composition in a fracture hematoma differs from that found in a muscle hematoma and that these divergences get more pronounced over time. By using a reproducible osteotomy model and muscle trauma in sheep the distributions of the immune cell subpopulations were evaluated 1 and 4 h after surgery. The cell amount within the first 4 h increased in both hematoma. The number of dead cells was higher in the muscle hematoma. One hour postoperatively the initial fracture hematoma revealed a lower granulocyte percentage compared to the muscle hematoma. The ratio of T helper to cytotoxic T cells was higher in the fracture hematoma compared to the muscle hematoma at both investigated time points. B cell percentage increased in the fracture but not in the muscle hematoma from 1 to 4 h. This is the first study that compares the immune cell subpopulations of a fracture and muscle hematoma.
  Journal of Orthopaedic Research 05/2009; 27(9):1147-51. · 2.81 Impact Factor