Fracture Healing Is Delayed in Immunodeficient NOD/scid‑IL2Rγcnull Mice

TY - JOUR

T1 - Fracture Healing Is Delayed in Immunodeficient NOD/scid‑IL2Rγcnull Mice

AU - Rapp, Anna E

AU - Bindl, Ronny

AU - Recknagel, Stefan

AU - Erbacher, Annika

AU - Müller, Ingo

AU - Schrezenmeier, Hubert

AU - Ehrnthaller, Christian

AU - Gebhard, Florian

AU - Ignatius, Anita

PY - 2016

Y1 - 2016

N2 - Following bone fracture, the repair process starts with an inflammatory reaction at the fracture site. Fracture healing is disturbed when the initial inflammation is increased or prolonged, whereby, a balanced inflammatory response is anticipated to be crucial for fracture healing, because it may induce down-stream responses leading to tissue repair. However, the impact of the immune response on fracture healing remains poorly understood. Here, we investigated bone healing in NOD/scid-IL2Rγcnull mice, which exhibit severe defects in innate and adaptive immunity, by biomechanical testing, histomorphometry and micro-computed tomography. We demonstrated that NOD/scid-IL2Rγcnull mice exhibited normal skeletal anatomy and a mild bone phenotype with a slightly reduced bone mass in the trabecular compartment in comparison to immunocompetent Balb/c mice. Fracture healing was impaired in immunodeficient NOD/scid-IL2Rγcnull mice. Callus bone content was unaffected during the early healing stage, whereas it was significantly reduced during the later healing period. Concomitantly, the amount of cartilage was significantly increased, indicating delayed endochondral ossification, most likely due to the decreased osteoclast activity observed in cells isolated from NOD/scid-IL2Rγcnull mice. Our results suggest that-under aseptic, uncomplicated conditions-the immediate immune response after fracture is non-essential for the initiation of bone formation. However, an intact immune system in general is important for successful bone healing, because endochondral ossification is delayed in immunodeficient NOD/scid-IL2Rγcnull mice.

AB - Following bone fracture, the repair process starts with an inflammatory reaction at the fracture site. Fracture healing is disturbed when the initial inflammation is increased or prolonged, whereby, a balanced inflammatory response is anticipated to be crucial for fracture healing, because it may induce down-stream responses leading to tissue repair. However, the impact of the immune response on fracture healing remains poorly understood. Here, we investigated bone healing in NOD/scid-IL2Rγcnull mice, which exhibit severe defects in innate and adaptive immunity, by biomechanical testing, histomorphometry and micro-computed tomography. We demonstrated that NOD/scid-IL2Rγcnull mice exhibited normal skeletal anatomy and a mild bone phenotype with a slightly reduced bone mass in the trabecular compartment in comparison to immunocompetent Balb/c mice. Fracture healing was impaired in immunodeficient NOD/scid-IL2Rγcnull mice. Callus bone content was unaffected during the early healing stage, whereas it was significantly reduced during the later healing period. Concomitantly, the amount of cartilage was significantly increased, indicating delayed endochondral ossification, most likely due to the decreased osteoclast activity observed in cells isolated from NOD/scid-IL2Rγcnull mice. Our results suggest that-under aseptic, uncomplicated conditions-the immediate immune response after fracture is non-essential for the initiation of bone formation. However, an intact immune system in general is important for successful bone healing, because endochondral ossification is delayed in immunodeficient NOD/scid-IL2Rγcnull mice.

U2 - 10.1371/journal.pone.0147465

DO - 10.1371/journal.pone.0147465

M3 - SCORING: Journal article

C2 - 26849055

VL - 11

SP - e0147465

JO - PLOS ONE

JF - PLOS ONE

SN - 1932-6203

IS - 2

ER -