Effect of testosterone on fracture healing in hypophysectomized rats

Targeted activation of androgen receptor signaling in the periosteum improves bone fracture repair

Low testosterone level is an independent predictor of osteoporotic fracture in elderly men as well as increased fracture risk in men undergoing androgen deprivation. Androgens and androgen receptor (AR) actions are essential for bone development and homeostasis but their linkage to fracture repair remains unclear. Here we found that AR is highly expressed in the periosteum cells and is co-localized with a mesenchymal progenitor cell marker, paired-related homeobox protein 1 (Prrx1), during bone fracture repair. Mice lacking the AR gene in the periosteum expressing Prrx1-cre (AR^-/Y;Prrx1::Cre) but not in the chondrocytes (AR^-/Y;Col-2::Cre) exhibits reduced callus size and new bone volume. Gene expression data analysis revealed that the expression of several collagens, integrins and cell adhesion molecules were downregulated in periosteum-derived progenitor cells (PDCs) from AR^-/Y;Prrx1::Cre mice. Mechanistically, androgens-AR signaling activates the AR/ARA55/FAK complex and induces the collagen-integrin α2β1 gene expression that is required for promoting the AR-mediated PDCs migration. Using mouse cortical-defect and femoral graft transplantation models, we proved that elimination of AR in periosteum of host mice impairs fracture healing, regardless of AR existence of transplanted donor graft. While testosterone implanted scaffolds failed to complete callus bridging across the fracture gap in AR^-/Y;Prrx1::Cre mice, cell-based transplantation using DPCs re-expressing AR could lead to rescue bone repair. In conclusion, targeting androgen/AR axis in the periosteum may provide a novel therapy approach to improve fracture healing.

Anabolic Androgenic Steroids in Orthopaedic Surgery: Current Concepts and Clinical Applications

Despite the well-documented effects of testosterone and its synthetic derivatives—collectively termed anabolic androgenic steroids (AASs)—on the musculoskeletal system, the therapeutic use of these agents has received limited investigation within the field of orthopaedic surgery. In the last 2 decades, preclinical and clinical research has started to identify promising applications of the short-term use of AASs in the perioperative period. There is evidence to suggest that AASs may improve postoperative recovery after anterior cruciate ligament reconstruction and total joint arthroplasty. In addition, AASs may augment the biological healing environment in specific clinical scenarios including muscle injury, fracture repair, and rotator cuff repair. Current literature fails to present strong evidence for or against the use of AASs in orthopaedics, but there is continuous research on this topic. The purpose of this study was to provide a comprehensive overview of the current status of AAS applications in orthopaedic surgery, with an emphasis on preclinical data, clinical studies, and future directions.

Systemically impaired fracture healing in small animal research: A review of fracture repair models

Fracture healing is a complex process requiring mechanical stability, an osteoconductive matrix, and osteoinductive and osteogenic biology. This intricate process is easily disrupted by various patient factors such as chronic disease and lifestyle. As the medical complexity and age of patients with fractures continue to increase, the importance of developing relevant experimental models is becoming paramount in preclinical research. The objective of this review is to describe the most common small animal models of systemically impaired fracture healing used in the orthopedic literature including osteoporosis, diabetes mellitus, smoking, alcohol use, obesity, and ageing. This review will provide orthopedic researchers with a summary of current models of systemically impaired fracture healing used in small animals and present an overview of the methods of induction for each condition.

Evaluating the affect and reversibility of opioid-induced androgen deficiency in an orthopaedic animal fracture model

BACKGROUND

Opioid pain medications are the basis for analgesia after orthopaedic injuries and procedures. However, opioids have many adverse effects, including opioid-induced androgen deficiency.

QUESTIONS/PURPOSES

We evaluated the occurrence and affect of opioid-induced androgen deficiency on osseous union and its ability to be reversed. Additional focus was placed on its perioperative onset and its duration in an orthopaedic animal model.

METHODS

A femoral osteotomy was created in 75 Sprague-Dawley rats. Postoperatively, animals were randomized into three treatment groups: control, morphine, and morphine plus testosterone. Testosterone levels were recorded preoperatively and at 48 hours, 4 weeks, and 8 weeks postoperatively. Some animals were euthanized at 4 weeks and others at 8 weeks postoperatively. Histology and micro-CT scans were used to evaluate callus. Three-point bend testing was performed to evaluate callus strength.

RESULTS

Serum testosterone levels in the morphine group showed decreased baseline levels of 2.2 ng/mL, 1.4 ng/mL, and 1.4 ng/mL (p < 0.001), whereas the morphine plus testosterone supplementation group showed increased serum levels at 41.7 ng/mL, 11.8 ng/mL, and 19.8 ng/mL (p < 0.001) compared with control animals (3.3 ng/mL, 5.8 ng/mL, 5.2 ng/mL) at 48 hours, 4 weeks, and 8 weeks, respectively. Compared with control animals, histology and micro-CT showed an impedance of callus maturation in the two experimental groups. Morphine-treated animals showed reduction in callus strength at 8 weeks (30% of the contralateral unfractured femur strength compared with 49% seen in the control animals at 8 weeks; p = 0.048); this finding was not fully reversed by testosterone supplementation (33% of the contralateral femur strength; p = 0.171).

CONCLUSIONS

Opioid-induced androgen deficiency occurred in this orthopaedic animal model. Although we previously showed that morphine inhibits callus maturation, the current study did not show a rescue of the morphine-treated animals with testosterone supplementation in either morphologic or mechanical testing. Testosterone suppression associated with opioid administration occurred almost immediately (within 48 hours) and was suppressed continually throughout the 8-week duration of study.

CLINICAL RELEVANCE

Opioid-induced androgen deficiency occurs during the perioperative orthopaedic period. Although its clinical relevance remains unknown, further evaluation is needed to determine if supplementation is warranted during the perioperative period.