Propranolol Reverses Impaired Fracture Healing Response Observed With Selective Serotonin Reuptake Inhibitor Treatment

Role of the Peripheral Nervous System in Skeletal Development and Regeneration: Controversies and Clinical Implications

PURPOSE OF REVIEW

This review examines the diverse functional relationships that exist between the peripheral nervous system (PNS) and bone, including key advances over the past century that inform our efforts to translate these discoveries for skeletal repair.

RECENT FINDINGS

The innervation of the bone during development, homeostasis, and regeneration is highly patterned. Consistent with this, there have been nearly 100 studies over the past century that have used denervation approaches to isolate the effects of the different branches of the PNS on the bone. Overall, a common theme of balance emerges whereby an orchestration of both local and systemic neural functions must align to promote optimal skeletal repair while limiting negative consequences such as pain. An improved understanding of the functional bidirectional pathways linking the PNS and bone has important implications for skeletal development and regeneration. Clinical advances over the next century will necessitate a rigorous identification of the mechanisms underlying these effects that is cautious not to oversimplify the in vivo condition in diverse states of health and disease.

Non-psychoactive Cannabidiol Prevents Osteoporosis in an Animal Model and Increases Cell Viability, Proliferation, and Osteogenic Gene Expression in Human Skeletal Stem and Progenitor Cells

Cannabidiol (CBD), the non-psychoactive component of the Cannabis sativa plant, is marketed as a potential therapeutic agent and has been studied for its roles in reducing inflammation and managing neuropathic pain. Some studies have reported that CB1 and CB2 receptor activation can attenuate and reverse bone loss in experimental animal models. Despite this, little is known about the impact of CBD on fracture healing. We investigated the effects of CBD in vitro using human osteoprogenitor cells and in vivo via murine femur fracture and osteoporosis models. In vitro mesenchymal stem cells were treated with increasing concentrations of crystalized pharmaceutical grade CBD or vehicle solution. Cell viability and proliferation were significantly increased in cells treated with CBD compared to vehicle control. Osteocalcin expression was also significantly higher in the CBD-treated human stem cells compared to vehicle control. In vivo the effect of CBD on bone mineral density and fracture healing in mice was examined using a two-phase experimental approach. Fluoxetine was used for pharmacologic induction of osteoporosis and surgical oophorectomy (OVX) was used for hormonal induction of osteoporosis. X-ray and microCT analysis showed that CBD prevented both fluoxetine- and OVX-induced osteoporosis. We found that while OVX resulted in delayed bone healing in control mice, CBD-pretreated mice exhibited normal bone healing. Collectively these in vitro and in vivo findings suggest that CBD exerts cell-specific effects which can be exploited to enhance bone metabolism. These findings also indicate that CBD usage in an osteoporotic population may positively impact bone morphology, warranting further research.

Rosiglitazone induces adipogenesis of both marrow and periosteum derived mesenchymal stem cells during endochondral fracture healing

BACKGROUND

Type 2 diabetes mellitus (T2DM) afflicts about six percent of the global population, and these patients suffer from a two-fold increased fracture risk. Thiazolidinediones (TZDs), including rosiglitazone, are commonly used medications in T2DM because they have a low incidence of monotherapy failure. It is known that rosiglitazone is associated with secondary osteoporosis, further increasing the fracture risk in an already susceptible population. However, it is not yet understood how rosiglitazone impacts endochondral bone healing after fracture. The aim of this study is to elucidate how rosiglitazone treatment impacts endochondral fracture healing, and how rosiglitazone influences the differentiation of skeletal stem and progenitor cells from the bone marrow and the periosteum.

METHODS

An in-vivo mouse femur fracture model was employed to evaluate differences in fracture healing between mice treated with and without rosiglitazone chow. Fracture healing was assessed with histology and micro computed tomography (μCT). In-vitro assays utilized isolated mouse bone marrow stromal cells and periosteal cells to investigate how rosiglitazone impacts the osteogenic capability and adipogenicity of these cells.

RESULTS

The in-vivo mouse femur fracture model showed that fracture callus in mice treated with rosiglitazone had significantly more adipose content than those of control mice that did not receive rosiglitazone. In addition, μCT analysis showed that rosiglitazone treated mice had significantly greater bone volume, but overall greater porosity when compared to control mice. In-vitro experimentation showed significantly less osteogenesis and more adipogenesis in bone marrow derived progenitor cells that were cultured in osteogenic media. In addition, rosiglitazone treatment alone caused significant increases in adipogenesis in both bone marrow and periosteum derived cells.

CONCLUSION

Rosiglitazone impairs endochondral fracture healing in mice by increasing adipogenesis and decreasing osteogenesis of both bone marrow and periosteum derived skeletal progenitor cells.

Effects of social stress and fluoxetine treatment on fracture healing in a rat femur fracture model

BACKGROUND

Mental stress and depressive disorders have negative effect on bone biology and increase fracture risk. Fluoxetine is a widely used selective serotonin reuptake inhibitor in the treatment of these disorders. We aimed to evaluate the effects of social stress and fluoxetine treatment on fracture healing.

METHODS

This study was performed with 32 male Sprague-Dawley® rats. Rats were randomly divided into four groups with eight rats in each group. Social stress regimen was performed in groups 3 and 4 for 15 days. Placebo for groups 1 and 3 and fluoxetine for groups 2 and 4 was administrated. Rat femur open (osteotomy) fracture model was performed. Placebo and fluoxetine were continued to be given to the same groups for four weeks until sacrification of animals. Sacrificed right femurs of subjects were evaluated histologically and radiologically. The obtained data were statistically analyzed using the SPSS 23 (Statistical Package for the Social Sciences) program.

RESULTS

Fracture healing score that evaluates the fracture healing quantitatively based on histological scale and bone mineral density of group 3 were significantly lower than other groups, and there was no significant difference between other groups. Inflammation score of group 2 was significantly lower than group 3. Group 1 had higher new callus formation/original cortex volume than group 2 and group 3. In immunohistochemical evaluation, the H-score of BMP-7/osteoblast in group 3 was lower than in group 1. The H-score of CD34 in group 3 was lower than in group 1.

DISCUSSION

The positive and negative effects of fluoxetine, which is used in the treatment of depressive disorders, on wound, tendon, or bone healing have been shown in the literature. In this study, we showed the negative effects of depression on the early stages of fracture healing. Although fluoxetine had no detrimental effect on fracture healing in non-depressive rats, impaired fracture healing was reversed and better radiological and histological findings were obtained in depressive rats treated with fluoxetine. Our findings indicate that fluoxetine, which minimizes the negative effects of social stress on bone healing, can be used safely in the treatment of depressive disorders in patients with fractures.