Identification of the miRNAome in human fracture callus and nonunion tissues

Early total care and damage control orthopaedics result in partially contrasting patterns of microRNA expression at the fracture site and in the systemic circulation : an animal study

Aims

The aims of this study, using a porcine model of multiple trauma, were to investigate the expression of microRNAs at the fracture site, in the fracture haematoma (fxH) and in the fractured bone, compared with a remote unfractured long bone, to characterize the patterns of expression of circulating microRNAs in plasma, and identify and validate messenger RNA (mRNA) targets of the microRNAs.

Methods

Two multiple trauma treatment strategies were compared: early total care (ETC) and damage control orthopaedics (DCO). For this study, fxH, fractured bone, unfractured control bone, plasma, lung, and liver samples were harvested. MicroRNAs were analyzed using quantitative real-time polymerase chain reaction arrays, and the identified mRNA targets were validated in vivo in the bone, fxH, lung, and liver tissue.

Results

MicroRNA expression was associated with the trauma treatment strategy and differed depending on the type of sample. In the ETC group, a more advanced fracture healing response, as reflected by the expression of osteogenic microRNAs, was seen compared with the DCO group. DCO treatment resulted in a more balanced immune response in the systemic circulation as represented by significant upregulations of several anti-inflammatory microRNAs. The in vivo validation of the abundance of putative mRNA targets reflected the levels of microRNAs which were identified.

Conclusion

Local and systemic microRNA patterns of expression were identified, specific for the treatment strategy in multiple trauma, which corresponded with the expression of mRNA at the fracture site and in target organs. These findings match clinical observations and offer insights into the cellular communication which may underlie the effects of using different surgical strategies in patients with multiple trauma, both locally and systemically. We also identified a systemic involvement of microRNAs in multiple trauma which may include distant cellular communication between injured tissues. Further research may further describe the temporospatial role of circulating microRNAs after multiple trauma, their potential role in communication between organs, and prospective therapeutic applications.

Teriparatide as a non-surgical salvage therapy for prolonged humerus fracture nonunion: A case report and literature review

BACKGROUND

Fracture nonunion represents a challenging complication during fracture repair, often necessitating surgical intervention. Teriparatide, a recombinant human parathyroid hormone, has demonstrated promise in enhancing fracture healing, although its efficacy in treating established nonunion remains under investigation.

CASE SUMMARY

We report a case of a 27-year-old male who presented with a right humerus fracture following a traffic accident. Despite undergoing open reduction and internal fixation, the fracture resulted in a delayed union and subsequent nonunion. After 4 years of conservative management, teriparatide treatment was initiated due to persistent nonunion. Teriparatide injections were administered daily for 6 months, resulting in complete fracture healing and resolution of pain.

CONCLUSION

Our case demonstrates the successful use of teriparatide in treating a prolonged nonunion of a humerus fracture. Teriparatide may provide a valuable therapeutic option for established bone nonunion, even in cases that have not responded to conservative treatments.

Activation of Wnt signaling in human fracture callus and nonunion tissues

The Wnt signaling pathway is a key molecular process during fracture repair. Although much of what we now know about the role of this pathway in bone is derived from in vitro and animal studies, the same cannot be said about humans. As such, we hypothesized that Wnt signaling will also be a key process in humans during physiological fracture healing as well as in the development of a nonunion (hypertrophic and oligotrophic). We further hypothesized that the expression of Wnt-signaling pathway genes/proteins would exhibit a differential expression pattern between physiological fracture callus and the pathological nonunion tissues. We tested these two hypotheses by examining the mRNA levels of key Wnt-signaling related genes: ligands (WNT4, WNT10a), receptors (FZD4, LRP5, LRP6), inhibitors (DKK1, SOST) and modulators (CTNNB1 and PORCN). RNA sequencing from calluses as well as from the two nonunion tissue types, revealed that all of these genes were expressed at about the same level in these three tissue types. Further, spatial expression experiments identified the cells responsible of producing these proteins. Robust expression was detected in osteoblasts for the majority of these genes except SOST which displayed low expression, but in contrast, was mostly detected in osteocytes. Many of these genes were also expressed by callus chondrocytes as well. Taken together, these results confirm that Wnt signaling is indeed active during both human physiological fracture healing as well as in pathological nonunions.

Human nonunion tissues display differential gene expression in comparison to physiological fracture callus

The healing of bone fractures can become aberrant and lead to nonunions which in turn have a negative impact on patient health. Understanding why a bone fails to normally heal will enable us to make a positive impact in a patient's life. While we have a wealth of molecular data on rodent models of fracture repair, it is not the same with humans. As such, there is still a lack of information regarding the molecular differences between normal physiological repair and nonunions. This study was designed to address this gap in our molecular knowledge of the human repair process by comparing differentially expressed genes (DEGs) between physiological fracture callus and two different nonunion types, hypertrophic (HNU) and oligotrophic (ONU). RNA sequencing data revealed over ∼18,000 genes in each sample. Using the physiological callus as the control and the nonunion samples as the experimental groups, bioinformatic analyses identified 67 and 81 statistically significant DEGs for HNU and ONU, respectively. Out of the 67 DEGs for the HNU, 34 and 33 were up and down-regulated, respectively. Similarly, out of the 81 DEGs for the ONU, 48 and 33 were up and down-regulated, respectively. Additionally, we also identified common genes between the two nonunion samples; 8 (10.8 %) upregulated and 12 (22.2 %) downregulated. We further identified many biological processes, with several statistically significant ones. Some of these were related to muscle and were common between the two nonunion samples. This study represents the first comprehensive attempt to understand the global molecular events occurring in human nonunion biology. With further research, we can perhaps decipher new molecular pathways involved in aberrant healing of human bone fractures that can be therapeutically targeted.