In silico study of principal sex hormone effects on post-injury synovial inflammatory response

Mineralized tissue loss at the femoral ACL enthesis in young male ACL-injured patients

Purpose

Primary anterior cruciate ligament (ACL) reconstruction graft failure remains a significant health concern in young patients. Despite the high incidence of poor graft integration in these patients and the resulting high failure rate, little consideration has been given to the quality of the bone into which the graft is anchored at reconstruction. Therefore, we investigated post ACL injury mineralized tissue changes in the ACL femoral entheses of young males and compared them to changes previously reported for young females.

Methods

ACL femoral entheses and adjacent bone specimens were harvested from the injured knees of 51 young males during primary ACL reconstructive surgery and from 10 non-injured male cadaveric donors. The specimens were imaged via nano-computed tomography and analyzed for volumetric bone mineral density (vBMD) and architectural changes.

Results

Male femoral ACL explant specimens had significantly lower cortical vBMD (p < 0.001), lower relative bone volume (BV/TV, p = 0.027) and greater cortical bone porosity (Ct.Po, p = 0.027) but similar trabecular bone parameters (p's > 0.05) to those of control specimens from male cadaveric donors. Cortical and trabecular bone loss increased significantly with time from ACL injury to reconstructive surgery (p's < 0.05). While cortical loss occurred in both males and females, significant trabecular loss occurred only in females (p = 0.009).

Conclusion

Femoral entheseal bone loss occurs in males following ACL injury. This bone loss increases with time following ACL injury, with cortical bone loss occurring sooner after injury than trabecular bone loss. The effects of ACL injury and time from injury to surgery on trabecular bone microarchitecture differed between male and female patients.

Level of Evidence

N/A.

Unraveling the complex interplay of sex, endocrinology, and inflammation in post-Injury articular cartilage breakdown through in silico modeling

The onset of degenerative joint diseases such as post-traumatic osteoarthritis (PTOA) are associated with joint injury, biomechanical changes, and synovial biochemical anomalies. Sex and reproductive endocrinology have been emerging as potential risk factors, with epidemiological evidence revealing that female's exhibit higher PTOA risk and poorer outcomes post-injury compared to males. Sex hormones, including estradiol, progesterone, and testosterone, have been shown to regulate inflammatory signaling in immune and synovial cells, yet their collective impact on injury-induced joint inflammation and catabolism is poorly understood. Using an in silico kinetic model, we investigated the effects of sex-specific endocrine states on post-injury mechanisms in the human synovial joint. Our model results reveal that heightened estradiol levels in pre-menopausal females during the peri-ovulatory phase increase interleukin (IL)-1β expression and suppress IL-10 expression within the synovium after a simulated injury. Conversely, elevated testosterone levels in males decrease post-injury IL-1β, tumor necrosis factor alpha (TNF)-α, and stromelysin (MMP)-3 expression while increasing IL-10 production compared to females. Gaining insight into the effects of sex hormones on injury-induced inflammation and cartilage degradation provides a basis for designing future experimental and clinical studies to explore their effects on the synovial system, with a particular focus on the female sex.

The involvement and significance of M2 macrophages in neuropathic pain following spinal cord injury: a systematic review

Neuropathic pain (NeP) is a type of persistent pain initiated by diseases or injuries of the nervous system. Although the underlying pathophysiological mechanisms of NeP are poorly understood, the immune system plays a key role in this condition. M2 macrophages have a key role in tissue healing and the reduction of inflammation. This systematic study aims to provide an overview of the role and importance of M2 macrophages in NeP after spinal cord injury (SCI). A comprehensive systematic review was conducted utilizing Scopus, PubMed, Embase, and ISI Web of Science databases. Two independent reviewers conducted the article selection. All publications examine the impact of M2 macrophages on NeP following spinal cord injuries. A quality assessment was conducted on bias entities that had been predetermined. Eleven papers met the criteria. According to the findings, focusing on immune cell polarization presents viable therapeutic options for treating NeP and enhancing recovery after SCI. M2 macrophages are essential for reducing neuropathic pain and promoting recovery after spinal cord injury. The modulation of M2 macrophages by a number of therapeutic approaches, including ivermectin-functionalized MWCNTs, isorhamnetin, Neuregulin-1 administration, TMEM16F inhibition, lentivirus-mediated delivery of anti-inflammatory cytokines, epigallocatechin-3-gallate, and red-light therapy promotes neuroregeneration, decreases neuroinflammatory cytokines, and reduces NeP. The results of these preclinical investigations must, however, be interpreted with caution, according to the quality assessment and risk of bias analysis of the studies that were included. Targeting M2 macrophages may have therapeutic benefits as they are essential for the management of NeP and recovery following spinal cord damage.

The alterations in nerve growth factor concentration in plasma and synovial fluid before and after total knee arthroplasty

Total knee arthroplasty (TKA) is an effective procedure for pain relief; however, the emergence of postsurgical pain remains a concern. In this study, we investigated the production of nerve growth factor (NGF) and mediators that affect NGF production and their function in the synovial fluid and plasma after TKA. This study included 19 patients (20 knees) who had rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and knee osteoarthritis (OA) who underwent TKA, categorized into OA and non-OA groups. The levels of NGF, inflammatory cytokines, and lipid mediators were analyzed before and after surgery. The intraoperative synovial fluid NGF concentration was more than seven times higher in the non-OA group than in the OA group. The intra-articular NGF levels increased significantly by more than threefold postoperatively in the OA group but not in the non-OA group. Moreover, the levels of inflammatory cytokines and lipid mediators were increased in the synovial fluid of both groups. The intra-articular cytokines or NGF concentrations positively correlated with postoperative pain. Targeted NGF control has the potential to alleviate postsurgical pain in TKA, especially in patients with OA, emphasizing the importance of understanding NGF dynamics under different knee conditions.

Common Sources of Inflammation and Their Impact on Hematopoietic Stem Cell Biology

Purpose of Review

Inflammatory signals have emerged as critical regulators of hematopoietic stem cell (HSC) function. Specifically, HSCs are highly responsive to acute changes in systemic inflammation and this influences not only their division rate but also their lineage fate. Identifying how inflammation regulates HSCs and shapes the blood system is crucial to understanding the mechanisms underpinning these processes, as well as potential links between them.

Recent Findings

A widening array of physiologic and pathologic processes involving heightened inflammation are now recognized to critically affect HSC biology and blood lineage production. Conditions documented to affect HSC function include not only acute and chronic infections but also autoinflammatory conditions, irradiation injury, and physiologic states such as aging and obesity.

Summary

Recognizing the contexts during which inflammation affects primitive hematopoiesis is essential to improving our understanding of HSC biology and informing new therapeutic interventions against maladaptive hematopoiesis that occurs during inflammatory diseases, infections, and cancer-related disorders.