Identification and quantification of nociceptive Schwann cells in mice with and without Streptozotocin-induced diabetes

Molecular mechanisms of neuropathic pain

Peripheral neuropathic pain, which occurs after a lesion or disease affecting the peripheral somatosensory nervous system, is a complex and challenging condition to treat. This chapter will cover molecular mechanisms underlying the pathophysiology of peripheral neuropathic pain, focusing on (1) sensitization of nociceptors, (2) neuro-immune crosstalk, and (3) axonal degeneration and regeneration. The chapter will also emphasize the importance of identifying novel therapeutic targets in non-neuronal cells. A comprehensive understanding of how changes at both neuronal and non-neuronal levels contribute to peripheral neuropathic pain may significantly improve pain management and treatment options, expanding to topical application that bypass the side effects associated with systemic administration.

Animal models of neuropathic pain

Animal models continue to be crucial to developing our understanding of the molecular, cellular, and neurophysiological mechanisms that lead to neuropathic pain. The overwhelming majority of animal studies use rodent models, ranging from surgical and trauma-induced models to those induced by metabolic diseases, genetic mutations, viruses, neurotoxic drugs, and cancer. We discuss the clinical relevance of the available models and the pain behavior tests commonly used as outcome measures. Finally, we summarize the refinements that have been proposed to improve the ability of animal model studies to predict clinical efficacy.

Advancing Pain Understanding and Drug Discovery: Insights from Preclinical Models and Recent Research Findings

Despite major advancements in our understanding of its fundamental causes, pain-both acute and chronic-remains a serious health concern. Various preclinical investigations utilizing diverse animal, cellular, and alternative models are required and frequently demanded by regulatory approval bodies to bridge the gap between the lab and the clinic. Investigating naturally occurring painful disorders can speed up medication development at the preclinical and clinical levels by illuminating molecular pathways. A wide range of animal models related to pain have been developed to elucidate pathophysiological mechanisms and aid in identifying novel targets for treatment. Pain sometimes drugs fail clinically, causing high translational costs due to poor selection and the use of preclinical tools and reporting. To improve the study of pain in a clinical context, researchers have been creating innovative models over the past few decades that better represent pathological pain conditions. In this paper, we provide a summary of traditional animal models, including rodents, cellular models, human volunteers, and alternative models, as well as the specific characteristics of pain diseases they model. However, a more rigorous approach to preclinical research and cutting-edge analgesic technologies may be necessary to successfully create novel analgesics. The research highlights from this review emphasize new opportunities to develop research that includes animals and non-animals using proven methods pertinent to comprehending and treating human suffering. This review highlights the value of using a variety of modern pain models in animals before human trials. These models can help us understand the different mechanisms behind various pain types. This will ultimately lead to the development of more effective pain medications.

Structural changes in Schwann cells and nerve fibres in type 1 diabetes: relationship with diabetic polyneuropathy

AIMS/HYPOTHESIS

Our aim was to investigate structural changes of cutaneous Schwann cells (SCs), including nociceptive Schwann cells (nSCs) and axons, in individuals with diabetic polyneuropathy. We also aimed to investigate the relationship between these changes and peripheral neuropathic symptoms in type 1 diabetes.

METHODS

Skin biopsies (3 mm) taken from carefully phenotyped participants with type 1 diabetes without polyneuropathy (T1D, n=25), type 1 diabetes with painless diabetic polyneuropathy (T1DPN, n=30) and type 1 diabetes with painful diabetic polyneuropathy (P-T1DPN, n=27), and from healthy control individuals (n=25) were immunostained with relevant antibodies to visualise SCs and nerve fibres. Stereological methods were used to quantify the expression of cutaneous SCs and nerve fibres.

RESULTS

There was a difference in the number density of nSCs not abutting to nerve fibres between the groups (p=0.004) but not in the number density of nSCs abutting to nerve fibres, nor in solitary or total subepidermal SC soma number density. The overall dermal SC expression (measured by dermal SC area fraction and subepidermal SC process density) and peripheral nerve fibre expression (measured by intraepidermal nerve fibre density, dermal nerve fibre area fraction and subepidermal nerve fibre density) differed between the groups (all p<0.05): significant differences were seen in participants with T1DPN and P-T1DPN compared with those without diabetic polyneuropathy (healthy control and T1D groups) (all p<0.05). No difference was found between participants in the T1DPN and P-T1DPN group, nor between participants in the T1D and healthy control group (all p>0.05). Correlational analysis showed that cutaneous SC processes and nerve fibres were highly associated, and they were weakly negatively correlated with different neuropathy measures.

CONCLUSIONS/INTERPRETATION

Cutaneous SC processes and nerves, but not SC soma, are degenerated and interdependent in individuals with diabetic polyneuropathy. However, an increase in structurally damaged nSCs was seen in individuals with diabetic polyneuropathy. Furthermore, dermal SC processes and nerve fibres correlate weakly with clinical measures of neuropathy and may play a partial role in the pathophysiology of diabetic polyneuropathy in type 1 diabetes.

Addition of Docetaxel to Androgen Receptor Axis-targeted Therapy and Androgen Deprivation Therapy in Metastatic Hormone-sensitive Prostate Cancer: A Network Meta-analysis

CONTEXT

Randomized controlled trials (RCTs) have shown that addition of docetaxel or androgen receptor axis-targeted therapy (ARAT) to androgen deprivation therapy (ADT) or addition of ARAT to ADT and docetaxel improves overall survival (OS) in metastatic hormone-sensitive prostate cancer (mHSPC). However, it is unknown whether docetaxel, when given as part of triplet therapy, has an independent OS benefit.

OBJECTIVE

To compare the efficacy of ADT plus ARAT with the triplet of ADT, ARAT, and docetaxel through a network meta-analysis (NMA) of RCTs in mHSPC.

EVIDENCE ACQUISITION

Bibliographic databases and conference proceedings were searched in March 2022 for RCTs that evaluated the addition of docetaxel, ARAT, or both to ADT in mHSPC. The primary endpoint was OS. Standard random-effect NMA and Bayesian analyses were performed to compare ADT plus ARAT with triplet therapy.

EVIDENCE SYNTHESIS

Eleven RCTs (n = 11 546) were eligible. Compared with ADT plus ARAT, the triplet had a nonsignificant OS benefit (hazard ratio [HR] 0.89, 95% confidence interval [CI] 0.68-1.16), while ADT plus docetaxel (HR 1.16 [0.94-1.43]) and ADT alone (HR 1.46 [1.30-1.64]) had an increased risk of death. By P-score ordering, the triplet was the most effective treatment strategy (P score = 0.936) followed by ADT plus ARAT (P score = 0.704). The triplet had a 77% likelihood of being the best treatment strategy compared with a 23% likelihood for ADT plus ARAT.

CONCLUSIONS

The triplet of ADT, ARAT, and docetaxel was the highest ranked treatment strategy, but it did not confer a statistically significant OS benefit over ADT plus ARAT. This NMA provides the highest-level comparative evidence for these treatment approaches in the initial management of mHSPC.

PATIENT SUMMARY

We synthesized the available evidence from clinical trials conducted in newly diagnosed metastatic prostate cancer to compare the survival of patients receiving triplet therapy (androgen receptor axis-targeted therapy [ARAT], androgen deprivation therapy [ADT], and docetaxel) with those receiving only ARAT and ADT. We conclude that the triplet is a somewhat more effective treatment approach.