Background & Aims
The interplay between non-neuronal cells and nerve afferents in the epidermis has a prominent role in health and disease. Painful Diabetic Neuropathy (PDN), one of the most common and intractable complications of diabetes, is indeed characterized by the remodeling of cutaneous innervation and neuropathic pain(1). Even though increasing evidence suggests an important role for epidermal non-neuronal cells, such as resident immune cells, in the development of PDN (2,3), the mechanisms underlying this neuropathy remain largely unknown.
Methods
To investigate how epidermal cells communicate with cutaneous afferents and how this communication affects PDN, we have adopted an experimental approach that combines a mouse model of PDN and skin biopsies from PDN patients. We performed single-cell RNA sequencing (scRNA-seq) of the epidermis in mice fed a high-fat diet (HFD, 42% fat) and a regular diet (RD, 11% fat) for 10 weeks, including both male and female subjects. Previously, we demonstrated that HFD mice develop glucose intolerance, mechanical allodynia, and small fiber neuropathy(4,5). Furthermore, we conducted Spatial Transcriptomics using the 10X Genomics Visium method on skin biopsy sections from well-clinically characterized PDN patients and controls.
Results
Unsupervised clustering of scRNAseq data from HFD and RD mouse epidermis revealed several distinct clusters, including keratinocytes and Langerhans Cells (LCs), a population of resident antigen-presenting cells sharing a common ontogeny with macrophages and thus considered resident-macrophages. We observed a significant increase in LCs in the epidermis of HFD mice, suggesting their role in promoting neuronal excitability. We demonstrated that LCs are crucial in neuro-immune communication and may be involved in axonal degeneration/regeneration in PDN via semaphorin-plexin pathways. Following cell sorting, we applied a multiplex cytokine profiling method to identify a panel of inflammatory molecules secreted by LCs, potentially linked to the onset and maintenance of PDN. Furthermore, to gain a more comprehensive understanding of the skin microenvironment in PDN, we characterized the spatial transcriptomic landscape of the skin in patients with PDN and controls and validated key targets.
Conclusions
Our findings highlight the pivotal role of Langerhans cells in the development of PDN, revealing their functional association with sensory afferent neurons in the epidermis. The disrupted neuron-immune communication between LCs and cutaneous afferents may be responsible for the neuropathic pain in PDN and the remodeling of cutaneous innervation in both mice and PDN patients. Identifying LCs as disease-driving immune cells may pave the way for topical therapeutic treatment strategies for PDN, specifically targeting LCs in the epidermis, such as antigen-specific immunotherapies.
References
(1)Gylfadottir SS, Christensen DH, Nicolaisen SK, Andersen H, Callaghan BC, Itani M, Khan KS, Kristensen AG, Nielsen JS, Sindrup SH, Andersen NT, Jensen TS, Thomsen RW, Finnerup NB. Diabetic polyneuropathy and pain, prevalence, and patient characteristics: a cross-sectional questionnaire study of 5,514 patients with recently diagnosed type 2 diabetes. Pain. 2020. doi: 10.1097/j.pain.0000000000001744.
(2)Casanova-Molla, Jordi, Morales, Merche, Planas-Rigol, Ester, Bosch, Anna, Calvo, Maria, Grau-Junyent, Josep Maria, Valls-Solé, Josep. Epidermal Langerhans cells in small fiber neuropathies. Pain 2012. doi: 10.1016/j.pain.2012.01.021
(3)Dauch, J.R., Bender, D.E., Luna-Wong, L.A. et al. Neurogenic factor-induced Langerhans cell activation in diabetic mice with mechanical allodynia. J Neuroinflammation 2013. doi: 10.1186/1742-2094-10-64
(4)Jayaraj ND, Bhattacharyya BJ, Belmadani AA, Ren D, Rathwell CA, Hackelberg S, Hopkins BE, Gupta HR, Miller RJ, Menichella DM. Reducing CXCR4-mediated nociceptor hyperexcitability reverses painful diabetic neuropathy. J Clin Invest. 2018. doi: 10.1172/JCI92117
(5)George, Dale S., Jayaraj, Nirupa D., Pacifico, Paola, Ren, Dongjun, Sriram, Nikhil, Miller, Rachel E., Malfait, Anne-Marie, Miller, Richard J., Menichella, Daniela M., The Mas-related G protein–coupled receptor d (Mrgprd) mediates pain hypersensitivity in painful diabetic neuropathy. Pain 2023. doi: 10.1097/j.pain.0000000000003120
Presenting Author
Paola Pacifico
Poster Authors
Paola Pacifico
PHD
Northwestern University
Lead Author
Nirupa Jayaraj
Feinberg School of Medicine, Northwestern University Chicago
Lead Author
Dongjun Ren
Feinberg School of Medicine, Northwestern University Chicago
Lead Author
Dale George
PHD
Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL
Lead Author
James Coy-Dibley
Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL
Lead Author
Richard Miller
PhD
Feinberg School of Medicine, Northwestern University Chicago
Lead Author
Daniela Menichella
Feinberg School of Medicine, Northwestern University Chicago
Lead Author
Topics
- Models: Chronic Pain - Neuropathic