Telogen Effluvium - a review of the science and current obstacles

Telogen effluvium (TE) is a common cause of diffuse non-scarring hair loss that is usually precipitated by physiological stress such as childbirth or sudden weight loss. Despite its high rate of remission, this phenomenon of sudden excessive hair loss can be very worrisome and upsetting for affected individuals and may significantly impact their quality of life. Due to the multifactorial causes and precipitants of TE, it is often challenging to diagnose and manage. Further, the mechanisms through which physiological stress influences the human hair cycle is unknown, and there are no targeted treatments for the management of TE. This review will describe the approach in making a diagnosis of TE, summarize the latest developments made in understanding the mechanisms of TE, outline the treatments tried, and recommend ways for advancing the study of this dermatological condition.

Apcdd1 is a dual BMP/Wnt inhibitor in the developing nervous system and skin

Animal development and homeostasis depend on precise temporal and spatial intercellular signaling. Components shared between signaling pathways, generally thought to decrease specificity, paradoxically can also provide a solution to pathway coordination. Here we show that the Bone Morphogenetic Protein (BMP) and Wnt signaling pathways share Apcdd1 as a common inhibitor and that Apcdd1 is a taxon-restricted gene with novel domains and signaling functions. Previously, we showed that Apcdd1 inhibits Wnt signaling (Shimomura et al., 2010), here we find that Apcdd1 potently inhibits BMP signaling in body axis formation and neural differentiation in chicken, frog, zebrafish. Furthermore, we find that Apcdd1 has an evolutionarily novel protein domain. Our results from experiments and modeling suggest that Apcdd1 may coordinate the outputs of two signaling pathways that are central to animal development and human disease.

Immune cell regulation of the hair cycle

The ability to manipulate the mammalian hair cycle will lead to novel therapies and strategies to combat all forms of alopecia. Thus, in addition to the epithelial-mesenchymal interactions in the hair follicle, niche and microenvironmental signals that accompany the phases of growth, regression and rest need to be scrutinized. Immune cells are well described in skin homeostasis and wound healing and have recently been shown to play an important role in the mammalian hair cycle. In this review, we will summarize our current knowledge of the role of immune cells in hair cycle control and discuss their relevance to human hair cycling disorders. Increased attention to this aspect of the hair cycle will provide new avenues to manipulate hair regeneration in humans and provide better insight into developing better ex vivo models of hair growth.

A Subset of TREM2+ Dermal Macrophages Secretes Oncostatin M to Maintain Hair Follicle Stem Cell Quiescence and Inhibit Hair Growth

Hair growth can be induced from resting mouse hair follicles by topical application of JAK inhibitors, suggesting that JAK-STAT signaling is required for maintaining hair follicle stem cells (HFSCs) in a quiescent state. Here, we show that Oncostatin M (OSM), an IL-6 family cytokine, negatively regulates hair growth by signaling through JAK-STAT5 to maintain HFSC quiescence. Genetic deletion of the OSM receptor or STAT5 can induce premature HFSC activation, suggesting that the resting telogen stage is actively maintained by the hair follicle niche. Single-cell RNA sequencing revealed that the OSM source is not intrinsic to the hair follicle itself and is instead a subset of TREM2⁺ macrophages that is enriched within the resting follicle and deceases immediately prior to HFSC activation. In vivo inhibition of macrophage function was sufficient to induce HFSC proliferation and hair cycle induction. Together these results clarify how JAK-STAT signaling actively inhibits hair growth.

Novel therapies for alopecia areata: The era of rational drug development

Treatments for alopecia areata (AA) have evolved over the decades from broad and nonspecific therapies to those that are now more targeted and rationally selected. This was achieved by means of close cooperation and communication between clinicians and basic scientists, which resulted in the elucidation and understanding of the unique pathophysiology of AA. In this review we discuss this evolution and how novel therapies for AA have changed over the decades, what we have in our current arsenal of drugs for this potentially devastating disease, and what the future holds.

Obstacles and solutions to screening psoriasis patients for cardiovascular risk factors

BACKGROUND

Psoriasis has been linked with cardiovascular risk factors (CVRFs), including the metabolic syndrome, yet many patients with psoriasis remain unscreened.

OBJECTIVE

To assess the reasons for lack of screening for CVRFs in psoriasis patients, and the impact of an education programme targeting these deficiencies.

METHODS

All patients with psoriasis, regardless of severity, and all dermatologists working at the National Skin Centre (NSC) in Singapore were surveyed over a 2-month period on their attitudes and knowledge regarding psoriasis and cardiovascular risk. This was followed by a targeted programme which was implemented over 2 months to address these identified deficiencies. Patients and doctors were surveyed a second time to assess the effects of the intervention.

RESULTS

Obstacles to screening included lack of patient knowledge, patients not considering screening important, and lack of time during the clinic consultation. After the intervention, there was a significant increase in the proportion of patients who were aware of increased cardiovascular risk in psoriasis (33.0% to 62%), with more patients attending screening (39.1% to 63.2%). While the level of doctors' knowledge did not significantly increase, there was an increase in the proportion of patients who were screened post-intervention (37.1% to 66.2%), and more doctors reported that they were more likely to screen psoriatic patients from an earlier age (30.2% to 58.1%).

CONCLUSIONS

The obstacles in implementing universal screening for CVRFs in psoriasis patients stem from patient, doctor and system factors. A comprehensive programme targeting all aspects of this ecosystem helps to achieve holistic care for patients with psoriasis.