Successful Improvement of Metabolic Disorders, Including Osteopenia, by a Dopamine Agonist in a Male Patient with Macro-Prolactinoma

Dopamine promotes osteogenic differentiation of PDLSCs by activating DRD1 and DRD2 during orthodontic tooth movement via ERK1/2 signaling pathway

Introduction

Orthodontic tooth movement (OTM) involves complex interactions between mechanical forces and periodontal tissue adaptation, mainly mediated by periodontal ligament cells, including periodontal ligament stem cells (PDLSCs), osteoblasts, and osteoclasts. Dopamine (DA), a neurotransmitter known for its critical role in bone metabolism, is investigated in this study for its potential to enhance osteogenic differentiation in PDLSCs, which are pivotal in OTM. This study examined the potential of DA to facilitate OTM by binding to DA receptors (D1R and D2R) and activating the ERK1/2 signaling pathway. We propose that DA's interaction with these receptors on PDLSCs could enhance osteogenic differentiation, thereby accelerating bone remodeling and reducing the duration of orthodontic treatments, which offering a novel approach to improve clinical outcomes in orthodontic care.

Methods

This study utilized a rat OTM model, micro-CT, histological analyses, and in vitro assays to investigate dopamine's effect on osteogenesis. PDLSCs were cultured and treated with DA, and cytotoxicity, osteogenic differentiation, gene and protein expression assessed.

Results

Dopamine administration significantly increased trabecular bone density and osteogenic marker expression in an OTM rat model. In vitro, DA at 10 nM optimally promoted human PDLSCs osteogenesis without affecting proliferation. Blocking DA receptors or inhibiting the ERK1/2 pathway attenuated these effects, underscoring the importance of dopaminergic signaling in tension-induced osteogenesis during OTM.

Conclusion

Taken together, our study reveals that local dopamine administration at a concentration of 10 nM not only enhances tension-induced osteogenesis in vivo but also significantly promotes osteogenic differentiation of PDLSCs in vitro through D1 and D2 receptor-mediated ERK1/2 signaling pathway activation.

Expression of Stem Cell Markers and Dopamine D2 Receptors in Human and Rat Prolactinomas

Background

Dopamine agonists (DAs) are the first-line treatment for prolactinomas. DAs primarily target the dopamine D2 receptor (D2R). Tumor stem-like cells (TSLCs) are associated with the tolerance to radiotherapy and chemotherapy. TSLCs have also been identified in pituitary adenomas. We aimed to characterize the expression pattern of stem cell markers and D2R in human and rat prolactinomas.

Material/Methods

Human prolactinoma specimens (n=14) were obtained from patients with surgical resection. The xenograft model of rat prolactinomas was generated by endermically injecting MMQ cells, HE and PRL were confirmed by immunohistochemical staining of tumor sections, and the expression of serum PRL was measured by ELISA. The expression of stem cell markers (CD133, Nestin, Oct4, and Sox2) and D2R in prolactinomas was detected by immunofluorescence. The proportion of CD133-expressing cells after DA treatment was evaluated by flow cytometry in vitro.

Results

We found that a small subpopulation of cells expressing stem cell markers existed both in human and rat prolactinomas. Furthermore, the CD133-expressing cells showed negative D2R expression. Conversely, the D2R-expressing cells showed negative CD133 expression. The proportion of CD133-expressing cells in surviving tumor cells was significantly increased after DA treatment.

Conclusions

Our results confirmed the existence of cells expressing stem cell markers in human and rat prolactinomas. Additionally, the CD133-expressing cells might resist DA therapy due to the lack of D2R expression.