Human periodontal ligament stem cells repair mental nerve injury

Mandibular Angle Osteotomy via Intraoral Approach: A 15-Year Experience from a Single Plastic Surgery Center in China

BACKGROUND

Mandibular angle osteotomy (MAO) using an intraoral approach is a common procedure for correcting square facial contours in the Asian population. While previous retrospective studies have primarily focused on complications rates, limited research has examined time-related trends and the epidemiological characteristics of the surgical population. A comprehensive study with a large sample size and long-term follow-up is crucial to enhance outcomes, minimize complications, provide evidence-based insights, and consolidate clinical experience.

METHODS

This retrospective study reviewed 3,501 MAO cases performed via an intraoral approach between January 2008 and December 2022. Patients were categorized into three cohorts based on admission dates: group A (January 2008 to December 2012), group B (January 2013 to December 2017), and group C (January 2018 to December 2022). Demographic data, complication rates, and patient-reported satisfaction scores were analyzed across the groups.

RESULTS

The average ages for groups A, B, and C were 27.38 ± 6.94, 27.41 ± 6.42, and 28.57 ± 6.65 years, respectively, with group C patients being significantly older than those in group B (P < 0.001). Gender distribution showed 48 males and 825 females in group A; 93 males and 1,097 females in group B; and 122 males and 1,316 females in group C, with significant difference between groups A and B (P = 0.039). Complication rates were 13.05% (114 cases) in group A, 5.54% (66 cases) in group B, and 2.50% (36 cases) in group C. Postoperative satisfaction scores for groups A, B, and C were 3.32 ± 0.64, 3.86 ± 0.54, and 4.42 ± 0.58, respectively, with significant improvements across groups (P < 0.05).

CONCLUSIONS

The demand for MAO has steadily increased, particularly among individuals aged 21 to 40, with a predominance of female patients. Expanding indications have led to more cases involving middle-aged, elderly, and male patients. Advancements in surgical techniques have contributed to better aesthetic outcomes and lower complication rates. The use of modified osteotomy procedures and digital technologies has enabled safer, more precise surgeries across diverse populations, resulting in significant improvements in lower facial contours.

LEVEL OF EVIDENCE IV

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Potential of dental pulp stem cells and their products in promoting peripheral nerve regeneration and their future applications

Peripheral nerve injury (PNI) seriously affects people's quality of life. Stem cell therapy is considered a promising new option for the clinical treatment of PNI. Dental stem cells, particularly dental pulp stem cells (DPSCs), are adult pluripotent stem cells derived from the neuroectoderm. DPSCs have significant potential in the field of neural tissue engineering due to their numerous advantages, such as easy isolation, multidifferentiation potential, low immunogenicity, and low transplant rejection rate. DPSCs are extensively used in tissue engineering and regenerative medicine, including for the treatment of sciatic nerve injury, facial nerve injury, spinal cord injury, and other neurodegenerative diseases. This article reviews research related to DPSCs and their advantages in treating PNI, aiming to summarize the therapeutic potential of DPSCs for PNI and the underlying mechanisms and providing valuable guidance and a foundation for future research.

Periodontal ligament stem cells as a promising therapeutic target for neural damage

BACKGROUND

The damaged neuronal cells of adult mammalian lack the regenerative ability to replace the neuronal connections. Periodontal ligament stem cells (PDLSCs) are the promising source for neuroregenerative applications that can improve the injured microenvironment of the damaged neural system. They provide neuronal progenitors and neurotrophic, anti-apoptotic and anti-inflammatory factors. In this study, we aimed to comprehensively explore the various neuronal differentiation potentials of PDLSCs for application in neural regeneration therapy.

MAIN TEXT

PDLSCs have superior potential to differentiate into various neural-like cells through a dedifferentiation stage followed by differentiation process without need for cell division. Diverse combination of nutritional factors can be used to induce the PDLSCs toward neural lineage. PDLSCs when coupled with biomaterials could have significant implications for neural tissue repair. PDLSCs can be a new clinical research target for Alzheimer's disease treatment, multiple sclerosis and cerebral ischemia. Moreover, PDLSCs have beneficial effects on retinal ganglion cell regeneration and photoreceptor survival. PDLSCs can be a great source for the repair of injured peripheral nerve through the expression of several neural growth factors and differentiation into Schwann cells.

CONCLUSION

In conclusion, these cells are an appealing source for utilizing in clinical treatment of the neuropathological disorders. Although significant in vitro and in vivo investigations were carried out in order for neural differentiation evaluation of these cells into diverse types of neurons, more preclinical and clinical studies are needed to elucidate their therapeutic potential for neural diseases.

Endometrium Derived Stem Cells as Potential Candidates in Nervous System Repair

Limited cell division and lack of endogenous repair mechanisms in the central nervous system, hampers tissue repair following neurodegenerative diseases or tissue injuries. Unlike central nervous system; peripheral nervous system has some capacity to repair after injury, but in case of critical sized defects the use of supporting cells in the neural guidance channels seems inevitable to obtain a satisfactory functional recovery. Stem cell therapies have provided new frontiers in the repair of nervous system largely through paracrine secretion mechanisms. The therapeutic potential of stem cells differs according to their tissue of origin, mode of isolation, administration route, and passage number. During the past decades, studies have been focused on stem cells harvested from disposable tissues such as menstrual blood or biopsies from endometrium. These cells are characterized by their high differentiation and proliferation potential, ease of harvest, and lack of ethical concerns. In the current review, we will discuss the prospects and challenges of endometrial stem cells' application in nervous system repair.

Neural crest derived stem cells from dental pulp and tooth-associated stem cells for peripheral nerve regeneration

The peripheral nerve injuries, representing some of the most common types of traumatic lesions affecting the nervous system, are highly invalidating for the patients besides being a huge social burden. Although peripheral nervous system owns a higher regenerative capacity than does central nervous system, mostly depending on Schwann cells intervention in injury repair, several factors determine the extent of functional outcome after healing. Based on the injury type, different therapeutic approaches have been investigated so far. Nerve grafting and Schwann cell transplantation have represented the gold standard treatment for peripheral nerve injuries, however these approaches own limitations, such as scarce donor nerve availability and donor site morbidity. Cell based therapies might provide a suitable tool for peripheral nerve regeneration, in fact, the ability of different stem cell types to differentiate towards Schwann cells in combination with the use of different scaffolds have been widely investigated in animal models of peripheral nerve injuries in the last decade. Dental pulp is a promising cell source for regenerative medicine, because of the ease of isolation procedures, stem cell proliferation and multipotency abilities, which are due to the embryological origin from neural crest. In this article we review the literature concerning the application of tooth derived stem cell populations combined with different conduits to peripheral nerve injuries animal models, highlighting their regenerative contribution exerted through either glial differentiation and neuroprotective/neurotrophic effects on the host tissue.

IL‑1β and TNF‑α suppress TGF‑β‑promoted NGF expression in periodontal ligament‑derived fibroblasts through inactivation of TGF‑β‑induced Smad2/3‑ and p38 MAPK‑mediated signals

Mechanosensitive (MS) neurons in the periodontal ligament (PDL) pass information to the trigeminal ganglion when excited by mechanical stimulation of the tooth. During occlusal tooth trauma of PDL tissues, MS neurons are injured, resulting in atrophic neurites and eventual degeneration of MS neurons. Nerve growth factor (NGF), a neurotrophic factor, serves important roles in the regeneration of injured sensory neurons. In the present study, the effect of pro‑inflammatory cytokines, including interleukin 1β (IL‑1β) and tumor necrosis factor α (TNF‑α), on transforming growth factor β1 (TGF‑β1)‑induced NGF expression was evaluated in rat PDL‑derived SCDC2 cells. It was observed that TGF‑β1 promoted NGF expression via Smad2/3 and p38 mitogen‑activated protein kinase (MAPK) activation. IL‑1β and TNF‑α suppressed the TGF‑β1‑induced activation of Smad2/3 and p38 MAPK, resulting in the abrogation of NGF expression. NGF secreted by TGF‑β1‑treated SCDC2 cells promoted neurite extension and the expression of tyrosine hydroxylase, a rate‑limiting enzyme in dopamine synthesis in rat pheochromocytoma PC12 cells. These results suggested that pro‑inflammatory cytokines suppressed the TGF‑β‑mediated expression of NGF in PDL‑derived fibroblasts through the inactivation of TGF‑β‑induced Smad2/3 and p38 MAPK signaling, possibly resulting in the disturbance of the regeneration of injured PDL neurons.

IL‑1β and TNF‑α suppress TGF‑β‑promoted NGF expression in periodontal ligament‑derived fibroblasts through inactivation of TGF‑β‑induced Smad2/3‑ and p38 MAPK‑mediated signals

Mechanosensitive (MS) neurons in the periodontal ligament (PDL) pass information to the trigeminal ganglion when excited by mechanical stimulation of the tooth. During occlusal tooth trauma of PDL tissues, MS neurons are injured, resulting in atrophic neurites and eventual degeneration of MS neurons. Nerve growth factor (NGF), a neurotrophic factor, serves important roles in the regeneration of injured sensory neurons. In the present study, the effect of pro‑inflammatory cytokines, including interleukin 1β (IL‑1β) and tumor necrosis factor α (TNF‑α), on transforming growth factor β1 (TGF‑β1)‑induced NGF expression was evaluated in rat PDL‑derived SCDC2 cells. It was observed that TGF‑β1 promoted NGF expression via Smad2/3 and p38 mitogen‑activated protein kinase (MAPK) activation. IL‑1β and TNF‑α suppressed the TGF‑β1‑induced activation of Smad2/3 and p38 MAPK, resulting in the abrogation of NGF expression. NGF secreted by TGF‑β1‑treated SCDC2 cells promoted neurite extension and the expression of tyrosine hydroxylase, a rate‑limiting enzyme in dopamine synthesis in rat pheochromocytoma PC12 cells. These results suggested that pro‑inflammatory cytokines suppressed the TGF‑β‑mediated expression of NGF in PDL‑derived fibroblasts through the inactivation of TGF‑β‑induced Smad2/3 and p38 MAPK signaling, possibly resulting in the disturbance of the regeneration of injured PDL neurons.

The neurotrophic effects of different human dental mesenchymal stem cells

The current gold standard treatment for peripheral nerve injury is nerve grafting but this has disadvantages such as donor site morbidity. New techniques focus on replacing these grafts with nerve conduits enhanced with growth factors and/or various cell types such as mesenchymal stem cells (MSCs). Dental-MSCs (D-MSCs) including stem cells obtained from apical papilla (SCAP), dental pulp stem cells (DPSC), and periodontal ligament stem cells (PDLSC) are potential sources of MSCs for nerve repair. Here we present the characterization of various D-MSCs from the same human donors for peripheral nerve regeneration. SCAP, DPSC and PDLSC expressed BDNF, GDNF, NGF, NTF3, ANGPT1 and VEGFA growth factor transcripts. Conditioned media from D-MSCs enhanced neurite outgrowth in an in vitro assay. Application of neutralizing antibodies showed that brain derived neurotrophic factor plays an important mechanistic role by which the D-MSCs stimulate neurite outgrowth. SCAP, DPSC and PDLSC were used to treat a 10 mm nerve gap defect in a rat sciatic nerve injury model. All the stem cell types significantly enhanced axon regeneration after two weeks and showed neuroprotective effects on the dorsal root ganglia neurons. Overall the results suggested SCAP to be the optimal dental stem cell type for peripheral nerve repair.

The Neurovascular Properties of Dental Stem Cells and Their Importance in Dental Tissue Engineering

Within the field of tissue engineering, natural tissues are reconstructed by combining growth factors, stem cells, and different biomaterials to serve as a scaffold for novel tissue growth. As adequate vascularization and innervation are essential components for the viability of regenerated tissues, there is a high need for easily accessible stem cells that are capable of supporting these functions. Within the human tooth and its surrounding tissues, different stem cell populations can be distinguished, such as dental pulp stem cells, stem cells from human deciduous teeth, stem cells from the apical papilla, dental follicle stem cells, and periodontal ligament stem cells. Given their straightforward and relatively easy isolation from extracted third molars, dental stem cells (DSCs) have become an attractive source of mesenchymal-like stem cells. Over the past decade, there have been numerous studies supporting the angiogenic, neuroprotective, and neurotrophic effects of the DSC secretome. Together with their ability to differentiate into endothelial cells and neural cell types, this makes DSCs suitable candidates for dental tissue engineering and nerve injury repair.

IL-7 suppresses osteogenic differentiation of periodontal ligament stem cells through inactivation of mitogen-activated protein kinase pathway

Periodontal ligament stem cells (PDLSCs) are tissue-specific mesenchymal stem cells (MSCs), having an important role in regenerative therapy for teeth loss. Interleukin-7 (IL-7) is a key cytokine produced by stromal cells including MSCs, and exhibits specific roles for B and T cell development and osteoblasts differentiation of multiple myeloma. However, the effect of IL-7 on osteogenic differentiation of PDLSCs remains unclear. Therefore, in the present study we determined whether IL-7 affects the proliferation and osteogenic differentiation of PDLSCs in vitro and explored the associated signaling pathways for IL-7-mediated cell differentiation. The results demonstrated that the isolated human PDLSCs possessed MSCs features, highly expressing CD90, CD44, CD105, CD29 and CD73, and almost did not expressed CD34, CD45, CD11b, CD14 and CD117. IL-7 could not significantly affect the proliferation of PDLSCs, but it decreased their osteogenic differentiation and inhibited alkaline phosphatase (ALP) activity. The results of quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blotting exhibited that the expression levels of Runx-2, SP7 and osteocalcin (OCN) were significantly reduced by IL-7. Further studies indicated that IL-7 did not significantly change JNK, ERK1/2 and p38 protein production, but markedly suppressed their phosphorylation levels. These data suggest that IL-7 inhibits the osteogenic differentiation of PDLSCs probably via inactivation of mitogen-activated protein kinase (MAPK) signaling pathway.