Mesenchymal Stem Cell Therapy in Submandibular Salivary Gland Allotransplantation: Experimental Study

Oral ulcer treatment using human tonsil-derived mesenchymal stem cells encapsulated in trimethyl chitosan hydrogel: an animal model study

BACKGROUND

Oral ulcers are a common side effect of chemotherapy and affect patients' quality of life. While stem cell transplantation is a potential treatment for oral ulcers, its efficacy is limited as the stem cells tend to remain in the affected area for a short time. This study aims to develop a treatment for oral ulcers by using trimethyl chitosan (TMC) hydrogel with human tonsil-derived stem cells (hTMSCs) to increase the therapeutic effect of stem cells and investigate their effectiveness.

METHODS

Animals were divided into four experimental groups: Control, TMC hydrogel, hTMSCs, and hTMSCs loaded in TMC hydrogel (Hydrogel + hTMSCs) (each n = 8). Oral ulcers were chemically induced by anesthetizing the rats followed by injection of dilute acetic acid in the right buccal mucosa. After confirming the presence of oral ulcers in the animals, a single subcutaneous injection of 100 µL of each treatment was applied to the ulcer area. Histological analyses were performed to measure inflammatory cells, oral mucosal thickness, and fibrosis levels. The expression level of inflammatory cytokines was also measured using RT-PCR to gauge therapeutic the effect.

RESULTS

The ulcer size was significantly reduced in the TMC hydrogel + hTMSCs group compared to the control group. The stem cells in the tissue were only observed until Day 3 in the hTMSCs treated group, while the injected stem cells in the TMC Hydrogel + hTMSCs group were still present until day 7. Cytokine analysis related to the inflammatory response in the tissue confirmed that the TMC Hydrogel + hTMSCs treated group demonstrated superior wound healing compared to other experimental groups.

CONCLUSION

This study has shown that the adhesion and viability of current stem cell therapies can be resolved by utilizing a hydrogel prepared with TMC and combining it with hTMSCs. The combined treatment can promote rapid healing of oral cavity wounds by enhancing anti-inflammatory effects and expediting wound healing. Therefore, hTMSC loaded in TMC hydrogel was the most effective wound-healing approach among all four treatment groups prolonging stem cell survival. However, further research is necessary to minimize the initial inflammatory response of biomaterials and assess the safety and long-term effects for potential clinical applications.

Salivary Gland Transplantation as a Promising Approach for Tear Film Restoration in Severe Dry Eye Disease

With increased awareness of dry eye disease (DED), a multitude of therapeutic options have become available. Nevertheless, the treatment of severe DED remains difficult. In a patient whose DED is related to the loss of lacrimal function without severe destruction of the salivary glands, autologous transplantation of the latter as functioning exocrine tissue to rebuild a stable tear film is an attractive idea. All three major and minor salivary glands have been used for such transplantation. Due to the complications associated with and unfavorable prognosis of parotid duct and sublingual gland transplantation, surgeons now prefer to use the submandibular gland (SMG) for such procedures. The transplantation of the SMG not only has a high survival rate, but also improves dry eye symptoms and signs for more than 20 years post-surgery. The regulation of the secretion of the transplanted SMG is critical because the denervated SMG changes its mechanism of secretion. Innovative procedures have been developed to stimulate secretion in order to prevent the obstruction of the Wharton's duct and to decrease secretion when postoperative "epiphora" occurs. Among the minor salivary glands, the transplantation of the labial salivary glands is the most successful in the long-term. The measurement of the flow rates of minor salivary glands and donor-site selection are critical steps before surgery.

Salivary Gland Bioengineering

Salivary gland dysfunction affects millions globally, and tissue engineering may provide a promising therapeutic avenue. This review delves into the current state of salivary gland tissue engineering research, starting with a study of normal salivary gland development and function. It discusses the impact of fibrosis and cellular senescence on salivary gland pathologies. A diverse range of cells suitable for tissue engineering including cell lines, primary salivary gland cells, and stem cells are examined. Moreover, the paper explores various supportive biomaterials and scaffold fabrication methodologies that enhance salivary gland cell survival, differentiation, and engraftment. Innovative engineering strategies for the improvement of vascularization, innervation, and engraftment of engineered salivary gland tissue, including bioprinting, microfluidic hydrogels, mesh electronics, and nanoparticles, are also evaluated. This review underscores the promising potential of this research field for the treatment of salivary gland dysfunction and suggests directions for future exploration.

cGAS-STING pathway in ischemia-reperfusion injury: a potential target to improve transplantation outcomes

Transplantation is an important life-saving therapeutic choice for patients with organ or tissue failure once all other treatment options are exhausted. However, most allografts become damaged over an extended period, and post-transplantation survival is limited. Ischemia reperfusion injury (IRI) tends to be associated with a poor prognosis; resultant severe primary graft dysfunction is the main cause of transplant failure. Targeting the cGAS-STING pathway has recently been shown to be an effective approach for improving transplantation outcomes, when activated or inhibited cGAS-STING pathway, IRI can be alleviated by regulating inflammatory response and programmed cell death. Thus, continuing efforts to develop selective agonists and antagonists may bring great hopes to post-transplant patient. In this mini-review, we reviewed the role of the cGAS-STING pathway in transplantation, and summarized the crosstalk between this pathway and inflammatory response and programmed cell death during IRI, aiming to provide novel insights into the development of therapies to improve patient outcome after transplantation.

Efficacy of mesenchymal stem cell therapy in rodent models of radiation-induced xerostomia and oral mucositis: a systematic review

BACKGROUND

Radiation-induced xerostomia and oral mucositis are serious complications of radiation therapy for head and neck cancers. Current treatment options have limited efficacy. Mesenchymal stem cell (MSC) therapy has shown promising results in supporting the restoration of glandular secretion function and the regeneration of damaged tissues. This study aim to (1) assess the quality of evidence for MSCs treatment in rodent models of radiation-induced oral complications and (2) determine whether MSCs can improve the therapeutic effect of radiation-induced oral mucositis.

METHODS

Intervention studies using MSCs in rodent models were comprehensively retrieved in the Pubmed, Medline, Embase, Web of Science, and Cochrane library databases on June 1, 2022. The quality of all in vivo experiments was assessed using SYRCLE, and this article is written following the PRISMA guidelines.

RESULTS

A total of 12 studies were included in this systematic review. The study found that in animal models of radiation-induced xerostomia, MSCs could increase salivary protein secretion, improve SFR, shorten the salivary lag time, anti-apoptosis, etc. In animal models of radiation-induced oral mucositis, MSCs improve the micromorphology and macromorphology of RIOM. Moreover, the effect of MSCs on the modification of ulcer duration and latency may be related to the time of MSCs transplantation but further studies are needed.

CONCLUSION

The results of our systematic review suggest that MSCs appeared to be effective in the treatment of radiation-induced xerostomia and oral mucositis.

Drug Therapeutics Delivery to the Salivary Glands: Intraglandular and Intraductal Injections

Salivary gland hypofunction and xerostomia following pathological conditions like Sjogren's syndrome or head and neck radiotherapy usually lead to tremendous impairment of oral health, speech, and swallowing. The use of systemic drugs to alleviate the symptoms of these conditions has been associated with various adverse effects. Techniques of local drug delivery to the salivary gland have grown enormously to address this problem properly. The techniques include intraglandular and intraductal injections. In this chapter, we will provide a review of the literature for both techniques while incorporating our lab experience in using them.

Encapsulation of Primary Salivary Gland Acinar Cell Clusters and Intercalated Ducts (AIDUCs) within Matrix Metalloproteinase (MMP)-Degradable Hydrogels to Maintain Tissue Structure and Function

Progress in the development of salivary gland regenerative strategies is limited by poor maintenance of the secretory function of salivary gland cells (SGCs) in vitro. To reduce the precipitous loss of secretory function, a modified approach to isolate intact acinar cell clusters and intercalated ducts (AIDUCs), rather than commonly used single cell suspension, is investigated. This isolation approach yields AIDUCs that maintain many of the cell-cell and cell-matrix interactions of intact glands. Encapsulation of AIDUCs in matrix metalloproteinase (MMP)-degradable PEG hydrogels promotes self-assembly into salivary gland mimetics (SGm) with acinar-like structure. Expression of Mist1, a transcription factor associated with secretory function, is detectable throughout the in vitro culture period up to 14 days. Immunohistochemistry also confirms expression of acinar cell markers (NKCC1, PIP and AQP5), duct cell markers (K7 and K5), and myoepithelial cell markers (SMA). Robust carbachol and ATP-stimulated calcium flux is observed within the SGm for up to 14 days after encapsulation, indicating that secretory function is maintained. Though some acinar-to-ductal metaplasia is observed within SGm, it is reduced compared to previous reports. In conclusion, cell-cell interactions maintained within AIDUCs together with the hydrogel microenvironment may be a promising platform for salivary gland regenerative strategies.

Tissue Engineering of Oral Mucosa and Salivary Gland: Disease Modeling and Clinical Applications

Oral mucosa and salivary gland are composed of complex and dynamic networks of extracellular matrix, multiple cell types, vasculature, and various biochemical agents. Two-dimensional (2D) cell culture is commonly used in testing new drugs and experimental therapies. However, 2D cell culture cannot fully replicate the architecture, physiological, and pathological microenvironment of living human oral mucosa and salivary glands. Recent microengineering techniques offer state of the science cell culture models that can recapitulate human organ structures and functions. This narrative review describes emerging in vitro models of oral and salivary gland tissue such as 3D cell culture models, spheroid and organoid models, tissue-on-a-chip, and functional decellularized scaffolds. Clinical applications of these models are also discussed in this review.

Magnetic resonance imaging of enhanced nerve repair with mesenchymal stem cells combined with microenvironment immunomodulation in neurotmesis

INTRODUCTION

The immuno-microenvironment of injured nerves adversely affects mesenchymal stem cell (MSC) therapy for neurotmesis. Magnetic resonance imaging (MRI) can be used noninvasively to monitor nerve degeneration and regeneration. The aim of this study was to investigate nerve repair after MSC transplantation combined with microenvironment immunomodulation in neurotmesis by using multiparametric MRI.

METHODS

Rats with sciatic nerve transection and surgical coaptation were treated with MSCs combined with immunomodulation or MSCs alone. Serial multiparametric MRI examinations were performed over an 8-week period after surgery.

RESULTS

Nerves treated with MSCs combined with immunomodulation showed better functional recovery, rapid recovery of nerve T2, fractional anisotropy and radial diffusivity values, and more rapid restoration of the fiber tracks than nerves treated with MSCs alone.

DISCUSSION

Transplantation of MSCs in combination with immunomodulation can exert a synergistic repair effect on neurotmesis, which can be monitored by multiparametric MRI.