Marrow-Derived Autologous Stromal Cells for the Restoration of Salivary Hypofunction (MARSH): Study protocol for a phase 1 dose-escalation trial of patients with xerostomia after radiation therapy for head and neck cancer

Evaluation and management of dry mouth and its complications in rheumatology practice

INTRODUCTION

The symptom of dry mouth has multiple potential etiologies and can be a diagnostic clue to the presence of common systemic diseases encountered in rheumatology practice. The presence of decreased saliva flow (i.e. salivary hypofunction) defines a subset of dry mouth patients in whom there may be reversible drug effects, an iatrogenic insult such as head and neck irradiation, or a disease that directly involves the salivary glands (e.g. Sjögren's disease). The assessment of salivary hypofunction includes sialometry, salivary gland imaging, salivary gland biopsy, and an assessment for relevant systemic diseases. Optimal management of dry mouth requires accurate definition of its cause, followed by general measures that serve to alleviate its symptoms and prevent its complications.

AREAS COVERED

Through a literature search on xerostomia and salivary hypofunction, we provide an overview of the causes of dry mouth, highlight the potential impact of salivary hypofunction on oral and systemic health, detail routine evaluation methods and treatment strategies, and emphasize the importance of collaboration with oral health care providers.

EXPERT OPINION

Our Expert Opinion is provided on unmet needs in the management of dry mouth and relevant research progress in the field.

Mesenchymal stem cell-derived HGF attenuates radiation-induced senescence in salivary glands via compensatory proliferation

BACKGROUND & AIM

Irradiation of the salivary glands during head and neck cancer treatment induces cellular senescence in response to DNA damage and contributes to radiation-induced hyposalivation by affecting the salivary gland stem/progenitor cell (SGSC) niche. Cellular senescence, such as that induced by radiation, is a state of cell-cycle arrest, accompanied by an altered pro-inflammatory secretome known as the senescence-associated secretory phenotype (SASP) with potential detrimental effects on the surrounding microenvironment. We hypothesized that the pro-regenerative properties of mesenchymal stem cells (MSCs) may attenuate cellular senescence post-irradiation. Therefore, here we evaluated the effects of adipose-derived MSCs (ADSCs) on the radiation-induced response of salivary gland organoids (SGOs).

METHODS

Proteomic analyses to identify soluble mediators released by ADSCs co-cultured with SGOS revealed secretion of hepatocyte growth factor (HGF) in ADSCs, suggesting a possible role in the stem cell crosstalk. Next, the effect of recombinant HGF in the culture media of ex vivo grown salivary gland cells was tested in 2D monolayers and 3D organoid models.

RESULTS

Treatment with HGF robustly increased salivary gland cell proliferation. Importantly, HGF supplementation post-irradiation enhanced proliferation at lower doses of radiation (0, 3, 7 Gy), but not at higher doses (10, 14 Gy) where most cells stained positive for senescence-associated beta-galactosidase. Furthermore, HGF had no effect on the senescence-associated secretory phenotype (SASP) of irradiated SGOs, suggesting there may be compensatory proliferation by cell-division competent cells instead of a reversal of cellular senescence after irradiation.

CONCLUSION

ADSCs may positively influence radiation recovery through HGF secretion and can promote the ex vivo expansion of salivary gland stem/progenitor cells to enhance the effects of co-transplanted SGSC.

Recent progress in regenerative therapy for damaged salivary glands: From bench to bedside

OBJECTIVE

For functional restoration of salivary glands (SGs) injured by radiation therapy or Sjögren's syndrome (SS), various experimental approaches, such as gene therapy, tissue engineering, and cell-based therapy, have been proposed. This narrative review summarized recent progresses in research using cell-based therapies, including promising trials that could lead to bench-to-clinic applications.

METHODS

A literature review based on PubMed publications in the last two decades was performed to summarize progresses in cell-based therapies for SG dysfunction.

RESULTS

Over 100 experimental studies have shown the therapeutic potential of several types of cells, such as SG stem cells and mesenchymal stem cells, as well as effectively conditioned mononuclear cells, in both radiation injury and SS animal models. These therapies affect to slow fibrosis progression and stimulate tissue regeneration in atrophic glands. However, to date, only a total of seven studies have been developed to the stage of clinical study, showing the safety and preliminary efficacy.

CONCLUSION

To lead the radical effectiveness expected in cell-based therapy, advances in reverse translational research and in innovative experimental research, based on the findings of recent clinical studies, will be critical in the next decade.

Post-radiation xerostomia therapy with allogeneic mesenchymal stromal stem cells in patients with head and neck cancer: study protocol for phase I clinical trial

BACKGROUND

Xerostomia is a common side effect of radiotherapy in patients with head and neck tumors that negatively affects quality of life. There is no known effective standard treatment for xerostomia. Here, we present the study protocol used to evaluate the safety and preliminary efficacy of allogeneic mesenchymal stromal stem cells (MSCs) derived from umbilical cord tissue.

PATIENTS AND METHODS

Ten oropharyngeal cancer patients with post-radiation xerostomia and no evidence of disease recurrence 2 or more years after (chemo)irradiation (intervention group) and 10 healthy volunteers (control group) will be enrolled in this nonrandomized, open-label, phase I exploratory study. MSCs from umbilical cord tissue will be inserted under ultrasound guidance into both parotid glands and both submandibular glands of the patients. Toxicity of the procedure will be assessed according to CTCAE v5.0 criteria at days 0, 1, 5, 28, and 120. Efficacy will be assessed by measuring salivary flow and analyzing its composition, scintigraphic evaluation of MSC grafting, retention, and migration, and questionnaires measuring subjective xerostomia and quality of life. In addition, the radiological, functional, and morphological characteristics of the salivary tissue will be assessed before, at 4 weeks, and at 4 months after the procedure. In the control group subjects, only salivary flow rate and salivary composition will be determined.

DISCUSSION

The use of allogeneic MSCs from umbilical cord tissue represents an innovative approach for the treatment of xerostomia after radiation. Due to the noninvasive collection procedure, flexibility of cryobanking, and biological advantages, xerostomia therapy using allogeneic MSCs from umbilical cord tissue may have an advantage over other similar therapies.

Non-pharmacologic interventions for management of radiation-induced dry mouth: A systematic review

OBJECTIVES

Radiation-induced dry mouth negatively impacts patients' oral health and quality of life. Currently, evidence-based recommendation for non-pharmacologic interventions is still lacking. This study aimed to systematically review clinical trials evaluating the efficacy of non-pharmacologic interventions in cancer patients with radiation-induced dry mouth.

METHODS

Randomized controlled trials from 2000 were searched from 4 databases, including MEDLINE, Cochrane, Embase via OVID, and SCOPUS, up to December 16th, 2022 (PROSPERO registration CRD42022378405). The risk of bias was assessed using the revised Cochrane risk of bias assessment tool.

RESULTS

Twenty-one studies were included: 11 on artificial saliva, 4 on electrical nerve stimulation (TENS), 2 on acupuncture, and one study each on low-level laser therapy, stem cells, chewing gum, and probiotics. Overall bias was low, medium, and high in 33%, 48%, and 19% of the studies, respectively. Certain artificial saliva products and TENS were shown to improve dry mouth symptoms and salivary flow rate (SFR). One study showed that stem cell transplantation significantly increased SFR.

CONCLUSIONS

The evidence suggested that certain artificial saliva products and TENS are promising management. However, the evidence was still limited due to heterogeneity of interventions and outcome measurements. Thus, future studies using standard measurements and long-term follow-up are warranted.

Cell-Free Therapies: The Use of Cell Extracts to Mitigate Irradiation-Injured Salivary Glands

Radiotherapy is a standard treatment for head and neck cancer patients worldwide. However, millions of patients who received radiotherapy consequently suffer from xerostomia because of irreversible damage to salivary glands (SGs) caused by irradiation (IR). Current treatments for IR-induced SG hypofunction only provide temporary symptom alleviation but do not repair the damaged SG, thus resulting in limited treatment efficacy. Therefore, there has recently been a growing interest in regenerative treatments, such as cell-free therapies. This review aims to summarize cell-free therapies for IR-induced SG, with a particular emphasis on utilizing diverse cell extract (CE) administrations. Cell extract is a group of heterogeneous mixtures containing multifunctional inter-cellular molecules. This review discusses the current knowledge of CE's components and efficacy. We propose optimal approaches to improve cell extract treatment from multiple perspectives (e.g., delivery routes, preparation methods, and other details regarding CE administration). In addition, the advantages and limitations of CE treatment are systematically discussed by comparing it to other cell-free (such as conditioned media and exosomes) and cell-based therapies. Although a comprehensive identification of the bioactive factors within CEs and their mechanisms of action have yet to be fully understood, we propose cell extract therapy as an effective, practical, user-friendly, and safe option to conventional therapies in IR-induced SG.

Human Bone Marrow Cell Extracts Mitigate Radiation Injury to Salivary Gland

Mitigation of irradiation injury to salivary glands was previously reported using a cell-free extract from mouse bone marrow. However, to bring this potential therapy a step closer to clinical application, a human bone marrow cell extract (BMCE) needs to be tested. Here, we report that irradiation-induced injury of salivary glands in immunocompetent mice treated with human BMCE secreted 50% more saliva than saline-injected mice, and BMCE did not cause additional acute inflammatory reaction. In addition, to identify the cell fraction in BMCE with the most therapeutic activity, we sorted human bone marrow into 3 cell fractions (mononuclear, granulocyte, and red blood cells) and tested their respective cell extracts. We identified that the mononuclear cell extract (MCE) provided the best therapeutic efficacy. It increased salivary flow 50% to 73% for 16 wk, preserved salivary parenchymal and stromal cells, and doubled cell proliferation rates while producing less inflammatory response. In contrast, the cell extract of granulocytes was of shorter efficacy and induced an acute inflammatory response, while that from red blood cells was not therapeutically effective for salivary function. Several proangiogenic (MMP-8, MMP-9, VEGF, uPA) and antiangiogenic factors (TSP-1, PF4, TIMP-1, PAI-1) were identified in MCE. Added advantages of BMCE and MCE for potential clinical use were that cell extracts from both male and female donors were comparably bioactive and that cell extracts could be stored and transported much more conveniently than cells. These findings suggest human BMCE, specifically the MCE fraction, is a promising therapy against irradiation-induced salivary hypofunction.

Quantification of very late xerostomia in head and neck cancer patients after irradiation

Objective

Radiation therapy (RT) for head and neck cancer (HNC) can result in severe xerostomia, or the subjective feeling of dry mouth. Characterizing xerostomia is critical to designing future clinical trials investigating how to improve HNC patients' quality of life (QoL). Few studies have investigated the very late (>5 years post-RT) effects of RT for HNC. We undertook preliminary studies quantifying very late xerostomia.

Methods

Six adults who underwent RT for HNC at least 5 years prior and reported xerostomia were enrolled. Five healthy adults without a self-reported history of HNC or xerostomia were enrolled as controls. All participants completed three validated surveys to measure xerostomia-related QoL. Salivary production rates were measured and compositional analysis of the saliva and oral microbiome was completed.

Results

The QoL survey scores for the HNC participants were significantly worse as compared to the control participants. The HNC participants produced less unstimulated saliva (p = .02) but not less stimulated saliva. The median salivary mucin significantly higher in HNC participants than in control participants (p = .02). There was no significant difference between the pH, amylase, or total protein. Microbiome analysis revealed alpha diversity to be significantly lower in the HNC participants.

Conclusion

In the survivors of HNC who suffer from late toxicities, multiple means of measuring toxicity may be useful. We found that in patients with radiation-induced xerostomia over 5 years after therapy, not only were the QoL surveys significantly worse, as expected, but other measurements such as mucin and oral microbiome diversity were also significantly different.

Level of evidence

3.

Human Mesenchymal Stromal Cells Do Not Cause Radioprotection of Head-and-Neck Squamous Cell Carcinoma

Radiotherapy of head-and-neck squamous cell carcinoma (HNSCC) can cause considerable normal tissue injuries, and mesenchymal stromal cells (MSCs) have been shown to aid regeneration of irradiation-damaged normal tissues. However, utilization of MSC-based treatments for HNSCC patients undergoing radiotherapy is hampered by concerns regarding potential radioprotective effects. We therefore investigated the influence of MSCs on the radiosensitivity of HNSCCs. Several human papillomavirus (HPV)-negative and HPV-positive HNSCCs were co-cultured with human bone marrow-derived MSCs using two-dimensional and three-dimensional assays. Clonogenic survival, proliferation, and viability of HNSCCs after radiotherapy were assessed depending on MSC co-culture. Flow cytometry analyses were conducted to examine the influence of MSCs on irradiation-induced cell cycle distribution and apoptosis induction in HNSCCs. Immunofluorescence stainings of γH2AX were conducted to determine the levels of residual irradiation-induced DNA double-strand breaks. Levels of connective tissue growth factor (CTGF), a multifunctional pro-tumorigenic cytokine, were analyzed using enzyme-linked immunosorbent assays. Neither direct MSC co-culture nor MSC-conditioned medium exerted radioprotective effects on HNSCCs as determined by clonogenic survival, proliferation, and viability assays. Consistently, three-dimensional microwell arrays revealed no radioprotective effects of MSCs. Irradiation resulted in a G2/M arrest of HNSCCs at 96 h independently of MSC co-culture. HNSCCs’ apoptosis rates were increased by irradiation irrespective of MSCs. Numbers of residual γH2AX foci after irradiation with 2 or 8 Gy were comparable between mono- and co-cultures. MSC mono-cultures and HNSCC-MSC co-cultures exhibited comparable CTGF levels. We did not detect radioprotective effects of human MSCs on HNSCCs. Our results suggest that the usage of MSC-based therapies for radiotherapy-related toxicities in HNSCC patients may be safe in the context of absent radioprotection.

Bioengineering in salivary gland regeneration

Salivary gland (SG) dysfunction impairs the life quality of many patients, such as patients with radiation therapy for head and neck cancer and patients with Sjögren’s syndrome. Multiple SG engineering strategies have been considered for SG regeneration, repair, or whole organ replacement. An in-depth understanding of the development and differentiation of epithelial stem and progenitor cells niche during SG branching morphogenesis and signaling pathways involved in cell–cell communication constitute a prerequisite to the development of suitable bioengineering solutions. This review summarizes the essential bioengineering features to be considered to fabricate an engineered functional SG model using various cell types, biomaterials, active agents, and matrix fabrication methods. Furthermore, recent innovative and promising approaches to engineering SG models are described. Finally, this review discusses the different challenges and future perspectives in SG bioengineering.