Bone marrow cells are a source of undifferentiated cells to prevent Sjögren's syndrome and to preserve salivary glands function in the non-obese diabetic mice

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.

Salivary Gland Function, Development and Regeneration

Salivary glands produce and secrete saliva, which is essential for maintaining oral health and overall health. Understanding both the unique structure and physiological function of salivary glands, as well as how they are affected by disease and injury will direct the development of therapy to repair and regenerate them. Significant recent advances, particularly in the OMICS field, increase our understanding of how salivary glands develop at the cellular, molecular and genetic levels; the signaling pathways involved, the dynamics of progenitor cell lineages in development, homeostasis and regeneration and the role of the extracellular matrix microenvironment. These provide a template for cell and gene therapies as well as bioengineering approaches to repair or regenerate salivary function.

Treatment of Sjögren's Syndrome with Mesenchymal Stem Cells: A Systematic Review

Mesenchymal stem cells (MSCs) are ubiquitous in the human body. Mesenchymal stem cells were initially isolated from bone marrow and later from other organs such as fatty tissues, umbilical cords, and gingiva. Their secretory capacities give them interesting immunomodulatory properties in cell therapy. Some studies have explored the use of MSCs to treat Sjögren’s syndrome (SS), a chronic inflammatory autoimmune disease that mainly affects exocrine glands, including salivary and lacrimal glands, although current treatments are only palliative. This systematic review summarizes the current data about the application of MSCs in SS. Reports show improvements in salivary secretions and a decrease in lymphocytic infiltration in salivary glands in patients and mice with SS after intravenous or infra-peritoneal injections of MSCs. MSC injections led to a decrease in inflammatory cytokines and an increase in anti-inflammatory cytokines. However, the intrinsic mechanism of action of these MSCs currently remains unknown.

Salivary hypofunction: An update on therapeutic strategies

OBJECTIVE

To perform a literature review addressing the therapeutic strategies for salivary hypofunction.

BACKGROUND

Qualitative and quantitative salivary dysfunctions predispose to changes in the oral mucosa and teeth, cause impairment to oral functions and negative impact on quality of life.

MATERIALS AND METHODS

A MEDLINE/PubMed search was conducted using the terms "Xerostomia" AND, "Saliva Artificial" OR, "Citric Acid," "Malic Acid," "Chewing Gum," "Acupuncture" OR, "Pilocarpine" OR, "Bethanechol" OR, "Cevimeline" OR, "Hyperbaric Oxygen Therapy" OR, "Stem Cell Therapy" OR "Genetic Therapy" and their Mesh Terms.

RESULTS

We selected 25 clinical trials investigating the effects of salivary substitutes, chewing gum, malic and citric acids, pilocarpine, cevimeline, bethanechol, acupuncture, hyperbaric oxygen therapy and regenerative therapies on salivary hypofunction. In most studies, the number of participants was low and the follow-up times short. The therapeutic modalities were classified according to the level of evidence on salivary dysfunction.

CONCLUSIONS

Pilocarpine and cevimeline had the strongest evidence of beneficial effect on salivary hypofunction. Citric and malic acids increase salivary flow but also increase the risk of erosion and dental caries. There are no controlled clinical trials supporting the efficacy of acupuncture, stem cell therapy and gene therapy on salivary dysfunction, although clinical observations suggest a promising effect. There is no evidence supporting salivary substitutes, chewing gum, bethanechol or hyperbaric oxygen on the treatment of salivary hypofunction.

Optimal timing and frequency of bone marrow soup therapy for functional restoration of salivary glands injured by single-dose or fractionated irradiation

Injections of bone marrow (BM) cell extract, known as 'BM soup', were previously reported to mitigate ionizing radiation (IR) injury to salivary glands (SGs). However, the optimal starting time and frequency to maintain BM soup therapeutic efficacy remains unknown. This study tested the optimal starting time and frequency of BM soup injections in mice radiated with either a single dose or a fractionated dose. First, BM soup treatment was started at 1, 3 or 7 weeks post-IR; positive (non-IR) and negative (IR) control mice received injections of saline (vehicle control). Second, BM soup-treated mice received injections at different frequencies (1, 2, 3 and 5 weekly injections). Third, a 'fractionated-dose radiation' model to injure mouse SGs was developed (5 Gy × 5 days) and compared with the single high dose radiation model. All mice (n = 65) were followed for 16 weeks post-IR. The results showed that starting injections of BM soup between 1 and 3 weeks mitigated the effect of IR-induced injury to SGs and improved the restoration of salivary function. Although the therapeutic effect of BM soup lessens after 8 weeks, it can be sustained by increasing the frequency of weekly injections. Moreover, both single-dose and fractionated-dose radiation models are efficient and comparable in inducing SG injury and BM soup treatments are effective in restoring salivary function in both radiation models. In conclusion, starting injections of BM soup within 3 weeks post-radiation, with 5 weekly injections, maintains 90-100% of saliva flow in radiated mice.

Effect of mesenchymal stem cells on Sjögren-like mice and the microRNA expression profiles of splenic CD4+ T cells

Mesenchymal stem cells (MSCs) serve immuno-regulatory functions and offer a promising novel treatment for certain autoimmune diseases. The present study investigated the therapeutic effect of mice bone marrow (BM)-MSCs on mice with relatively late stage of Sjögren-like disease and the impact of BM-MSCs on the microRNA (miRNA) expression profiles of splenic CD4+ T cells. Female NOD/Ltj mice were randomized into two groups: The disease group (n=8) and the MSC-treated group (n=8). Female ICR mice served as the healthy control group (n=8). The MSC-treated group received an injection of MSCs when they were 26 weeks old. Water intake, blood glucose and salivary flow rate were measured and submandibular glands were resected and stained with hematoxylin and eosin to calculate the focus score. The concentrations of interleukin (IL)-2, IL-6, hepatocyte growth factor, interferon γ, IL-10, prostaglandin E2, transforming growth factor β1 and tumor necrosis factor-α in serum were measured using ELISA. The expression of miRNAs in splenic CD4+ T cells were measured using deep sequencing. The results demonstrated that treatment with BM-MSCs prevented a decline in the salivary flow rate and lymphocyte infiltration in the salivary glands of NOD mice, indicating that MSC-treatment had a therapeutic effect on NOD mice with relatively late stage of Sjögren-like disease. ELISA and deep sequencing results showed that the three groups of mice had different serum concentrations of cytokines/growth factors and different miRNA expression profiles of splenic CD4+ T cells. This implies that the alteration in serum levels of cytokines/growth factors and miRNA expression profiles of splenic CD4+ T cells may explain the therapeutic effect MSCs have on Sjögren's syndrome.

Compact Bone-Derived Multipotent Mesenchymal Stromal Cells (MSCs) for the Treatment of Sjogren's-like Disease in NOD Mice

Compact bone (cortical or dense bone) is among the organs that contain multipotent mesenchymal stromal cells (MSCs). Unlike bone marrow plugs where MSCs were initially isolated, compact bone has minimal (amount of) hematopoietic cells and thus facilitates the MSCs isolation process. In vitro, MSCs from compact bone show multipotency and differentiation into mesenchymal tissues such as bone, adipose, and cartilage, under certain conditions. MSCs therapy has been promising in preclinical and clinical studies against autoimmune diseases. Not only can MSCs replace the lost tissue through their regenerative properties, but they can also control the autoimmune attacks by immunoregulatory cytokines. This protocol describes the use of compact bone-derived MSCs to preserve salivary function (saliva flow/output) in the NOD (nonobese diabetic) mouse model affected with Sjogren's-like disease.

Quantitative analysis of protein and gene expression in salivary glands of Sjogren's-like disease NOD mice treated by bone marrow soup

Background

Bone marrow cell extract (termed as BM Soup) has been demonstrated to repair irradiated salivary glands (SGs) and restore saliva secretion in our previous study. In the present study, we aim to investigate if the function of damaged SGs in non-obese diabetic (NOD) mice can be restored by BM Soup treatment and the molecular alterations associated with the treatment.

Methods

Whole BM cells were lysed and soluble intracellular contents (“BM Soup”) were injected I.V. into NOD mice. Tandem mass tagging with 2-D liquid chromatography-mass spectrometry was used to quantify proteins in the submandibular glands (SMGs) between untreated and BM Soup-treated mice. Quantitative PCR was used to identify genes with altered expression in the treated mice.

Results BM Soup

restored salivary flow rates to normal levels and significantly reduced the focus scores of SMGs in NOD mice. More than 1800 proteins in SMG cells were quantified by the proteomic approach. Many SMG proteins involved in inflammation and apoptosis were found to be down-regulated whereas those involved in salivary gland biology and development/regeneration were up-regulated in the BM Soup-treated mice. qPCR analysis also revealed expression changes of growth factors and cytokines in the SMGs of the treated NOD mice.

Conclusion

BM Soup treatment is effective to restore the function of damaged SGs in NOD mice. Through gene/protein expression analysis, we have found that BM Soup treatment might effectuate via inhibiting apoptosis, focal adhesion and inflammation whereas promoting development, regeneration and differentiation of the SG cells in NOD mice. These findings provide important insights on the potential mechanisms underlying the BM Soup treatment for functional restoration of damaged SGs in NOD mice. Additional studies are needed to further confirm the identified target genes and their related signaling pathways that are responsible for the BM Soup treatment.

Treatment for salivary gland hypofunction at both initial and advanced stages of Sjögren-like disease: a comparative study of bone marrow therapy versus spleen cell therapy with a 1-year monitoring period

BACKGROUND AIMS

Non-obese diabetic mice (NOD) exhibit autoimmune Sjögren-like disease (SS-like). We reported previously that a combined-therapy consisting of immuno- and cell-based therapy rescued NOD from SS-like. However, therapies tested to date on NOD mice were aimed at the initial phase of SS-like. It is unknown whether therapies are effective in restoring salivary function when given at an advanced phase of SS-like.

METHODS

The efficacy of two therapies (bone marrow versus spleen cells) was compared head-to-head for halting/reversing salivary hypofunction at two critical time points of SS-like (7-week-old NOD with normal saliva output and 20-week-old NOD with minimal saliva). NOD mice were divided into four groups: (i) control, (ii) complete Freund's adjuvant (CFA), (iii) bone marrow transplants with CFA or (iv) spleen cell transplants with CFA. Mice were monitored 8-12 months after therapy.

RESULTS

Both cell therapies were effective during the initial phase of SS-like; salivary flow rates were maintained between 80-100% of pre-symptomatic levels. Spleen cell therapy was better than bone marrow when administered in the initial phase of SS-like. When cell therapies were given at an advanced phase of SS-like (20 weeks and older), salivary flow rates improved but were at best 50% of pre-symptomatic levels. Both cell therapies decreased tumor necrosis factor-α, transforming growth factor-β1 levels and T and B cells while increasing epidermal growth factor and regulatory T cells. Elevated serum epidermal growth factor levels were measured in spleen-treated mice.

CONCLUSIONS

A therapeutic effect in advanced phase disease, albeit in mice, holds promise for humans in which Sjögren syndrome is generally not diagnosed until a late stage.

Ixeris dentata-induced regulation of amylase synthesis and secretion in glucose-treated human salivary gland cells

The endoplasmic reticulum (ER) is an organelle which controls synthesis of secretory and membrane proteins. Alterations in protein folding capacity, leading to ER stress, can be observed in patients with diabetes and related diseases such as xerostomia. The objectives of this study were to investigate the effects of Ixeris dentata (IXD) extract, which has been used for diabetes treatment, and compounds purified from IXD, 8-epidesacylcynaropicrin-3-O-beta-glucopyranoside (ID-57D), on amylase synthesis and secretion in human salivary gland (HSG) cells exposed to a high concentration of glucose. A high concentration of glucose in the experimental medium of cultured cells can model diabetes in vitro. IXD extracts and ID-57D increased oxidative folding-associated protein expression, including p-IRE-1α, PDI and ERO-1α, with the enhanced oxidative folding pattern seen in HSG cells transiently exposed to a high concentration of glucose. Moreover, the treatments reduced the ER stress response, such as the expression of GRP78, maintaining amylase synthesis and secretion in chronically glucose-exposed HSG cells. This study suggests the potential therapeutic value of IXD extract for the treatment of diabetes or its complications such as xerostomia.

Paracrine effects of bone marrow soup restore organ function, regeneration, and repair in salivary glands damaged by irradiation

BACKGROUND

There are reports that bone marrow cell (BM) transplants repaired irradiated salivary glands (SGs) and re-established saliva secretion. However, the mechanisms of action behind these reports have not been elucidated.

METHODS

To test if a paracrine mechanism was the main effect behind this reported improvement in salivary organ function, whole BM cells were lysed and its soluble intracellular contents (termed as "BM Soup") injected into mice with irradiation-injured SGs. The hypothesis was that BM Soup would protect salivary cells, increase tissue neovascularization, function, and regeneration. Two minor aims were also tested a) comparing two routes of delivering BM Soup, intravenous (I.V.) versus intra-glandular injections, and b) comparing the age of the BM Soup's donors. The treatment-comparison group consisted of irradiated mice receiving injections of living whole BM cells. Control mice received irradiation and injections of saline or sham-irradiation. All mice were followed for 8 weeks post-irradiation.

RESULTS

BM Soup restored salivary flow rates to normal levels, protected salivary acinar, ductal, myoepithelial, and progenitor cells, increased cell proliferation and blood vessels, and up-regulated expression of tissue remodeling/repair/regenerative genes (MMP2, CyclinD1, BMP7, EGF, NGF). BM Soup was as an efficient therapeutic agent as injections of live BM cells. Both intra-glandular or I.V. injections of BM Soup, and from both young and older mouse donors were as effective in repairing irradiated SGs. The intra-glandular route reduced injection frequency/dosage by four-fold.

CONCLUSION

BM Soup, which contains only the cell by-products, can be advantageously used to repair irradiation-damaged SGs rather than transplanting whole live BM cells which carry the risk of differentiating into unwanted/tumorigenic cell types in SGs.

Mesenchymal stromal cells improve salivary function and reduce lymphocytic infiltrates in mice with Sjögren's-like disease

BACKGROUND

Non-obese diabetic (NOD) mice develop Sjögren's-like disease (SS-like) with loss of saliva flow and increased lymphocytic infiltrates in salivary glands (SGs). There are recent reports using multipotent mesenchymal stromal cells (MSCs) as a therapeutic strategy for autoimmune diseases due to their anti-inflammatory and immunomodulatory capabilities. This paper proposed a combined immuno- and cell-based therapy consisting of: A) an injection of complete Freund's adjuvant (CFA) to eradicate autoreactive T lymphocytes, and B) transplantations of MSCs to reselect lymphocytes. The objective of this was to test the effectiveness of CD45(-)/TER119(-) cells (MSCs) in re-establishing salivary function and in reducing the number of lymphocytic infiltrates (foci) in SGs. The second objective was to study if the mechanisms underlying a decrease in inflammation (focus score) was due to CFA, MSCs, or CFA+MSCs combined.

METHODOLOGY/PRINCIPAL FINDINGS

Donor MSCs were isolated from bones of male transgenic eGFP mice. Eight week-old female NOD mice received one of the following treatments: insulin, CFA, MSC, or CFA+MSC (combined therapy). Mice were followed for 14 weeks post-therapy. CD45(-)/TER119(-) cells demonstrated characteristics of MSCs as they were positive for Sca-1, CD106, CD105, CD73, CD29, CD44, negative for CD45, TER119, CD11b, had high number of CFU-F, and differentiated into osteocytes, chondrocytes and adipocytes. Both MSC and MSC+CFA groups prevented loss of saliva flow and reduced lymphocytic infiltrations in SGs. Moreover, the influx of T and B cells decreased in all foci in MSC and MSC+CFA groups, while the frequency of Foxp3(+) (T(reg)) cell was increased. MSC-therapy alone reduced inflammation (TNF-α, TGF-β), but the combination of MSC+CFA reduced inflammation and increased the regenerative potential of SGs (FGF-2, EGF).

CONCLUSIONS/SIGNIFICANCE

The combined use of MSC+CFA was effective in both preventing saliva secretion loss and reducing lymphocytic influx in salivary glands.

Bone marrow-derived cells: A potential approach for the treatment of xerostomia

Transplantations of bone marrow-derived cells (BMDCs) are traditionally used for hematologic diseases, but there are increasing numbers of clinical trials using BMDC treatments for non-hematologic disorders, including autoimmune diseases. BMDCs are recently reported to improve organ functions. This paper will review available reports supporting the role of BMDCs in reducing xerostomia (i.e. re-establishing salivary gland functions) due to head and neck irradiation for cancer therapies and in Sjögren's syndrome. There are reports that BMDCs provide a beneficial effect on the saliva production. BMDCs positively affect blood vessels stability and regeneration in irradiated salivary glands. Also, BMDCs provide an immunomodulatory activity in mice with Sjögren's-like disease. While the exact mechanisms by which BMDCs improve organ functions remain controversial, there is preliminary evidence that a combination of them (such as cell transdifferentiation, vasculogenesis, and paracrine effect) occur in salivary glands.