Bioprinting salivary gland models and their regenerative applications.

OBJECTIVE: Salivary gland (SG) hypofunction is a common clinical condition arising from radiotherapy to suppress head and neck cancers. The radiation often destroys the SG secretory acini, and glands are left with limited regenerative potential. Due to the complex architecture of SG acini and ducts, three-dimensional (3D) bioprinting platforms have emerged to spatially define these in vitro epithelial units and develop mini-organs or organoids for regeneration. Due to the limited body of evidence, this comprehensive review highlights the advantages and challenges of bioprinting platforms for SG regeneration. METHODS: SG microtissue engineering strategies such as magnetic 3D bioassembly of cells and microfluidic coaxial 3D bioprinting of cell-laden microfibers and microtubes have been proposed to replace the damaged acinar units, avoid the use of xenogeneic matrices (like Matrigel), and restore salivary flow. RESULTS: Replacing the SG damaged organ is challenging due to its complex architecture, which combines a ductal network with acinar epithelial units to facilitate a unidirectional flow of saliva. Our research group was the first to develop 3D bioassembly SG epithelial functional organoids with innervation to respond to both cholinergic and adrenergic stimulation. More recently, microtissue engineering using coaxial 3D bioprinting of hydrogel microfibers and microtubes could also supported the formation of viable epithelial units. Both bioprinting approaches could overcome the need for Matrigel by facilitating the assembly of adult stem cells, such as human dental pulp stem cells, and primary SG cells into micro-sized 3D constructs able to produce their own matrix and self-organize into micro-modular tissue clusters with lumenized areas. Furthermore, extracellular vesicle (EV) therapies from organoid-derived secretome were also designed and validated ex vivo for SG regeneration after radiation damage. CONCLUSION: Magnetic 3D bioassembly and microfluidic coaxial bioprinting platforms have the potential to create SG mini-organs for regenerative applications via organoid transplantation or organoid-derived EV therapies.

Advances in the application of iron oxide nanoparticles (IONs and SPIONs) in three-dimensional cell culture systems.

BACKGROUND: The field of tissue engineering has remarkably progressed through the integration of nanotechnology and the widespread use of magnetic nanoparticles. These nanoparticles have resulted in innovative methods for three-dimensional (3D) cell culture platforms, including the generation of spheroids, organoids, and tissue-mimetic cultures, where they play a pivotal role. Notably, iron oxide nanoparticles and superparamagnetic iron oxide nanoparticles have emerged as indispensable tools for non-contact manipulation of cells within these 3D environments. The variety and modification of the physical and chemical properties of magnetic nanoparticles have profound impacts on cellular mechanisms, metabolic processes, and overall biological function. This review article focuses on the applications of magnetic nanoparticles, elucidating their advantages and potential pitfalls when integrated into 3D cell culture systems. This review aims to shed light on the transformative potential of magnetic nanoparticles in terms of tissue engineering and their capacity to improve the cultivation and manipulation of cells in 3D environments.

Identifying potential immuno-oncology targets in salivary gland mucoepidermoid carcinoma based on inflammatory status and treatment response.

BACKGROUND: Mucoepidermoid carcinoma is a rare salivary gland malignant tumour. This study aimed to investigate inflammatory and immune signatures of mucoepidermoid carcinoma by identifying potential proteo-transcriptomic biomarkers towards the development of precision immuno-oncology treatment strategies. METHODS: A total of 30 biopsies obtained from patients diagnosed with mucoepidermoid carcinoma between 2013 and 2022 were analysed after H&E staining for scoring of histological inflammatory stroma subtypes and inflammatory hotspots with QuPath. Multiplex immunofluorescence staining and NanoString nCounter PanCancer IO 360™ panel were used to assess stroma and tumour inflammation signatures in high grade mucoepidermoid carcinoma cases in the tumour microenvironment via proteomics and transcriptomics, respectively. RESULTS: Inflammatory cells within the histological inflammatory stroma inflammatory (HIS-INF/hot) tumour neighbourhoods were greater compared to the histological inflammatory stroma-immune desert (HIS-ID/cold) (p = 0.001). A similar trend was observed between treatment non-responders and responders in stroma neighbourhoods (p = 0.0625) and in stroma-to-interface inflammatory hotspots (p = 0.0081), indicating an augmented inflammatory response in hot tumours and non-responders. Furthermore, there were striking differences in the expression of pan-immune leukocyte marker CD45 between responders and non responders particularly in the tumour neighbourhoods (p = 0.0341), but such were not robust for PD-1 and macrophage fractions. Additionally, transcriptomic analysis revealed key differences in leukocyte activation profiles between responders and non-responders. CONCLUSION: This preliminary report unveils the importance of assessing immune leukocyte cellular fractions and pathways for future prognostic biomarker discoveries in mucoepidermoid carcinoma as per the involvement of CD45-driven inflammatory and immune mediators in high grade mucoepidermoid carcinoma in non-responders to treatment. These findings will potentially contribute to the development of novel personalised immunotherapies.

Trehalose versus carboxymethylcellulose oral spray for relieving radiation-induced xerostomia in head and neck cancer patients: a randomized controlled trial.

BACKGROUND: The aim of this study was to investigate the effect of trehalose oral spray to relieve radiation-induced xerostomia on a randomized controlled trial (RCT). METHODS: Prior to RCT, the effect of trehalose (5-20%) on the epithelial growth of fetal mouse salivary gland (SG) explants was evaluated to confirm if 10% trehalose exerted the best epithelial outcomes. Participants who completed radiotherapy for head and neck cancer (HNC) treatment were enrolled in a double-blind RCT, according to inclusion and exclusion criteria as per the CONSORT statement. The experimental group (n = 35) received 10% trehalose spray, while the control group (n = 35) received carboxymethylcellulose (CMC) spray to apply intra-orally 4 times/day for 14 days. Salivary pH and unstimulated salivary flow rate were recorded pre- and post-interventions. The Xerostomia-related Quality of Life scale (XeQoLs) was filled, and scores assessed post-interventions. RESULTS: In the SG explant model, pro-acinar epithelial growth and mitosis was supported by 10% topical trehalose. As for RCT outcomes, salivary pH and unstimulated salivary flow rate were significantly improved after use of 10% trehalose spray when compared to CMC (p < 0.05). Participants reported an improvement of XeQoLs dimension scores after using trehalose or CMC oral sprays in terms of physical, pain/discomfort, and psychological dimensions (p < 0.05), but not social (p > 0.05). When comparing between CMC and trehalose sprays, XeQoLs total scores were not statistically different (p > 0.05). CONCLUSIONS: The 10% trehalose spray improved salivary pH, unstimulated salivary flow rate, and the quality-of-life dimensions linked with physical, pain/discomfort, and psychological signs. The clinical efficacy of 10% trehalose spray was equivalent with CMC-based saliva substitutes for relieving radiation-induced xerostomia; therefore, trehalose may be suggested in alternative to CMC-based oral spray.(Thai Clinical Trials Registry; https://www.thaiclinicaltrials.org/ TCTR20190817004).

Salivary gland regeneration: from salivary gland stem cells to three-dimensional bioprinting.

Hyposalivation and severe dry mouth syndrome are the most common complications in patients with head and neck cancer (HNC) after receiving radiation therapy. Conventional treatment for hyposalivation relies on the use of sialogogues such as pilocarpine; however, their efficacy is constrained by the limited number of remnant acinar cells after radiation. After radiotherapy, the salivary gland (SG) secretory parenchyma is largely destroyed, and due to the reduced stem cell niche, this gland has poor regenerative potential. To tackle this, researchers must be able to generate highly complex cellularized 3D constructs for clinical transplantation via technologies, including those that involve bioprinting of cells and biomaterials. A potential stem cell source with promising clinical outcomes to reserve dry mouth is adipose mesenchymal stem cells (AdMSC). MSC-like cells like human dental pulp stem cells (hDPSC) have been tested in novel magnetic bioprinting platforms using nanoparticles that can bind cell membranes by electrostatic interaction, as well as their paracrine signals arising from extracellular vesicles. Both magnetized cells and their secretome cues were found to increase epithelial and neuronal growth of in vitro and ex vivo irradiated SG models. Interestingly, these magnetic bioprinting platforms can be applied as a high-throughput drug screening system due to the consistency in structure and functions of their organoids. Recently, exogenous decellularized porcine ECM was added to this magnetic platform to stimulate an ideal environment for cell tethering, proliferation, and/or differentiation. The combination of these SG tissue biofabrication strategies will promptly allow for in vitro organoid formation and establishment of cellular senescent organoids for aging models, but challenges remain in terms of epithelial polarization and lumen formation for unidirectional fluid flow. Current magnetic bioprinting nanotechnologies can provide promising functional and aging features to in vitro craniofacial exocrine gland organoids, which can be utilized for novel drug discovery and/or clinical transplantation.

Plant molecular farming-derived epidermal growth factor revolutionizes hydrogels for improving glandular epithelial organoid biofabrication.

Epidermal growth factor (EGF) is a known signaling cue essential towards the development and organoid biofabrication particularly for exocrine glands. This study developed an in vitro EGF delivery platform with Nicotiana benthamiana plant-produced EGF (P-EGF) encapsulated on hyaluronic acid/alginate (HA/Alg) hydrogel to improve the effectiveness of glandular organoid biofabrication in short-term culture systems. Primary submandibular gland epithelial cells were treated with 5 - 20 ng/mL of P-EGF and commercially available bacteria-derived EGF (B-EGF). Cell proliferation and metabolic activity were measured by MTT and luciferase-based ATP assays. P-EGF and B-EGF 5 - 20 ng/mL promoted glandular epithelial cell proliferation during 6 culture days on a comparable fashion. Organoid forming efficiency and cellular viability, ATP-dependent activity and expansion were evaluated using two EGF delivery systems, HA/Alg-based encapsulation and media supplementation. Phosphate buffered saline (PBS) was used as a control vehicle. Epithelial organoids fabricated from PBS-, B-EGF-, and P-EGF-encapsulated hydrogels were characterized genotypically, phenotypically and by functional assays. P-EGF-encapsulated hydrogel enhanced organoid formation efficiency and cellular viability and metabolism relative to P-EGF supplementation. At culture day 3, epithelial organoids developed from P-EGF-encapsulated HA/Alg platform contained functional cell clusters expressing specific glandular epithelial markers such as exocrine pro-acinar (AQP5, NKCC1, CHRM1, CHRM3, Mist1), ductal (K18, Krt19), and myoepithelial (α-SMA, Acta2), and possessed a high mitotic activity (38-62% Ki67 cells) with a large epithelial progenitor population (∼70% K14 cells). The P-EGF encapsulation strikingly upregulated the expression of pro-acinar AQP5 cells through culture time when compared to others (B-EGF, PBS). Thus, the utilization of Nicotiana benthamiana in molecular farming can produce EGF biologicals amenable to encapsulation in HA/Alg-based in vitro platforms, which can effectively and promptly induce the biofabrication of exocrine gland organoids.

Magnetic bioassembly platforms towards the generation of extracellular vesicles from human salivary gland functional organoids for epithelial repair.

Salivary glands (SG) are exocrine organs with secretory units commonly injured by radiotherapy. Bio-engineered organoids and extracellular vesicles (EV) are currently under investigation as potential strategies for SG repair. Herein, three-dimensional (3D) cultures of SG functional organoids (SGo) and human dental pulp stem cells (hDPSC) were generated by magnetic 3D bioassembly (M3DB) platforms. Fibroblast growth factor 10 (FGF10) was used to enrich the SGo in secretory epithelial units. After 11 culture days via M3DB, SGo displayed SG-specific acinar epithelial units with functional properties upon neurostimulation. To consistently develop 3D hDPSC in vitro, 3 culture days were sufficient to maintain hDPSC undifferentiated genotype and phenotype for EV generation. EV isolation was performed via sequential centrifugation of the conditioned media of hDPSC and SGo cultures. EV were characterized by nanoparticle tracking analysis, electron microscopy and immunoblotting. EV were in the exosome range for hDPSC (diameter: 88.03 ± 15.60 nm) and for SGo (123.15 ± 63.06 nm). Upon ex vivo administration, exosomes derived from SGo significantly stimulated epithelial growth (up to 60%), mitosis, epithelial progenitors and neuronal growth in injured SG; however, such biological effects were less distinctive with the ones derived from hDPSC. Next, these exosome biological effects were investigated by proteomic arrays. Mass spectrometry profiling of SGo exosomes predicted that cellular growth, development and signaling was due to known and undocumented molecular targets downstream of FGF10. Semaphorins were identified as one of the novel targets requiring further investigations. Thus, M3DB platforms can generate exosomes with potential to ameliorate SG epithelial damage.

Exogenous LIN28 Is Required for the Maintenance of Self-Renewal and Pluripotency in Presumptive Porcine-Induced Pluripotent Stem Cells.

Porcine species have been used in preclinical transplantation models for assessing the efficiency and safety of transplants before their application in human trials. Porcine-induced pluripotent stem cells (piPSCs) are traditionally established using four transcription factors (4TF): OCT4, SOX2, KLF4, and C-MYC. However, the inefficiencies in the reprogramming of piPSCs and the maintenance of their self-renewal and pluripotency remain challenges to be resolved. LIN28 was demonstrated to play a vital role in the induction of pluripotency in humans. To investigate whether this factor is similarly required by piPSCs, the effects of adding LIN28 to the 4TF induction method (5F approach) on the efficiency of piPSC reprogramming and maintenance of self-renewal and pluripotency were examined. Using a retroviral vector, porcine fetal fibroblasts were transfected with human OCT4, SOX2, KLF4, and C-MYC with or without LIN28. The colony morphology and chromosomal stability of these piPSC lines were examined and their pluripotency properties were characterized by investigating both their expression of pluripotency-associated genes and proteins and in vitro and in vivo differentiation capabilities. Alkaline phosphatase assay revealed the reprogramming efficiencies to be 0.33 and 0.17% for the 4TF and 5TF approaches, respectively, but the maintenance of self-renewal and pluripotency until passage 40 was 6.67 and 100%, respectively. Most of the 4TF-piPSC colonies were flat in shape, showed weak positivity for alkaline phosphatase, and expressed a significantly high level of SSEA-4 protein, except for one cell line (VSMUi001-A) whose properties were similar to those of the 5TF-piPSCs; that is, tightly packed and dome-like in shape, markedly positive for alkaline phosphatase, and expressing endogenous pluripotency genes (pOCT4, pSOX2, pNANOG, and pLIN28), significantly high levels of pluripotent proteins (OCT4, SOX2, NANOG, LIN28, and SSEA-1), and a significantly low level of SSEA-4 protein. VSMUi001-A and all 5F-piPSC lines formed embryoid bodies, underwent spontaneous cardiogenic differentiation with cardiac beating, expressed cardiomyocyte markers, and developed teratomas. In conclusion, in addition to the 4TF, LIN28 is required for the effective induction of piPSCs and the maintenance of their long-term self-renewal and pluripotency toward the development of all germ layers. These piPSCs have the potential applicability for veterinary science.

Epigallocatechin-3-Gallate Protects Pro-Acinar Epithelia Against Salivary Gland Radiation Injury.

Antioxidant agents are promising pharmaceuticals to prevent salivary gland (SG) epithelial injury from radiotherapy and their associated irreversible dry mouth symptoms. Epigallocatechin-3-gallate (EGCG) is a well-known antioxidant that can exert growth or inhibitory biological effects in normal or pathological tissues leading to disease prevention. The effects of EGCG in the various SG epithelial compartments are poorly understood during homeostasis and upon radiation (IR) injury. This study aims to: (1) determine whether EGCG can support epithelial proliferation during homeostasis; and (2) investigate what epithelial cells are protected by EGCG from IR injury. Ex vivo mouse SG were treated with EGCG from 7.5-30 µg/mL for up to 72 h. Next, SG epithelial branching morphogenesis was evaluated by bright-field microscopy, immunofluorescence, and gene expression arrays. To establish IR injury models, linear accelerator (LINAC) technologies were utilized, and radiation doses optimized. EGCG epithelial effects in these injury models were assessed using light, confocal and electron microscopy, the Griess assay, immunohistochemistry, and gene arrays. SG pretreated with EGCG 7.5 µg/mL promoted epithelial proliferation and the development of pro-acinar buds and ducts in regular homeostasis. Furthermore, EGCG increased the populations of epithelial progenitors in buds and ducts and pro-acinar cells, most probably due to its observed antioxidant activity after IR injury, which prevented epithelial apoptosis. Future studies will assess the potential for nanocarriers to increase the oral bioavailability of EGCG.

Trends in Salivary Gland Tissue Engineering: From Stem Cells to Secretome and Organoid Bioprinting.

Xerostomia or dry mouth are commonly diagnosed in head and neck cancer patients due to salivary gland (SG) epithelial injury after radiotherapy. Regenerative medicine has fetched the opportunity to replace or regenerate the SG epithelia and restore its secretory function. Early adult stem cell transplantation strategies in rodents have recently shown to improve clinical outcomes in radiotherapy-induced xerostomia in Phase 1/2 human trials. Mesenchymal stem cells from adipose tissue are the most promising, although the ones from the labial mucosa, bone marrow, or dental pulp have an attractive therapeutic value after successful findings in ex vivo and in vivo mouse models of SG injury. Emerging approaches using cell-free therapy with cell "extracts", "soups" or secretome components also exhibit favorable outcomes in the same rodent models. When compared to cell-based approaches, extracellular vesicles (EV) from the secretome (i.e., exosomes) can be easily extracted, quantified, and are more stable for long-term storage and use in SG tissue engineering. Additive manufacturing and three-dimensional bioprinting or bioassembly have an important role on generating spheroids or organoids for cell transplantation to ameliorate SG injury. Moreover, organoids can secrete EV, which may have a therapeutic potential worth to explore in future studies. In this review, we will describe the technological advancements and challenges of these different cell-based and cell-free strategies in SG tissue engineering and regeneration. Impact statement Salivary gland (SG)-like innervated epithelial organoids and the secretome produced from stem cells may constitute feasible therapeutic alternatives to regenerate the SG due to their user-friendly, short-lived, consistent, and scalable additive manufacturing processes. Bioprinting such human SG organoids toward in vitro drug discovery may further reduce the incorporation of animal-derived components to the tissue constructs and minimize the use of animal experimentation in SG regeneration. Despite such advancements, transplantation with human adipose-derived mesenchymal stem cells is the only tissue engineering strategy that has reached Phase 1/2 clinical trials and shown to enlarge the serous SG epithelium and improve salivary flow.

Generation of Porcine Induced Neural Stem Cells Using the Sendai Virus.

The reprogramming of cells into induced neural stem cells (iNSCs), which are faster and safer to generate than induced pluripotent stem cells, holds tremendous promise for fundamental and frontier research, as well as personalized cell-based therapies for neurological diseases. However, reprogramming cells with viral vectors increases the risk of tumor development due to vector and transgene integration in the host cell genome. To circumvent this issue, the Sendai virus (SeV) provides an alternative integration-free reprogramming method that removes the danger of genetic alterations and enhances the prospects of iNSCs from bench to bedside. Since pigs are among the most successful large animal models in biomedical research, porcine iNSCs (piNSCs) may serve as a disease model for both veterinary and human medicine. Here, we report the successful generation of piNSC lines from pig fibroblasts by employing the SeV. These piNSCs can be expanded for up to 40 passages in a monolayer culture and produce neurospheres in a suspension culture. These piNSCs express high levels of NSC markers (PAX6, SOX2, NESTIN, and VIMENTIN) and proliferation markers (KI67) using quantitative immunostaining and western blot analysis. Furthermore, piNSCs are multipotent, as they are capable of producing neurons and glia, as demonstrated by their expressions of TUJ1, MAP2, TH, MBP, and GFAP proteins. During the reprogramming of piNSCs with the SeV, no induced pluripotent stem cells developed, and the established piNSCs did not express OCT4, NANOG, and SSEA1. Hence, the use of the SeV can reprogram porcine somatic cells without first going through an intermediate pluripotent state. Our research produced piNSCs using SeV methods in novel, easily accessible large animal cell culture models for evaluating the efficacy of iNSC-based clinical translation in human medicine. Additionally, our piNSCs are potentially applicable in disease modeling in pigs and regenerative therapies in veterinary medicine.

Bioprinting Strategies for Secretory Epithelial Organoids.

Novel three-dimensional (3D) biofabrication platforms can allow magnetic 3D bioprinting (M3DB) by using magnetic nanoparticles to tag cells and then spatially arrange them in 3D around magnet dots. Here, we report an M3DB methodology to generate salivary gland-like epithelial organoids from stem cells. These organoids possess a neuronal network that responds to saliva neurostimulants.

Strategies for Developing Functional Secretory Epithelia from Porcine Salivary Gland Explant Outgrowth Culture Models.

Research efforts have been made to develop human salivary gland (SG) secretory epithelia for transplantation in patients with SG hypofunction and dry mouth (xerostomia). However, the limited availability of human biopsies hinders the generation of sufficient cell numbers for epithelia formation and regeneration. Porcine SG have several similarities to their human counterparts, hence could replace human cells in SG modelling studies in vitro. Our study aims to establish porcine SG explant outgrowth models to generate functional secretory epithelia for regeneration purposes to rescue hyposalivation. Cells were isolated and expanded from porcine submandibular and parotid gland explants. Flow cytometry, immunocytochemistry, and gene arrays were performed to assess proliferation, standard mesenchymal stem cell, and putative SG epithelial stem/progenitor cell markers. Epithelial differentiation was induced and different SG-specific markers investigated. Functional assays upon neurostimulation determined α-amylase activity, trans-epithelial electrical resistance, and calcium influx. Primary cells exhibited SG epithelial progenitors and proliferation markers. After differentiation, SG markers were abundantly expressed resembling epithelial lineages (E-cadherin, Krt5, Krt14), and myoepithelial (α-smooth muscle actin) and neuronal (ß3-tubulin, Chrm3) compartments. Differentiated cells from submandibular gland explant models displayed significantly greater proliferation, number of epithelial progenitors, amylase activity, and epithelial barrier function when compared to parotid gland models. Intracellular calcium was mobilized upon cholinergic and adrenergic neurostimulation. In summary, this study highlights new strategies to develop secretory epithelia from porcine SG explants, suitable for future proof-of-concept SG regeneration studies, as well as for testing novel muscarinic agonists and other biomolecules for dry mouth.

Unveiling Stem Cell Heterogeneity Toward the Development of Salivary Gland Regenerative Strategies.

Epithelial damage in the salivary gland (SG) resulting in irreversible dry mouth can be commonly induced by gamma radiation therapy. This radiation depletes the SG stem/progenitor cell niche slowing healing and natural gland regeneration. Biologists have been focused in understanding the development and differentiation of epithelial stem and progenitor cell niches during SG organogenesis. These organogenesis studies gave insights into novel cell-based therapies to recreate the three-dimensional (3D) salivary gland (SG) organ, recapitulate the SG native physiology, and restore saliva secretion. Such therapeutical strategies apply techniques that assemble, in a 3D organotypic culture, progenitor and stem cell lines to develop SG organ-like organoids or mini-transplants. Future studies will employ a combination of organoids, decellularized matrices, and smart biomaterials to create viable and functional SG transplants to repair the site of SG injury and reestablish saliva production.

A magnetic three-dimensional levitated primary cell culture system for the development of secretory salivary gland-like organoids.

Salivary gland (SG) hypofunction and oral dryness can be induced by radiotherapy for head and neck cancers or autoimmune disorders. These are common clinical conditions that involve loss of saliva-secreting epithelial cells. Several oral complications arise with SG hypofunction that interfere with routine daily activities such as chewing, swallowing, and speaking. Hence, there is a need for replacing these saliva-secreting cells. Recently, researchers have proposed to repair SG hypofunction via various cell-based approaches in three-dimensional (3D) scaffold-based systems. However, majority of the scaffolds used cannot be translated clinically due to the presence of non-human-based substrates. Herein, saliva-secreting organoids/mini-glands were developed using a new scaffold/substrate-free culture system named magnetic 3D levitation (M3DL), which assembles and levitates magnetized primary SG-derived cells (SGDCs), allowing them to produce their own extracellular matrices. Primary SGDCs were assembled in M3DL to generate SG-like organoids in well-established SG epithelial differentiation conditions for 7 days. After such culture time, these organoids consistently presented uniform spheres with greater cell viability and pro-mitotic cells, when compared with conventional salisphere cultures. Additionally, organoids formed by M3DL expressed SG-specific markers from different cellular compartments: acinar epithelial including adherens junctions (NKCC1, cholinergic muscarinic receptor type 3, E-cadherin, and EpCAM); ductal epithelial and myoepithelial (cytokeratin 14 and α-smooth muscle actin); and neuronal (ß3-tubulin and vesicular acetylcholine transferase). Lastly, intracellular calcium and α-amylase activity assays showed functional organoids with SG-specific secretory activity upon cholinergic stimulation. Thus, the functional organoid produced herein indicate that this M3DL system can be a promising tool to generate SG-like mini-glands for SG secretory repair.

Engineering innervated secretory epithelial organoids by magnetic three-dimensional bioprinting for stimulating epithelial growth in salivary glands.

Current saliva-based stimulation therapies for radiotherapy-induced xerostomia are not fully effective due to the presence of damaged secretory epithelia and nerves in the salivary gland (SG). Hence, three-dimensional bio-engineered organoids are essential to regenerate the damaged SG. Herein, a recently validated three-dimensional (3D) biofabrication system, the magnetic 3D bioprinting (M3DB), is tested to generate innervated secretory epithelial organoids from a neural crest-derived mesenchymal stem cell, the human dental pulp stem cell (hDPSC). Cells are tagged with magnetic nanoparticles (MNP) and spatially arranged with magnet dots to generate 3D spheroids. Next, a SG epithelial differentiation stage was completed with fibroblast growth factor 10 (4-400 ng/ml) to recapitulate SG epithelial morphogenesis and neurogenesis. The SG organoids were then transplanted into ex vivo model to evaluate their epithelial growth and innervation. M3DB-formed spheroids exhibited both high cell viability rate (>90%) and stable ATP intracellular activity compared to MNP-free spheroids. After differentiation, spheroids expressed SG epithelial compartments including secretory epithelial, ductal, myoepithelial, and neuronal. Fabricated organoids also produced salivary α-amylase upon FGF10 stimulation, and intracellular calcium mobilization and trans-epithelial resistance was elicited upon neurostimulation with different neurotransmitters. After transplantation, the SG-like organoids significantly stimulated epithelial and neuronal growth in damaged SG. It is the first time bio-functional innervated SG-like organoids are bioprinted. Thus, this is an important step towards SG regeneration and the treatment of radiotherapy-induced xerostomia.

Neurturin Gene Therapy Protects Parasympathetic Function to Prevent Irradiation-Induced Murine Salivary Gland Hypofunction.

Head and neck cancer patients treated with irradiation often present irreversible salivary gland hypofunction for which no conventional treatment exists. We recently showed that recombinant neurturin, a neurotrophic factor, improves epithelial regeneration of mouse salivary glands in ex vivo culture after irradiation by reducing apoptosis of parasympathetic neurons. Parasympathetic innervation is essential to maintain progenitor cells during gland development and for regeneration of adult glands. Here, we investigated whether a neurturin-expressing adenovirus could be used for gene therapy in vivo to protect parasympathetic neurons and prevent gland hypofunction after irradiation. First, ex vivo fetal salivary gland culture was used to compare the neurturin adenovirus with recombinant neurturin, showing they both improve growth after irradiation by reducing neuronal apoptosis and increasing innervation. Then, the neurturin adenovirus was delivered to mouse salivary glands in vivo, 24 hr before irradiation, and compared with a control adenovirus. The control-treated glands have ∼50% reduction in salivary flow 60 days post-irradiation, whereas neurturin-treated glands have similar flow to nonirradiated glands. Further, markers of parasympathetic function, including vesicular acetylcholine transporter, decreased with irradiation, but not with neurturin treatment. Our findings suggest that in vivo neurturin gene therapy prior to irradiation protects parasympathetic function and prevents irradiation-induced hypofunction.

Generation of a pig induced pluripotent stem cell (piPSC) line from embryonic fibroblasts by incorporating LIN28 to the four transcriptional factor-mediated reprogramming: VSMUi001-D.

Pig induced pluripotent stem cell (piPSC) line was generated from embryonic fibroblast cells using retroviral transduction approaches carrying human transcriptional factors: OCT4, SOX2, KLF4, c-MYC and LIN28. The generated piPSC line, VSMUi001-D, was positive for alkaline phosphatase activity and expressed the pluripotency associated transcription factors including OCT4, SOX2, NANOG and surface markers SSEA-1, all iPSC hallmarks of authenticity. Furthermore, VSMUi001-D exhibited a normal karyotype and formed embryoid bodies in vitro and teratomas in vivo. Upon cardiac differentiation, VSMUi001-D displayed spontaneous beating and expressed cardiomyocyte markers, like cardiac Troponin T.

Concise Review: Salivary Gland Regeneration: Therapeutic Approaches from Stem Cells to Tissue Organoids.

The human salivary gland (SG) has an elegant architecture of epithelial acini, connecting ductal branching structures, vascular and neuronal networks that together function to produce and secrete saliva. This review focuses on the translation of cell- and tissue-based research toward therapies for patients suffering from SG hypofunction and related dry mouth syndrome (xerostomia), as a consequence of radiation therapy or systemic disease. We will broadly review the recent literature and discuss the clinical prospects of stem/progenitor cell and tissue-based therapies for SG repair and/or regeneration. Thus far, several strategies have been proposed for the purpose of restoring SG function: (1) transplanting autologous SG-derived epithelial stem/progenitor cells; (2) exploiting non-epithelial cells and/or their bioactive lysates; and (3) tissue engineering approaches using 3D (three-dimensional) biomaterials loaded with SG cells and/or bioactive cues to mimic in vivo SGs. We predict that further scientific improvement in each of these areas will translate to effective therapies toward the repair of damaged glands and the development of miniature SG organoids for the fundamental restoration of saliva secretion. Stem Cells 2017;35:97-105.

Three-Dimensional Bioprinting Nanotechnologies towards Clinical Application of Stem Cells and Their Secretome in Salivary Gland Regeneration.

Salivary gland (SG) functional damage and severe dry mouth (or xerostomia) are commonly observed in a wide range of medical conditions from autoimmune to metabolic disorders as well as after radiotherapy to treat specific head and neck cancers. No effective therapy has been developed to completely restore the SG functional damage on the long-term and reverse the poor quality of life of xerostomia patients. Cell- and secretome-based strategies are currently being tested in vitro and in vivo for the repair and/or regeneration of the damaged SG using (1) epithelial SG stem/progenitor cells from salispheres or explant cultures as well as (2) nonepithelial stem cell types and/or their bioactive secretome. These strategies will be the focus of our review. Herein, innovative 3D bioprinting nanotechnologies for the generation of organotypic cultures and SG organoids/mini-glands will also be discussed. These bioprinting technologies will allow researchers to analyze the secretome components and extracellular matrix production, as well as their biofunctional effects in 3D mini-glands ex vivo. Improving our understanding of the SG secretome is critical to develop effective secretome-based therapies towards the regeneration and/or repair of all SG compartments for proper restoration of saliva secretion and flow into the oral cavity.