The Hippo signaling pathway effector YAP promotes salivary gland regeneration after injury

3D Spheroid Cultures for Salivary Gland Tissue Engineering: Effects of Fibroblast on Epithelial Cell Function

Three-dimensional (3D) spheroid cultures are crucial for modeling salivary gland (SG) morphogenesis and advancing regenerative medicine. This study evaluated the effects of varying ratios of mouse SG-derived epithelial cells co-cultured with human dermal fibroblasts (hDFs), identifying a 2:1 ratio (spheroids containing 67% EpCAMpos cells with 33% hDFs) as optimal for preserving native SG-derived epithelial cell phenotypes. At this ratio, 67% EpCAMpos spheroids maintained structural integrity and demonstrated a significant reduction in apoptosis and senescence markers, specifically, cleaved caspase-3 (Cc3) and Serpine1, alongside an enhanced expression of the progenitor marker Keratin 5 (KRT5). This highlights the pivotal role of fibroblasts in supporting epithelial cell function in 3D cultures. These spheroids provide a useful model for developing SG tissues that closely mimic physiological properties. Despite promising results, these findings are preliminary and require further validation under diverse conditions and across different SG models.

Duct ligation/de-ligation model: exploring mechanisms for salivary gland injury and regeneration

Sialadenitis and sialadenitis-induced sialopathy are typically caused by obstruction of the salivary gland ducts. Atrophy of the salivary glands in experimental animals caused by duct ligation exhibits a histopathology similar to that of salivary gland sialadenitis. Therefore, a variety of duct ligation/de-ligation models have been commonly employed to study salivary gland injury and regeneration. Duct ligation is mainly characterised by apoptosis and activation of different signaling pathways in parenchymal cells, which eventually leads to gland atrophy and progressive dysfunction. By contrast, duct de-ligation can initiate the recovery of gland structure and function by regenerating the secretory tissue. This review summarizes the animal duct ligation/de-ligation models that have been used for the examination of pathological fundamentals in salivary disorders, in order to unravel the pathological changes and underlying mechanisms involved in salivary gland injury and regeneration. These experimental models have contributed to developing effective and curative strategies for gland dysfunction and providing plausible solutions for overcoming salivary disorders.

Bioengineered Salivary Gland Microtissues─A Review of 3D Cellular Models and their Applications

Salivary glands (SGs) play a vital role in maintaining oral health through the production and release of saliva. Injury to SGs can lead to gland hypofunction and a decrease in saliva secretion manifesting as xerostomia. While symptomatic treatments for xerostomia exist, effective permanent solutions are still lacking, emphasizing the need for innovative approaches. Significant progress has been made in the field of three-dimensional (3D) SG bioengineering for applications in gland regeneration. This has been achieved through a major focus on cell culture techniques, including soluble cues and biomaterial components of the 3D niche. Cells derived from both adult and embryonic SGs have highlighted key in vitro characteristics of SG 3D models. While still in its first decade of exploration, SG spheroids and organoids have so far served as crucial tools to study SG pathophysiology. This review, based on a literature search over the past decade, covers the importance of SG cell types in the realm of their isolation, sourcing, and culture conditions that modulate the 3D microenvironment. We discuss different biomaterials employed for SG culture and the current advances made in bioengineering SG models using them. The success of these 3D cellular models are further evaluated in the context of their applications in organ transplantation and in vitro disease modeling.

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.

Comparative genomics studies on the stk gene family in vertebrates: From the bighead carp (Hypophthalmichthys nobilis) genome

The mammalian sterile 20-like (MST) family belongs to the serine/threonine protein kinase (STK) superfamily and participates in a variety of biological processes, such as cell apoptosis, polarity, migration, immune regulation, inflammatory responses, and cancer. In the economically important bighead carp (Hypophthalmichthys nobilis), the STK gene family and immune-related biological functions may be helpful in increasing its economic yield. However, the comprehensive role of STKs in the bighead carp remains unclear. In this study, the five stk sequences from the bighead carp were divided into two classes: stk3/4 and stk24/25/26. Gene structure and motif prediction analyses confirmed that stk is conserved in the bighead carp. Compared to 26 other vertebrate species, teleosts (including bighead carp) possess more stk members because of teleost-specific whole-genome duplication. Synteny analysis revealed that stk3, stk24, stk25, and stk26 have been relatively conserved in bighead carp during evolution. Meanwhile, stk4 was lost in most Cyprinid species, including bighead carp, during evolution. RNA-seq data revealed that STK expression was associated with various pathogens, and the expression of these STKs (Hnstk3, Hnstk24a, Hnstk24b, Hnstk25, and Hnstk26) was different in seven tissues of bighead carp. In addition, we showed that STK expression levels were dramatically altered in the head kidney and that stk24 was involved in defense against Aeromonas hydrophila. This study provides a molecular basis for the analysis of stk function in bighead carp, and can be used as a reference for further phylogenomics.

Function of stem cells in radiation-induced damage

PURPOSE

The aim of this review is to discuss previous studies on the function of stem cells in radiation-induced damage, and the factors affecting these processes, in the hope of improving our understanding of the different stem cells and the communication networks surrounding them. This is essential for the development of effective stem cell-based therapies to regenerate or replace normal tissues damaged by radiation.

CONCLUSION

In salivary glands, senescence-associated cytokines and inflammation-associated cells have a greater effect on stem cells. In the intestinal glands, Paneth cells strongly affect stem cell-mediated tissue regeneration after radiation treatment. In the pancreas, β-cells as well as protein C receptor positive (Procr) cells are expected to be key cells in the treatment of diabetes. In the bone marrow, a variety of cytokines such as CXC-chemokine ligand 12 (CXCL12) and stem cell factor (SCF), contribute to the functional recovery of hematopoietic stem cells after irradiation.

Hydrogels for Salivary Gland Tissue Engineering

Mimicking the complex architecture of salivary glands (SGs) outside their native niche is challenging due their multicellular and highly branched organization. However, significant progress has been made to recapitulate the gland structure and function using several in vitro and ex vivo models. Hydrogels are polymers with the potential to retain a large volume of water inside their three-dimensional structure, thus simulating extracellular matrix properties that are essential for the cell and tissue integrity. Hydrogel-based culture of SG cells has seen a tremendous success in terms of developing platforms for cell expansion, building an artificial gland, and for use in transplantation to rescue loss of SG function. Both natural and synthetic hydrogels have been used widely in SG tissue engineering applications owing to their properties that support the proliferation, reorganization, and polarization of SG epithelial cells. While recent improvements in hydrogel properties are essential to establish more sophisticated models, the emphasis should still be made towards supporting factors such as mechanotransduction and associated signaling cues. In this concise review, we discuss considerations of an ideal hydrogel-based biomaterial for SG engineering and their associated signaling pathways. We also discuss the current advances made in natural and synthetic hydrogels for SG tissue engineering applications.