The Spleen as an Optimal Site for Islet Transplantation and a Source of Mesenchymal Stem Cells

Impact of oxygen and glucose availability on the viability and connectivity of islet cells: A computational study of reconstructed avascular human islets

The experimental study and transplantation of pancreatic islets requires their isolation from the surrounding tissue, and therefore, from the vasculature. Under these conditions, avascular islets rely on the diffusion of peripheral oxygen and nutrients to comply with the requirements of islet cells while responding to changes in body glucose. As a complement to the experimental work, computational models have been widely used to estimate how avascular islets would be affected by the hypoxic conditions found both in culture and transplant sites. However, previous models have been based on simplified representations of pancreatic islets which has limited the reach of the simulations performed. Aiming to contribute with a more realistic model of avascular human islets, in this work we used architectures of human islets reconstructed from experimental data to simulate the availability of oxygen for α, β and δ-cells, emulating culture and transplant conditions at different glucose concentrations. The modeling approach proposed allowed us to quantitatively estimate how the loss of cells due to severe hypoxia would impact interactions between islet cells, ultimately segregating the islet into disconnected subnetworks. According to the simulations performed, islet encapsulation, by reducing the oxygen available within the islets, could severely compromise cell viability. Moreover, our model suggests that even without encapsulation, only microislets composed of less than 100 cells would remain viable in oxygenation conditions found in transplant sites. Overall, in this article we delineate a novel modeling methodology to simulate detailed avascular islets in experimental and transplant conditions with potential applications in the field of islet encapsulation.

Hydrogel-Encapsulated Pancreatic Islet Cells as a Promising Strategy for Diabetic Cell Therapy

Islet transplantation has now become a promising treatment for insulin-deficient diabetes mellitus. Compared to traditional diabetes treatments, cell therapy can restore endogenous insulin supplementation, but its large-scale clinical application is impeded by donor shortages, immune rejection, and unsuitable transplantation sites. To overcome these challenges, an increasing number of studies have attempted to transplant hydrogel-encapsulated islet cells to treat diabetes. This review mainly focuses on the strategy of hydrogel-encapsulated pancreatic islet cells for diabetic cell therapy, including different cell sources encapsulated in hydrogels, encapsulation methods, hydrogel types, and a series of accessorial manners to improve transplantation outcomes. In addition, the formation and application challenges as well as prospects are also presented.

3D printed VEGF-CPO biomaterial scaffold to promote subcutaneous vascularization and survival of transplanted islets for the treatment of diabetes

Diabetes is a complex metabolic disease and islet transplantation is a promising approach for the treatment of diabetes. Unfortunately, the transplanted islets at the subcutaneous site are also affected by various adverse factors such as poor vascularization and hypoxia. In this study, we utilize biocompatible copolymers l-lactide and D,l-lactide to manufacture a biomaterial scaffold with a mesh-like structure via 3D printing technology, providing a material foundation for encapsulating pancreatic islet cells. The scaffold maintains the sustained release of vascular endothelial growth factor (VEGF) and a slow release of oxygen from calcium peroxide (CPO), thereby regulating the microenvironment for islet survival. This helps to improve insufficient subcutaneous vascularization and reduce islet death due to hypoxia post-transplantation. By pre-implanting VEGF-CPO scaffolds subcutaneously into diabetic rats, a sufficiently vascularized site is formed, thereby ensuring early survival of transplanted islets. In a word, the VEGF-CPO scaffold shows good biocompatibility both in vitro and in vivo, avoids the adverse effects on the implanted islets, and displays promising clinical transformation prospects.

Advancements in innate immune regulation strategies in islet transplantation

As a newly emerging organ transplantation technique, islet transplantation has shown the advantages of minimal trauma and high safety since it was first carried out. The proposal of the Edmonton protocol, which has been widely applied, was a breakthrough in this method. However, direct contact between islets and portal vein blood will cause a robust innate immune response leading to massive apoptosis of the graft, and macrophages play an essential role in the innate immune response. Therefore, therapeutic strategies targeting macrophages in the innate immune response have become a popular research topic in recent years. This paper will summarize and analyze recent research on strategies for regulating innate immunity, primarily focusing on macrophages, in the field of islet transplantation, including drug therapy, optimization of islet preparation process, islet engineering and Mesenchymal stem cells cotransplantation. We also expounded the heterogeneity, plasticity and activation mechanism of macrophages in islet transplantation, providing a theoretical basis for further research.

Reversal of Hyperglycemia by Subcutaneous Islet Engraftment Using an Atelocollagen Sponge as a Scaffold

Type 1 diabetes mellitus (T1DM) affects 8.4 million people worldwide, with patients primarily relying on exogenous insulin injections to maintain blood glucose levels. Islet transplantation via the portal vein has allowed for the direct internal release of insulin by glucose-sensitive islets. However, this method might not be desirable for future cell therapy transplanting pluripotent stem cell-derived β cells, facing challenges including difficulties in cell retrieval and graft loss due to the instant blood-mediated inflammatory reaction (IBMIR). Here, we established a subcutaneous transplantation protocol using an atelocollagen sponge as a scaffold. While the subcutaneous site has many advantages, the lack of a vascular bed limits its application. To address this issue, we performed angiogenesis stimulation at the transplantation site using bFGF absorbed in a gelatin sponge (Spongel), significantly improving the microvascular area. Our in vivo experiments also revealed angiogenesis stimulation is crucial for reversing hyperglycemia in streptozotocin (STZ)-induced diabetic mice. In addition to the angiogenic treatment, an atelocollagen sponge is used to carry the islets and helps avoid graft leakage. With 800 mouse islets delivered by the atelocollagen sponge, the STZ-induced diabetic mice showed a reversal of hyperglycemia and normalized glucose intolerance. Their normoglycemia was maintained until the graft was removed. Analysis of the harvested islet grafts exhibited a high vascularization and preserved morphologies, suggesting that using an atelocollagen sponge as a scaffold helps maintain the viability of the islet grafts.

Multiple Dimensions of using Mesenchymal Stem Cells for Treating Liver Diseases: From Bench to Beside

Liver diseases impose a huge burden worldwide. Although hepatocyte transplantation has long been considered as a potential strategy for treating liver diseases, its clinical implementation has created some obvious limitations. As an alternative strategy, cell therapy, particularly mesenchymal stem cell (MSC) transplantation, is widely used in treating different liver diseases, including acute liver disease, acute-on-chronic liver failure, hepatitis B/C virus, autoimmune hepatitis, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, alcoholic liver disease, liver fibrosis, liver cirrhosis, and hepatocellular carcinoma. Here, we summarize the status of MSC transplantation in treating liver diseases, focusing on the therapeutic mechanisms, including differentiation into hepatocyte-like cells, immunomodulating function with a variety of immune cells, paracrine effects via the secretion of various cytokines and extracellular vesicles, and facilitation of homing and engraftment. Some improved perspectives and current challenges are also addressed. In summary, MSCs have great potential in the treatment of liver diseases based on their multi-faceted characteristics, and more accurate mechanisms and novel therapeutic strategies stemming from MSCs will facilitate clinical practice.

Type 1 diabetes and engineering enhanced islet transplantation

The development of new therapeutic approaches to treat type 1 diabetes mellitus (T1D) relies on the precise understanding and deciphering of insulin-secreting β-cell biology, as well as the mechanisms responsible for their autoimmune destruction. β-cell or islet transplantation is viewed as a potential long-term therapy for the millions of patients with diabetes. To advance the field of insulin-secreting cell transplantation, two main research areas are currently investigated by the scientific community: (1) the identification of the developmental pathways that drive the differentiation of stem cells into insulin-producing cells, providing an inexhaustible source of cells; and (2) transplantation strategies and engineered transplants to provide protection and enhance the functionality of transplanted cells. In this review, we discuss the biology of pancreatic β-cells, pathology of T1D and current state of β-cell differentiation. We give a comprehensive view and discuss the different possibilities to engineer enhanced insulin-secreting cell/islet transplantation from a translational perspective.

Immune-Protective Formulations and Process Strategies for Improved Survival and Function of Transplanted Islets

Type 1 diabetes (T1D) is an autoimmune disease caused by the immune system attacking and destroying insulin-producing β cells in the pancreas. Islet transplantation is becoming one of the most promising therapies for T1D patients. However, its clinical use is limited by substantial cell loss after islet infusion, closely related to immune reactions, including instant blood-mediated inflammatory responses, oxidative stress, and direct autoimmune attack. Especially the grafted islets are not only exposed to allogeneic immune rejection after transplantation but are also subjected to an autoimmune process that caused the original disease. Due to the development and convergence of expertise in biomaterials, nanotechnology, and immunology, protective strategies are being investigated to address this issue, including exploring novel immune protective agents, encapsulating islets with biomaterials, and searching for alternative implantation sites, or co-transplantation with functional cells. These methods have significantly increased the survival rate and function of the transplanted islets. However, most studies are still limited to animal experiments and need further studies. In this review, we introduced the immunological challenges for islet graft and summarized the recent developments in immune-protective strategies to improve the outcomes of islet transplantation.

Adipose-derived stem cells alleviate liver injury induced by type 1 diabetes mellitus by inhibiting mitochondrial stress and attenuating inflammation

Background

Type 1 diabetes mellitus (T1D) is a worldwide health priority due to autoimmune destruction and is associated with an increased risk of multiorgan complications. Among these complications, effective interventions for liver injury, which can progress to liver fibrosis and hepatocellular carcinoma, are lacking. Although stem cell injection has a therapeutic effect on T1D, whether it can cure liver injury and the underlying mechanisms need further investigation.

Methods

Sprague–Dawley rats with streptozotocin (STZ)-induced T1D were treated with adipose-derived stem cell (ADSC) or PBS via the tail vein formed the ADSC group or STZ group. Body weights and blood glucose levels were examined weekly for 6 weeks. RNA-seq and PCR array were used to detect the difference in gene expression of the livers between groups.

Results

In this study, we found that ADSCs injection alleviated hepatic oxidative stress and injury and improved liver function in rats with T1D; potential mechanisms included cytokine activity, energy metabolism and immune regulation were potentially involved, as determined by RNA-seq. Moreover, ADSC treatment altered the fibroblast growth factor 21 (FGF21) and transforming growth factor β (TGF-β) levels in T1D rat livers, implying its repair capacity. Disordered intracellular energy metabolism, which is closely related to mitochondrial stress and dysfunction, was inhibited by ADSC treatment. PCR array and ingenuity pathway analyses suggested that the ADSC-induced suppression of mitochondrial stress is related to decreased necroptosis and apoptosis. Moreover, mitochondria-related alterations caused liver inflammation, resulting in liver injury involving the T lymphocyte-mediated immune response.

Conclusions

Overall, these results improve our understanding of the curative effect of ADSCs on T1D complications: ADSCs attenuate liver injury by inhibiting mitochondrial stress (apoptosis and dysfunctional energy metabolism) and alleviating inflammation (inflammasome expression and immune disorder). These results are important for early intervention in liver injury and for delaying the development of liver lesions in patients with T1D.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02760-z.

Cytological, Histochemical, and Ultrastructural Study of the Human Fetal Spleen of Various Gestational Age With Future Implications in Splenic Transplantation: An Anatomical Perspective

Purpose: The spleen is a fist-sized largest lymphoid organ located in the left hypochondrium. It has a unique location, embryological and histological structure that differs significantly from other lymphoid organs. The present work was undertaken to study the microscopic and ultramicroscopic histogenesis patterns of the spleen in relation to gestational age.

Methods: The splenic tissue of nine aborted fetuses of various gestational ages was studied. For cytology study, special stains like Masson’s trichrome, Periodic Acid-Schiff, and Reticulin were used; immunohistochemical staining was performed with triple antibodies (C-myc, Ki-67, and Ber-H2); and for ultrastructure study, aluminum mounted specimens coated with gold and argon gas were observed under scanning electron microscopy (SEM).

Results: Microscopy and immunohistochemistry showed the developmental changes in the spleen from the emergence of the primordium to the end of the embryonic period in all stages of fetogenesis. The spleen primordium of a fetus at the developmental stage of the primary vascular reticulum was seen in the first trimester fetuses. The primordium is comprised mainly of mesenchymal tissue; numerous lymphocytes invading the area surrounding the central artery forming the periarterial lymphoid sheaths (PALS) were seen surrounded by venous sinuses in the early second trimester fetuses.

Conclusion: The organizational changes in the reticuloendothelial system and microstructure of the spleen during fetogenesis are very crucial to achieving adult morphology in the future. Histogenesis of the fetal spleen follows a multistep process depending upon the gestational age. Any deviation from normalcy may lead to structural and functional abnormality later in life.

Immunoengineering Biomaterials in Cell-Based Therapy for Type 1 Diabetes

Type 1 diabetes (T1D) is caused by low insulin production and chronic hyperglycemia due to the destruction of pancreatic β-cells. Cell transplantation is an attractive alternative approach compared to insulin injection. However, cell therapy has been limited by major challenges including life-long requirements for immunosuppressive drugs in order to prevent host immune responses. Encapsulation of the transplanted cells can solve the problem of immune rejection, by providing a physical barrier between the transplanted cells and the recipient's immune cells. Despite current disputes in cell encapsulation approaches, thanks to recent advances in the fields of biomaterials and transplantation immunology, extensive effort has been dedicated to immunoengineering strategies in combination with encapsulation technologies to overcome the problem of the host's immune responses. The current review summarizes the most commonly used encapsulation and immunoengineering strategies combined with cell therapy which has been applied as a novel approach to improve cell replacement therapies for the management of T1D. Recent advances in the fields of biomaterial design, nanotechnology, as well as deeper knowledge about immune modulation had significantly improved cell encapsulation strategies. However, further progress requires the combined application of novel immunoengineering approaches and islet/ß-cell transplantation.

Tissue engineering and 3D printing of bioartificial pancreas for regenerative medicine in diabetes

Diabetes is a severe chronic disease worldwide. In various types of diabetes, the pancreatic beta cells fail to secrete sufficient insulin, at some point, to regulate blood glucose levels. Therefore, the replacement of dysfunctional pancreas, islets of Langerhans, or even the insulin-secreting beta cells facilitates physiological regulation of blood glucose levels. However, the current lack of sufficient donor human islets for cell replacement therapy precludes a routine and absolute cure for most of the existing diabetes cases globally. It is envisioned that tissue engineering of a bioartificial pancreas will revolutionize regenerative medicine and the treatment of diabetes. In this review, we discuss the anatomy and physiology of the pancreas, and identify the clinical considerations for engineering a bioartificial pancreas. Subsequently, we dissect the bioengineering problem based on the design of the device, the biomaterial used, and the cells involved. Last but not least, we highlight current tissue engineering challenges and explore potential directions for future work.

Donor Recipient Chimeric Cells Induce Chimerism and Extend Survival of Vascularized Composite Allografts

This study evaluated the efficacy of donor recipient chimeric cell (DRCC) therapy created by fusion of donor and recipient derived bone marrow cells (BMC) in chimerism and tolerance induction in a rat vascularized composite allograft (VCA) model. Twenty-four VCA (groin flaps) from MHC-mismatched ACI (RT1^a) donors were transplanted to Lewis (RT1^l) recipients. Rats were randomly divided into (n = 6/group): Group 1—untreated controls, Groups 2—7-day immunosuppression controls, Group 3—DRCC, and Group 4—DRCC with 7-day anti-αβTCR monoclonal antibody and cyclosporine A protocol. DRCC created by polyethylene glycol-mediated fusion of ACI and Lewis BMC were cultured and transplanted (2–4 × 10⁶) to VCA recipients via intraosseous delivery route. Flow cytometry assessed peripheral blood chimerism while fluorescent microscopy and PCR tested the presence of DRCC in the recipient’s blood, bone marrow (BM), and lymphoid organs at the study endpoint (VCA rejection). No complications were observed after DRCC intraosseous delivery. Group 4 presented the longest average VCA survival (79.3 ± 30.9 days) followed by Group 2 (53.3 ± 13.6 days), Group 3 (18 ± 7.5 days), and Group 1 (8.5 ± 1 days). The highest chimerism level was detected in Group 4 (57.9 ± 6.2%) at day 7 post-transplant. The chimerism declined at day 21 post-transplant and remained at 10% level during the entire follow-up period. Single dose of DRCC therapy induced long-term multilineage chimerism and extended VCA survival. DRCC introduces a novel concept of customized donor-recipient cell-based therapy supporting solid organ and VCA transplants.

Advances in Pancreatic Islet Transplantation Sites for the Treatment of Diabetes

Diabetes is a complex disease that affects over 400 million people worldwide. The life-long insulin injections and continuous blood glucose monitoring required in type 1 diabetes (T1D) represent a tremendous clinical and economic burdens that urges the need for a medical solution. Pancreatic islet transplantation holds great promise in the treatment of T1D; however, the difficulty in regulating post-transplantation immune reactions to avoid both allogenic and autoimmune graft rejection represent a bottleneck in the field of islet transplantation. Cell replacement strategies have been performed in hepatic, intramuscular, omentum, and subcutaneous sites, and have been performed in both animal models and human patients. However more optimal transplantation sites and methods of improving islet graft survival are needed to successfully translate these studies to a clinical relevant therapy. In this review, we summarize the current progress in the field as well as methods and sites of islet transplantation, including stem cell-derived functional human islets. We also discuss the contribution of immune cells, vessel formation, extracellular matrix, and nutritional supply on islet graft survival. Developing new transplantation sites with emerging technologies to improve islet graft survival and simplify immune regulation will greatly benefit the future success of islet cell therapy in the treatment of diabetes.

Mechanism of Transplanted Islet Engraftment in Visceral White Adipose Tissue

BACKGROUND

White adipose tissue (WAT) is a candidate transplantation site for islets. However, the mechanism of islet engraftment in WAT has not been fully investigated. In this study, we attempted to clarify the therapeutic effect and mechanism of islet transplantation into visceral WAT.

METHODS

Two hundred mouse islets were transplanted into epididymal WAT of syngeneic diabetic mice by wrapping islets with the tissue (fat-covered group). Mice that received intraperitoneal and renal subcapsular islet transplantations were used as negative and positive control groups, respectively.

RESULTS

The transplant efficacy, including improvements in blood glucose and plasma insulin levels and in glucose tolerance tests, of the fat-covered group was superior to the negative control group and almost equal to the positive control group. Vessel density of engrafted islets in the fat-covered group was higher than that in the positive control group. It was speculated that the mechanism of islet engraftment in WAT might consist of trapping islets in WAT, adhesion of islets via a combination of adhesion factors (fibronectin and integrin β1), and promotion of angiogenesis in islets by expression of angiogenic factors induced by adiponectin.

CONCLUSIONS

Visceral WAT is an important candidate for islet transplantation. Adhesion factors and adiponectin might contribute to islet engraftment into WAT. Further studies to elucidate the detailed mechanism are necessary.

Splenic lesion mimicking breast metastasis: The first description of splenic parenchymal endometriosis

Introduction:

Splenic parenchymal endometriosis has never been described to date. We report here the case of real parenchymal endometriosis of the spleen.

Case description:

In this case, a 54-year-old female patient presented a histologically proven metastatic recurrence of breast cancer in the internal breast chain. The CT-scan also detected a large cystic structure developed from the spleen, but non-suspected to be metastasis. The patient was treated with chemotherapy (paclitaxel) and a combination of targeted therapies (everolimus and trastuzumab). While a complete radiological and biological response was noted at 2 months, the splenic cyst gradually decreased over the years. When targeted therapies were stopped, a reincrease of the splenic lesion and de novo significant hypermetabolism of the splenic parenchyma on 18F-FDG PET scan were observed. A splenectomy was finally performed and revealed splenic parenchymal endometriosis.

Conclusion:

This case once again highlights the complexity of endometriosis disease, from a pathophysiological point of view, but also the difficulties of radiological characterisation, and diagnostic management.

White Adipose Tissue as a Site for Islet Transplantation

Although islet transplantation is recognized as a useful cellular replacement therapy for severe diabetes, surgeons face difficulties in islet engraftment. The transplant site is a pivotal factor that influences the engraftment. Although the liver is the current representative site for clinical islet transplantation, it is not the best site because of limitations in immunity, inflammation, and hypoxia. White adipose tissue, including omentum, is recognized as a useful candidate site for islet transplantation. Its effectiveness has been evaluated in not only various basic and translational studies using small and large animals but also in some recent clinical trials. In this review, we attempt to shed light on the characteristics and usefulness of white adipose tissue as a transplant site for islets.

White Adipose Tissue as a Site for Islet Transplantation

Although islet transplantation is recognized as a useful cellular replacement therapy for severe diabetes, surgeons face difficulties in islet engraftment. The transplant site is a pivotal factor that influences the engraftment. Although the liver is the current representative site for clinical islet transplantation, it is not the best site because of limitations in immunity, inflammation, and hypoxia. White adipose tissue, including omentum, is recognized as a useful candidate site for islet transplantation. Its effectiveness has been evaluated in not only various basic and translational studies using small and large animals but also in some recent clinical trials. In this review, we attempt to shed light on the characteristics and usefulness of white adipose tissue as a transplant site for islets.

Comparative Study of Two Different Islet Transplantation Sites in Mice: Hepatic Sinus Tract vs Splenic Parenchyma

Although 90% of clinical islet transplantations are performed via the portal vein approach, it is still far from the ideal transplant site. Alternative islet transplant sites are promising to reduce the islet dose required to reverse hyperglycemia, thereby improving the efficiency of islet transplantation. The aim of this study was to compare the differences in survival and metabolic function of islet grafts transplanted into the hepatic sinus tract (HST) and the splenic parenchyma (SP). Approximately 300 syngeneic mouse islets were transplanted into the HST (n = 6) and the SP (n = 6) of recipient diabetic mice, respectively. After transplantation, the glycemic control, glucose tolerance, and morphology of islet grafts were evaluated and compared in each group. The nonfasting blood glucose of the two groups of mice receiving islet transplantation gradually decreased to the normal range and sustained for more than 100 d. There is no significant difference in the time required to restore normoglycemia (P > 0.05). The results of the glucose tolerance test showed that the SP group presented a smaller area under the curve than the HST group (P < 0.05). Histopathological results showed that islet grafts in the HST and the SP were characterized with normal islet morphology and robust insulin production. Compared with the HST, islet transplantation in the SP presents better blood glucose regulation, although there is no significant difference in the time required to restore normoglycemia.

The spleen contributes to the increase in PMN-MDSCs in orthotopic H22 hepatoma mice

Myeloid-derived suppressor cells (MDSCs) are classified into polymorphonuclear (PMN)-MDSCs and monocytic (M)-MDSCs. The predominant subtype of MDSCs in hepatocellular carcinoma (HCC) is still elusive. The spleen is the largest immune organ in the body and is the origin of many cells. It is still unknown whether the spleen is the origin of MDSCs. In this study, we investigated the expression, origin and mobilization of the predominant MDSC subtype in H22 orthotopic hepatoma mice. Compared with M-MDSCs, PMN-MDSCs were increased and dominant in the spleen, peripheral blood and tumor tissues. Splenectomy could decrease the percentages of PMN-MDSCs in the peripheral blood and tumor tissues, increase the frequencies of NK cells in the peripheral blood and CD3⁺CD4⁺T, CD3⁺CD8⁺T, NK and NKT cells in the tumor tissues, reduce the tumor weight and the amounts of ascites, and prolong survival time in hepatoma mice. The levels of chemokine (CC motif) ligand 9 (CCL9) and chemokine (CC motif) ligand 2 (CCL2) were elevated in the peripheral blood of tumor-bearing (TB) mice, and their receptors CCR1 and CCR2 were expressed on spleen PMN-MDSCs. Migration assay showed that CCL2 and CCL9 could attract spleen PMN-MDSCs in vitro. These results indicate that PMN-MDSCs were increased and dominant in orthotopic H22 hepatoma mice, the spleen contributed to the increase of PMN-MDSCs, and PMN-MDSCs could be mobilized from the spleen to the peripheral blood by CCL9 and CCL2, thus facilitated tumor growth.

Considerations for an Alternative Site of Islet Cell Transplantation

Islet cell transplantation has been limited most by poor graft survival. Optimizing the site of transplantation could improve clinical outcomes by minimizing required donor cells, increasing graft integration, and simplifying the transplantation and monitoring process. In this article, we review the history and significant human and animal data for clinically relevant sites, including the liver, spleen, and kidney subcapsule, and identify promising new sites for further research. While the liver was the first studied site and has been used the most in clinical practice, the majority of transplanted islets become necrotic. We review the potential causes for graft death, including the instant blood-mediated inflammatory reaction, exposure to immunosuppressive agents, and low oxygen tension. Significant research exists on alternative sites for islet cell transplantation, suggesting a promising future for patients undergoing pancreatectomy.

Host Lymphotoxin-β Receptor Signaling Is Crucial for Angiogenesis of Metanephric Tissue Transplanted into Lymphoid Sites

The mouse lymph node (LN) can provide a niche to grow metanephric kidney to maturity. Here, we show that signaling through the lymphotoxin-β receptor (LTβR) is critical for kidney organogenesis both in the LN and the omentum. By transplanting kidney rudiments either in the LNs of mice undergoing LTβR antagonist treatment or in the omenta of Ltbr knockout (Ltbr-/-) mice, the host LTβR signals were found to be crucial for obtaining a well-vascularized kidney graft. Indeed, defective LTβR signaling correlated with decreased expression of endothelial and angiogenic markers in kidney grafts as well as structural alterations. Because the number of glomerular endothelial cells expressing the LTβR target nuclear factor κB-inducing kinase (NIK) decreased in the absence of a functional LTβR, it was speculated that an LTβR/NIK axis mediated the angiogenetic signals required for successful ectopic kidney organogenesis, given the established role of NIK in neovascularization. However, the transplantation of kidney rudiments in omenta of Nik-/- mice revealed that NIK is dispensable for ectopic kidney vascular integration and maturation. Finally, defective LTβR signaling impaired compensatory glomerular adaptation to renal mass reduction, indicating that kidney regeneration approaches, besides whole kidney reconstruction, might benefit from the presence of LTβR signals.

Kidney-in-a-lymph node: A novel organogenesis assay to model human renal development and test nephron progenitor cell fates

Stem cell-derived organoids are emerging as sophisticated models for studying development and disease and as potential sources for developing organ substitutes. Unfortunately, although organoids containing renal structures have been generated from mouse and human pluripotent stem cells, there are still critical unanswered questions that are difficult to attain via in vitro systems, including whether these nonvascularized organoids have a stable and physiologically relevant phenotype or whether a suitable transplantation site for long-term in vivo studies can be identified. Even orthotopic engraftment of organoid cultures in the adult does not provide an environment conducive to vascularization and functional differentiation. Previously, we showed that the lymph node offers an alternative transplantation site where mouse metanephroi can differentiate into mature renal structures with excretory, homeostatic, and endocrine functions. Here, we show that the lymph node lends itself well as a niche to also grow human primary kidney rudiments and can additionally be viewed as a platform to interrogate emerging renal organoid cultures. Our study has a wide-ranging impact for tissue engineering approaches to rebuild functional tissues in vivo including-but not limited to-the kidney.

Regenerative and Transplantation Medicine: Cellular Therapy Using Adipose Tissue-Derived Mesenchymal Stromal Cells for Type 1 Diabetes Mellitus

Type 1 diabetes mellitus (T1DM) is caused by the autoimmune targeting of pancreatic β-cells, and, in the advanced stage, severe hypoinsulinemia due to islet destruction. In patients with T1DM, continuous exogenous insulin therapy cannot be avoided. However, an insufficient dose of insulin easily induces extreme hyperglycemia or diabetic ketoacidosis, and intensive insulin therapy may cause hypoglycemic symptoms including hypoglycemic shock. While these insulin therapies are efficacious in most patients, some additional therapies are warranted to support the control of blood glucose levels and reduce the risk of hypoglycemia in patients who respond poorly despite receiving appropriate treatment. There has been a recent gain in the popularity of cellular therapies using mesenchymal stromal cells (MSCs) in various clinical fields, owing to their multipotentiality, capacity for self-renewal, and regenerative and immunomodulatory potential. In particular, adipose tissue-derived MSCs (ADMSCs) have become a focus in the clinical setting due to the abundance and easy isolation of these cells. In this review, we outline the possible therapeutic benefits of ADMSC for the treatment of T1DM.

The relationship of spleen stiffness value measured by shear wave elastography with age, gender, and spleen size in healthy volunteers

PURPOSE

The aim of this study is to evaluate spleen stiffness values with shear wave elastography (SWE) quantitatively in healthy adults and investigate the relationship of spleen stiffness with age, gender, and spleen size.

METHODS

This study included 65 healthy individuals. Spleen stiffness measurement was obtained with 2 dimensional (2-D) SWE method from the middle portion of spleen and calculated in kilopascals by taking the average of three valid measurements. Longitudinal and transverse spleen sizes were measured. The relationship of spleen stiffness with age, gender, and spleen size was investigated. The association between spleen size and age and gender was also evaluated.

RESULTS

The mean spleen stiffness value was 13.82 ± 2.91 kPa, and the spleen stiffness was not affected by age, gender, or spleen size. Longitudinal spleen size was significantly lower in females than that in males. Moreover, there was a significant negative correlation between longitudinal spleen size and age (r = 0.247, p = 0.048).

CONCLUSION

Spleen stiffness can be quantitatively measured by 2-D SWE, and the spleen stiffness is not affected by age, gender, and spleen size. The values obtained in this study can be used as normal base values in examination of different spleen pathologies.