Urine-Derived Stem Cells for Regenerative Medicine: Basic Biology, Applications, and Challenges

Challenges of therapeutic applications and regenerative capacities of urine based stem cells in oral, and maxillofacial reconstruction

Urine-derived stem cells (USCs) have gained the attention of researchers in the biomedical field in the past few years . Regarding the several varieties of cells that have been used for this purpose, USCs have demonstrated mesenchymal stem cell-like properties, such as differentiation and immunomodulation. Furthermore, they could be differentiated into several lineages. This is very interesting for regenerative techniques based on cell therapy. This review will embark on describing their separation, and profiling. We will specifically describe the USCs characteristics, in addition to their differentiation potential. Then, we will introduce and explore the primary uses of USCs. These involve thier utilization as a platform to produce stem cells, however, we shall concentrate on the utilization of USCs for therapeutic, and regenerative orofacial applications, providing an in-depth evaluation of this purpose. The final portion will address the limitations and challenges of their implementation in regenerative dentistry.

MSCs-Derived Decellularised Matrix: Cellular Responses and Regenerative Dentistry

The decellularised extracellular matrix (dECM) of in vitro cell culture is a naturally derived biomaterial formed by the removal of cellular components. The compositions of molecules in the extracellular matrix (ECM) differ depending on various factors, including the culture conditions. Cell-derived ECM provides a 3-dimensional structure that has a complex influence on cell signalling, which in turn affects cell survival and differentiation. This review describes the effects of dECM derived from mesenchymal stem cells (MSCs) on cell responses, including cell migration, cell proliferation, and cell differentiation in vitro. Published articles were searched in the PubMed databases in 2005 to 2022, with assigned keywords (MSCs and decellularisation and cell culture). The 41 articles were reviewed, with the following criteria. (1) ECM was produced exclusively from MSCs; (2) decellularisation processes were performed; and (3) the dECM production was discussed in terms of culture systems and specific supplementations that are suitable for creating the dECM biomaterials. The dECM derived from MSCs supports cell adhesion, enhances cell proliferation, and promotes cell differentiation. Importantly, dECM derived from dental MSCs shows promise in regenerative dentistry applications. Therefore, the literature strongly supports cell-based dECMs as a promising option for innovative tissue engineering approaches for regenerative medicine.

Stem Cell-Derived Extracellular Vesicles: Promising Therapeutic Opportunities for Diabetic Wound Healing

Wound healing is a sophisticated and orderly process of cellular interactions in which the body restores tissue architecture and functionality following injury. Healing of chronic diabetic wounds is difficult due to impaired blood circulation, a reduced immune response, and disrupted cellular repair mechanisms, which are often associated with diabetes. Stem cell-derived extracellular vesicles (SC-EVs) hold the regenerative potential, encapsulating a diverse cargo of proteins, RNAs, and cytokines, presenting a safe, bioactivity, and less ethical issues than other treatments. SC-EVs orchestrate multiple regenerative processes by modulating cellular communication, increasing angiogenesis, and promoting the recruitment and differentiation of progenitor cells, thereby potentiating the reparative milieu for diabetic wound healing. Therefore, this review investigated the effects and mechanisms of EVs from various stem cells in diabetic wound healing, as well as their limitations and challenges. Continued exploration of SC-EVs has the potential to revolutionize diabetic wound care.

Urine-Derived Stem Cells Reverse Bleomycin‑Induced Experimental Pulmonary Fibrosis by Inhibition of the TGF-β1-Smad2/3 Pathway

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive lung interstitial lesions with the disease pathophysiology incompletely understood, which is a serious and fatal disorder with limited treatment options. Mesenchymal stem cells (MSCs) have exhibited promising therapeutic capability for IPF. While most types of MSCs are obtained invasively, urine-derived stem cells (USCs) can be gained in a safe, noninvasive, and inexpensive procedure, which are readily available and reported to exhibit no risk of teratoma formation or oncogenic potential in vivo, sounding alternative to other MSCs. This study aims to investigate the therapeutic effect and mechanism of USCs on IPF, using a bleomycin (BLM)-induced IPF model in mice.

METHODS

Cell surface marker examination by flow cytometry analysis and cell differentiation culture were used to characterize USCs obtained from healthy individuals. BLM was instilled endotracheally in adult C57BL/6 mice, followed by USCs or human bone marrow-derived mesenchymal stem cells (BMSCs) treatment by tail vein injection on day 14. Mice were euthanized on day 14 before administration or day 21 for the evaluation of pulmonary histopathology and hydroxyproline (HYP) content. Inflammatory factors of the lung, including transforming growth factor (TGF)-β1, TNF-α, IL-6, MMP2 were analyzed by quantitative real-time PCR (qRT-PCR). Additionally, immunohistochemistry (IHC) and western blotting (WB) were applied to evaluate the expression of α-SMA and activation of TGF-β1-Smad2/3 in lung.

RESULTS

USCs highly expressed CD29 and CD90, showing negative expression of hematopoietic stem cell markers (CD45, CD34) and could differentiate into, at least, bone and fat in vitro. In mice challenged with BLM, septal thickening and prominent fibrosis were observed on day 14, with higher HYP content and mRNA levels of TGF-β1, TNF-α and IL-6 exhibited, compared to untreated mice. USCs could migrate to lung and accumulate there in mouse model after intravenous injection. Transplantation of USCs into BLM-induced mice improved their pulmonary histopathology, decreasing Ashcroft score, Szapiel score, HYP content and mRNA levels of TGF-β1 and MMP2 of lung, similar to the effects of BMSCs. IHC and WB further revealed that USCs could inhibit activation of the TGF‑β1-Smad2/3 pathway of lung in vivo.

CONCLUSIONS

Transplantation of USCs effectively reverses pulmonary fibrotic phenotype in an experimental IPF model, inhibiting the TGF-β1-Smad2/3 pathway, a key driver of fibrosis. These results suggest the therapeutic application of USCs for IPF, instead of other types of MSCs obtained invasively.

The Inhibition of Fibrosis and Inflammation in Obstructive Kidney Injury via the miR-122-5p/SOX2 Axis Using USC-Exos

Background: Fibrosis and inflammation due to ureteropelvic junction obstruction substantially contributes to poor renal function. Urine-derived stem-cell-derived exosomes (USC-Exos) have therapeutic effects through paracrine. Methods: In vitro, the effects of USC-Exos on the biological functions of HK-2 and human umbilical vein endothelial cells were tested. Cell inflammation and fibrosis were induced by transforming growth factor-β1 and interleukin-1β, and their anti-inflammatory and antifibrotic effects were observed after exogenous addition of USC-Exos. Through high-throughput sequencing of microRNA in USC-Exos, the pathways and key microRNAs were selected. Then, the antifibrotic and anti-inflammatory effects of exosomal miR-122-5p and target genes were verified. The role of the miR-122-5p/SOX2 axis in anti-inflammatory and antifibrotic effects was verified. In vivo, a rabbit model of partial unilateral ureteral obstruction (PUUO) was established. Magnetic resonance imaging recorded the volume of the renal pelvis after modeling, and renal tissue was pathologically analyzed. Results: We examined the role of USC-Exos and their miR-122-5p content in obstructive kidney injury. These Exos exhibit antifibrotic and anti-inflammatory activities. SOX2 is the hub gene in PUUO and negatively related to renal function. We confirmed the binding relationship between miR-122-5p and SOX2. The anti-inflammatory and antifibrotic effects of miR-122-5p were inhibited, indicating that miR-122-5p has anti-inflammatory and antifibrotic effects by inhibiting SOX2 expression. In vivo, the PUUO group showed typical obstructive kidney injury after modeling. After USC-Exo treatment, the shape of the renal pelvis shown a remarkable improvement, and inflammation and fibrosis decreased. Conclusions: We confirmed that miR-122-5p from USC-Exos targeting SOX2 is a new molecular target for postoperative recovery treatment of obstructive kidney injury.

Circ DENND4C inhibits pyroptosis and alleviates ischemia-reperfusion acute kidney injury by exosomes secreted from human urine-derived stem cells

Acute kidney injury (AKI) is a disease characterised by acute onset, high mortality, and poor prognosis, and is mainly caused by ischemia-reperfusion (I/R). Human urine-derived stem cells (USCs) exhibit antioxidant, anti-inflammatory, and anti-apoptotic cytoprotective effects. Previously, we found that exosomes from USCs had the ability to inhibit apoptosis and protect kidneys from I/R injury. This study aimed to investigate the role of USC-derived exosomes (USC-Exos) in reducing pyroptosis and alleviating I/R-AKI. Models of HK-2 cells hypoxia-reoxygenation (H/R) and I/R kidney injury was established in Sprague Dawley rats to simulate AKI in vitro and in vivo. USC-Exos were isolated using ultracentrifugation and identified via electron microscopy and western blotting. USC-Exos were co-cultured with HK-2 cells and injected into rats via the tail vein. The expression of pyroptosis-related molecules (GSDMD, caspase-1, and NLRP-3) was verified using PCR and western blotting. Changes in renal function were reflected in the serum creatinine, urea, and cystatin C levels. The degree of renal injury was determined using haematoxylin and eosin and immunohistochemical staining. The levels of IL-1β and IL-18 were detected using enzyme-linked immunosorbent assay (ELISA) to verify the role of USC-Exos in pyroptosis. Differentially expressed circRNAs in I/R rat kidneys were screened by transcriptome sequencing, and a dual-luciferase experiment was used to verify the interaction between upstream and downstream molecules. Ischemia-reperfusion resulted in significantly impaired renal function and expression of pyroptosis molecules, and significantly increased concentrations of inflammatory factors. These effects were reversed by injecting USC-Exos. Circ DENND4C was the most significantly decreased circRNA in I/R rat renal tissue, and knock-down of circ DENND4C can aggravate AKI in vivo and in vitro. DAVID(http://david.abcc.ncifcrf.gov) website showed that miR 138-5p/FOXO3a is a potential downstream target of circ DENND4C. Knock-down of circ DENND4C in HK-2 cells resulted in increased expression of miR 138-5p and increased miR 138-5p can reverse the regulation of FOXO3a. Dual-luciferase assay verified the reverse interaction between circ DENND4C, miR 138-5p, and FOXO3a. Exosomes promote cell proliferation and inhibit the activation of NLR family pyrin domain containing 3 through the circ DENND4C/miR 138-5p/FOXO3a pathway, thereby reducing pyroptosis and AKI. Circ DENND4C may be a potential therapeutic target for AKI.

Targeted therapy for peri-prosthetic osteolysis using macrophage membrane-encapsulated human urine-derived stem cell extracellular vesicles

Aseptic loosening of the prosthesis is a severe complication after joint replacement. It is of great practical significance and social value to discover the prevention and treatment strategies for this condition. Exosomes from urine-derived stem cells (Exos) have great potential in promoting bone repair, reconstruction, and regulating bone metabolism. However, they are easily eliminated by macrophages and incapable of targeting the osteolysis zone. In this study, based on macrophage "homing" into periprosthetic osteolysis region and cell membrane encapsulating nanotechnology, exosomes from urine-derived stem cells were encapsulated with macrophage membrane (MM) to prevent periprosthetic osteolysis. We found that macrophage membrane encapsulated urine-derived stem cell-derived exosomes (MM-Exos) can be targeted delivery to the osteolysis zone and enhance the therapeutic effectiveness of Exos, which alleviated wear particles-induced calvarial osteolysis. Furthermore, MM-Exos could provide immunological camouflage and allow the Exos to avoid phagocytosis by macrophages and stimulate cellular uptake by bone marrow-derived stem cells (BMSCs). Therefore, we demonstrated the unique ability of the macrophage membrane as a targeted transport of exosomes from urine-derived stem cells for the prevention and treatment of periprosthetic osteolysis. These biomimetic nanoparticles provided a new therapeutic exosome delivery system for preventing wear particles-induced osteolysis. STATEMENT OF SIGNIFICANCE: Macrophage membrane encapsulated urine-derived stem cell-derived exosomes (MM-Exos) can be targeted delivery to the osteolysis zone and enhance the therapeutic effect of Exos on peri‑prosthetic osteolysis prevention. MM-Exos could allow the Exos to avoid phagocytosis by macrophages and promote the uptake of Exos by BMSCs.

Stem cell therapy combined with controlled release of growth factors for the treatment of sphincter dysfunction

Sphincter dysfunction often occurs at the end of tubule organs such as the urethra, anus, or gastroesophageal sphincters. It is the primary consequence of neuromuscular impairment caused by trauma, inflammation, and aging. Despite intensive efforts to recover sphincter function, pharmacological treatments have not achieved significant improvement. Cell- or growth factor-based therapy is a promising approach for neuromuscular regeneration and the recovery of sphincter function. However, a decrease in cell retention and viability, or the short half-life and rapid degradation of growth factors after implantation, remain obstacles to the translation of these therapies to the clinic. Natural biomaterials provide unique tools for controlled growth factor delivery, which leads to better outcomes for sphincter function recovery in vivo when stem cells and growth factors are co-administrated, in comparison to the delivery of single therapies. In this review, we discuss the role of stem cells combined with the controlled release of growth factors, the methods used for delivery, their potential therapeutic role in neuromuscular repair, and the outcomes of preclinical studies using combination therapy, with the hope of providing new therapeutic strategies to treat incontinence or sphincter dysfunction of the urethra, anus, or gastroesophageal tissues, respectively.

Bioactive ECM-Loaded SIS Generated by the Optimized Decellularization Process Exhibits Skin Wound Healing Ability in Type I Diabetic Rats

Patients with diabetes have 15-25% chance for developing diabetic ulcers as a severe complication and formidable challenge for clinicians. Conventional treatment for diabetic ulcers is to surgically remove the necrotic skin, clean the wound, and cover it with skin flaps. However, skin flap often has a limited efficacy, and its acquisition requires a second surgery, which may bring additional risk for the patient. Skin tissue engineering has brought a new solution for diabetic ulcers. Herein, we have developed a bioactive patch through a compound culture and the optimized decellularization strategy. The patch was prepared from porcine small intestinal submucosa (SIS) and modified by an extracellular matrix (ECM) derived from urine-derived stem cells (USCs), which have low immunogenicity while retaining cytokines for angiogenesis and tissue regeneration. The protocol included the optimization of the decellularization time and the establishment of the methods. Furthermore, the in vitro mechanism of wound healing ability of the patch was investigated, and its feasibility for skin wound healing was assessed through an antishrinkage full-thickness skin defect model in type I diabetic rats. As shown, the patch displayed comparable effectiveness to the USCs-loaded SIS. Our findings suggested that this optimized decellularization protocol may provide a strategy for cell-loaded scaffolds that require the removal of cellular material while retaining sufficient bioactive components in the ECM for further applications.

Cell Sheet Technology as an Engineering-Based Approach to Bone Regeneration

Bone defects that are congenital or the result of infection, malignancy, or trauma represent a challenge to the global healthcare system. To address this issue, multiple research groups have been developing novel cell sheet technology (CST)-based approaches to promote bone regeneration. These methods hold promise for use in regenerative medicine because they preserve cell-cell contacts, cell-extracellular matrix interactions, and the protein makeup of cell membranes. This review introduces the concept and preparation system of the cell sheet (CS), explores the application of CST in bone regeneration, highlights the current states of the bone regeneration via CST, and offers perspectives on the challenges and future research direction of translating current knowledge from the lab to the clinic.

Sources, Selection, and Microenvironmental Preconditioning of Cells for Urethral Tissue Engineering

Urethral stricture is a common urinary tract disorder in men that can be caused by iatrogenic causes, trauma, inflammation, or infection and often requires reconstructive surgery. The current therapeutic approach for complex urethral strictures usually involves reconstruction with autologous tissue from the oral mucosa. With the goal of overcoming the lack of sufficient autologous tissue and donor site morbidity, research over the past two decades has focused on cell-based tissue-engineered substitutes. While the main focus has been on autologous cells from the penile tissue, bladder, and oral cavity, stem cells from sources such as adipose tissue and urine are competing candidates for future urethral regeneration due to their ease of collection, high proliferative capacity, maturation potential, and paracrine function. This review addresses the sources, advantages, and limitations of cells for tissue engineering in the urethra and discusses recent approaches to improve cell survival, growth, and differentiation by mimicking the mechanical and biophysical properties of the extracellular environment.

Application of mesenchymal stem cell-derived exosomes from different sources in intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a main cause of lower back pain, leading to psychological and economic burdens to patients. Physical therapy only delays pain in patients but cannot eliminate the cause of IVDD. Surgery is required when the patient cannot tolerate pain or has severe neurological symptoms. Although surgical resection of IVD or decompression of the laminae eliminates the diseased segment, it damages adjacent normal IVD. There is also a risk of re-protrusion after IVD removal. Cell therapy has played a crucial role in the development of regenerative medicine. Cell transplantation promotes regeneration of degenerative tissue. However, owing to the lack of vascular structure in IVD, sufficient nutrients cannot be provided for transplanted mesenchymal stem cells (MSCs). In addition, dead cells release harmful substances that aggravate IVDD. Extracellular vesicles (EVs) have been extensively studied as an emerging therapeutic approach. EVs generated by paracrine MSCs retain the potential of MSCs and serve as carriers to deliver their contents to target cells to regulate target cell activity. Owing to their double-layered membrane structure, EVs have a low immunogenicity and no immune rejection. Therefore, EVs are considered an emerging therapeutic modality in IVDD. However, they are limited by mass production and low loading rates. In this review, the structure of IVD and advantages of EVs are introduced, and the application of MSC-EVs in IVDD is discussed. The current limitations of EVs and future applications are described.