Cell extracts from spleen and adipose tissues restore function to irradiation‐injured salivary glands

The extracts of osteoblast developed from adipose-derived stem cell and its role in osteogenesis

Cell-based therapy has become an achievable choice in regenerative medicines, particularly for musculoskeletal disorders. Adipose-derived stem cells (ASCs) are an outstanding resource because of their ability and functions. Nevertheless, the use of cells for treatment comes with difficulties in operation and safety. The immunological barrier is also a major limitation of cell therapy, which can lead to unexpected results. Cell-derived products, such as cell extracts, have gained a lot of attention to overcome these limitations. The goal of this study was to optimize the production of ASC-osteoblast extracts as well as their involvement in osteogenesis. The extracts were prepared using a freeze-thaw method with varying temperatures and durations. Overall, osteogenic-associated proteins and osteoinductive potential of the extracts prepared from the osteogenic-induced ASCs were assessed. Our results demonstrated that the freeze-thaw approach is practicable for cell extracts production, with minor differences in temperature and duration having no effect on protein concentration. The ASC-osteoblast extracts contain a significant level of essential specialized proteins that promote osteogenicity. Hence, the freeze-thaw method is applicable for extract preparation and ASC-osteoblast extracts may be beneficial as an optional facilitating biologics in bone anabolic treatment and bone regeneration.

Enhanced potent immunosuppression of intracellular adipose tissue-derived stem cell extract by priming with three-dimensional spheroid formation

Immunomodulatory properties of mesenchymal stem cells are widely studied, supporting the use of MSCs as cell-based therapy in immunological diseases. This study aims to generate cell-free MSC extract and improves their immunomodulatory potential. Intracellular extracts were prepared from adipose-derived stem cells (ADSC) spheroid via a freeze-thawing method. The immunomodulatory capacities of ADSC spheroid extracts were investigated in vitro, including lymphocyte proliferation, T regulatory cell expansion, and macrophage assays. A comparative study was conducted with ADSC monolayer extract. The key immunomodulatory mediators presented in ADSC extract were identified. The results revealed that ADSC spheroid extract could suppress lymphocyte activation while enhancing T regulatory cell expansion. Immunomodulatory molecules such as COX-2, TSG-6, and TGF-β1 were upregulated in ADSC priming via spheroid culture. Selective inhibition of COX-2 abrogates the effect of ADSC extract on inducing T regulatory cell expansion. Thus, ADSC spheroid extract gains high efficacy in regulating the immune responses which are associated in part by COX-2 generation. Furthermore, ADSC spheroid extract possessed a potent anti-inflammation by manipulation of TNF-α production from LPS-activated macrophage. Our current study has highlighted the opportunity of using cell-free extracts from adipose tissue-derived mesenchymal stem cells spheroid as novel immunomodulators for the treatment of immunological-associated diseases.

Recent progress in regenerative therapy for damaged salivary glands: From bench to bedside

OBJECTIVE

For functional restoration of salivary glands (SGs) injured by radiation therapy or Sjögren's syndrome (SS), various experimental approaches, such as gene therapy, tissue engineering, and cell-based therapy, have been proposed. This narrative review summarized recent progresses in research using cell-based therapies, including promising trials that could lead to bench-to-clinic applications.

METHODS

A literature review based on PubMed publications in the last two decades was performed to summarize progresses in cell-based therapies for SG dysfunction.

RESULTS

Over 100 experimental studies have shown the therapeutic potential of several types of cells, such as SG stem cells and mesenchymal stem cells, as well as effectively conditioned mononuclear cells, in both radiation injury and SS animal models. These therapies affect to slow fibrosis progression and stimulate tissue regeneration in atrophic glands. However, to date, only a total of seven studies have been developed to the stage of clinical study, showing the safety and preliminary efficacy.

CONCLUSION

To lead the radical effectiveness expected in cell-based therapy, advances in reverse translational research and in innovative experimental research, based on the findings of recent clinical studies, will be critical in the next decade.

Human Bone Marrow Cell Extracts Mitigate Radiation Injury to Salivary Gland

Mitigation of irradiation injury to salivary glands was previously reported using a cell-free extract from mouse bone marrow. However, to bring this potential therapy a step closer to clinical application, a human bone marrow cell extract (BMCE) needs to be tested. Here, we report that irradiation-induced injury of salivary glands in immunocompetent mice treated with human BMCE secreted 50% more saliva than saline-injected mice, and BMCE did not cause additional acute inflammatory reaction. In addition, to identify the cell fraction in BMCE with the most therapeutic activity, we sorted human bone marrow into 3 cell fractions (mononuclear, granulocyte, and red blood cells) and tested their respective cell extracts. We identified that the mononuclear cell extract (MCE) provided the best therapeutic efficacy. It increased salivary flow 50% to 73% for 16 wk, preserved salivary parenchymal and stromal cells, and doubled cell proliferation rates while producing less inflammatory response. In contrast, the cell extract of granulocytes was of shorter efficacy and induced an acute inflammatory response, while that from red blood cells was not therapeutically effective for salivary function. Several proangiogenic (MMP-8, MMP-9, VEGF, uPA) and antiangiogenic factors (TSP-1, PF4, TIMP-1, PAI-1) were identified in MCE. Added advantages of BMCE and MCE for potential clinical use were that cell extracts from both male and female donors were comparably bioactive and that cell extracts could be stored and transported much more conveniently than cells. These findings suggest human BMCE, specifically the MCE fraction, is a promising therapy against irradiation-induced salivary hypofunction.

Mechanism, Prevention, and Treatment of Radiation-Induced Salivary Gland Injury Related to Oxidative Stress

Radiation therapy is a common treatment for head and neck cancers. However, because of the presence of nerve structures (brain stem, spinal cord, and brachial plexus), salivary glands (SGs), mucous membranes, and swallowing muscles in the head and neck regions, radiotherapy inevitably causes damage to these normal tissues. Among them, SG injury is a serious adverse event, and its clinical manifestations include changes in taste, difficulty chewing and swallowing, oral infections, and dental caries. These clinical symptoms seriously reduce a patient’s quality of life. Therefore, it is important to clarify the mechanism of SG injury caused by radiotherapy. Although the mechanism of radiation-induced SG injury has not yet been determined, recent studies have shown that the mechanisms of calcium signaling, microvascular injury, cellular senescence, and apoptosis are closely related to oxidative stress. In this article, we review the mechanism by which radiotherapy causes oxidative stress and damages the SGs. In addition, we discuss effective methods to prevent and treat radiation-induced SG damage.

Labial Stem Cell Extract Mitigates Injury to Irradiated Salivary Glands

Stem cell-based therapies could provide a permanent treatment for salivary gland (SG) hypofunction caused by ionizing radiation (IR) injury. However, current challenges for SG stem cells to reach the clinic include surgical invasiveness, amount of tissue needed, cell delivery, and storage methods. The objective of this study was to develop a clinically less invasive method to isolate and expand human SG stem cells and then to obtain a cell-free extract to be used as a therapy for IR-injured SGs. Human labial glands were biopsied, and labial stem cells (LSCs) were expanded by explant culture. The LSC extract (LSCE) was obtained by releasing the cellular components after 3 freeze-thaw cycles and 17,000g force centrifugation. LSCE was injected intravenously into mice that had their SGs injured with 13-Gy IR. Positive (non-IR) and negative (IR) control mice received injections of saline (vehicle control). Three pieces of labial glands (0.1 g weight) could expand 1 to 2 million cells. LSCs had a doubling time of 18.8 h; could differentiate into osteocytes, adipocytes, and chondrocytes; and were positive for mesenchymal stem cell markers. Both angiogenic (FGF-1, FGF-2, KGF, angiopoietin, uPA, VEGF) and antiangiogenic factors (PAI-1, TIMP-1, TSP-1, CD26) were detected in LSCE. In addition, some angiogenic factors (PEDF, PTX3, VEGF) possessed neurotrophic functions. Mice treated with LSCE had 50% to 60% higher salivary flow rate than saline-treated mice at 8 and 12 wk post-IR. Saliva lag time measurements also confirmed that LSCE restored SG function. Histologic analyses of parotids and submandibular glands reported comparable numbers of acinar cells, blood vessels, and parasympathetic nerves and cell proliferation rates in sham IR and LSCE-treated mice, though significantly lower in saline-treated mice. An explant culture method can harvest a large number of LSCs from small pieces of labial glands. LSCE showed clinical potential to mitigate IR-injured SGs.

Towards Lacrimal Gland Regeneration: Current Concepts and Experimental Approaches

Dry eye disease (DED) is a complex and multifactorial disease resulting in a continual cycle of tear hyperosmolarity and inflammation. Patients suffering from DED experience severe pain and visual impairments leading to a reduced quality of life. Aqueous-deficient dry eye (ADDE), mainly caused through a loss of functional lacrimal gland tissue, results in the most severe forms of DED. Despite a high prevalence, the current treatments remain palliative and may be insufficient to alleviate the symptoms. Consequently, investigations on experimental approaches for in situ lacrimal gland regeneration are of great clinical interest. This article reviews the current knowledge about processes involved in lacrimal gland regeneration, about lacrimal gland resident stem cells, and offers deductions about possible concepts for in situ lacrimal gland regeneration. Promising starting points might be the utilization of therapeutic proteins, such as bone morphogenetic protein 7, mesenchymal stem cells (MSC) or MSC-based treatments such as conditioned medium, lyophilized cell extracts or adult acinar cells. This review further summarizes current experimental approaches for the treatment of ADDE in animal models and patients. Approaches investigating side population stem cells, epithelial progenitor cells and MSC showed that the transplantation of these cells had therapeutic effects on ADDE. However, the most promising and best-studied experimental approach is the use of MSC for induction/enhancement of in situ lacrimal gland regeneration. Their immunomodulatory effects, low immunogenicity, promotion of tissue regeneration and involvement during spontaneous lacrimal regeneration are favorable traits for clinical applications. In addition, the efficacy and safety of allogeneic MSC transplantation have already been demonstrated in a small patient cohort.