Regenerative Medicine Strategies Research Articles

Regenerative medicine strategies for hair growth and regeneration: A narrative review of literature.

Hair loss, or alopecia, is associated with several psychosocial and medical comorbidities, and it remains an economic burden to individuals and the society. Alopecia is attributable to varied mechanisms and features a multifactorial predisposition, and the available conventional medical interventions have several limitations. Thus, several therapeutic strategies for alopecia in regenerative medicine are currently being explored, with increasing evidence suggesting that mesenchymal stem cell (MSC) implantation, MSC-derived secretome treatment, and blood-derived platelet-rich plasma therapies are potential treatment options. In this review, we searched the Cochrane Library, MEDLINE (PubMed), EMBASE, and Scopus using various combinations of terms, such as "stem cell," "alopecia," "hair loss," "Androgenetic alopecia," "male-pattern hair loss," "female-pattern hair loss," "regenerative hair growth," "cell therapy," "mesenchymal stem cells," "MSC-derived extracellular vesicles," "MSC-derived exosomes," and "platelet-rich plasma" and summarized the most promising regenerative treatments for alopecia. Moreover, further opportunities of improving efficacy and innovative strategies for promoting clinical application were discussed.

Single-cell profiling reveals a potent role of quercetin in promoting hair regeneration.

Hair loss affects millions of people at some time in their life, and safe and efficient treatments for hair loss are a significant unmet medical need. We report that topical delivery of quercetin (Que) stimulates resting hair follicles to grow with rapid follicular keratinocyte proliferation and replenishes perifollicular microvasculature in mice. We construct dynamic single-cell transcriptome landscape over the course of hair regrowth and find that Que treatment stimulates the differentiation trajectory in the hair follicles and induces an angiogenic signature in dermal endothelial cells by activating HIF-1α in endothelial cells. Skin administration of a HIF-1α agonist partially recapitulates the pro-angiogenesis and hair-growing effects of Que. Together, these findings provide a molecular understanding for the efficacy of Que in hair regrowth, which underscores the translational potential of targeting the hair follicle niche as a strategy for regenerative medicine, and suggest a route of pharmacological intervention that may promote hair regrowth.

Does Melatonin Associated with Nanostructured Calcium Phosphate Improve Alveolar Bone Repair?

Background and objectives: Calcium phosphates have been widely used as bone substitutes, but their properties are limited to osteoconduction. The association of calcium phosphates with osteoinductive bioactive molecules has been used as a strategy in regenerative medicine. Melatonin has been studied due to its cell protection and antioxidant functions, reducing osteoclastic activity and stimulating newly formed bone. This study aimed to evaluate the effect of topical application of melatonin associated with nanostructured carbonated hydroxyapatite microspheres in the alveolar bone repair of Wistar rats through histological and histomorphometric analysis. Materials and Methods: Thirty female Wistar rats (300 g) were used, divided randomly into three experimental groups (n = 10), G1: nanostructured carbonated hydroxyapatite microspheres associated with melatonin gel (CHA-M); G2: nanostructured carbonated hydroxyapatite (CHA); G3: blood clot (without alveolar filling). The animals were euthanized after 7 and 42 days of the postoperative period and processed for histological and histomorphometric evaluation. Kruskal-Wallis and Dunn's post-test were applied to investigate statistical differences between the groups at the same time point for new bone and connective tissue variables. Mann-Whitney was used to assess statistical differences between different time points and in the biomaterial variable. Results: Results showed a greater volume of residual biomaterial in the CHA-M than the CHA group (p = 0.007), and there were no significant differences in terms of newly formed bone and connective tissue between CHA and CHA-M after 42 days. Conclusions: This study concluded that both biomaterials improved alveolar bone repair from 7 to 42 days after surgery, and the association of CHA with melatonin gel reduced the biomaterial's biodegradation at the implanted site but did not improve the alveolar bone repair.

Future perspective of stem cell-derived exosomes: Cell-free therapeutic strategies for retinal degeneration

With continued expansion of the aged population, the number of patients with retinal degeneration, which is a leading cause of vision loss worldwide, is growing. Stem cell therapies offer hope for regeneration and repair of damaged retinal tissue. Recent reports have highlighted stem cell-derived paracrine mediators, such as exosomes, which appear to exert a therapeutic benefit similar to their cell of origin and do not carry the risk of cell transplantation. One speculated role is that exosomes likely mediate intercellular communication and material exchange. This review depicts the molecular mechanisms underlying exosome-based therapy, especially in retina degeneration diseases. In the future, the use of stem cell-derived exosomes could be considered a novel and cell-free therapeutic strategy in regenerative medicine.

Drug-preloadable methacrylated gelatin microspheres fabricated using an aqueous two-phase system

Gelatin microspheres (GMS) can retain biomolecules and be incorporated into artificial tissues and organs for tissue regeneration. However, the inactivation of biomolecules during the conventional fabrication process of GMS requires postloading of biomolecules to prefabricated GMS. Herein, a novel method for fabricating drug-preloaded GMS using a water-in-water (w/w) emulsification technique, is reported. A highly concentrated gelatin methacrylate (Gm) solution containing fibroblast growth factor 2 (FGF2), a model drug, was emulsified in a highly concentrated polyethylene glycol solution, and the mixture was irradiated with ultraviolet light. The obtained water-in-water gelatin methacrylate microspheres (w/w GmMS) were superior to conventional GMS in terms of stability, FGF2-loading efficiency, and sustained release of FGF2. The FGF2-loaded w/w GmMS efficiently activated the proliferation of adipose tissue-derived mesenchymal stem cells (ASCs). In addition, FGF2-loaded w/w GmMS incorporated into multicellular spheroids of ASCs increased the viability of ASCs in the spheroids. The therapeutic efficacy of ASC spheroids in a wound healing mouse model was significantly improved by the incorporation of FGF2-loaded w/w GmMS. These results indicate that drug-preloadable w/w GmMS can be widely applied in tissue engineering and regenerative medicine strategies.

Meet the First Authors.

HomeCirculation ResearchVol. 131, No. 10Meet the First Authors Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBMeet the First Authors Originally published27 Oct 2022https://doi.org/10.1161/RES.0000000000000580Circulation Research. 2022;131:790–791Sox17 Deficiency Promotes PAH via c-Met Activation (p 792)Download figureDownload PowerPointDr Chan Soon Park is a clinical fellow in the Division of Cardiology at Seoul National University Hospital (SNUH). He earned his BS and MS in Medicine from Seoul National University and his PhD in Medical Science and Engineering from Korea Advanced Institute of Science and Technology (KAIST). During the PhD program in Graduate School of Medical Science and Engineering in KAIST, he was able to learn basic and translational research, the importance of which has been increasingly emphasized in the development of novel and clinically relevant therapeutic strategies in the field of cardiology. Dr Park continues to expand his research in the roles of endothelial cells in various cardiovascular diseases (CVDs) beyond pulmonary arterial hypertension. He also has interests in clinical research, including the association between metabolic profiles and CVDs as well as the role of imaging in CVD risk stratification. Outside of work, he enjoys hiking and spending time with his family.Prohibitin2 Maintains VSMC Contractile Phenotype (p 807)Download figureDownload PowerPointDr Yiting Jia is a postdoctoral fellow at Peking University Health Science Center (PI: Dr Wei Kong and Dr Caihong Yun). He earned his PhD from Peking University. His early experience in research was focused on metabolism reprogramming, lysosome biology and cardiovascular diseases. Now he is gearing up to become an independent research investigator. Outside of work, he enjoys soccer, tennis and listening to music.Download figureDownload PowerPointDr Chenfeng Mao is a research associate at the Beijing Institute of Biotechnology in Beijing, China. He earned a PhD in human physiology from the Department of Physiology and Pathophysiology in Peking University (mentor, Dr Wei Kong). His research focuses on extracellular matrix microenvironment on vascular remodeling during physiological and disease state. Outside of work he enjoys playing badminton.MED1, BMP/TGF-β and Pulmonary Hypertension (p 828)Download figureDownload PowerPointDr Chen Wang earned her PhD from Xi’ an Jiaotong University. During her PhD studies, she was also trained in the laboratory of Dr Ingrid Fleming at the Institute of Vascular Research, Goethe University. Her research focuses on endothelial dysfunction involved in vascular diseases. She was awarded the “Paul Dudley White International Scholar” from ATVB in 2022 and has published several first-author papers including in Circulation and Circulation Research. Her career goal is to become a physician scientist working on cardiovascular diseases and related translational research. Outside of work, she enjoys traveling, music and baking.Download figureDownload PowerPointYuanming Xing is a PhD candidate in internal medicine at Xi’an Jiaotong University. She also studied computational biology at Warshel Institute for Computational Biology at the Chinese University of Hong Kong-Shenzhen. She is interested in endothelial function in cardiovascular diseases and has published several papers in the related fields. Her career plan is to become a physician who is also proficient in computational biology. She enjoys learning new things, especially what she may not be good at. In her spare time, she has a passion for animal rescue, computer programming and painting.Intrapericardial Exosomes Repair Heart via Foxo3 (p e135)Download figureDownload PowerPointDr Dashuai Zhu is a postdoctoral research fellow in the BioTherapeutics Lab, headed by Dr Ke Cheng (UNC Chapel Hill and North Carolina State University). Dashuai earned his PhD from the Nankai University, China, where he started his career on cardiac repair using tissue engineering and biomedical engineering approaches. His research focuses on regenerative medicine approaches for the treatment of heart disease, with a particular interest in cell and cell-free therapies for myocardial infarction and heart failure. He can be found on Twitter @das_zhu.Download figureDownload PowerPointDr Ke Huang is an assistant research professor in the Department of Molecular Biomedical Sciences at North Carolina State University. He earned his MD in 2008 from Shanxi Medical University and PhD from North Carolina State University. His postdoctral training was at Duke University. His research focuses on regenerative medicine strategies with a particular interest in adult stem cells, biomaterials and nanomedicine approaches. He can be found on [email protected] Previous Back to top Next FiguresReferencesRelatedDetails October 28, 2022Vol 131, Issue 10 Advertisement Article InformationMetrics © 2022 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000580PMID: 36302055 Originally publishedOctober 27, 2022 PDF download Advertisement SubjectsAgingCardiovascular DiseaseExercise

Achilles Tendons Display Region-Specific Transcriptomic Signatures Associated With Distinct Mechanical Properties

Background: Previous studies have examined the transcriptomes and mechanical properties of whole tendons in different regions of the body. However, less is known about these characteristics within a single tendon. Purpose: To develop a regional transcriptomic atlas and evaluate the region-specific mechanical properties of Achilles tendons. Study Design: Descriptive laboratory study. Methods: Achilles tendons from 2-month-old male Sprague Dawley rats were used. Tendons were isolated and divided into proximal, middle, and distal thirds for RNA sequencing (n = 5). For mechanical testing, the Achilles muscle-tendon-calcaneus unit was mounted in a custom-designed materials testing system with the unit clamped over the musculotendinous junction (MTJ) and the calcaneus secured at 90° of dorsiflexion (n = 9). Tendons were stretched to 20 N at a constant speed of 0.0167 mm/s. Cross-sectional area, strain, stress, and Young modulus were determined in each tendon region. Results: An open-access, interactive transcriptional atlas was generated that revealed distinct gene expression signatures in each tendon region. The proximal and distal regions had the largest differences in gene expression, with 2596 genes significantly differentially regulated at least 1.5-fold (q < .01). The proximal tendon displayed increased expression of genes resembling a tendon phenotype and increased expression of nerve cell markers. The distal region displayed increases in genes involved in extracellular matrix synthesis and remodeling, immune cell regulation, and a phenotype similar to cartilage and bone. There was a 3.72-fold increase in Young modulus from the proximal to middle region (P < .01) and an additional 1.34-fold increase from the middle to distal region (P = .027). Conclusion: Within a single tendon, there are region-specific transcriptomic signatures and mechanical properties, and there is likely a gradient in the biological and functional phenotype from the proximal origin at the MTJ to the distal insertion at the enthesis. Clinical Relevance: These findings improve our understanding of the underlying biological heterogeneity of tendon tissue and will help inform the future targeted use of regenerative medicine and tissue engineering strategies for patients with tendon disorders.

Gradual specialization of phagocytic ameboid cells may have impaired regenerative capacities in metazoan lineages.

Animal regeneration is a fascinating field of research that has captured the attention of many generations of scientists. Among the cellular mechanisms underlying tissue and organ regeneration, we highlight the role of phagocytic ameboid cells (PACs). Beyond their ability to engulf nutritional particles, microbes, and apoptotic cells, their involvement in regeneration has been widely documented. It has been extensively described that, at least in part, animal regenerative mechanisms rely on PACs that serve as a hub for a range of critical physiological functions, both in health and disease. Considering the phylogenetics of PAC evolution, and the loss and gain of nutritional, immunological, and regenerative potential across Metazoa, we aim to discuss when and how phagocytic activity was first co-opted to regenerative tissue repair. We propose that the gradual specialization of PACs during metazoan derivation may have contributed to the loss of regenerative potential in animals, with critical impacts on potential translational strategies for regenerative medicine.

Novel bioactive collagen-polyurethane-pectin scaffolds for potential application in bone regenerative medicine

Recently, the development of bioactive scaffolds that allow improved bone repair is of interest for hard tissue regenerative medicine strategies. The use of biopolymers with synthetic polymer represents an innovative alternative for this purpose due to its excellent capacity to mimic the bone extracellular matrix. In this work, scaffolds based on bovine tendon collagen and pectin derived from orange (Citrus sinensis) peels were designed. The surfaces were prepared by a polymeric semi-interpenetration process where linear pectin chains were interpenetrated in a polyurethane-crosslinked collagen matrix. The effect of pectin content (10–40 wt.%) on the structural, physicochemical and biological properties of this type of scaffolds was evaluated. The increment in pectin content generates amorphous, granular surfaces with interconnected porosity, improving crosslinking, decreasing swelling and accelerating its rate of degradation in physiological and proteolytic media, also promoting antibacterial capacity showing inhibition of growth of pathogens such as E. coli. Specifically, the scaffold with 20 wt.% pectin (CPc20) shows a mechanical improvement of 342 ± 12% (with respect to crosslinked collagen), allowing the mineralization of 15 ± 1.5% of carbonated apatite on its surface, showing no cytotoxic effects on fibroblasts and allowing their proliferation; in addition, it was determined that immune system cells such as human monocytes can secrete high levels of transforming growth factor beta (TGF-β) and low levels of tumor necrosis factor alpha (TNF-α), conditions required in the process of bone formation. These results demonstrate that these bioactive scaffolds could be applied in bone tissue regenerative medicine strategies.

Biodegradable and Antioxidant DNA Hydrogel as a Cytokine Delivery System for Diabetic Wound Healing.

Impaired diabetic wound healing is associated with the persistence of chronic inflammation and excessive oxidative stress, which has become one of the most serious clinical challenges. Wound dressings with anti-inflammatory and reactive oxygen species (ROS)-scavenging properties are desirable for diabetic wound treatment. In this study, a shape-adaptable, biodegradable, biocompatible, antioxidant, and immunomodulatory interleukin-33 (IL-33)-cytogel is developed by encapsulating IL-33into physically cross-linked DNA hydrogels and used as wound dressings to promote diabetic wound healing. The porous microstructures and biodegradable properties of the IL-33-cytogel ensure the local sustained-release of IL-33 in the wound area, where the sustained-release of IL-33 is maintained for at least 7 days. IL-33-cytogel can induce local accumulation of group 2 innate lymphoid cells (ILC2s) and regulatory T cells (Tregs), as well as M1-to-M2 transition at the wound sites. Additionally, the antioxidant and biocompatible characteristics of DNA hydrogels promote thescavengingofintracellular ROSwithout affecting cell viability. As a result, local inflammation in the diabetic wound area is resolved upon IL-33-cytogel treatment, which is accompanied by improved granulation tissue regeneration and accelerated wound closure. This study demonstrates a promising strategy in tissue engineering and regenerative medicine by incorporating DNA hydrogels and cytokine immunotherapy for promoting diabetic wound healing.

A study of the interactions between human osteoblast-like cells and polymer composites with functionalized graphene derivatives using 2D correlation spectroscopy (2D-COS)

In response to the growing need for development of modern biomaterials for applications in regenerative medicine strategies, the research presented here investigated the biological potential of two types of polymer nanocomposites. Graphene oxide (GO) and partially reduced graphene oxide (rGO) were incorporated into a poly(ε-caprolactone) (PCL) matrix, creating PCL/GO and PCL/rGO nanocomposites in the form of membranes. Proliferation of osteoblast-like cells (human U-2 OS cell line) on the surface of the studied materials confirmed their biological activity. Fluorescence microscopy was able to distinguish the different patterns of interaction between cells (depending on the type of material) after 15 days of the test run. Raman micro-spectroscopy and two-dimensional correlation spectroscopy (2D-COS) applied to Raman spectra distinguished the nature of cell-material interactions after only 8 days. Combination of these two techniques (Raman micro-spectroscopy and 2D-COS analysis) facilitated identification of a much more complex cellular response (especially from proteins) on the surface of PCL/GO. The presented approach can be regarded as a method for early study of the bioactivity of membrane materials.

Locally transplanted human urine-induced nephron progenitor cells contribute to renal repair in mice kidney with diabetic nephropathy

Chronic Kidney Disease (CKD) is increasingly recognized as a global public health issue. Diabetic nephropathy (DN), also known as diabetic kidney disease, is a leading cause of CKD. Regenerative medicine strategy employing nephron progenitor cells (NPCs) is worthy of consideration as an alternative to shortage of donor organs for kidney transplantation. In previous study, we successfully generated induced NPCs (iNPCs) from human urine-derived cells that resembled human embryonic stem cell-derived NPCs. Here, we aimed to investigate the therapeutic potential of iNPCs in DN animal model. The results revealed the therapeutic effect of iNPCs as follows: (1) diminished glomerular hypertrophy, (2) reduced tubulointerstitial fibrosis, (3) low blood urea nitrogen, serum creatinine and albuminuria value, (4) decreased inflammation/fibrosis, (5) enhanced renal regeneration and (6) confirmed safety. This study demonstrates that human iNPCs have a therapeutic potential as a cell source for transplantation in patients with kidney diseases.

Exploring the Genetic Basis of Dens Evaginatus Using Whole-Exome Sequencing

Dens evaginatus (DE) is a dental abnormality characterized by tubercles on the occlusal surfaces of teeth and is associated with the risk of pulpal inflammation due to fractures. The cause of DE remains unclear, as limited data are available to determine its etiology. The aim of this study was to investigate the genetic background of DE using whole-exome sequencing (WES). Saliva samples were collected from two patients of Family A and three patients of Family B, including an incident case of DE, and analyzed using WES. Rare variants were extracted from the WES data and filtered by family to extract candidate variants. Gene variants of TLR3 and MDC1 were identified as etiologic factors for DE. The variant MDC1 (c.3908C&gt;T) was identified to be damaging, according to the scores from Polymorphism Phenotyping v2. Our findings contribute towards an understanding of the etiology of DE, which would facilitate improved treatment to prevent the risk of DE fractures and pulpal inflammation. Understanding the mechanism of DE development may also be helpful for developing regenerative medicine and gene therapy strategies.

Advances for the treatment of lower extremity arterial disease associated with diabetes mellitus.

Lower extremity arterial disease (LEAD) is a major vascular complication of diabetes. Vascular endothelial cells dysfunction can exacerbate local ischemia, leading to a significant increase in amputation, disability, and even mortality in patients with diabetes combined with LEAD. Therefore, it is of great clinical importance to explore proper and effective treatments. Conventional treatments of diabetic LEAD include lifestyle management, medication, open surgery, endovascular treatment, and amputation. As interdisciplinary research emerges, regenerative medicine strategies have provided new insights to treat chronic limb threatening ischemia (CLTI). Therapeutic angiogenesis strategies, such as delivering growth factors, stem cells, drugs to ischemic tissues, have also been proposed to treat LEAD by fundamentally stimulating multidimensional vascular regeneration. Recent years have seen the rapid growth of tissue engineering technology; tissue-engineered biomaterials have been used to study the treatment of LEAD, such as encapsulation of growth factors and drugs in hydrogel to facilitate the restoration of blood perfusion in ischemic tissues of animals. The primary purpose of this review is to introduce treatments and novel biomaterials development in LEAD. Firstly, the pathogenesis of LEAD is briefly described. Secondly, conventional therapies and therapeutic angiogenesis strategies of LEAD are discussed. Finally, recent research advances and future perspectives on biomaterials in LEAD are proposed.

The Role of Polymeric Biomaterials in the Treatment of Articular Osteoarthritis.

Osteoarthritis is a high-prevalence joint disease characterized by the degradation of cartilage, subchondral bone thickening, and synovitis. Due to the inability of cartilage to self-repair, regenerative medicine strategies have become highly relevant in the management of osteoarthritis. Despite the great advances in medical and pharmaceutical sciences, current therapies stay unfulfilled, due to the inability of cartilage to repair itself. Additionally, the multifactorial etiology of the disease, including endogenous genetic dysfunctions and exogenous factors in many cases, also limits the formation of new cartilage extracellular matrix or impairs the regular recruiting of chondroprogenitor cells. Hence, current strategies for osteoarthritis management involve not only analgesics, anti-inflammatory drugs, and/or viscosupplementation but also polymeric biomaterials that are able to drive native cells to heal and repair the damaged cartilage. This review updates the most relevant research on osteoarthritis management that employs polymeric biomaterials capable of restoring the viscoelastic properties of cartilage, reducing the symptomatology, and favoring adequate cartilage regeneration properties.

Micro/nanometer-sized porous structure of zinc phosphate incorporated Ti(HPO4)2 hydrate bioceramic induces osteogenic gene expression and enhances osteoporotic bone regeneration

In this work, we describe the synthesis of an ideal bioceramic to which cells can easily respond that has geometry and composition that are similar to those of bone-like apatite. The successful preparation of bone-inspired titanium hydrate phosphate with an optimized weight percentage (∼1.1 wt%) of zinc in (Ti(HPO4)2/Zn3(PO4)2·nH2O) bioceramic could represent a potential regenerative framework for bone defect repair and bone void filler that would be useful for various clinical approaches. We have for the first time demonstrated the detailed physicochemical and biological characterizations of the bioceramic required to achieve a biocompatible and porous architecture that is similar to hydroxyapatite. In vitro studies have shown that the phosphate-rich titanium and zinc nanocomposite promote bone regeneration after stimulating MC3T3 − E1 and hBM-MSCs cells activity. The metallic ions and phosphate had the effects of enhancing the cell viability and osteogenic differentiation of the cells, as confirmed by the expression of bone-related markers that included ALP, Col1a1, RUNX2, OPN/Spp1, and OCN through qRT-PCR, Western blotting, and immunocytochemistry. Moreover, the bioceramic has been shown to significantly improves new bone growth in critical size calvarial defect in rat model. The findings of the present work are the first that show the bone regeneration effect of bioceramic, which could be crucial for subsidies of Ca–P-based artificial bone implant materials. Our results provide insight into the Ti(HPO4)2/Zn3(PO4)2(0.1)·nH2O bioceramic in osteogenesis which can help to establish a therapeutic strategy in bone tissue regenerative medicine.

Mesenchymal Stromal Cell Mitochondrial Transfer as a Cell Rescue Strategy in Regenerative Medicine: A Review of Evidence in Preclinical Models.

Mesenchymal stromal cells (MSC) have excellent clinical potential and numerous properties that ease its clinical translation. Mitochondria play a crucial role in energy metabolism, essential for cellular activities, such as proliferation, differentiation, and migration. However, mitochondrial dysfunction can occur due to diseases and pathological conditions. Research on mitochondrial transfer from MSCs to recipient cells has gained prominence. Numerous studies have demonstrated that mitochondrial transfer led to increased adenosine triphosphate (ATP) production, recovered mitochondrial bioenergetics, and rescued injured cells from apoptosis. However, the complex mechanisms that lead to mitochondrial transfer from healthy MSCs to damaged cells remain under investigation, and the factors contributing to mitochondrial bioenergetics recovery in recipient cells remain largely ambiguous. Therefore, this review demonstrates an overview of recent findings in preclinical studies reporting MSC mitochondrial transfer, comprised of information on cell sources, recipient cells, dosage, route of administration, mechanism of transfer, pathological conditions, and therapeutic effects. Further to the above, this research discusses the potential challenges of this therapy in its clinical settings and suggestions to overcome its challenges.

Transmembranous and enchondral osteogenesis in transplants of rat limb buds cultivated in serum- and protein-free culture medium.

Cartilage differentiates in rat limb buds cultivated in a chemically defined protein‐free medium in the same manner as in the richer serum‐supplemented medium. We aimed to investigate the remaining differentiation potential of pre‐cultivated limb buds by subsequent transplantation in vivo. Rat front (FLBs) and hind‐limb buds (HLBs) were isolated from Fischer rat dams at the 14th gestation day (GD 14) and cultivated at the air‐liquid interface in Eagle's Minimum Essential Medium (MEM) alone; with 5 μM of 5‐azacytidine (5azaC) or with rat serum (1:1). Overall growth was measured seven times during the culture by an ocular micrometre. After 14 days, explants were transplanted under the kidney capsule of adult males. Growth of limb buds was significantly lower in all limb buds cultivated in MEM than in those cultivated with serum. In MEM with 5azaC, growth of LBs was significantly lower only on day 3 of culture. Afterwards, it was higher throughout the culture period, although a statistically significant difference was assessed only for HLBs. In transplants, mixed structures developed with the differentiated transmembranous bone, cartilage with enchondral ossification, bone‐marrow, sebaceous gland, and hair that have never been found in vitro. Nerves differentiated only in transplants precultivated in the serum‐supplemented medium. We conclude that pre‐cultivation of LBs in a chemically defined protein‐free medium does not restrict osteogenesis and formation of epidermal appendages but is restrictive for neural tissue. These results are important for understanding limb development and regenerative medicine strategies.

Matrix stiffness regulates the immunomodulatory effects of mesenchymal stem cells on macrophages via AP1/TSG-6 signaling pathways

It is well-recognized that the matrix stiffness as an important stem cell niche can mediate stem cell behavior such as attachment, proliferation and differentiation, but how matrix stiffness affects the immunomodulatory efficacy of stem cells has been little explored, which, however, is of significant importance in determining the outcomes of stem cell-based therapies and engineered tissue mimics. We herein studied the immunomodulatory efficacy of mesenchymal stem cells (MSCs) in response to matrix stiffness by the evaluation of macrophage polarization in vitro and inflammatory response in vivo by subcutaneous implantation of MSC-laden hydrogels. Remarkably, we found that soft matrix enabled MSCs to produce significantly higher levels of immunomodulatory factors compared to stiff matrix, and induced the presence of more anti-inflammatory macrophages in vitro and attenuated macrophages-mediated inflammatory response in vivo. More importantly, we revealed stiffness-mediated immunoregulatory effect of MSCs was mainly attributed to tumor necrosis factor-α-stimulated protein 6 (TSG-6), which was mechanosensitively regulated by the MAPK and Hippo signaling pathway and downstream AP1 complex, and which in turn exerted an effect on macrophages through CD44 receptor to inhibit NF-κB pathway. To conclude, our results for the first time identify TSG-6 as the key factor in regulating immunomodulatory efficacy of MSCs in mechanical response, and can be potentially utilized to empower stem cell-based therapy and tissue engineering strategy in regenerative medicine. Statement of SignificanceMatrix stiffness as an important stem cell niche can mediate stem cell behavior such as attachment and differentiation, but how matrix stiffness affects the immunomodulatory efficacy of stem cells has been little explored, which, however, is of significant importance in determining the outcomes of stem cell-based therapies and engineered tissue mimics. Our results for the first time identify TSG-6 as the key factor in regulating the immunomodulatory efficacy of MSCs in mechanical response, which was regulated by the MAPK and Hippo signaling pathways and downstream AP1 complex, and which in turn exerted an effect on macrophages through CD44 receptor to inhibit NF-κB pathway, and can be potentially utilized to empower stem cell-based therapy and tissue engineering strategy in regenerative medicine.

Regenerative Medicine Therapies for Prevention of Abdominal Adhesions: A Scoping Review.

Globally, abdominal adhesions constitute a significant burden of morbidity and mortality. They represent the commonest complication of abdominal operations with a lifelong risk of multiple pathologies, including adhesive small bowel obstruction, female infertility, and chronic pain. Adhesions represent a problem of the entire abdomen, forming at the time of injury and progressing through multiple complex pathways. Clinically available preventative strategies are limited to barrier technologies. Significant knowledge gaps persist in the characterization and mitigation of the involved molecular pathways underlying adhesion formation. Thus, the objectives of this scoping review are to describe the known molecular pathophysiology implicated in abdominal adhesion formation and summarize novel preclinical regenerative medicine preventative strategies for potential future clinical investigation. A literature review was performed in accordance with the Preferred Reporting Items for Systematic Reviews Extension for Scoping Reviews. Included peer-reviewed publications were published within the last 5y and contained invivo preclinical experimental studies of postoperative adhesions with the assessment of underlying mechanisms of adhesion formation and successful therapy for adhesion prevention. Studies not involving regenerative medicine strategies were excluded. Data were qualitatively synthesized. A total of 1762 articles were identified. Of these, 1001 records were excluded by the described screening criteria. Sixty-eight full-text articles were evaluated for eligibility, and 11 studies were included for review. Novel and reliable preventative strategies are urgently needed. Recent experimental data propose novel regenerative medicine targets for adhesion prevention.