Perinatal tissues and cells in tissue engineering and regenerative medicine

Perspectives on the use of decellularized/devitalized and lyophilized human perinatal tissues for bone repair: Advantages and remaining challenges

Human amniotic membrane (hAM) has been extensively used for several decades as a bioactive scaffold for regenerative medicine. In its cryopreserved form-one of the main storage formats-the presence of viable cells has often been questioned. Furthermore, there is little published evidence of the role of endogenous amniotic cells from cryopreserved hAM in tissue repair. Some technologies, often patented and combined, have facilitated the use of hAM. Decellularization and devitalization processes have been developed to ensure its safety and prevent immune rejection. Lyophilization and dehydration methods have had a significant impact on clinical practices by enabling storage at room temperature in the operating room and making handling and cutting easier. Consequently, the commercialization of hAM has expanded, initially in the USA, and now in Europe. In the last decade, there has been growing interest in new perinatal tissues in clinical medicine. Similar processes have been adapted for these tissues to prevent immune or inflammatory reactions, and to improve storage and make them easier to use. For example, in the USA, many products marketed for wound healing undergo lyophilization, sometimes in combination with decellularization. Given our expertise, we wanted to highlight the potential of decellularized/devitalized and lyophilized perinatal tissues in regenerative medicine, particularly for bone repair. In this opinion paper, we discuss why these tissues represent the future of regenerative medicine, their potential drawbacks and strategies to overcome these challenges.

Role of dehydrated human amnion/chorion membrane in enhancing functional outcomes after robot-assisted radical prostatectomy: a systematic review and meta-analysis

BACKGROUND

Dehydrated human amnion/chorion membrane (dHACM) has shown potential in enhancing neurovascular recovery and functional outcomes in robot-assisted radical prostatectomy (RARP).

AIM

To evaluate the effects of dHACM on continence recovery, sexual function, and oncological outcomes in patients undergoing RARP.

METHODS

A systematic review and meta-analysis were conducted following PRISMA guidelines, analyzing data from PubMed, Cochrane, and EMBASE. Six retrospective studies comparing RARP with and without dHACM were included. Odds ratios (OR) and standardized mean differences (SMD) were calculated using a random-effects model.

OUTCOMES

The primary outcomes were continence and potency recovery, and secondary outcomes included biochemical recurrence (BCR).

RESULTS

The meta-analysis included 4072 patients (1699 experimental and 2373 control). dHACM significantly improved early continence recovery (SMD 1.78, 95% CI 1.26-2.34) at <3, 3, and 6 months postoperatively (OR 1.95, 95% CI 1.13-3.36; OR 2.17, 95% CI 1.52-3.09; and OR 1.70, 95% CI 1.10-2.63, respectively). Time to potency recovery was shorter (SMD -0.55, 95% CI -0.67 to -0.43), with significant improvements at <3, 3, 6, and 9 months (OR 1.67, 95% CI 1.25-2.23; OR 1.27, 95% CI 1.06-1.53; OR 1.41, 95% CI 1.15-1.72; and OR 1.51, 95% CI 1.16-1.97, respectively). There were no significant differences in BCR (OR 0.85, 95% CI 0.54-1.35).

CLINICAL IMPLICATIONS

dHACM offers potential as an adjunct to enhance functional recovery following RARP without compromising oncologic safety, but further high-quality studies are needed.

STRENGTHS & LIMITATIONS

Strengths include a comprehensive analysis of early functional outcomes and low heterogeneity in early potency and continence data. Limitations include reliance on retrospective studies and lack of randomized controlled trials.

CONCLUSION

dHACM may accelerate continence and sexual function recovery in early period after RARP while maintaining oncological outcomes, but further randomized studies are necessary to confirm these findings.

Human Chorionic Membrane-derived Tunable Hydrogels for Vascular Tissue Engineering Strategies

One of the foremost targets in the advancement of biomaterials to engineer vascularized tissues is not only to replicate the composition of the intended tissue but also to create thicker structures incorporating a vascular network for adequate nutrients and oxygen supply. For the first time, to the best of current knowledge, a clinically relevant biomaterial is developed, demonstrating that hydrogels made from the human decellularized extracellular matrix can exhibit robust mechanical properties (in the kPa range) and angiogenic capabilities simultaneously. These properties enable the culture and organization of human umbilical vein endothelial cells into tubular structures, maintaining their integrity for 14 days in vitro without the need for additional polymers or angiogenesis-related factors. This is achieved by repurposing the placenta chorionic membrane (CM), a medical waste with an exceptional biochemical composition, into a valuable resource for bioengineering purposes. After decellularization, the CM underwent chemical modification with methacryloyl groups, giving rise to methacrylated CM (CMMA). CMMA preserved key proteins, as well as glycosaminoglycans. The resulting hydrogels rapidly photopolymerize and have enhanced strength and customizable mechanical properties. Furthermore, they demonstrate angio-vasculogenic competence in vitro and in vivo, holding significant promise as a humanized platform for the engineering of vascularized tissues.

USE OF DECELLULARIZED HUMAN AMNIOTIC MEMBRANE IN INTESTINAL ANASTOMOSES: A STUDY IN RATS TREATED WITH 5-FLUOROURACIL

BACKGROUND

Nowdays, more relevant applications of perinatal derivatives, such as amniotic membrane (AM), are emerging in our environment as a source of biomaterials for use in different healing processes. The study of anastomosis healing associated with antimetabolic drugs such as 5-fluorouracil (5-FU) is a potential target of AM.

AIMS

To evaluate the healing effects of AM in rats treated with 5-FU at a dose of 20 mg/kg on the seventh day of postoperative evolution, regarding the parameters percentage of type I collagen (mature), cell viability, microvascular density and formation of granulation tissue.

METHODS

Thirty-two Wistar rats were used, submitted to colotomy and colorraphy, separated into four groups of eight, which received different treatments daily, intraperitoneally, until the day of sacrifice: saline solution (C), 20 mg/kg 5-FU, 20 mg/kg 5-FU and AM.

RESULTS

Treatment with 20 mg/kg of 5-FU, on the seventh postoperative day, induced adverse effects on the anastomotic healing process, evidenced by a decrease in the percentage of type I (mature) collagen, cell viability, microvascular density, fibrin-leukocyte scab formation and angiofibroblast proliferation; the use of AM under these conditions induced an improvement in the percentage of type I (mature) collagen.

CONCLUSIONS

Treatment with 20 mg/kg of 5-FU on the seventh postoperative day induced adverse effects on the anastomotic healing process, and the use of AM under these conditions induced an improvement in the percentage of type I (mature) collagen.

Advancing Myocardial Infarction Treatment: Harnessing Multi-Layered Recellularized Cardiac Patches with Fetal Myocardial Scaffolds and Acellular Amniotic Membrane

PURPOSE

Myocardial infarction (MI) is a leading cause of irreversible functional cardiac tissue loss, requiring novel regenerative strategies. This study assessed the potential therapeutic efficacy of recellularized cardiac patches, incorporating fetal myocardial scaffolds with rat fetal cardiomyocytes and acellular human amniotic membrane, in adult Wistar rat models of MI.

METHODS

Decellularized myocardial tissue was obtained from 14 to 16 week-old human fetuses that had been aborted. Chemical detergents (0.1% EDTA and 0.2% sodium dodecyl sulfate) were used to prepare the fetal extracellular matrix (ECM), which was characterized for bio-scaffold microstructure and biocompatibility via scanning electron microscopy (SEM) and MTT assay, respectively. Neonatal cardiomyocytes were extracted from the ventricles of one-day-old Wistar rats' littermates and characterized through immunostaining against Connexin-43 and α-smooth muscle actin. The isolated cells were seeded onto decellularized tissues and covered with decellularized amniotic membrane. Sixteen healthy adult Wistar rats were systematically allocated to control and MI groups. MI was induced via arterial ligation. Fourteen days post-operation, the MI group was received the engineered patches. Following a two-week post-implantation period, the animals were euthanized, and the hearts were harvested for the graft evaluation.

RESULTS

Histological analysis, DAPI staining, and ultra-structural examination corroborated the successful depletion of cellular elements, while maintaining the integrity of the fetal ECM and architecture. Subsequent histological and immunohistochemichal (IHC) evaluations confirmed effective cardiomyocyte seeding on the scaffolds. The application of these engineered patches in MI models resulted in increased angiogenesis, reduced fibrosis, and restricted scar tissue formation, with the implanted cardiomyocytes remaining viable at graft sites, indicating prospective in vivo cell viability.

CONCLUSIONS

This study suggests that multi-layered recellularized cardiac patches are a promising surgical intervention for myocardial infarction, showcasing significant potential by promoting angiogenesis, mitigating fibrosis, and minimizing scar tissue formation in MI models. These features are pivotal for enhancing the therapeutic outcomes in MI patients, focusing on the restoration of the myocardial structure and function post-infarction.

Leveraging Blood Components for 3D Printing Applications Through Programmable Ink Engineering Approaches

This study proposes a tunable ink engineering methodology to allow 3D printing processability of highly bioactive but otherwise low-viscous and unprintable blood-derived materials. The hypothesis relies on improving the viscoelasticity and shear thinning behavior of platelet lysates (PL) and albumins (BSA) solutions by covalent coupling, enabling simultaneous extrusion and photocrosslinking upon filament deposition. The available amine groups on proteins (PL and BSA) are exploited for coupling with carboxyl groups present in methacrylated proteins (hPLMA and BSAMA), by leveraging carbodiimide chemistry. This reaction enabled the creation of a pre-gel from these extremely low-viscous materials (≈ 1 Pa), with precise tuning of the reaction, resulting in inks with a range of controlled viscosities and elasticities. Shape-fidelity analysis is performed on 3D-printed multilayered constructs, demonstrating the ability to reach clinically relevant sizes (>2 cm in size). After photocrosslinking, the scaffolds showcased a mechanically robust structure with sustained protein release over time. Bioactivity is evaluated using human adipose-derived stem cells, resulting in increased viability and metabolic activity over time. The herein described research methodology widens the possibilities for the use of low-viscosity materials in 3D printing but also enables the direct application of patient and blood-derived materials in precision medicine.

Proteomic analysis of human Wharton's jelly mesenchymal stem/stromal cells and human amniotic epithelial stem cells: a comparison of therapeutic potential

Perinatal stem cells have prominent applications in cell therapy and regenerative medicine. Among them, human Wharton's jelly mesenchymal stem/stromal cells (hWJMSCs) and human amniotic epithelial stem cells (hAESCs) have been widely used. However, the distinction in the therapeutic potential of hWJMSCs and hAESCs is poorly understood. In this study, we reported the phenotypic differences between these two distinct cell types and provided the first systematic comparison of their therapeutic potential in terms of immunomodulation, extracellular matrix (ECM) remodelling, angiogenesis and antioxidative stress using proteomics. The results revealed that the two cell types presented different protein expression profiles and were both promising candidates for cell therapy. Both types of cells demonstrated angiogenic and antifibrotic potential, whereas hAESCs presented superior immunological tolerance and antioxidant properties, which were supported by a series of relevant in vitro assays. Our study provides clues for the selection of appropriate cell types for diverse indications in cell therapy, which contributes to the advancement of their clinical translation and application.

Harnessing the Anti-Inflammatory Effects of Perinatal Tissue Derived Therapies for the Treatment of Inflammatory Skin Diseases: A Comprehensive Review

Dealing with chronic inflammatory skin conditions like atopic dermatitis and psoriasis can be extremely difficult. Current treatments, such as topical corticosteroids, often have limitations and side effects. However, researchers have discovered that the placenta's remarkable properties may provide a breakthrough in effectively addressing these skin conditions. The placenta comprises three essential tissues: decidua, placental membrane, and umbilical cord. Placental derivatives have shown significant potential in treating psoriasis by reducing inflammatory cytokines and inhibiting keratinocyte proliferation. In the case of atopic dermatitis, umbilical cord stem cells have demonstrated anti-inflammatory effects by targeting critical factors and promoting anti-inflammatory cytokines. The scope of benefits associated with placental derivatives transcends these specific applications. They also potentially address other inflammatory skin diseases, such as vitiligo, by stimulating melanin production. Moreover, these derivatives have been leveraged in the treatment of pemphigus and epidermolysis bullosa (EB), showcasing potential as a wound dressing that could eliminate the necessity for painful dressing changes in EB patients. In summary, the integration of placental derivatives stands to revolutionize our approach to inflammatory skin conditions owing to their distinct properties and the prospective benefits they offer. This comprehensive review delves into the current applications of placental derivatives in addressing inflammatory skin diseases, presenting a novel treatment approach.

Amniotic Membrane-Derived Multichannel Hydrogels for Neural Tissue Repair

In the pursuit of advancing neural tissue regeneration, biomaterial scaffolds have emerged as promising candidates, offering potential solutions for nerve disruptions. Among these scaffolds, multichannel hydrogels, characterized by meticulously designed micrometer-scale channels, stand out as instrumental tools for guiding axonal growth and facilitating cellular interactions. This study explores the innovative application of human amniotic membranes modified with methacryloyl domains (AMMA) in neural stem cell (NSC) culture. AMMA hydrogels, possessing a tailored softness resembling the physiological environment, are prepared in the format of multichannel scaffolds to simulate native-like microarchitecture of nerve tracts. Preliminary experiments on AMMA hydrogel films showcase their potential for neural applications, demonstrating robust adhesion, proliferation, and differentiation of NSCs without the need for additional coatings. Transitioning into the 3D realm, the multichannel architecture fosters intricate neuronal networks guiding neurite extension longitudinally. Furthermore, the presence of synaptic vesicles within the cellular arrays suggests the establishment of functional synaptic connections, underscoring the physiological relevance of the developed neuronal networks. This work contributes to the ongoing efforts to find ethical, clinically translatable, and functionally relevant approaches for regenerative neuroscience.

Comparative analysis of aligned and random amniotic membrane-derived cryogels for neural tissue repair

The ordered arrangement of cells and extracellular matrix facilitates the seamless transmission of electrical signals along axons in the spinal cord and peripheral nerves. Therefore, restoring tissue geometry is crucial for neural regeneration. This study presents a novel method using proteins derived from the human amniotic membrane, which is modified with photoresponsive groups, to produce cryogels with aligned porosity. Freeze-casting was used to produce cryogels with longitudinally aligned pores, while cryogels with randomly distributed porosity were used as the control. The cryogels exhibited remarkable injectability and shape-recovery properties, essential for minimally invasive applications. Different tendencies in proliferation and differentiation were evident between aligned and random cryogels, underscoring the significance of the scaffold's microstructure in directing the behaviour of neural stem cells (NSC). Remarkably, aligned cryogels facilitated extensive cellular infiltration and migration, contrasting with NSC cultured on isotropic cryogels, which predominantly remained on the scaffold's surface throughout the proliferation experiment. Significantly, the proliferation assay demonstrated that on day 7, the aligned cryogels contained eight times more cells compared to the random cryogels. Consistent with the proliferation experiments, NSC exhibited the ability to differentiate into neurons within the aligned scaffolds and extend neurites longitudinally. In addition, differentiation assays showed a four-fold increase in the expression of neural markers in the cross-sections of the aligned cryogels. Conversely, the random cryogels exhibited minimal presence of cell bodies and extensions. The presence of synaptic vesicles on the anisotropic cryogels indicates the formation of functional synaptic connections, emphasizing the importance of the scaffold's microstructure in guiding neuronal reconnection.

Mining human clinical waste as a rich source of stem cells for neural regeneration

Neural diseases are challenging to treat and are regarded as one of the major causes of disability and morbidity in the world. Stem cells can provide a solution, by offering a mechanism to replace damaged circuitry. However, obtaining sufficient cell sources for neural regeneration remains a significant challenge. In recent years, waste-derived stem(-like) cells (WDS-lCs) extracted from both prenatal and adult clinical waste tissues/products, have gained increasing attention for application in neural tissue repair and remodeling. This often-overlooked pool of cells possesses favorable characteristics; including self-renewal, neural differentiation, secretion of neurogenic factors, cost-effectiveness, and low ethical concerns. Here, we offer a perspective regarding the biological properties, extraction protocols, and preclinical and clinical treatments where prenatal and adult WDS-lCs have been utilized for cell replacement therapy in neural applications, and the challenges involved in optimizing these approaches toward patient led therapies.

Advanced 3D In Vitro Lung Fibrosis Models: Contemporary Status, Clinical Uptake, and Prospective Outlooks

Fibrosis has been characterized as a global health problem and ranks as one of the primary causes of organ dysfunction. Currently, there is no cure for pulmonary fibrosis, and limited therapeutic options are available due to an inadequate understanding of the disease pathogenesis. The absence of advanced in vitro models replicating dynamic temporal changes observed in the tissue with the progression of the disease is a significant impediment in the development of novel antifibrotic treatments, which has motivated research on tissue-mimetic three-dimensional (3D) models. In this review, we summarize emerging trends in preparing advanced lung models to recapitulate biochemical and biomechanical processes associated with lung fibrogenesis. We begin by describing the importance of in vivo studies and highlighting the often poor correlation between preclinical research and clinical outcomes and the limitations of conventional cell culture in accurately simulating the 3D tissue microenvironment. Rapid advancement in biomaterials, biofabrication, biomicrofluidics, and related bioengineering techniques are enabling the preparation of in vitro models to reproduce the epithelium structure and operate as reliable drug screening strategies for precise prediction. Improving and understanding these model systems is necessary to find the cross-talks between growing cells and the stage at which myofibroblasts differentiate. These advanced models allow us to utilize the knowledge and identify, characterize, and hand pick medicines beneficial to the human community. The challenges of the current approaches, along with the opportunities for further research with potential for translation in this field, are presented toward developing novel treatments for pulmonary fibrosis.

An increase in Wharton's jelly membrane osteocompatibility by a genipin-cross-link

Wharton's Jelly (WJ) has attracted significant interest in the field of tissue healing thanks to its biological properties, including antibacterial activity and immunomodulation. However, due to the fast degradation and poor mechanical behavior in biological environment, its application in bone regeneration is compromised. Here, we proposed to use genipin as an efficient cross-linking agent to significantly improve the elasticity and the enzymatical stability of the WJ matrix. The degree of cross-linking, linear elastic moduli, and collagenase resistance varied over a wide range depending on genipin concentration. Furthermore, our results highlighted that an increase in genipin concentration led to a decreased surface wettability, therefore impairing cell attachment and proliferation. The genipin cross-linking prevented rapid in vitro and in vivo degradation, but led to an adverse host reaction and calcification. When implanted in the parietal bone defect, a limited parietal bone regeneration to the dura was observed. We conclude that genipin-cross-linked WJ is a versatile medical device however, a careful selection is required with regards to the genipin concentration.

Multilayer amnion-PCL nanofibrous membrane loaded with celecoxib exerts a therapeutic effect against tendon adhesion by improving the inflammatory microenvironment

Tendon adhesion is a common complication after tendon surgery. The inflammatory phase of tendon healing is characterized by the release of a large number of inflammatory factors, whose mediated excessive inflammatory response is an important cause of tendon adhesion formation. Nonsteroidal anti-inflammatory drugs(NSAIDs) were used to prevent tendon adhesions by reducing the inflammatory response. However, recent studies have shown that the NSAIDs partially impairs tendon healing. Therefore, optimizing the anti-adhesive membrane loaded with NSAIDs to mitigate the effects on tendon healing requires further in-depth study. Amniotic membranes(AM) are natural polymeric semi-permeable membranes from living organisms that are rich in matrix, growth factors, and other active ingredients. In this study, we used electrostatic spinning technology to construct multifunctional nanofiber membranes of the PCL membrane loaded with celecoxib and AM. In vitro cellular assays revealed that celecoxib-loaded PCL membranes significantly inhibited the adhesion and proliferation of fibroblasts with increasing concentrations of celecoxib. In a rabbit tendon repair model, biomechanical tests further confirmed that the PCL membrane loaded with celecoxib had better anti-adhesion effects. Further experimental studies revealed that the PCL/AM membrane improved the inflammatory microenvironment by downregulating the expression of pro-inflammatory factors such as COX-2, IL-1β, and TNF-α proteins; and inhibiting the synthesis of COL I and COL Ⅲ. The PCL/AM membrane can continuously release celecoxib to reduce the inflammatory response and deliver growth factors to the damaged area to build a suitable microenvironment for tendon repair, which provides a new direction to improve the repair efficiency of tendon.

Emerging Strategies for the Biofabrication of Multilayer Composite Amniotic Membranes for Biomedical Applications

The amniotic membrane (AM) is the innermost part of the fetal placenta, which surrounds and protects the fetus. Due to its structural components (stem cells, growth factors, and proteins), AMs display unique biological properties and are a widely available and cost-effective tissue. As a result, AMs have been used for a century as a natural biocompatible dressing for healing corneal and skin wounds. To further increase its properties and expand its applications, advanced hybrid materials based on AMs have recently been developed. One existing approach is to combine the AM with a secondary material to create composite membranes. This review highlights the increasing development of new multilayer composite-based AMs in recent years and focuses on the benefits of additive manufacturing technologies and electrospinning, the most commonly used strategy, in expanding their use for tissue engineering and clinical applications. The use of AMs and multilayer composite-based AMs in the context of nerve regeneration is particularly emphasized and other tissue engineering applications are also discussed. This review highlights that these electrospun multilayered composite membranes were mainly created using decellularized or de-epithelialized AMs, with both synthetic and natural polymers used as secondary materials. Finally, some suggestions are provided to further enhance the biological and mechanical properties of these composite membranes.

Multipotent fetal stem cells in reproductive biology research

Due to the limited accessibility of the in vivo situation, the scarcity of the human tissue, legal constraints, and ethical considerations, the underlying molecular mechanisms of disorders, such as preeclampsia, the pathological consequences of fetomaternal microchimerism, or infertility, are still not fully understood. And although substantial progress has already been made, the therapeutic strategies for reproductive system diseases are still facing limitations. In the recent years, it became more and more evident that stem cells are powerful tools for basic research in human reproduction and stem cell-based approaches moved into the center of endeavors to establish new clinical concepts. Multipotent fetal stem cells derived from the amniotic fluid, amniotic membrane, chorion leave, Wharton´s jelly, or placenta came to the fore because they are easy to acquire, are not associated with ethical concerns or covered by strict legal restrictions, and can be banked for autologous utilization later in life. Compared to adult stem cells, they exhibit a significantly higher differentiation potential and are much easier to propagate in vitro. Compared to pluripotent stem cells, they harbor less mutations, are not tumorigenic, and exhibit low immunogenicity. Studies on multipotent fetal stem cells can be invaluable to gain knowledge on the development of dysfunctional fetal cell types, to characterize the fetal stem cells migrating into the body of a pregnant woman in the context of fetomaternal microchimerism, and to obtain a more comprehensive picture of germ cell development in the course of in vitro differentiation experiments. The in vivo transplantation of fetal stem cells or their paracrine factors can mediate therapeutic effects in preeclampsia and can restore reproductive organ functions. Together with the use of fetal stem cell-derived gametes, such strategies could once help individuals, who do not develop functional gametes, to conceive genetically related children. Although there is still a long way to go, these developments regarding the usage of multipotent fetal stem cells in the clinic should continuously be accompanied by a wide and detailed ethical discussion.

Immunomodulatory hybrid micro-nanofiber scaffolds enhance vascular regeneration

The inertness of synthetic polymer materials and the insufficient mechanical strength of reprocessed decellularized extracellular matrix (dECM) limited their promotive efforts on tissue regeneration. Here, we prepared a hybrid scaffold composed of PCL microfibers and human placental extracellular matrix (pECM) nanofibers by co-electrospinning, which was grafted with heparin and further absorbed with IL-4. The hybrid scaffold with improved hemocompatibility firstly switched macrophages to anti-inflammatory phenotype (increased by 18.1%) and then promoted migration, NO production, tube formation of endothelial cells (ECs), and migration and maturation of vascular smooth muscle cells (VSMCs), and ECM deposition in vitro and in vivo. ECs coverage rate increased by 8.6% and the thickness of the smooth muscle layer was 1.8 times more than PCL grafts at 12 wks. Our study realized the complementary advantages of synthetic polymer materials and dECM materials, and opened intriguing perspectives for the design and construction of small-diameter vascular grafts (SDVGs) and immune-regulated materials for other tissue regeneration.

Smart stimuli-responsive injectable gels and hydrogels for drug delivery and tissue engineering applications: A review

Hydrogels are widely used biomaterials in the delivery of therapeutic agents, including drugs, genes, proteins, etc., as well as tissue engineering, due to obvious properties such as biocompatibility and their similarity to natural body tissues. Some of these substances have the feature of injectability, which means that the substance is injected into the desired place in the solution state and then turns into the gel, which makes it possible to administer them from a way with a minimal amount of invasion and eliminate the need for surgery to implant pre-formed materials. Gelation can be caused by a stimulus and/or spontaneously. Suppose this induces due to the effect of one or many stimuli. In that case, the material in question is called stimuli-responsive because it responds to the surrounding conditions. In this context, we introduce the different stimuli that cause gelation and investigate the different mechanisms of the transformation of the solution into the gel in them. Also, we study special structures, such as nano gels or nanocomposite gels.

Perinatal Tissue-Derived Allografts and Stromal Cells for the Treatment of Knee Osteoarthritis: A Review of Preclinical and Clinical Evidence

OBJECTIVE

The use of perinatal-derived tissues and mesenchymal stromal cells (MSCs) as alternative treatment options to corticosteroid and hyaluronic acid injections has been gaining popularity. However, their ability to attenuate osteoarthritic (OA) symptoms while also slowing the progression of the disease remains controversial. Thus, the objective of this article is to summarize the results from both preclinical and clinical studies evaluating the efficacy of perinatal-derived tissue allografts and MSCs for the treatment of OA.

DESIGN

A comprehensive literature search was conducted on databases including Pubmed, ScienceDirect, and Google Scholar beginning in March 2020 for both preclinical and clinical studies evaluating perinatal-derived tissues and MSCs in OA. Eighteen studies met the inclusion criteria and were used for this review.

RESULTS

Both animal models and early human clinical trials demonstrated that perinatal tissues could reduce joint inflammation and pain as well as improve range of motion and function in OA. Perinatal tissue-derived MSCs in animal studies have shown the potential to support chondrocyte proliferation while also decreasing inflammatory gene and protein expression. Limited clinical results suggest perinatal tissue-derived MSC sources may also be a viable alternative or adjunct to hyaluronic acid in reducing pain and symptoms in an arthritic joint.

CONCLUSIONS

Perinatal tissue-derived allografts and MSCs have promise as potential therapeutics for mitigating OA progression. However, further research is warranted to fully define the therapeutic mechanism(s) of action and safety of these biological therapies.

A Bioink Derived From Human Placenta Supporting Angiogenesis

Bioprinting is an emerging approach for constructing sophisticated tissue analogues with detailed architectures such as vascular networks, which requires bioink fulfill the highly printable property and provide a cell-friendly microenvironment mimicking native extracellular matrix (ECM). Here, we developed a human placental ECM-derived bioink (hp-bioink) meeting the requirements of 3D printing for printability and bioactivity. We first decellularized the human placenta, followed by enzymatic digestion, dialysis, lyophilization, and re-solubilization to convert the extracts into hp-bioink. Then, we demonstrated that 3%-5% of hp-bioink can be printed with self-standing and 1%-2% of hp-bioink can be embedded with suspended hydrogels. Moreover, hp-bioink supports HUVEC assembly in vitro and angiogenesis in mice in vivo. Our research enriched the bank of human-derived bioink, and provided a new opportunity to further accelerate bioprinting research and application.

High-Throughput Production of Microsponges from Platelet Lysate for Tissue Engineering Applications

Cell-based therapies require a large number of cells, as well as appropriate methods to deliver the cells to damaged tissue. Microcarriers provide an optimal platform for large-scale cell culture while also improving cell retention during cell delivery. However, this technology still presents significant challenges due to low-throughput fabrication methods and an inability of the microcarriers to recreate the properties of human tissue. This work proposes, for the first time, the use of methacryloyl platelet lysates (PLMA), a photocrosslinkable material derived from human platelet lysates, to produce porous microcarriers. Initially, high quantities of PLMA/alginate core-shell microcapsules are produced using coaxial electrospray. Subsequently, the microcapsules are collected, irradiated with ultraviolet light, washed, and freeze dried yielding PLMA microsponges. These microsponges are able to support the adhesion and proliferation of human adipose-derived stem cells, while also displaying potential in the assembly of autologous microtissues. Cell-laden microsponges were shown to self-organize into aggregates, suggesting possible applications in bottom-up tissue engineering applications. Impact Statement Microcarriers have increasingly been used as delivery platforms in cell therapy. Herein, the encapsulation of human-derived proteins in alginate microcapsules is proposed as a method to produce microcarriers from photopolymerizable materials. The capsules function as a template structure, which is then processed into spherical microparticles, which can be used in cell culture, cell delivery, and bottom-up assembly. As a proof of concept, this method was combined with lyophilization to process methacryloyl platelet lysates into injectable microsponges for cell delivery.

Fabrication and characterization of a pro-angiogenic hydrogel derived from the human placenta

Various hydrogels derived from the xenogeneic extracellular matrix (ECM) have been utilised to promote the repair and reconstruction of numerous tissues; however, there are few studies on hydrogels derived from allogeneic specimens. Human placenta derived hydrogels have been used in the therapy of ischaemic myocardium; however, their physicochemical properties and effects on cellular behaviour remain elusive. As the human placenta retains pro-angiogenic growth factors, it is hypothesized that the placenta hydrogels possess the potential to improve angiogenesis. In this study, a soluble decellularized human placenta matrix generated using a modified method could be stored in a powder form and could be used to form a hydrogel in vitro. Effective decellularization was evaluated by analysing the DNA content and histology images. The placenta hydrogel exhibited a fibrous porous morphology and was injectable. Fourier transform infrared (FTIR) spectroscopy revealed that the placenta hydrogel contained both collagen and sulfated glycosaminoglycans (GAGs). In addition, immunofluorescence imaging and enzyme-linked immunosorbent assay (ELISA) showed that the placenta hydrogel retained pro-angiogenic growth factors, including VEGF and bFGF, and transforming growth factor-β1 (TGF-β1). Further in vitro and in vivo analyses confirmed that the placenta hydrogel exerted better pro-angiogenic effects than a collagen type I hydrogel. Histological data also showed that the placenta hydrogels did not elicit a grave inflammatory response. In conclusion, the results suggest that placenta hydrogels may be deemed an attractive scaffold for regenerative medicine applications, especially in promoting vessel formation.

Decellularized Human Umbilical Cord Wharton Jelly Scaffold Improves Tendon Regeneration in a Rabbit Rotator Cuff Tendon Defect Model

BACKGROUND

Owing to limited self-healing capacity, failure of rotator cuff tendon healing is a common complication after surgery. Biological scaffolds have garnered attention owing to their potential to enhance healing outcomes.

PURPOSE

To verify the effect of the decellularized umbilical cord Wharton jelly (DUCWJ) scaffold as a bridging scaffold in a rabbit model of acute rotator cuff tendon defect.

STUDY DESIGN

Controlled laboratory study.

METHODS

We fabricated a DUCWJ scaffold using a physicochemical decellularized method, evaluating changes in the umbilical cord Wharton jelly before and after decellularization. Scanning electron microscopy and biomechanical testing were performed to determine the microstructure and mechanical properties. We assessed cytocompatibility and cell regulatory behavior of the scaffold toward tendon stem/progenitor cells (TSPCs). A supraspinatus tendon defect was created in 54 New Zealand White rabbits, allocated to the DUCWJ scaffold repair group and the negative control group (without scaffold). Histology, reverse transcription polymerase chain reaction, and biomechanical tensile strength were assessed at 4, 8, and 12 weeks postoperatively.

RESULTS

Decellularization completely removed cells from the umbilical cord Wharton jelly, retained a considerable amount of glycosaminoglycan and collagen, and preserved the microstructure and tensile strength. The DUCWJ scaffold facilitated migration and proliferation of TSPCs in vitro. Tendon-related gene expression revealed that the DUCWJ scaffold could maintain the tenocyte phenotype of TSPCs. In the in vivo study, the DUCWJ scaffold improved tendon healing and enhanced the biomechanical strength of repaired tendons. Histological evaluation scores of the DUCWJ group were significantly higher than those of the negative control at 4, 8, and 12 weeks after surgery (P < .05). In repaired tendon tissues, reverse transcription polymerase chain reaction findings revealed that the DUCWJ scaffold stimulated tendon development and maturation. Furthermore, an overall increase in ultimate load and tensile modulus was noted over time; the DUCWJ group presented better results than the negative control group (P < .05).

CONCLUSION

The DUCWJ scaffold has an excellent 3-dimensional porous structure, good biocompatibility, and fundamental biomechanical characteristics, and it promotes migration, attachment, and proliferation of TSPCs. The in vivo animal study demonstrated that the DUCWJ scaffold has potential for tendon regeneration in an acute rotator cuff tendon defect model.

CLINICAL RELEVANCE

DUCWJ scaffolds have potential as a regenerative material to augment rotator cuff healing in the clinical setting.

Designing highly customizable human based platforms for cell culture using proteins from the amniotic membrane

In the past few years researchers have witnessed a paradigm shift in the development of biomaterials for drug discovery, tissue engineering, and regenerative medicine. After the great advances resulting from the transition of the 2D to the 3D, the new focus has been to increase the clinical relevance of such systems, as well as avoid the use of animals, by developing platforms that better replicate the human physiology in vitro. In this sense, we envisage the use of human matrices extracted from ethically sourced and readily available tissues as an optimal and promising alternative to currently used approaches. Hereupon, we report for the first time the chemical modification of human ECM proteins from the amniotic membrane (AM) with photoresponsive groups to produce bioinks and hydrogel precursors to engineer customizable platforms that are representative of native tissues and capable of supporting long-term cell culture. Our results demonstrated an efficient decellularization, liquefaction and functionalization of AM-derived ECM with methacryloyl domains (AMMA), with production of stable and versatile hydrogels. Mechanical characterization evidenced an increased compression strength as a function of methacrylation degree and decellularized ECM concentration. Three-dimensional (3D) stem cell culture in the AMMA hydrogels resulted in viable and proliferative cells up to 7 days; moreover, the mouldable character of the hydrogel precursors permits the processing of patterned hydrogel constructs allowing the control over cellular alignment and elongation, or microgels with highly tunable shape.

Developing a pro-angiogenic placenta derived amniochorionic scaffold with two exposed basement membranes as substrates for cultivating endothelial cells

Decellularized and de-epithelialized placenta membranes have widely been used as scaffolds and grafts in tissue engineering and regenerative medicine. Exceptional pro-angiogenic and biomechanical properties and low immunogenicity have made the amniochorionic membrane a unique substrate which provides an enriched niche for cellular growth. Herein, an optimized combination of enzymatic solutions (based on streptokinase) with mechanical scrapping is used to remove the amniotic epithelium and chorion trophoblastic layer, which resulted in exposing the basement membranes of both sides without their separation and subsequent damages to the in-between spongy layer. Biomechanical and biodegradability properties, endothelial proliferation capacity, and in vivo pro-angiogenic capabilities of the substrate were also evaluated. Histological staining, immunohistochemistry (IHC) staining for collagen IV, and scanning electron microscope demonstrated that the underlying amniotic and chorionic basement membranes remained intact while the epithelial and trophoblastic layers were entirely removed without considerable damage to basement membranes. The biomechanical evaluation showed that the scaffold is suturable. Proliferation assay, real-time polymerase chain reaction for endothelial adhesion molecules, and IHC demonstrated that both side basement membranes could support the growth of endothelial cells without altering endothelial characteristics. The dorsal skinfold chamber animal model indicated that both side basement membranes could promote angiogenesis. This bi-sided substrate with two exposed surfaces for cultivating various cells would have potential applications in the skin, cardiac, vascularized composite allografts, and microvascular tissue engineering.

Systematic Review of the Application of Perinatal Derivatives in Animal Models on Cutaneous Wound Healing

Knowledge of the beneficial effects of perinatal derivatives (PnD) in wound healing goes back to the early 1900s when the human fetal amniotic membrane served as a biological dressing to treat burns and skin ulcerations. Since the twenty-first century, isolated cells from perinatal tissues and their secretomes have gained increasing scientific interest, as they can be obtained non-invasively, have anti-inflammatory, anti-cancer, and anti-fibrotic characteristics, and are immunologically tolerated in vivo. Many studies that apply PnD in pre-clinical cutaneous wound healing models show large variations in the choice of the animal species (e.g., large animals, rodents), the choice of diabetic or non-diabetic animals, the type of injury (full-thickness wounds, burns, radiation-induced wounds, skin flaps), the source and type of PnD (placenta, umbilical cord, fetal membranes, cells, secretomes, tissue extracts), the method of administration (topical application, intradermal/subcutaneous injection, intravenous or intraperitoneal injection, subcutaneous implantation), and the type of delivery systems (e.g., hydrogels, synthetic or natural biomaterials as carriers for transplanted cells, extracts or secretomes). This review provides a comprehensive and integrative overview of the application of PnD in wound healing to assess its efficacy in preclinical animal models. We highlight the advantages and limitations of the most commonly used animal models and evaluate the impact of the type of PnD, the route of administration, and the dose of cells/secretome application in correlation with the wound healing outcome. This review is a collaborative effort from the COST SPRINT Action (CA17116), which broadly aims at approaching consensus for different aspects of PnD research, such as providing inputs for future standards for the preclinical application of PnD in wound healing.

Colony Forming Potential and Protein Composition of Commercial Umbilical Cord Allograft Products in Comparison With Autologous Orthobiologics

BACKGROUND

Umbilical cord (UC) connective tissues contain plastic-adherent, colony forming unit-fibroblasts (CFU-Fs) amenable to culture expansion for potential therapeutic use. Recently, UC-derived allograft products have been made available to practitioners in orthopaedics and other specialties, by companies purporting "stem cell"-based healing. However, such marketing claims conflict with existing regulations for these human tissues, generating questions over the cellular and protein composition of current commercially available UC allograft products.

PURPOSE

To evaluate commercial UC allograft products for viable cells, CFU-Fs, and protein makeup.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Five commercial UC allograft products claiming to contain viable, undescribed "stem cells," 2 obtained from UC blood (UCB) and 3 from UC tissue (UCT), were analyzed. Image-based methods were used to measure cell concentration and viability, a traditional CFU-F assay was used to evaluate in vitro behavior indicative of a connective tissue progenitor cell phenotype often referred to as mesenchymal stem/stromal cells, and quantitative immunoassay arrays were used to measure a combination of cytokines and growth factors. Bone marrow concentrate (BMC) and plasma derived from the blood and bone marrow of middle-aged individuals served as comparative controls for cell culture and protein analyses, respectively.

RESULTS

Viable cells were identified within all 5 UC allograft products, with those derived from UCB having greater percentages of living cells (40%-59%) than those from UCT (1%-22%). Compared with autologous BMC (>95% viability and >300 million living cells), no CFU-Fs were observed within any UC allograft product (<15 million living cells). Moreover, a substantial number of proteins, particularly those within UCB allograft products, were undetectable or present at lower concentrations compared with blood and bone marrow plasma controls. Interestingly, several important growth factors and cytokines, including basic fibroblast growth factor, hepatocyte growth factor, interleukin-1 receptor antagonist, and osteoprotegerin, were most prevalent in 1 or more UCT allograft products as compared with blood and bone marrow plasma.

CONCLUSION

CFU-Fs, often referred to as stem cells, were not found within any of the commercial UC allograft products analyzed, and clinicians should remain wary of marketing claims stating otherwise.

CLINICAL RELEVANCE

Any therapeutic benefit of current UC allograft products in orthopaedic medicine is more likely to be attributed to their protein composition (UCT > UCB) or inclusion of cells without colony forming potential (UCB > UCT).

Microfluidic Tools for Enhanced Characterization of Therapeutic Stem Cells and Prediction of Their Potential Antimicrobial Secretome

Antibiotic resistance is creating enormous attention on the development of new antibiotic-free therapy strategies for bacterial diseases. Mesenchymal stromal stem cells (MSCs) are the most promising candidates in current clinical trials and included in several cell-therapy protocols. Together with the well-known immunomodulatory and regenerative potential of the MSC secretome, these cells have shown direct and indirect anti-bacterial effects. However, the low reproducibility and standardization of MSCs from different sources are the current limitations prior to the purification of cell-free secreted antimicrobial peptides and exosomes. In order to improve MSC characterization, novel label-free functional tests, evaluating the biophysical properties of the cells, will be advantageous for their cell profiling, population sorting, and quality control. We discuss the potential of emerging microfluidic technologies providing new insights into density, shape, and size of live cells, starting from heterogeneous or 3D cultured samples. The prospective application of these technologies to studying MSC populations may contribute to developing new biopharmaceutical strategies with a view to naturally overcoming bacterial defense mechanisms.

Growth factor loading on aliphatic polyester scaffolds

Cells, scaffolds and growth factors are three elements of tissue engineering. The success of tissue engineering methods relies on precise and dynamic interactions between cells, scaffolds and growth factors. Aliphatic polyester scaffolds are promising tissue engineering scaffolds that possess good mechanical properties, low immunogenicity, non-toxicity, and adjustable degradation rates. How growth factors can be loaded onto/into aliphatic polyester scaffolds and be constantly released with the required bioactivity to regulate cell growth and promote defect tissue repair and regeneration has become the main concern of tissue engineering researchers. In this review, the existing main methods of loading growth factors on aliphatic polyester scaffolds, the release behavior of loaded growth factors and their positive effects on cell, tissue repair and regeneration are introduced. Advantages and shortcomings of each method also are mentioned. It is still a great challenge to control the release of loaded growth factors at a certain time and at a concentration simulating the biological environment of native tissue.

Proteinaceous Hydrogels for Bioengineering Advanced 3D Tumor Models

The establishment of tumor microenvironment using biomimetic in vitro models that recapitulate key tumor hallmarks including the tumor supporting extracellular matrix (ECM) is in high demand for accelerating the discovery and preclinical validation of more effective anticancer therapeutics. To date, ECM-mimetic hydrogels have been widely explored for 3D in vitro disease modeling owing to their bioactive properties that can be further adapted to the biochemical and biophysical properties of native tumors. Gathering on this momentum, herein the current landscape of intrinsically bioactive protein and peptide hydrogels that have been employed for 3D tumor modeling are discussed. Initially, the importance of recreating such microenvironment and the main considerations for generating ECM-mimetic 3D hydrogel in vitro tumor models are showcased. A comprehensive discussion focusing protein, peptide, or hybrid ECM-mimetic platforms employed for modeling cancer cells/stroma cross-talk and for the preclinical evaluation of candidate anticancer therapies is also provided. Further development of tumor-tunable, proteinaceous or peptide 3D microtesting platforms with microenvironment-specific biophysical and biomolecular cues will contribute to better mimic the in vivo scenario, and improve the predictability of preclinical screening of generalized or personalized therapeutics.

A Review of Placenta and Umbilical Cord-Derived Stem Cells and the Immunomodulatory Basis of Their Therapeutic Potential in Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a devastating lung disorder of preterm infants as a result of an aberrant reparative response following exposures to various antenatal and postnatal insults. Despite sophisticated medical treatment in this modern era, the incidence of BPD remains unabated. The current strategies to prevent and treat BPD have met with limited success. The emergence of stem cell therapy may be a potential breakthrough in mitigating this complex chronic lung disorder. Over the last two decades, the human placenta and umbilical cord have gained increasing attention as a highly potential source of stem cells. Placenta-derived stem cells (PDSCs) and umbilical cord-derived stem cells (UCDSCs) display several advantages such as immune tolerance and are generally devoid of ethical constraints, in addition to their stemness qualities. They possess the characteristics of both embryonic and mesenchymal stromal/stem cells. Recently, there are many preclinical studies investigating the use of these cells as therapeutic agents in neonatal disease models for clinical applications. In this review, we describe the preclinical and clinical studies using PDSCs and UCDSCs as treatment in animal models of BPD. The source of these stem cells, routes of administration, and effects on immunomodulation, inflammation and regeneration in the injured lung are also discussed. Lastly, a brief description summarized the completed and ongoing clinical trials using PDSCs and UCDSCs as therapeutic agents in preventing or treating BPD. Due to the complexity of BPD, the development of a safe and efficient therapeutic agent remains a major challenge to both clinicians and researchers.

Current Status and Future Prospects of Perinatal Stem Cells

The placenta is a temporary organ that is discarded after birth and is one of the most promising sources of various cells and tissues for use in regenerative medicine and tissue engineering, both in experimental and clinical settings. The placenta has unique, intrinsic features because it plays many roles during gestation: it is formed by cells from two individuals (mother and fetus), contributes to the development and growth of an allogeneic fetus, and has two independent and interacting circulatory systems. Different stem and progenitor cell types can be isolated from the different perinatal tissues making them particularly interesting candidates for use in cell therapy and regenerative medicine. The primary source of perinatal stem cells is cord blood. Cord blood has been a well-known source of hematopoietic stem/progenitor cells since 1974. Biobanked cord blood has been used to treat different hematological and immunological disorders for over 30 years. Other perinatal tissues that are routinely discarded as medical waste contain non-hematopoietic cells with potential therapeutic value. Indeed, in advanced perinatal cell therapy trials, mesenchymal stromal cells are the most commonly used. Here, we review one by one the different perinatal tissues and the different perinatal stem cells isolated with their phenotypical characteristics and the preclinical uses of these cells in numerous pathologies. An overview of clinical applications of perinatal derived cells is also described with special emphasis on the clinical trials being carried out to treat COVID19 pneumonia. Furthermore, we describe the use of new technologies in the field of perinatal stem cells and the future directions and challenges of this fascinating and rapidly progressing field of perinatal cells and regenerative medicine.

Mesenchymal Stromal Cells as Potential Antimicrobial for Veterinary Use-A Comprehensive Review

The emergence of “superbugs” resistant to antimicrobial medications threatens populations both veterinary and human. The current crisis has come about from the widespread use of the limited number of antimicrobials available in the treatment of livestock, companion animal, and human patients. A different approach must be sought to find alternatives to or enhancements of present conventional antimicrobials. Mesenchymal stromal cells (MSC) have antimicrobial properties that may help solve this problem. In the first part of the review, we explore the various mechanisms at work across species that help explain how MSCs influence microbial survival. We then discuss the findings of recent equine, canine, and bovine studies examining MSC antimicrobial properties in which MSCs are found to have significant effects on a variety of bacterial species either alone or in combination with antibiotics. Finally, information on the influence that various antimicrobials may have on MSC function is reviewed. MSCs exert their effect directly through the secretion of various bioactive factors or indirectly through the recruitment and activation of host immune cells. MSCs may soon become a valuable tool for veterinarians treating antimicrobial resistant infections. However, a great deal of work remains for the development of optimal MSC production conditions and testing for efficacy on different indications and species.