Regenerative Medicine: lessons from Mother Nature

Inflammatory diseases: Function of LncRNAs in their emergence and the role of mesenchymal stem cell secretome in their treatment

One of the best treatments for inflammatory diseases such as COVID-19, respiratory diseases and brain diseases is treatment with stem cells. Here we investigate the effect of stem cell therapy in the treatment of brain diseases.Preclinical studies have shown promising results, including improved functional recovery and tissue repair in animal models of neurodegenerative diseases, strokes,and traumatic brain injuries. However,ethical implications, safety concerns, and regulatory frameworks necessitate thorough evaluation before transitioning to clinical applications. Additionally, the complex nature of the brain and its intricate cellular environment present unique obstacles that must be overcome to ensure the successful integration and functionality of genetically engineered MSCs. The careful navigation of this path will determine whether the application of genetically engineered MSCs in brain tissue regeneration ultimately lives up to the hype surrounding it.

Hopes and opportunities of stem cells from human exfoliated deciduous teeth (SHED) in cartilage tissue regeneration

Cartilage lesions are common conditions, affecting elderly and non-athletic populations. Despite recent advances, cartilage regeneration remains a major challenge today. The absence of an inflammatory response following damage and the inability of stem cells to penetrate into the healing site due to the absence of blood and lymph vessels are assumed to hinder joint repair. Stem cell-based regeneration and tissue engineering have opened new horizons for treatment. With advances in biological sciences, especially stem cell research, the function of various growth factors in the regulation of cell proliferation and differentiation has been established. Mesenchymal stem cells (MSCs) isolated from different tissues have been shown to increase into therapeutically relevant cell numbers and differentiate into mature chondrocytes. As MSCs can differentiate and become engrafted inside the host, they are considered suitable candidates for cartilage regeneration. Stem cells from human exfoliated deciduous teeth (SHED) provide a novel and non-invasive source of MSCs. Due to their simple isolation, chondrogenic differentiation potential, and minimal immunogenicity, they can be an interesting option for cartilage regeneration. Recent studies have reported that SHED-derived secretome contains biomolecules and compounds that efficiently promote regeneration in damaged tissues, including cartilage. Overall, this review highlighted the advances and challenges of cartilage regeneration using stem cell-based therapies by focusing on SHED.

A Population of M2 Macrophages Associated With Bone Formation

We previously identified transient brown adipocyte-like cells associated with heterotopic ossification (HO). These ancillary cells support new vessel synthesis essential to bone formation. Recent studies have shown that the M2 macrophage contributes to tissue regeneration in a similar way. To further define the phenotype of these brown adipocyte-like cells they were isolated and characterized by single-cell RNAseq (scRNAseq). Analysis of the transcriptome and the presence of surface markers specific for macrophages suggest that these cells are M2 macrophages. To validate these findings, clodronate liposomes were delivered to the tissues during HO, and the results showed both a significant reduction in these macrophages as well as bone formation. These cells were isolated and shown in culture to polarize towards either M1 or M2 similar to other macrophages. To confirm that these are M2 macrophages, mice received lipopolysacheride (LPS), which induces proinflammation and M1 macrophages. The results showed a significant decrease in this specific population and bone formation, suggesting an essential role for M2 macrophages in the production of bone. To determine if these macrophages are specific to HO, we isolated these cells using fluorescence-activated cell sorting (FACS) from a bone defect model and subjected them to scRNAseq. Surprisingly, the macrophage populations overlapped between the two groups (HO-derived versus callus) suggesting that they may be essential ancillary cells for bone formation in general and not selective to HO. Of further note, their unique metabolism and lipogenic properties suggest the potential for unique cross talk between these cells and the newly forming bone.

Study of Natural Longlife Juvenility and Tissue Regeneration in Caudate Amphibians and Potential Application of Resulting Data in Biomedicine

The review considers the molecular, cellular, organismal, and ontogenetic properties of Urodela that exhibit the highest regenerative abilities among tetrapods. The genome specifics and the expression of genes associated with cell plasticity are analyzed. The simplification of tissue structure is shown using the examples of the sensory retina and brain in mature Urodela. Cells of these and some other tissues are ready to initiate proliferation and manifest the plasticity of their phenotype as well as the correct integration into the pre-existing or de novo forming tissue structure. Without excluding other factors that determine regeneration, the pedomorphosis and juvenile properties, identified on different levels of Urodele amphibians, are assumed to be the main explanation for their high regenerative abilities. These properties, being fundamental for tissue regeneration, have been lost by amniotes. Experiments aimed at mammalian cell rejuvenation currently use various approaches. They include, in particular, methods that use secretomes from regenerating tissues of caudate amphibians and fish for inducing regenerative responses of cells. Such an approach, along with those developed on the basis of knowledge about the molecular and genetic nature and age dependence of regeneration, may become one more step in the development of regenerative medicine.

Human Adipose Tissue Derivatives as a Potent Native Biomaterial for Tissue Regenerative Therapies

BACKGROUND

Human adipose tissue is a great source of translatable biomaterials owing to its ease of availability and simple processing. Reusing discardable adipose tissue for tissue regeneration helps in mimicking the exact native microenvironment of tissue. Over the past 10 years, extraction, processing, tuning and fabrication of adipose tissue have grabbed the attention owing to their native therapeutic and regenerative potential. The present work gives the overview of next generation biomaterials derived from human adipose tissue and their development with clinical relevance.

METHODS

Around 300 articles have been reviewed to widen the knowledge on the isolation, characterization techniques and medical applications of human adipose tissue and its derivatives from bench to bedside. The prospective applications of adipose tissue derivatives like autologous fat graft, stromal vascular fraction, stem cells, preadipocyte, adipokines and extracellular matrix, their behavioural mechanism, rational property of providing native bioenvironment, circumventing their translational abilities, recent advances in featuring them clinically have been reviewed extensively to reveal the dormant side of human adipose tissue.

RESULTS

Basic understanding about the molecular and structural aspect of human adipose tissue is necessary to employ it constructively. This review has nailed the productive usage of human adipose tissue, in a stepwise manner from exploring the methods of extracting derivatives, concerns during processing and its formulations to turning them into functional biomaterials. Their performance as functional biomaterials for skin regeneration, wound healing, soft tissue defects, stem cell and other regenerative therapies under in vitro and in vivo conditions emphasizes the translational efficiency of adipose tissue derivatives.

CONCLUSION

In the recent years, research interest has inclination towards constructive tissue engineering and regenerative therapies. Unravelling the maximum utilization of human adipose tissue derivatives paves a way for improving existing tissue regeneration and cellular based therapies and other biomedical applications.

Hard Tissue Augmentation of Aged Bone by Means of a Tin-Free PLLA-PCL Co-Polymer Exhibiting in vivo Anergy and Long-Term Structural Stability

BACKGROUND

Due to aging, tissue regeneration gradually declines. Contemporary strategies to promote tissue-specific regeneration, in particular in elderly patients, often include synthetic material apt for implantation primarily aiming at upholding body functions and regaining appropriate anatomical and functional integrity.

OBJECTIVE

Biomaterials suitable for complex reconstruction surgical procedures have to exert high physicochemical stability and biocompatibility.

METHOD

A polymer made of poly-L-lactic acid and poly-ε-caprolactone was synthesized by means of a novel tin-free catalytic process. The material was tested in a bioreactor-assisted perfusion culture and implanted in a sheep model for lateral augmentation of the mandible. Histological and volumetric evaluation was performed 3 and 6 months post-implantation.

RESULTS

After synthesis the material could be further refined by cryogrinding and sintering, thus yielding differently porous scaffolds that exhibited a firm and stable appearance. In perfusion culture, no disintegration was observed for extended periods of up to 7 weeks, while mesenchymal stromal cells readily attached to the material, steadily proliferated, and deposited extracellular calcium. The material was tested in vivo together with autologous bone marrow-derived stromal cells. Up to 6 months post-implantation, the material hardly changed in shape with composition also refraining from foreign body reactions.

CONCLUSION

Given the long-term shape stability in vivo, featuring imperceptible degradation and little scarring as well as exerting good compatibility to cells and surrounding tissues, this novel biomaterial is suitable as a space filler in large anatomical defects.