Hybrid complexes of high and low molecular weight hyaluronan delay in vitro replicative senescence of mesenchymal stromal cells: a pilot study for future therapeutic application

A Mesenchymal stem cell Aging Framework, from Mechanisms to Strategies

Mesenchymal stem cells (MSCs) are extensively researched for therapeutic applications in tissue engineering and show significant potential for clinical use. Intrinsic or extrinsic factors causing senescence may lead to reduced proliferation, aberrant differentiation, weakened immunoregulation, and increased inflammation, ultimately limiting the potential of MSCs. It is crucial to comprehend the molecular pathways and internal processes responsible for the decline in MSC function due to senescence in order to devise innovative approaches for rejuvenating senescent MSCs and enhancing MSC treatment. We investigate the main molecular processes involved in senescence, aiming to provide a thorough understanding of senescence-related issues in MSCs. Additionally, we analyze the most recent advancements in cutting-edge approaches to combat MSC senescence based on current research. We are curious whether the aging process of stem cells results in a permanent "memory" and if cellular reprogramming may potentially revert the aging epigenome to a more youthful state.

Highly Concentrated Stabilized Hybrid Complexes of Hyaluronic Acid: Rheological and Biological Assessment of Compatibility with Adipose Tissue and Derived Stromal Cells towards Regenerative Medicine

Cells and extracts derived from adipose tissue are gaining increasing attention not only in plastic surgery and for aesthetic purposes but also in regenerative medicine. The ability of hyaluronan (HA) to support human adipose stromal cell (hASC) viability and differentiation has been investigated. However, the compatibility of adipose tissue with HA-based formulation in terms of biophysical and rheological properties has not been fully addressed, although it is a key feature for tissue integration and in vivo performance. In this study, the biophysical and biochemical properties of highly concentrated (45 mg/mL) high/low-molecular-weight HA hybrid cooperative complex were assessed with a further focus on the potential application in adipose tissue augmentation/regeneration. Specifically, HA hybrid complex rheological behavior was observed in combination with different adipose tissue ratios, and hyaluronidase-catalyzed degradation was compared to that of a high-molecular-weight HA (HHA). Moreover, the HA hybrid complex's ability to induce in vitro hASCs differentiation towards adipose phenotype was evaluated in comparison to HHA, performing Oil Red O staining and analyzing gene/protein expression of PPAR-γ, adiponectin, and leptin. Both treatments supported hASCs differentiation, with the HA hybrid complex showing better results. These outcomes may open new frontiers in regenerative medicine, supporting the injection of highly concentrated hybrid formulations in fat compartments, eventually enhancing residing staminal cell differentiation and improving cell/growth factor persistence towards tissue regeneration districts.

Adult Mesenchymal Stem Cells in Presence of Glycosaminoglycans

The application of adult mesenchymal stem cells (MSCs) in the field of tissue regeneration is of increasing interest to the scientific community. In particular, scaffolds and/or hydrogel based on glycosaminoglycans (GAGs) play a pivotal role due to their ability to support the in vitro growth and differentiation of MSCs toward a specific phenotype. Here, we describe different possible approaches to develop GAGs-based biomaterials, hydrogel, and polymeric viscous solutions in order to assess/develop a suitable biomimetic environment. To sustain MSCs viability and promote their differentiation for potential therapeutic applications.

Restoring Adipose Tissue Homeostasis in Response to Aging: Initial Clinical Experience with Profhilo Structura®

The aim of the case series was to determine the efficacy of a new medical device developed for adipose tissue restoration in the face. The medical device used the patented NAHYCO® Hybrid Technology to deliver 45 mg of high- (1400 ± 200 kDa) and 45 mg of low- (100 ± 20 kDa) molecular-weight hyaluronan, in 2 mL. Patients and methods: Twenty-two volunteers, aged 36-60 years. Two mL of Profhilo® Structura was injected using a 25 G cannula for each hemiface, into superficial fat compartment along the line from the preauricular area to the mandibular angle. Two injections were performed, and Profhilo Structura's effect on restoring adipose tissue was evaluated immediately after treatment, and over a 6-month follow-up. The studied medical device revealed a pseudoplastic behavior and consistency that allowed easy extrusion from a syringe. It showed a lower viscosity compared to dermal fillers, based on crosslinked HA. Clinically, the soft tissue thickness increased immediately after injection, and the clinical improvement persisted across a 6-month follow-up. The self-reported satisfaction with the treatment showed an amelioration in the midface of all the subjects enrolled, with no adverse effects. Profhilo® Structura demonstrated a peculiar fat compartment integration, with a regenerating effect on adipose tissue senescence. The skin thickening and compaction effects were similar to those obtained using chemically crosslinked dermal fillers, while a natural look was preserved, and the use of crosslinking agents was avoided.

Metformin promotes angiogenesis by enhancing VEGFa secretion by adipose-derived stem cells via the autophagy pathway

Human adipose tissue-derived stem cell (ADSC) derivatives are cell-free, with low immunogenicity and no potential tumourigenicity, making them ideal for aiding wound healing. However, variable quality has impeded their clinical application. Metformin (MET) is a 5' adenosine monophosphate-activated protein kinase activator associated with autophagic activation. In this study, we assessed the potential applicability and underlying mechanisms of MET-treated ADSC derivatives in enhancing angiogenesis. We employed various scientific techniques to evaluate the influence of MET on ADSC, assess angiogenesis and autophagy in MET-treated ADSC in vitro, and examine whether MET-treated ADSC increase angiogenesis. We found that low MET concentrations exerted no appreciable effect on ADSC proliferation. However, MET was observed to enhance the angiogenic capacity and autophagy of ADSC. MET-induced autophagy was associated with increased vascular endothelial growth factor A production and release, which contributed to promoting the therapeutic efficacy of ADSC. In vivo experiments confirmed that in contrast to untreated ADSC, MET-treated ADSC promoted angiogenesis. Our findings thus indicate that the application of MET-treated ADSC would be an effective approach to accelerate wound healing by promoting angiogenesis at wound sites.

Mesenchymal stem cells combined with autocrosslinked hyaluronic acid improve mouse ovarian function by activating the PI3K-AKT pathway in a paracrine manner

Background

Declining ovarian function in advance-aged women and in premature ovarian insufficiency (POI) patients seriously affects quality of life, and there is currently no effective treatment to rescue ovarian function in clinic. Stem cell transplantation is a promising therapeutic strategy for ovarian aging, but its clinical application is limited due to the low efficiency and unclear mechanism. Here, a novel combination of umbilical cord-mesenchymal stem cells (UC-MSCs) and autocrosslinked hyaluronic acid (HA) gel is explored to rescue ovarian reserve and fecundity in POI and naturally aging mice.

Methods

To investigate HA prolonged the survival after UC-MSCs transplantation, PCR and immunofluorescence were performed to track the cells on day 1, 3, 7 and 14 after transplantation. The effects of HA on UC-MSCs were analyzed by CCK8 assay, RNA-sequencing and 440 cytokine array. In vivo experiments were conducted to evaluate the therapeutic effects of UC-MSCs combined with HA transplantation in 4-vinylcyclohexene diepoxide (VCD)-induced POI mice and naturally aging mice model. Ovarian function was analyzed by ovarian morphology, follicle counts, estrous cycle, hormone levels and fertility ability. To investigate the mechanisms of stem cell therapy, conditioned medium was collected from UC-MSCs and fibroblast. Both in vitro ovarian culture model and 440 cytokine array were applied to assess the paracrine effect and determine the underlying mechanism. Hepatocyte growth factor (HGF) was identified as an effective factor and verified by HGF cytokine/neutralization antibody supplementation into ovarian culture system.

Results

HA not only prolongs the retention of UC-MSCs in the ovary, but also boosts their secretory function, and UC-MSCs promote follicular survival by activating the PI3K-AKT pathway through a paracrine mechanism both in vitro and in vivo. More importantly, HGF is identified as the key functional cytokine secreted by MSCs.

Conclusions

The results show that HA is an excellent cell scaffold to improve the treatment efficiency of UC-MSCs for ovarian aging under both physiological and pathological conditions, and the therapeutic mechanism is through activation of the PI3K-AKT pathway via HGF. These findings will facilitate the clinical application of MSCs transplantation for ovarian disorders.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02724-3.

An Overview of Soft Tissue Fillers for Cosmetic Dermatology: From Filling to Regenerative Medicine

Hyaluronic acid (HA)-based injectable filling agents are at the forefront of the current demand for noninvasive dermatological procedures for the correction of age-related soft tissue defects. The present review aims to summarize currently available HA-based products and critically appraise their differences in rheological nature and clinical application. Linear HA (LHA) gels may be supplemented with amino acids, lipoic acid, vitamins, nucleosides, or minerals for synergistic antiaging and antioxidant benefits (polycomponent LHA). HA hydrogels can be generated via chemical or physical crosslinking, which increases their elasticity and decreases viscosity. The performance of crosslinked fillers depends on HA concentration, degree of crosslinking, elastic modulus, cohesivity, and type of crosslinking agent employed. PEG-crosslinked LHA displays improved elasticity and resistance to degradation, and lower swelling rates as compared to BDDE-crosslinked LHA. Physical crosslinking stabilizes HA hydrogels without employing exogenous chemical compounds or altering hyaluronans’ natural molecular structure. Thermally stabilized hybrid cooperative HA complexes (HCC) are a formulation of high- and low-molecular-weight (H-HA and L-HA) hyaluronans, achieving high HA concentration, low viscosity with optimal tissue diffusion, and a duration comparable to weakly cross-linked gel. Our critical analysis evidences the importance of understanding different fillers’ properties to assist physicians in selecting the most appropriate filler for specific uses and for predictable and sustainable results.

Metformin enhances the osteogenesis and angiogenesis of human umbilical cord mesenchymal stem cells for tissue regeneration engineering

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are a potential clinical material in regenerative medicine applications. Metformin has shown safety and effectiveness as a clinical drug. However, the effect of metformin as a treatment on hUC-MSCs is unclear. Our research aimed to explore the effects of metformin on the osteogenesis, adipogenesis and angiogenesis of hUC-MSCs, and attempted to explain the molecular fluctuations of metformin through the mapping of protein profiles. Proliferation assay, osteogenic and adipogenic differentiation induction, cell cycle, flow cytometry, quantitative proteomics techniques and bioinformatics analysis were used to detect the influences of metformin treatment on hUC-MSCs. Our results demonstrated that low concentrations of metformin promoted the proliferation of hUC-MSCs, but high concentrations of metformin inhibited it. Metformin exhibited promotion of osteogenesis but inhibition of adipogenesis. Metformin treated hUC-MSCs up-regulated the expression of osteogenic marker ALP, OCN and RUNX2, but down-regulated the expression of adipogenic markers PPARγ and LPL. Proteomics analysis found that up-regulation of differentially expressed proteins in metformin treatment group involved the biological process of cell migration in Gene Ontology analysis. Metformin enhanced cell migration of HUVEC in a co-culture system, and hUC-MSCs treated with metformin exhibited stronger angiogenesis in vitro and in vivo compared to the hUC-MSCs group. The results of RT-qPCR revealed that the SCF and VEGFR2 were raised in metformin treatment. This study can promote the application of hUC-MSCs treated with metformin to tissue engineering for vascular reconstruction and angiogenesis.

Hyaluronan-Based Gel Promotes Human Dental Pulp Stem Cells Bone Differentiation by Activating YAP/TAZ Pathway

BACKGROUND

Hyaluronans exist in different forms, accordingly with molecular weight and degree of crosslinking. Here, we tested the capability to induce osteogenic differentiation in hDPSCs (human dental pulp stem cells) of three hyaluronans forms: linear pharmaceutical-grade hyaluronans at high and (HHA) low molecular weight (LHA) and hybrid cooperative complexes (HCC), containing both sizes.

METHODS

hDPSCs were treated with HHA, LHA, HCC for 7, 14 and 21 days. The effects of hyaluronans on osteogenic differentiation were evaluated by qRT-PCR and WB of osteogenic markers and by Alizarin Red S staining. To identify the involved pathway, CD44 was analyzed by immunofluorescence, and YAP/TAZ expression was measured by qRT-PCR. Moreover, YAP/TAZ inhibitor-1 was used, and the loss of function of YAP/TAZ was evaluated by qRT-PCR, WB and immunofluorescence.

RESULTS

We showed that all hyaluronans improves osteogenesis. Among these, HCC is the main inducer of osteogenesis, along with overexpression of bone related markers and upregulating CD44. We also found that this biological process is subordinate to the activation of YAP/TAZ pathway.

CONCLUSIONS

We found that HA's molecular weight can have a relevant impact on HA performance for bone regeneration, and we unveil a new molecular mechanism by which HA acts on stem cells.

Timely Supplementation of Hydrogels Containing Sulfated or Unsulfated Chondroitin and Hyaluronic Acid Affects Mesenchymal Stromal Cells Commitment Toward Chondrogenic Differentiation

Mesenchymal stromal cells (MSCs) are currently used for cartilage cell therapy because of their well proven capacity to differentiate in chondrocytes. The advantage of MSC-based therapy is the possibility of producing a high number of chondrocytes for implants. The transplant procedure, however, has some limitations, since MSCs may produce non-functional chondrocytes. This limit has been challenged by cultivating MSC in media with hydrogels containing hyaluronic acid (HA), extractive chondroitin sulfate (CS), or bio-fermentative unsulphated chondroitin (BC) alone or in combination. Nevertheless, a clear study of the effect of glycosaminoglycans (GAGs) on chondrocyte differentiation is still lacking, especially for the newly obtained unsulfated chondroitin of biotechnological origin. Are these GAGs playing a role in the commitment of stem cells to chondrocyte progenitors and in the differentiation of progenitors to mature chondrocytes? Alternatively, do they have a role only in one of these biological processes? We evaluated the role of HA, CS, and - above all - BC in cell commitment and chondrocyte differentiation of MSCs by supplementing these GAGs in different phases of in vitro cultivation. Our data provided evidence that a combination of HA and CS or of HA and BC supplemented during the terminal in vitro differentiation and not during cell commitment of MSCs improved chondrocytes differentiation without the presence of fibrosis (reduced expression of Type I collagen). This result suggests that a careful evaluation of extracellular cues for chondrocyte differentiation is fundamental to obtaining a proper maturation process.

[Paradigm shift in understanding hyaluronic acid filler effects]

Hyaluronic acid (hyaluron; HA) is an important constituent of the extracellular matrix and has an age-dependent decrease in tissue concentration. While natural HA is rapidly degraded, filler cross-linked HA achieve a half-life of 6-12 months. Such fillers enjoy increasing popularity in esthetic medicine and are versatile tools. Although HA fillers can activate fibroblasts it is of minor importance for long-term results. Fillers are injected into subcutaneous adipose tissue. Their interaction with somatic stem cells and mature adipocytes has gained increasing interest. Cross-linked HA can indeed support proliferation of pre-adipocytes, stimulate their differentiation into mature adipocytes and protect the mature cells from senescence, apoptosis and lipolysis. This view offers a new perspective on the development of future fillers for esthetic medicine.

Silencing Smad7 potentiates BMP2-induced chondrogenic differentiation and inhibits endochondral ossification in human synovial-derived mesenchymal stromal cells

BACKGROUND

Bone morphogenetic protein 2 (BMP2) is a promising chondrogenic growth factor for cartilage tissue-engineering, but it also induces robust endochondral ossification. Human synovial-derived mesenchymal stromal cells (hSMSCs) have attracted great interest due to their poor potential for differentiation into osteogenic lineages. Smad7 plays a significant in the endochondral ossification. In this study, we explored a new method to amplify the BMP2-induced chondrogenic differentiation of hSMSCs by downregulating Smad7 and applying a cellular scaffold.

METHODS

hSMSCs were isolated from human knee joint synovium from 3 donors through adhesion growth. In vitro and in vivo models of the chondrogenic differentiation of hSMSCs were established. Transgenic expression of BMP2 and silencing of Smad7 and Smad7 was achieved by adenoviral vectors. The osteogenic differentiation was detected by alkaline phosphatase staining, alizarin red staining, and RT-PCR analysis of the osteogenic genes RUNX2, Osterix, and Osteocalcin. The chondrogenic differentiation was detected by Alcian blue staining and RT-PCR analysis of the chondrogenic genes SOX9, COL2, and aggrecan. Hypertrophic differentiation was detected by the markers COL10 and MMP13. A subcutaneous stem cell implantation model was established with polyethylene glycol citrate-co-N-isopropylacrylamide (PPCN) scaffolds and athymic nude mice (3/group, 4-6 week-old female) and evaluated by micro-CT, H&E staining, and Alcian blue staining. An immunohistochemistry assay was used to detected COL1 and COL2, and an immunofluorescence assay was used to detect COL10 and MMP13.

RESULTS

These hSMSCs identified by flow cytometry. These hSMSCs exhibited lower osteo-differentiation potential than iMads and C3H10T1/2-cells. When Smad7 was silenced in BMP2-induced hSMSCs, the chondrogenic differentiation genes SOX9, COL2, and aggrecan were enhanced in vitro. Additionally, it silencing Smad7 led to a decrease in the hypertrophic differentiation genes COL10 and MMP13. In subcutaneous stem cell implantation assays, immunofluorescence and immunohistochemical staining demonstrated that silencing Smad7 increased the number of COL2-positive cells and decreased the expression of COL1, COL10, and MMP13.

CONCLUSION

This study suggests that the application of hSMSCs, cell scaffolds, and silencing Smad7 can potentiate BMP2-induced chondrogenic differentiation and inhibit endochondral ossification. Thus, inhibiting the expression of Smad7 in BMP2-induced hSMSC differentiation may be a new strategy for cartilage tissue-engineering.

Low Molecular Weight Hyaluronic Acid Effect on Dental Pulp Stem Cells In Vitro

Hyaluronic acid (HA) and dental pulp stem cells (DPSCs) are attractive research topics, and their combined use in the field of tissue engineering seems to be very promising. HA is a natural extracellular biopolymer found in various tissues, including dental pulp, and due to its biocompatibility and biodegradability, it is also a suitable scaffold material. However, low molecular weight (LMW) fragments, produced by enzymatic cleavage of HA, have different bioactive properties to high molecular weight (HMW) HA. Thus, the impact of HA must be assessed separately for each molecular weight fraction. In this study, we present the effect of three LMW-HA fragments (800, 1600, and 15,000 Da) on DPSCs in vitro. Discrete biological parameters such as DPSC viability, morphology, and cell surface marker expression were determined. Following treatment with LMW-HA, DPSCs initially presented with an acute reduction in proliferation (p < 0.0016) and soon recovered in subsequent passages. They displayed significant size reduction (p = 0.0078, p = 0.0019, p = 0.0098) while maintaining high expression of DPSC markers (CD29, CD44, CD73, CD90). However, in contrast to controls, a significant phenotypic shift (p < 0.05; CD29, CD34, CD90, CD106, CD117, CD146, CD166) of surface markers was observed. These findings provide a basis for further detailed investigations and present a strong argument for the importance of HA scaffold degradation kinetics analysis.

Biochemical and physical actions of hyaluronic acid delivered by intradermal jet injection route

Administration of exogenous hyaluronic acid (HA) by liquid jet injection is considered as a beneficial therapy for dermatology conditions. This paper reviews variety of the factors which would optimize the clinical output of hyaluronic acid in this treatment modality. A pneumatically accelerated jet penetrates the epidermis and spherically spreads micro-droplets of HA in the dermis without significant damage to the tissue and blood vessels. Kinetic energy of the jet activates two parallel mechanisms of action-mechanical and biological-which act synergistically to initiate and augment the regenerative effect. Jet-induced micro-trauma stimulates collagen synthesis and tissue repair without inflammation. Aside from the biophysical stimulation of dermal fibroblast, the biomolecular properties of exogenous HA provide excellent clinical results for skin atrophy, remodeling of dermal scarring, and reverse formation of fibrotic tissue. The effect is mediated by HA-specific cell receptors and depends on molecular weight and the rheological properties of HA polymer. Skin mechanical properties play a key role in predicting HA dispersion patterns. Tolerability and safety of the treatment approach are determined by the jet's physical impact on the tissue and/or by the safety profile of the injected material. Although pneumatic jet delivery of a hyaluronic acid has a limited use in clinical practice, this treatment approach has a strong potential for extended implementation in esthetic dermatology. The synergistic mechanism has significant advantages of predictable and rapid clinical outcomes with a low discomfort. Additional well-designed investigations are required for establishing a scientific foundation and guidelines for this treatment modality.

An in vitro study to assess the effect of hyaluronan-based gels on muscle-derived cells: Highlighting a new perspective in regenerative medicine

Hyaluronan (HA) is a nonsulfated glycosaminoglycan that has been widely used for biomedical applications. Here, we have analyzed the effect of HA on the rescue of primary cells under stress as well as its potential to recover muscle atrophy and validated the developed model in vitro using primary muscle cells derived from rats. The potentials of different HAs were elucidated through comparative analyses using pharmaceutical grade a) high (HHA) and b) low molecular weight (LHA) hyaluronans, c) hybrid cooperative complexes (HCC) of HA in three experimental set-ups. The cells were characterized based on the expression of myogenin, a muscle-specific biomarker, and the proliferation was analyzed using Time-Lapse Video Microscopy (TLVM). Cell viability in response to H₂O₂ challenge was evaluated by 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, and the expression of the superoxide dismutase enzyme (SOD-2) was assessed by western blotting. Additionally, in order to establish an in vitro model of atrophy, muscle cells were treated with tumor necrosis factor-alpha (TNF-α), along with hyaluronans. The expression of Atrogin, MuRF-1, nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-kB), and Forkhead-box-(Fox)-O-3 (FoxO3a) was evaluated by western blotting to elucidate the molecular mechanism of atrophy. The results showed that HCC and HHA increased cell proliferation by 1.15 and 2.3 folds in comparison to un-treated cells (control), respectively. Moreover, both pre- and post-treatments of HAs restored the cell viability, and the SOD-2 expression was found to be reduced by 1.5 fold in HA-treated cells as compared to the stressed condition. Specifically in atrophic stressed cells, HCC revealed a noteworthy beneficial effect on the myogenic biomarkers indicating that it could be used as a promising platform for tissue regeneration with specific attention to muscle cell protection against stressful agents.

A bone matrix-simulating scaffold to alleviate replicative senescence of mesenchymal stem cells during long-term expansion

Replicative senescence during in vitro augmentation, which is mostly induced by the loss of physiological microenvironment, hinders the application of mesenchymal stem cells (MSCs) in the clinic. Here, we investigated whether MSCs senescence could be prevented by bio-scaffold mimicking the natural tissue matrix. Human umbilical cord mesenchymal stem cells (hUCMSCs) exhibited a senescent phenotype during a long-term passage in the conventional culture dish. To fabricate the bone matrix, a naturally based matrix composed of nano-hydroxyapatite/chitosan/poly lactide-co-glycolide (nHA/CS/PLGA) was produced. Long-term passage resulted in an obvious increase in the expression of senescence markers and a reduction in the expression of master genes involved in tissue regeneration. Functional assay confirmed that nHA/CS/PLGA scaffold preserved the proliferation and differentiation of hUCMSCs even after being passaged 27 times. Moreover, in vivo ectopic bone formation assay revealed that the bone formation of hUCMSCs cultured on the nano-scaffolds for the long term was as robust as the cells in the early passage. In summary, our results demonstrate that nHA/CS/PLGA scaffold effectively preserves the stemness and youth of hUCMSCs in the long-term passage. Taken advantage of its compatibility and bioactivity, nHA/CS/PLGA scaffold is of great potential in large-scale expansion of MSCs for stem cell therapy and tissue engineering.

Nanomaterials and Aging

As the proportion of the elderly population increases, more and more people suffer from aging-related diseases. Even if aging is inevitable, prolonging the time of healthy aging, delaying the progression of aging-related diseases, and the incidence of morbidity can greatly alleviate the pressure on individuals and society. Current research and exploration in the field of materials related to aging are expanding tremendously. Here, we present a summary of recent research in the field of nanomaterials relevant to aging. Some nanomaterials, such as silica nanomaterials (NMs) and carbon nanotubes, cause damage to the cells similar to aging processes. Other nanomaterials such as fullerenes and metalbased nanomaterials can protect the body from endogenous and exogenous harmful substances such as ROS by virtue of their excellent reducing properties. Another new type of nucleic acid nanomaterial, tetrahedral framework nucleic acids, works effectively against cell damage. This material selectively clears existing senescent cells in the tissue and thus prevents the development of the chronic inflammatory environment caused by senescent cells secreting senescence-associated secretory phenotype to the surroundings. We believe that nanomaterials have tremendous potential to advance the understanding and treatment of aging-related disorders, and today's research only represents the beginning stages.

Hyaluronan Induces a Mitochondrial Functional Switch in Fast-Proliferating Human Mesenchymal Stem

Background and Objectives

Hyaluronan preserves the proliferation and differentiation potential of mesenchymal stem cells. Supplementation of low-concentration hyaluronan (SHA) in stem cells culture medium increases its proliferative rate, whereas coated-surface hyaluronan (CHA) maintains cells in a slow-proliferating mode. We have previously demonstrated that in CHA, the metabolic proliferative state of stem cells was influenced by upregulating mitochondrial biogenesis and function. However, the effect of SHA on stem cells' energetic status remains unknown. In this study, we demonstrate the effect that low-concentration SHA at 0.001 mg/ml (SHA0.001) and high-concentration SHA at 5 mg/ml (SHA5) exert on stem cells' mitochondrial function compared with CHA and noncoated tissue culture surface (control).

Methods and Results

Fast-proliferating human placenta-derived mesenchymal stem cells (PDMSCs) cultured on SHA0.001 exhibited reduced mitochondrial mass, lower mitochondrial DNA copy number, and lower oxygen consumption rate compared with slow-proliferating PDMSCs cultured on CHA at 5.0 (CHA5) or 30 μg/cm² (CHA30). The reduced mitochondrial biogenesis observed in SHA0.001 was accompanied by a 2-fold increased ATP content and lactate production, suggesting that hyaluronan-induced fast-proliferating PDMSCs may rely less on mitochondrial function as an energy source and induce a mitochondrial functional switch to glycolysis.

Conclusions

PDMSCs cultured on both CHA and SHA exhibited a reduction in reactive oxygen species levels. The results from this study clarify our understandings on the effect of hyaluronan on stem cells and provide important insights into the effect of distinct supplementation methods used during cell therapies.

Hyaluronic Acid (HA), Platelet-Rich Plasm and Extracorporeal Shock Wave Therapy (ESWT) promote human chondrocyte regeneration in vitro and ESWT-mediated increase of CD44 expression enhances their susceptibility to HA treatment

Novel strategies have been proposed for articular cartilage damage occurring during osteoarthritis (OA) and -among these- Extracorporeal Shock Wave Therapy (ESWT), intra-articular injections of Platelet-Rich Plasma (PRP) or Hyaluronic Acid (HA) revealed encouraging results. To investigate the possible mechanisms responsible for those clinical benefits, we established primary cultures of human chondrocytes derived from cartilage explants and measured the in vitro effects of ESW, PRP and HA therapies. After molecular/morphological cell characterization, we assessed those effects on the functional activities of the chondrocyte cell cultures, at the protein and molecular levels. ESWT significantly prevented the progressive dedifferentiation that spontaneously occurs during prolonged chondrocyte culture. We then attested the efficiency of all such treatments to stimulate the expression of markers of chondrogenic potential such as SOX9 and COL2A, to increase the Ki67 proliferation index as well as to antagonize the traditional marker of chondrosenescence p16INK4a (known as Cdkn2a). Furthermore, all our samples showed an ESW- and HA-mediated enhancement of migratory and anti-inflammatory activity onto the cytokine-rich environment characterizing OA. Taken together, those results suggest a regenerative effect of such therapies on primary human chondrocytes in vitro. Moreover, we also show for the first time that ESW treatment induces the surface expression of major hyaluronan cell receptor CD44 allowing the increase of COL2A/COL1A ratio upon HA administration. Therefore, this work suggests that ESW-induced CD44 overexpression enhances the in vitro cell susceptibility of human chondrocytes to HA, presumably favouring the repair of degenerated cartilage.

Identification of senescent cells in multipotent mesenchymal stromal cell cultures: Current methods and future directions

Regardless of their tissue of origin, multipotent mesenchymal stromal cells (MSCs) are commonly expanded in vitro for several population doublings to achieve a sufficient number of cells for therapy. Prolonged MSC expansion has been shown to result in phenotypical, morphological and gene expression changes in MSCs, which ultimately lead to the state of senescence. The presence of senescent cells in therapeutic MSC batches is undesirable because it reduces their viability, differentiation potential and trophic capabilities. Additionally, senescent cells acquire senescence-activated secretory phenotype, which may not only induce apoptosis in the neighboring host cells following MSC transplantation, but also trigger local inflammatory reactions. This review outlines the current and promising new methodologies for the identification of senescent cells in MSC cultures, with a particular emphasis on non-destructive and label-free methodologies. Technologies allowing identification of individual senescent cells, based on new surface markers, offer potential advantage for targeted senescent cell removal using new-generation senolytic agents, and subsequent production of therapeutic MSC batches fully devoid of senescent cells. Methods or a combination of methods that are non-destructive and label-free, for example, involving cell size and spectroscopic measurements, could be the best way forward because they do not modify the cells of interest, thus maximizing the final output of therapeutic-grade MSC cultures. The further incorporation of machine learning methods has also recently shown promise in facilitating, automating and enhancing the analysis of these measured data.

Novel Hybrid Gels Made of High and Low Molecular Weight Hyaluronic Acid Induce Proliferation and Reduce Inflammation in an Osteoarthritis In Vitro Model Based on Human Synoviocytes and Chondrocytes

High molecular weight hyaluronan (H-HA) has a pivotal role in the maintenance of normal functions of synovial fluid and structure of the articular joint, but it has been shown that its concentration is reduced in patients affected by degenerative cartilage diseases, such as osteoarthritis (OA). The aim of this study was to investigate the anti-inflammatory effects and properties of hybrid cooperative complexes based on high and low molecular weight hyaluronan (HCC) compared to H-HA on human primary cells derived by pathological joints. In addition, the rheological behavior of HCC was evaluated in order to define their potential as viscosupplement gel in degenerated joints. The experiments were performed using an in vitro model of OA based on human chondrocytes and synoviocytes isolated from degenerated joints of patients hospitalized for surgical replacement. In order to assess the anti-inflammatory effects of HCC, we evaluated NF-kB, COMP-2, IL-6, and IL-8 as specific markers at the transcriptional and/or protein level. Moreover, the proliferative properties of HCC were assessed using time lapse video microscopy. We showed that chondrocytes and synoviocytes clearly presented an altered cytokine profile compatible with a severe ongoing inflammation status. H-HA and, above all, HCC significantly reduced levels of the specific biomarkers evaluated and improved cartilage healing. The rheological profile indicated HCC suitability for intra-articular injection in joint diseases. HCC viscoelastic properties and the protective/anti-inflammatory effect on human chondrocytes and synoviocytes suggest the novel HCC-based gels as a valid support for OA management.