Donor age effects on in vitro chondrogenic and osteogenic differentiation performance of equine bone marrow- and adipose tissue-derived mesenchymal stromal cells

Mesenchymal stromal/stem cell tissue source and in vitro expansion impact extracellular vesicle protein and miRNA compositions as well as angiogenic and immunomodulatory capacities

Recently, therapies utilizing extracellular vesicles (EVs) derived from mesenchymal stromal/stem cells (MSCs) have begun to show promise in clinical trials. However, EV therapeutic potential varies with MSC tissue source and in vitro expansion through passaging. To find the optimal MSC source for clinically translatable EV-derived therapies, this study aims to compare the angiogenic and immunomodulatory potentials and the protein and miRNA cargo compositions of EVs isolated from the two most common clinical sources of adult MSCs, bone marrow and adipose tissue, across different passage numbers. Primary bone marrow-derived MSCs (BMSCs) and adipose-derived MSCs (ASCs) were isolated from adult female Lewis rats and expanded in vitro to the indicated passage numbers (P2, P4, and P8). EVs were isolated from the culture medium of P2, P4, and P8 BMSCs and ASCs and characterized for EV size, number, surface markers, protein content, and morphology. EVs isolated from different tissue sources showed different EV yields per cell, EV sizes, and protein yield per EV. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses of proteomics data and miRNA seq data identified key proteins and pathways associated with differences between BMSC-EVs and ASC-EVs, as well as differences due to passage number. In vitro tube formation assays employing human umbilical vein endothelial cells suggested that both tissue source and passage number had significant effects on the angiogenic capacity of EVs. With or without lipopolysaccharide (LPS) stimulation, EVs more significantly impacted expression of M2-macrophage genes (IL-10, Arg1, TGFβ) than M1-macrophage genes (IL-6, NOS2, TNFα). By correlating the proteomics analyses with the miRNA seq analysis and differences observed in our in vitro immunomodulatory, angiogenic, and proliferation assays, this study highlights the trade-offs that may be necessary in selecting the optimal MSC source for development of clinical EV therapies.

Microfragmented abdominal adipose tissue-derived stem cells from knee osteoarthritis patients aged 29-65 years demonstrate in vitro stemness and low levels of cellular senescence

Purpose

To investigate the level of cellular senescence in stem cells derived from microfragmented abdominal adipose tissue harvested from patients with knee osteoarthritis (OA).

Methods

Stem cells harvested from microfragmented abdominal adipose tissue from 20 patients with knee OA, aged 29-65 years (mean = 49.8, SD = 9.58), were analysed as a function of patient age and compared with control cells exhibiting signs of cellular senescence. Steady-state mRNA levels of a panel of genes associated with senescence were measured by qPCR. Intracellular senescence-associated proteins p16 and p21, and senescence-associated β-galactosidase activity were measured by flow cytometry. Cellular proliferation was assessed using a 5-ethynyl-2'-deoxyuridine proliferation assay. Stemness was assessed by stem cell surface markers using flow cytometry and the capacity to undergo adipogenic and osteogenic differentiation in vitro.

Results

No correlation was found between cellular senescence levels of the microfragmented adipose tissue-derived stem cells and patient age for any of the standard assays used to quantify senescence. The level of cellular senescence was generally low across all senescence-associated assays compared to the positive senescence control. Stemness was verified for all samples. An increased capacity to undergo adipogenic differentiation was shown with increasing patient age (p = 0.02). No effect of patient age was found for osteogenic differentiation.

Conclusions

Autologous microfragmented adipose tissue-derived stem cells may be used in clinical trials of knee OA of patients aged 29-65 years, at least until passage 4, as they show stemness potential and negligible senescence in vitro.

Level of Evidence

Not applicable.

Bone Marrow Stimulation Does Not Lead to Lower Retear Rates, Better Functional Outcomes, or Higher Complication Rates at Short-Term Follow-Up for Arthroscopic Rotator Cuff Repair: A Meta-analysis of Randomized Controlled Trials

PURPOSE

To determine the effect of bone marrow stimulation (BMS) on retear rates, functional outcomes, and complication rates in patients who underwent arthroscopic rotator cuff repair (RCR) through a meta-analysis of randomized controlled trials.

METHODS

PubMed, EMBASE, Web of Science, and The Cochrane Library were searched on March 25, 2023. Two evaluators independently screened the literature, extracted data, and assessed the methodologic quality of the enrolled studies. Meta-analysis was conducted using RevMan software, version 5.4.

RESULTS

A total of 7 randomized controlled trials with 638 patients were included. The evaluation of rotator cuff tendon integrity was conducted using distinct imaging modalities. Specifically, 259 patients underwent magnetic resonance imaging whereas 208 patients underwent ultrasound. Additionally, a subset of 95 patients underwent either of these modalities; however, the precise distribution between these 2 modalities was not explicitly delineated. Compared with RCR alone, RCR combined with BMS provided similar retear rates (P = .51, I2 = 46%), Constant-Murley scores (P = .14, I2 = 0%), American Shoulder and Elbow Surgeons (standardized shoulder assessment form) scores (P = .56, I2 = 0%), Western Ontario Rotator Cuff Index scores (P = .20, I2 = 0%), visual analog scale scores (P = .19, I2 = 0%), forward flexion (P = .18, I2 = 0%), external rotation (P = .62, I2 = 0%), severe complication rates (P = .56, I2 = 0%), and mild complication rates (P = .10, I2 = 0%).

CONCLUSIONS

Compared with the outcomes observed after isolated arthroscopic RCR, arthroscopic RCR with BMS showed comparable results in terms of retear rate, functional outcomes, and incidence of complications.

LEVEL OF EVIDENCE

Level II, meta-analysis of Level I and II studies.

Proteoglycans in Mechanobiology of Tissues and Organs: Normal Functions and Mechanopathology

Proteoglycans (PGs) are a diverse class of glycoconjugates that serve critical functions in normal mechanobiology and mechanopathology. Both the protein cores and attached glycosaminoglycan (GAG) chains function in mechanically-sensitive processes, and loss of either can contribute to development of pathological conditions. PGs function as key components of the extracellular matrix (ECM) where they can serve as mechanosensors in mechanosensitive tissues including bone, cartilage, tendon, blood vessels and soft organs. The mechanical properties of these tissues depend on the presence and function of PGs, which play important roles in tissue elasticity, osmolarity and pressure sensing, and response to physical activity. Tissue responses depend on cell surface mechanoreceptors that include integrins, CD44, voltage sensitive ion channels, transient receptor potential (TRP) and piezo channels. PGs contribute to cell and molecular interplay in wound healing, fibrosis, and cancer, where they transduce the mechanical properties of the ECM and influence the progression of various context-specific conditions and diseases. The PGs that are most important in mechanobiology vary depending on the tissue and its functions and functional needs. Perlecan, for example, is important in the mechanobiology of basement membranes, cardiac and skeletal muscle, while aggrecan plays a primary role in the mechanical properties of cartilage and joints. A variety of techniques have been used to study the mechanobiology of PGs, including atomic force microscopy, mouse knockout models, and in vitro cell culture experiments with 3D organoid models. These studies have helped to elucidate the tissue-specific roles that PGs play in cell-level mechanosensing and tissue mechanics. Overall, the study of PGs in mechanobiology is yielding fundamental new concepts in the molecular basis of mechanosensing that can open the door to the development of new treatments for a host of conditions related to mechanopathology.

Interactions Between Biologic Therapies and Other Treatment Modalities

Biologic therapies are becoming increasingly utilized by veterinarians. The literature regarding the interaction of biologic therapies with other therapeutics is still in its infancy. Initial studies have examined the effects of exercise, stress, various pharmaceutical interventions, extracorporeal shockwave, therapeutic laser, and hyperbaric oxygen on biologic therapies. Continued research is imperative as owners and veterinarians increasingly choose a multimodal approach to injury and illness. Further, understanding the effects of concurrently administered treatments and pharmaceuticals as well as the health status of the horse is imperative to providing the optimal therapeutic outcome.

Overview of Equine Stem Cells: Sources, Practices, and Potential Safety Concerns

Over the past 2 decades, equine veterinarians are turning increasingly to stem cell therapies to repair damaged tissues or to promote healing through modulation of the immune system. Research is ongoing into optimizing practices associated with stem cell product transport, dosage, and administration. Culture-expanded equine mesenchymal stem cell therapies seem safe, even when used allogeneically, but various safety concerns should be considered. Stem cells and cellular reprogramming tools hold great promise for future equine therapies.

Influence of the Anatomical Site on Adipose Tissue-Derived Stromal Cells' Biological Profile and Osteogenic Potential in Companion Animals

Adipose tissue-derived stromal cells (ADSCs) have generated considerable interest in the field of veterinary medicine, particularly for their potential in therapeutic strategies focused on bone regeneration. These cells possess unique biological characteristics, including their regenerative capacity and their ability to produce bioactive molecules. However, it is crucial to recognize that the characteristics of ADSCs can vary depending on the animal species and the site from which they are derived, such as the subcutaneous and visceral regions (SCAT and VAT, respectively). Thus, the present work aimed to comprehensively review the different traits of ADSCs isolated from diverse anatomical sites in companion animals, i.e., dogs, cats, and horses, in terms of immunophenotype, morphology, proliferation, and osteogenic differentiation potential. The findings indicate that the immunophenotype, proliferation, and osteogenic potential of ADSCs differ according to tissue origin and species. Generally, the proliferation rate is higher in VAT-derived ADSCs in dogs and horses, whereas in cats, the proliferation rate appears to be similar in both cells isolated from SCAT and VAT regions. In terms of osteogenic differentiation potential, VAT-derived ADSCs demonstrate the highest capability in cats, whereas SCAT-derived ADSCs exhibit superior potential in horses. Interestingly, in dogs, VAT-derived cells appear to have greater potential than those isolated from SCAT. Within the VAT, ADSCs derived from the falciform ligament and omentum show increased osteogenic potential, compared to cells isolated from other anatomical locations. Consequently, considering these disparities, optimizing isolation protocols becomes pivotal, tailoring them to the specific target species and therapeutic aims, and judiciously selecting the anatomical site for ADSC isolation. This approach holds promise to enhance the efficacy of ADSCs-based bone regenerative therapies.

Successful isolation of viable stem cells from cryopreserved microfragmented human adipose tissue from patients with knee osteoarthritis - a comparative study of isolation by tissue explant culture and enzymatic digestion

PURPOSE

To investigate if viable stem cells could be isolated and expanded from cryopreserved microfragmented adipose tissue (AT) harvested from patients with knee osteoarthritis.

METHODS

Microfragmented abdominal AT from knee osteoarthritis patients was cryopreserved at -80 °C in cryoprotectant-medium. The samples were thawed for stem cell isolation by tissue explant culture (TEC) and enzymatic digestion (ED), respectively. Viability, population doublings, and doubling time were assessed by trypan blue staining and flow cytometry. Cell type and senescence-associated β-galactosidase activity were analyzed by flow cytometry. Osteogenic and adipogenic differentiation was assessed quantitatively by Alizarin-Red-S and Oil-Red-O staining, respectively.

RESULTS

Microfragmented AT from 7 patients was cryopreserved for a period of 46-150 days (mean (SD) 115.9 days (44.3 days)). Viable stem cells were successfully recovered and expanded from all patients using both isolation methods with no significant difference in viable population doublings or doubling time from passage 1 to 3 (p > 0.05). Low levels of senescence-associated β-galactosidase activity was detected for both methods with no significant difference between TEC and ED (p = 0.17). Stemness was verified by stem cell surface markers and osteogenic and adipogenic differentiation performance. Adventitial stem cells (CD31^-CD34⁺CD45^-CD90⁺CD146^-), pericytes (CD31^-CD34^-CD45^-CD90⁺CD146⁺), transitional pericytes (CD31^-CD34⁺CD45^-CD90⁺CD146⁺), and CD271⁺ stem cells (CD31^-CD45^-CD90⁺CD271⁺) were identified using both methods. More pericytes were present when using TEC (25% (24%)) compared to ED (3% (2%)) at passage 4 (p = 0.04).

CONCLUSIONS

Viable stem cells can be isolated and expanded from cryopreserved microfragmented AT using both TEC and ED. TEC provides more clinically relevant pericytes than ED.

Use of Brain-Derived Stem/Progenitor Cells and Derived Extracellular Vesicles to Repair Damaged Neural Tissues: Lessons Learned from Connective Tissue Repair Regarding Variables Limiting Progress and Approaches to Overcome Limitations

Pluripotent neural stem or progenitor cells (NSC/NPC) have been reported in the brains of adult preclinical models for decades, as have mesenchymal stem/stromal cells (MSC) been reported in a variety of tissues from adults. Based on their in vitro capabilities, these cell types have been used extensively in attempts to repair/regenerate brain and connective tissues, respectively. In addition, MSC have also been used in attempts to repair compromised brain centres. However, success in treating chronic neural degenerative conditions such as Alzheimer's disease, Parkinson's disease, and others with NSC/NPC has been limited, as have the use of MSC in the treatment of chronic osteoarthritis, a condition affecting millions of individuals. However, connective tissues are likely less complex than neural tissues regarding cell organization and regulatory integration, but some insights have been gleaned from the studies regarding connective tissue healing with MSC that may inform studies attempting to initiate repair and regeneration of neural tissues compromised acutely or chronically by trauma or disease. This review will discuss the similarities and differences in the applications of NSC/NPC and MSC, where some lessons have been learned, and potential approaches that could be used going forward to enhance progress in the application of cellular therapy to facilitate repair and regeneration of complex structures in the brain. In particular, variables that may need to be controlled to enhance success are discussed, as are different approaches such as the use of extracellular vesicles from stem/progenitor cells that could be used to stimulate endogenous cells to repair the tissues rather than consider cell replacement as the primary option. Caveats to all these efforts relate to whether cellular repair initiatives will have long-term success if the initiators for neural diseases are not controlled, and whether such cellular initiatives will have long-term success in a subset of patients if the neural diseases are heterogeneous and have multiple etiologies.

Immunosenescence and inflammaging in the aged horse

The equine population in the United States and worldwide now includes a higher percentage of geriatric horses than ever previously recorded, and as methods to treat and manage elderly equids are developed and refined, this aging population will likely continue to expand. A better understanding of how horses age and the effect of age on immunity and disease susceptibility is needed to enable targeted preventative healthcare strategies for aged horses. This review article outlines the current state of knowledge regarding the effect of aging on immunity, vaccine responsiveness, and disease risk in the horse, highlighting similarities and differences to what is observed in aged humans. Horses show similar but milder age-related alterations in immune function to those reported in people. Decreases in lymphocyte proliferation and antibody production and diminished response to vaccination have all been documented in elderly horses, however, increased risk of infectious disease is not commonly reported. Aged horses also show evidence of a proinflammatory state (inflammaging) yet appear less susceptible to the chronic diseases of people for which inflammation is a risk factor. Information is currently lacking as to why the horse does not experience the same risk of age-related disease (e.g., cancer, heart disease, neurodegeneration) as people, although a lack of negative lifestyle habits, differences in diet, exercise, genetics and physiology may all contribute to improved health outcomes in the older horse.