Synovial mesenchymal stem cells in vivo: Potential key players for joint regeneration

The Hunt Is On! In Pursuit of the Ideal Stem Cell Population for Cartilage Regeneration

Cartilage injury and degeneration are hallmarks of osteoarthritis (OA), the most common joint disease. OA is a major contributor to pain, loss of function, and reduced quality of life. Over the last decade, considerable research efforts have focused on cell-based therapies, including several stem cell-derived approaches to reverse the cartilage alterations associated with OA. Although several tissue sources for deriving cell-based therapies have been identified, none of the resident stem cell populations have adequately fulfilled the promise of curing OA. Indeed, many cell products do not contain true stem cells. As well, issues with aggressive marketing efforts, combined with a lack of evidence regarding efficacy, lead the several national regulatory bodies to discontinue the use of stem cell therapy for OA until more robust evidence becomes available. A review of the evidence is timely to address the status of cell-based cartilage regeneration. The promise of stem cell therapy is not new and has been used successfully to treat non-arthritic diseases, such as hematopoietic and muscle disorders. These fields of regenerative therapy have the advantage of a considerable foundation of knowledge in the area of stem cell repair mechanisms, the role of the stem cell niche, and niche-supporting cells. This foundation is lacking in the field of cartilage repair. So, where should we look for the ideal stem cell to regenerate cartilage? It has recently been discovered that cartilage itself may contain a population of SC-like progenitors. Other potential tissues include stem cell-rich dental pulp and the adolescent growth plate, the latter of which contains chondrocyte progenitors essential for producing the cartilage scaffold needed for bone growth. In this article, we review the progress on stem cell therapies for arthritic disorders, focusing on the various stem cell populations previously used for cartilage regeneration, successful cases of stem cell therapies in muscle and hemopoietic disorders, some of the reasons why these other fields have been successful (i.e., "lessons learned" to be applied to OA stem cell therapy), and finally, novel potential sources of stem cells for regenerating damaged cartilage in vivo.

Donor-matched comparison of chondrogenic progenitors resident in human infrapatellar fat pad, synovium, and periosteum - implications for cartilage repair

Purpose: There is a clinical need to better characterize tissue sources being used for stem cell therapies. This study focuses on comparison of cells and connective tissue progenitors (CTPs) derived from native human infrapatellar fatpad (IPFP), synovium (SYN), and periosteum (PERI). Materials and Methods: IPFP, SYN, PERI were harvested from twenty-eight patients undergoing arthroplasty. CTPs were quantitatively characterized using automated colony-forming-unit assay to compare total nucleated cell concentration-[Cell], cells/mg; prevalence-(P_CTP), CTPs/million nucleated cells; CTP concentration-[CTP], CTPs/mg; proliferation and differentiation potential; and correlate outcomes with patient's age and gender. Results: [Cell] did not differ between IPFP, SYN, and PERI. P_CTP was influenced by age and gender: patients >60 years, IPFP and SYN had higher P_CTP than PERI (p < 0.001) and females had higher P_CTP in IPFP (p < 0.001) and SYN (p = 0.001) than PERI. [CTP] was influenced by age: patients <50 years, SYN (p = 0.0165) and PERI (p < 0.001) had higher [CTP] than IPFP; patients between 60 and 69 years, SYN (p < 0.001) had higher [CTP] than PERI; patients >70 years, IPFP (p = 0.006) had higher [CTP] than PERI. In patients >60 years, proliferation potential of CTPs differed significantly (SYN>IPFP>PERI); however, differentiation potentials were comparable between all three tissue sources. Conclusion: SYN and IPFP may serve as a preferred tissue source for patients >60 years, and PERI along with SYN and IPFP may serve as a preferred tissue source for patients <60 years for cartilage repair. However, the heterogeneity among the CTPs in any given tissue source suggests performance-based selection might be useful to optimize cell-sourcing strategies to improve efficacy of cellular therapies for cartilage repair.

Tendon contains more stem cells than bone at the rotator cuff repair site

BACKGROUND

The rotator cuff (RC) repair failure rate is high. Tendon and bone represent sources of mesenchymal stem cells (MSCs), but the number of MSCs from each has not been compared. Bone channeling may increase bone-derived MSC numbers participating in enthesis re-formation at the "footprint" repair site. The effect of preoperative channeling on increasing bone MSC numbers has never been reported. We asked (1) whether bone contains more MSCs than tendon at the time of arthroscopic repair and (2) whether bone preoperative channeling at the RC repair site increases the number of bone-derived MSCs at the time of surgery.

METHODS

In 23 participants undergoing arthroscopic RC repair, bone was sampled from the footprint and tendon was sampled from the distal supraspinatus. We randomized participants to the channeling or no-channeling group 5 to 7 days before surgery. We enumerated MSCs from both tissues using the colony-forming unit-fibroblast (CFU-F) assay (10 per group). We identified MSC identity using flow cytometry and MSC tri-differentiation capacity (n = 3).

RESULTS

Tendon CFU-F per gram exceeded bone CFU-F per gram for both groups (479 ± 173 CFU-F/g vs. 162 ± 54 CFU-F/g for channeling [P = .036] and 1334 ± 393 CFU-F/g vs. 284 ± 88 CFU-F/g for no channeling [P = .009]). Ninety-nine percent of cultured cells satisfied the MSC definition criteria.

CONCLUSIONS

The distal supraspinatus tendon contained more MSCs per gram than the humeral footprint. Tendon may represent an important and overlooked MSC source for postoperative enthesis re-formation. Further studies are needed to evaluate the repair role of tendon MSCs and to recommend bone channeling in RC repair.

Transplantation of human skeletal muscle-derived progenitor cells ameliorates knee osteoarthritis in streptozotocin-induced diabetic mice

The epidemiological and experimental evidence suggests that diabetes can be an independent risk factor for osteoarthritis. The osteoarthritis-like cartilage damage has been shown in streptozotocin-induced diabetic mice. The therapeutic effects of human skeletal muscle-derived progenitor cells (HSMPCs) on diabetic osteoarthritis still remain unclear. Here, we investigated the therapeutic potential of HSMPCs on diabetic knee osteoarthritis. The in vitro chondrogenic ability of HSMPCs was determined by pellet culture assay. Male mice were used to develop the model of streptozotocin-induced type 1 diabetes and its related osteoarthritis. HSMPCs were injected intra-articularly to rescue osteoarthritis. Protein expressions of advanced glycation end-products, cyclooxygenase-2, and type-2 collagen in tissues were determined by immunohistochemistry. The pellet culture assay showed that HSMPCs cultured in differentiation medium for chondrogenesis significantly produced larger pellets with an overproduction of extracellular matrix than in growth medium. In in vivo experiments, intra-articular injection of HSMPCs for 4 weeks significantly prevented the progression of degenerative changes in the cartilage of streptozotocin-induced diabetic mice, including an obvious increase of total articular cartilage thickness and a decrease of fibrous cartilage thickness. HSMPCs transplantation also exerted the decline in advanced glycation end-products and cyclooxygenase-2 protein expression, but increased the type-2 collagen protein expression in streptozotocin-induced osteoarthritic cartilages. Moreover, HSMPCs transplantation also inhibited the increased serum interleukin-6 and matrix metalloproteinase-3 levels in diabetic mice. These results demonstrated for the first time that HSMPCs transplantation ameliorates cartilage degeneration in diabetes-related osteoarthritis mice. These findings suggest that HSMPCs transplantation may apply as a potential therapeutic use of diabetes-related osteoarthritis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1886-1893, 2017.

Comparative study of equine mesenchymal stem cells from healthy and injured synovial tissues: an in vitro assessment

Background

Bone marrow and adipose tissues are known sources of mesenchymal stem cells (MSCs) in horses; however, synovial tissues might be a promising alternative. The aim of this study was to evaluate phenotypic characteristics and differentiation potential of equine MSCs from synovial fluid (SF) and synovial membrane (SM) of healthy joints (SF-H and SM-H), joints with osteoarthritis (SF-OA and SM-OA) and joints with osteochondritis dissecans (SF-OCD and SM-OCD) to determine the most suitable synovial source for an allogeneic therapy cell bank.

Methods

Expression of the markers CD90, CD105, CD44, and CD34 in SF-H, SM-H, SF-OA, SM-OA, SF-OCD and SM-OCD was verified by flow cytometry, and expression of cytokeratin, vimentin, PGP 9.5, PCNA, lysozyme, nanog, and Oct4 was verified by immunocytochemistry. MSCs were cultured and evaluated for their chondrogenic, osteogenic and adipogenic differentiation potential. Final quantification of extracellular matrix and mineralized matrix was determined using AxioVision software. A tumorigenicity test was conducted in Balb-C^nu/nu mice to verify the safety of the MSCs from these sources.

Results

Cultured cells from SF and SM exhibited fibroblastoid morphology and the ability to adhere to plastic. The time elapsed between primary culture and the third passage was approximately 73 days for SF-H, 89 days for SF-OCD, 60 days for SF-OA, 68 days for SM-H, 57 days for SM-OCD and 54 days for SM-OA. The doubling time for SF-OCD was higher than that for other cells at the first passage (P < 0.05). MSCs from synovial tissues showed positive expression of the markers CD90, CD44, lysozyme, PGP 9.5, PCNA and vimentin and were able to differentiate into chondrogenic (21 days) and osteogenic (21 days) lineages, and, although poorly, into adipogenic lineages (14 days). The areas staining positive for extracellular matrix in the SF-H and SM-H groups were larger than those in the SF-OA and SM-OA groups (P < 0.05). The positive mineralized matrix area in the SF-H group was larger than those in all the other groups (P < 0.05). The studied cells exhibited no tumorigenic effects.

Conclusions

SF and SM are viable sources of equine MSCs. All sources studied provide suitable MSCs for an allogeneic therapy cell bank; nevertheless, MSCs from healthy joints may be preferable for cell banking purposes because they exhibit better chondrogenic differentiation capacity.

Multipotent mesenchymal stem cells from human subacromial bursa: potential for cell based tendon tissue engineering

Rotator cuff injuries are a common clinical problem either as a result of overuse or aging. Biological approaches to tendon repair that involve use of scaffolding materials or cell-based approaches are currently being investigated. The cell-based approaches are focused on applying multipotent mesenchymal stem cells (MSCs) mostly harvested from bone marrow. In the present study, we focused on characterizing cells harvested from tissues associated with rotator cuff tendons based on an assumption that these cells would be more appropriate for tendon repair. We isolated MSCs from bursa tissue associated with rotator cuff tendons and characterized them for multilineage differentiation in vitro and in vivo. Human bursa was obtained from patients undergoing rotator cuff surgery and cells within were isolated using collagenase and dispase digestion. The cells isolated from the tissues were characterized for osteoblastic, adipogenic, chondrogenic, and tenogenic differentiation in vitro and in vivo. The results showed that the cells isolated from bursa tissue exhibited MSCs characteristics as evidenced by the expression of putative cell surface markers attributed to MSCs. The cells exhibited high proliferative capacity and differentiated toward cells of mesenchymal lineages with high efficiency. Bursa-derived cells expressed markers of tenocytes when treated with bone morphogenetic protein-12 (BMP-12) and assumed aligned morphology in culture. Bursa cells pretreated with BMP-12 and seeded in ceramic scaffolds formed extensive bone, as well as tendon-like tissue in vivo. Bone formation was demonstrated by histological analysis and immunofluorescence for DMP-1 in tissue sections made from the scaffolds seeded with the cells. Tendon-like tissue formed in vivo consisted of parallel collagen fibres typical of tendon tissues. Bursa-derived cells also formed a fibrocartilagenous tissue in the ceramic scaffolds. Taken together, the results demonstrate a new source of MSCs with a high potential for application in tendon repair.

Isolation, characterization, and differentiation of stem cells for cartilage regeneration

The goal of tissue engineering is to create a functional replacement for tissues damaged by injury or disease. In many cases, impaired tissues cannot provide viable cells, leading to the investigation of stem cells as a possible alternative. Cartilage, in particular, may benefit from the use of stem cells since the tissue has low cellularity and cannot effectively repair itself. To address this need, researchers are investigating the chondrogenic capabilities of several multipotent stem cell sources, including adult and extra-embryonic mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and induced pluripotent stem cells (iPSCs). Comparative studies indicate that each cell type has advantages and disadvantages, and while direct comparisons are difficult to make, published data suggest some sources may be more promising for cartilage regeneration than others. In this review, we identify current approaches for isolating and chondrogenically differentiating MSCs from bone marrow, fat, synovium, muscle, and peripheral blood, as well as cells from extra-embryonic tissues, ESCs, and iPSCs. Additionally, we assess chondrogenic induction with growth factors, identifying standard cocktails used for each stem cell type. Cell-only (pellet) and scaffold-based studies are also included, as is a discussion of in vivo results.