The addition of mesenchymal stem cells in a bioabsorbable scaffold does not enhance tendon healing after a repair of rotator cuff tear.

PURPOSE: The purpose of the study is to evaluate the healing potential of a full-thickness tendon defect in the rotator cuff of rabbits using a bioabsorbable scaffold impregnated with bone marrow-mesenchymal stem cells (BM-MSCs) or rotator cuff-derived mesenchymal stem cells (RC-MSCs). METHODS: Sixteen adult rabbits were subjected to a full-thickness rotator cuff deficit. Rabbits were randomly assigned to four groups of four animals. In Group 0 (control), the deficit was left untreated. In Group 1, the deficit was treated with a single synthetic scaffold alone. In Group 2, the deficit was treated with the previous scaffold loaded with allogeneic BM-MSCs. In Group 3, the deficit was treated with the previous scaffold loaded with allogenic RC-MSCs. After animal sacrifice, tissue samples were subjected to histological and immunohistochemical analysis. RESULTS: Group 1 showed the highest mean tendon maturing score (15.3 ± 0.9) postoperatively, being significantly higher, in comparison to groups 0, 2 and 3 (p = 0.01, 0.02 and 0.01, respectively). Group 1 showed the highest mean collagen I/collagen III ratio (1.4 ± 0.8) postoperatively but without any statistical significance. CONCLUSIONS: The utilization of MSCs in rotator cuff repair in a rabbit model has not been associated with an enhancement in tendon healing in 16 weeks postoperatively, in comparison to controls and bioabsorbable scaffolds. The addition of MSCs does not result in better rotator cuff healing. LEVEL OF EVIDENCE: Not applicable. This is an animal study.

Adipose-Derived Stem Cells and Tacrolimus Improve Nerve Regeneration in a Rat Sciatic Nerve Defect Model.

This study compared the effect of undifferentiated adipose-derived stem cells (ADSCs) vs tacrolimus (FK506) in peripheral nerve regeneration in a rat sciatic nerve complete transection model. Forty Wistar rats were equally distributed in four groups. In the SHAM surgery group, the sciatic nerve was exposed and no further intervention was done. In the conduit-alone group (the SLN group), a 10-mm nerve gap was created and bridged with a fibrin conduit filled in with normal saline. In the FK506 group, the fibrin conduit was injected with soluble FK506. In the ADSC group, the conduit was impregnated with undifferentiated ADSCs. Nerve regeneration was assessed by means of walking track analysis, electromyography, and neurohistomorphometry. Clinically and microscopically, nerve regeneration was achieved in all groups at 12 weeks. Walking track analysis confirmed functional recovery in the FK506 and ADSC groups, but there was no difference between them. Recovery in function was also achieved in the SLN group, but it was inferior (P<.05). Electromyography demonstrated superior nerve regeneration in the FK506 and ADSC groups compared with the SLN group (P<.05), with no difference between the FK506 and ADSC groups. Similarly, histology showed no difference between the FK506 and ADSC groups, although both outperformed the SLN group (P<.05). No complications were observed. Successful peripheral nerve regeneration can be accomplished after a 10-mm nerve defect treated with nerve conduits. Superior nerve regeneration may be expected when the conduits are loaded with undifferentiated ADSCs or FK506, with similar outcomes for ADSCs and FK506. [Orthopedics. 2023;46(6):e353-e361.].

Superiority of synovial membrane mesenchymal stem cells in chondrogenesis, osteogenesis, myogenesis and tenogenesis in a rabbit model.

Engineering complex tissues is perhaps the most ambitious goal of all tissue engineers. Despite significant advances in tissue engineering, which have resulted in successful engineering of simple tissues such as skin and cartilage, there are a number of challenges that remain in engineering of complex, hybrid tissue structures, such as osteochondral tissue. Mesenchymal stem cells (MSCs) have the capacity to highly proliferate in an undifferentiated state and the potential to differentiate into a variety of different lineages, providing a promising single cell source to produce multiple cell types. MSC obtained from adult human contribute to the regeneration of mesenchymal tissues such as bone, cartilage, fat, muscle, tendon and marrow stroma. In the present study, the regeneration capacity of multipotent MSCs derived from different tissues in the rabbit were compared. Specifically the aim of this study was to isolate and characterize rabbit adult stem cell populations from bone marrow, adipose, synovial membrane, rotator cuff, ligament and tendon and assess their cell morphology, growth rate, cell surface markers and differentiation capacity. MSCs derived from synovial membrane showed superiority in terms of chondrogenesis, osteogenesis, myogenesis and tenogenesis, suggesting that synovial membrane-derived MSCs would be a good candidate for efforts to regenerate musculoskeletal tissues.

Harvesting, Isolation and Differentiation of Rat Adipose-Derived Stem Cells.

BACKGROUND: Adipose tissue is one of the most attractive sources of stem cells because it can be easily harvested and yields a greater stromal cell density. The multilineage potential of adiposederived stem cells (ADSCs) demonstrates their significant impact within the field of tissue engineering, with studies successfully demonstrating the ability to produce a range of tissue types. However, although a broad spectrum of applications has already been suggested, many important scientific and medical questions remain unanswered before the clinical application of ADSCs in humans. Importantly, clarification of the biology and identification of the differences of ADSCs from various areas of the body is required. In this continuous endeavor, research in rat models plays an important role in the development of new knowledge. METHODS: A literature review was done to summarize all information regarding harvesting, isolation, expansion, cryopreservation and differentiation of rat ADSCs. A Wistar rat model was also used to describe harvesting sites of adipose tissue, and to characterize the ADSCs using Fourier-transform infrared (FT-IR) spectroscopy and phase contrast microscopy. AIMS: To discuss all relevant considerations for harvesting, culture, differentiation and phenotypic characterization of ADSCs, to provide a comprehensive roadmap of this process, to identify the differences between ADSCs obtained from various adipose tissues of the rat, and to provide FT-IR spectroscopy marker bands that could be used as fingerprints to differentiate the types of adipose tissues.

Bone morphogenetic protein signaling in musculoskeletal cancer.

PURPOSE: Bone morphogenetic proteins (BMPs) belong to the transforming growth factor-ß (TGF-ß) superfamily of proteins; they were initially named after their ability to induce ectopic bone formation. Published studies have proved BMPs' role in a variety of biological processes such as embryogenesis and patterning of body axes, and maintaining adult tissue homeostasis. Other studies have focused on BMPs properties, functions and possible involvement in skeletal diseases, including cancer. METHODS: A literature search mainly paying attention to the role of BMPs in musculoskeletal tumors was performed in electronic databases. RESULTS: This article discusses BMPs synthesis and signaling, and summarizes their prominent roles in the skeletal system for the differentiation of osteoblasts, osteocytes and chondrocytes. CONCLUSIONS: The review emphasizes on the role of BMP signaling in the initiation and progression of musculoskeletal cancer.

Directed neural differentiation of mouse embryonic stem cells is a sensitive system for the identification of novel Hox gene effectors.

The evolutionarily conserved Hox family of homeodomain transcription factors plays fundamental roles in regulating cell specification along the anterior posterior axis during development of all bilaterian animals by controlling cell fate choices in a highly localized, extracellular signal and cell context dependent manner. Some studies have established downstream target genes in specific systems but their identification is insufficient to explain either the ability of Hox genes to direct homeotic transformations or the breadth of their patterning potential. To begin delineating Hox gene function in neural development we used a mouse ES cell based system that combines efficient neural differentiation with inducible Hoxb1 expression. Gene expression profiling suggested that Hoxb1 acted as both activator and repressor in the short term but predominantly as a repressor in the long run. Activated and repressed genes segregated in distinct processes suggesting that, in the context examined, Hoxb1 blocked differentiation while activating genes related to early developmental processes, wnt and cell surface receptor linked signal transduction and cell-to-cell communication. To further elucidate aspects of Hoxb1 function we used loss and gain of function approaches in the mouse and chick embryos. We show that Hoxb1 acts as an activator to establish the full expression domain of CRABPI and II in rhombomere 4 and as a repressor to restrict expression of Lhx5 and Lhx9. Thus the Hoxb1 patterning activity includes the regulation of the cellular response to retinoic acid and the delay of the expression of genes that commit cells to neural differentiation. The results of this study show that ES neural differentiation and inducible Hox gene expression can be used as a sensitive model system to systematically identify Hox novel target genes, delineate their interactions with signaling pathways in dictating cell fate and define the extent of functional overlap among different Hox genes.