Inverse agonism of retinoic acid receptors directs epiblast cells into the paraxial mesoderm lineage.

We have investigated the differentiation of paraxial mesoderm from mouse embryonic stem cells utilizing a Tbx6-EYFP/Brachyury (T)-Cherry dual reporter system. Differentiation from the mouse ESC state directly into mesoderm via Wnt pathway activation was low, but augmented by treatment with AGN193109, a pan-retinoic acid receptor inverse agonist. After five days of differentiation, T cells increased from 12.

Coated Sutures.

The addition of specific proteins or growth factors onto sutures would provide a direct application of exogenous factors to promote tissue repair. The higher levels of growth factors and cytokines may optimize the healing environment and promote tissue recovery. Despite this proposed benefit, the current orthopedic literature on the use of coated sutures is limited.

Gdf5 progenitors give rise to fibrocartilage cells that mineralize via hedgehog signaling to form the zonal enthesis.

The sequence of events that leads to the formation of a functionally graded enthesis is not clearly defined. The current study demonstrates that clonal expansion of Gdf5 progenitors contributes to linear growth of the enthesis. Prior to mineralization, Col1+ cells in the enthesis appose Col2+ cells of the underlying primary cartilage.

Growth factor delivery vehicles for tendon injuries: Mesenchymal stem cells and Platelet Rich Plasma.

Background: tendon tissue shows limited regeneration potential with formation of scar tissue and inferior mechanical properties. The capacity of several growth factors to improve the healing response and decrease scar formation is described in different preclinical studies. Besides the application of isolated growth factors, current research focuses on two further strategies to improve the healing response in tendon injuries: platelet rich plasma (PRP) and mesenchymal stem cells (MSCs).

The enthesis: a review of the tendon-to-bone insertion.

The integration of tendon into bone occurs at a specialized interface known as the enthesis. The fibrous tendon to bone enthesis is established through a structurally continuous gradient from uncalcified tendon to calcified bone. The enthesis exhibits gradients in tissue organization classified into four distinct zones with varying cellular compositions, mechanical properties, and functions in order to facilitate joint movement.

US definitions, current use, and FDA stance on use of platelet-rich plasma in sports medicine.

With increased utilization of platelet-rich plasma (PRP), it is important for clinicians to understand the United States, the Food and Drug Administration (FDA) regulatory role and stance on PRP. Blood products such as PRP fall under the prevue of FDA's Center for Biologics Evaluation and Research (CBER). CBER is responsible for regulating human cells, tissues, and cellular and tissue-based products.

Rotational and translational stability of different methods for direct acromioclavicular ligament repair in anatomic acromioclavicular joint reconstruction.

Background: Many reconstructions of acromioclavicular (AC) joint dislocations have focused on the coracoclavicular (CC) ligaments and neglected the functional contribution of the AC ligaments and the deltotrapezial fascia.

Purpose: To compare the modifications of previously published methods for direct AC reconstruction in addition to a CC reconstruction. The hypothesis was that there would be significant differences within the variations of surgical reconstructions.

Learning about PRP using cell-based models.

Studies using in vitro cell models enable evaluation of the effects of different PRP products under very controlled and standardized conditions. Therefore the results of such studies build the basis for understanding the variable results of clinical studies on the use of PRPs. The main lessons learned through the use of in vitro cell models are that many different PRP products exist and researchers have to report on component variation within each product.

Variability of platelet-rich plasma preparations.

Platelet-rich plasma (PRP) as a clinical treatment for bone, muscle, tendon, and cartilage injury has gained popularity in the field of orthopedic sports medicine. The use of a patient's own blood is an appealing aspect of PRP treatment, as the resulting plasma preparation is considered relatively benign in comparison with more common, potentially caustic treatments such as corticosteroids and anesthetics. Although appealing, the autologous nature of PRP introduces variability to plasma preparations, creating challenges for both the researcher and the clinician.

The future role of mesenchymal stem cells in the management of shoulder disorders.

Purpose: Biologics may help to optimize the healing environment after rotator cuff repair. Mesenchymal stem cells (MSCs) may have the potential to regenerate a physiological enthesis, thereby improving healing at the repair site after rotator cuff repair.

Methods: The PubMed database was searched in May 2013.

The effect of ketorolac tromethamine, methylprednisolone, and platelet-rich plasma on human chondrocyte and tenocyte viability.

Purpose: The purpose of this study was to evaluate the effect on cell viability of the isolated and combined use of allogeneic platelet-rich plasma (PRP) and ketorolac tromethamine on human chondrocytes and tenocytes in a highly controlled in vitro environment.

Methods: PRP was produced from 8 subjects. Human chondrocytes (Lonza, Hopkinton, MA) and tenocytes isolated from samples of the long head of the biceps tendons were treated in culture with PRP, ketorolac tromethamine, and methylprednisolone, both alone and in combination.

Comparison of mesenchymal stem cells (osteoprogenitors) harvested from proximal humerus and distal femur during arthroscopic surgery.

Purpose: The aim of this study was to examine the relations between age, gender, and number of viable mesenchymal stem cells (MSCs) in concentrated bone marrow (BM) obtained from the proximal humerus and distal femur during arthroscopic surgery.

Methods: BM was aspirated from either the proximal humerus (n = 55) or distal femur (n = 29) during arthroscopic surgery in 84 patients (51.3 ± 11.

Platelet-rich plasma: the PAW classification system.

Platelet-rich plasma (PRP) has been the subject of hundreds of publications in recent years. Reports of its effects in tissue, both positive and negative, have generated great interest in the orthopaedic community. Protocols for PRP preparation vary widely between authors and are often not well documented in the literature, making results difficult to compare or replicate.

Stability of double-row rotator cuff repair is not adversely affected by scaffold interposition between tendon and bone.

Background: Rotator cuff reconstructions may be improved by adding growth factors, cells, or other biologic factors into the repair zone. This usually requires a biological carrier (scaffold) to be integrated into the construct and placed in the area of tendon-to-bone healing. This needs to be done without affecting the constructs mechanics.