Morphometric analysis of growing tenocytes in the superficial digital flexor tendon of piglets

Janus Membranes Patch Achieves High-Quality Tendon Repair: Inhibiting Exogenous Healing and Promoting Endogenous Healing

The imbalance between endogenous and exogenous healing is the fundamental reason for the poor tendon healing. In this study, a Janus patch was developed to promote endogenous healing and inhibit exogenous healing, leading to improved tendon repair. The upper layer of the patch is a poly(dl-lactide-co-glycolide)/polycaprolactone (PLGA/PCL) nanomembrane (PMCP-NM) modified with poly(2-methylacryloxyethyl phosphocholine) (PMPC), which created a lubricated and antifouling surface, preventing cell invasion and mechanical activation. The lower layer is a PLGA/PCL fiber membrane loaded with fibrin (Fb) (Fb-NM), serving as a temporary chemotactic scaffold to regulate the regenerative microenvironment. In vitro, the Janus patch effectively reduced 92.41% cell adhesion and 79.89% motion friction. In vivo, the patch inhibited tendon adhesion through the TGF-β/Smad signaling pathway and promoted tendon maturation. This Janus patch is expected to provide a practical basis and theoretical guidance for high-quality soft tissue repair.

Evaluation of canine adipose-derived multipotent stromal cell differentiation to ligamentoblasts on tensioned collagen type I templates in a custom bioreactor culture system

OBJECTIVE

To evaluate differentiation of canine adipose-derived multipotent stromal cells (ASCs) into ligamentoblasts on tensioned collagen type I (Col1) templates in a perfusion culture system.

SAMPLES

Infrapatellar fat pad ASCs from healthy stifle joints of 6 female mixed-breed dogs.

PROCEDURES

Third-passage ASCs (6 × 10⁶ cells/template) were loaded onto suture-augmented Col1 templates under 15% static strain in perfusion bioreactors. Forty-eight ASC-Col1 constructs were incubated with ligamentogenic (ligamentogenic constructs; n = 24) or stromal medium (stromal constructs; 24) for up to 21 days. Specimens were collected from each construct after 2 hours (day 0) and 7, 14, and 21 days of culture. Cell number, viability, distribution, and morphology; construct collagen content; culture medium procollagen-I-N-terminal peptide concentration; and gene expression were compared between ligamentogenic and stromal constructs.

RESULTS

ASCs adhered to collagen fibers. Cell numbers increased from days 0 to 7 and days 14 to 21 for both construct types. Relative to stromal constructs, cell morphology and extracellular matrix were more mature and collagen content on day 21 and procollagen-I-N-terminal peptide concentration on days 7 and 21 were greater for ligamentogenic constructs. Ligamentogenic constructs had increased expression of the genes biglycan on day 7, decorin throughout the culture period, and Col1, tenomodulin, fibronectin, and tenascin-c on day 21; expression of Col1, tenomodulin, and tenascin-c increased between days 7 and 21.

CONCLUSIONS AND CLINICAL RELEVANCE

Ligamentogenic medium was superior to stromal medium for differentiation of ASCs to ligamentoblasts on suture-augmented Col1 scaffolds. Customized ligament neotissue may augment treatment options for dogs with cranial cruciate ligament rupture.

Ultrastructural study of the three-dimensional tenocyte network in newly hatched chick Achilles tendons using serial block face-scanning electron microscopy

The lateral cytoplasmic processes of tenocytes extend to form three-dimensional network surrounding collagen fibers. It is unknown whether connections between two cytoplasmic processes involve overlapping of the processes or merely surface contact. In this study, the two-dimensional and three-dimensional structure of tenocytes in the Achilles tendons of the newly hatched chicks were studied using transmission electron microscopy and serial block face-scanning electron microscopy. Observation of the two-dimensional structures revealed various forms of cellular connections, including connections between the cytoplasmic processes of adjacent tenocytes and between the cytoplasmic process of tenocytes and fibroblasts. Three-dimensional observation showed spike-like cytoplasmic processes extending from one tenocyte that interlocked with cytoplasmic processes from other tenocytes. Cytoplasmic processes from each tenocyte within the chick tendons interlocked to ensure a tight cell-to-cell connection around growing collagen fibers. A cellular network formed by these cytoplasmic processes surrounds each collagen fiber. Cell-cell junctions, which were suggested to be gap junctions, observed at sites of cytoplasmic process overlap most likely represent the major route for communication between tenocytes associated with fibroblasts, enabling vital signals important for maintaining the cell and tendon integrity to be transmitted.