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  • Author or Editor: Kelly S. Santangelo x
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Objective—To evaluate 2 commercially available transfection reagents for transfection efficiency and distribution of small interfering RNA (siRNA) molecules to chondrocytes in monolayer cultures and full-thickness cartilage explants from guinea pigs and horses.

Sample—Cartilage explants from 5 one-month-old and 3 adult guinea pigs and 5 adult clinically normal horses.

Procedures—Monolayer chondrocytes and uniform cartilage explants were exposed to 1 of 2 siRNA transfection complexes according to manufacturers' protocols (1μM [1×]). Additionally, monolayer chondrocytes were exposed to 2× the suggested amount of a proprietary siRNA molecule. Full-thickness cartilage explants were treated with 1× (1μM), 2× (2μM), and 4× (4μM) or 1× (0.13μM), 4× (0.52μM), and 8× (1.04μM) the recommended concentrations of the proprietary siRNA and the cationic liposome siRNA, respectively, in equivalent media volumes. Use of fluorescent siRNA duplexes allowed quantification of transfected cells via flow cytometry and direct visualization of the depth and distribution of in situ transfection via fluorescent microscopy.

Results—With both transfection reagents, > 90% of monolayer chondrocytes were transfected. In explants, only use of the proprietary molecule achieved > 50% transfection efficiency, whereas use of the cationic liposome achieved < 20%. Only the proprietary molecule-treated cartilage consistently contained fluorescent cells throughout all zones; the cationic liposome-transfected chondrocytes were restricted to explant surfaces.

Conclusions and Clinical Relevance—Robust transfection of chondrocytes in monolayer was achieved with both reagents, but only use of the proprietary molecule attained effective full-thickness transfection of explants that may allow relevant transcript reduction via RNAi.

Full access
in American Journal of Veterinary Research


Objective—To evaluate early cellular influences of bone morphogenetic protein (BMP)12 and BMP2 on equine superficial digital flexor tenocytes (SDFTNs) and equine bone marrow–derived mesenchymal stem cells (BMDMSCs).

Animals—9 adult clinically normal horses.

Procedures—BMDMSCs and SDFTNs were cultured in monolayer, either untreated or transduced with adenovirus encoding green fluorescent protein, adenovirus encoding BMP12, or adenovirus encoding BMP2. Cytomorphologic, cytochemical, immunocytochemical, and reverse transcriptase–quantitative PCR (RT-qPCR) analyses were performed on days 3 and 6. Genetic profiling for effects of BMP12 was evaluated by use of an equine gene expression microarray on day 6.

Results—BMDMSCs and SDFTNs had high BMP12 gene expression and remained viable and healthy for at least 6 days. Type l collagen immunocytochemical staining for SDFTNs and tenocyte-like morphology for SDFTNs and BMDMSCs were greatest in BMP12 cells. Cartilage oligomeric matrix protein, as determined via RT-qPCR assay, and chondroitin sulfate, as determined via gene expression microarray analysis, were upregulated relative to control groups in SDFTN-BMP12 cells. The BMDMSCs and SDFTNs became mineralized with BMP2, but not BMP12. Superficial digital flexor tenocytes responded to BMP12 with upregulation of genes relevant to tendon healing and without mineralization as seen with BMP2.

Conclusions and Clinical Relevance—Targeted equine SDFTNs may respond to BMP12 with improved tenocyte morphology and without mineralization, as seen with BMP2. Bone marrow–derived mesenchymal stem cells may be able to serve as a cell delivery method for BMP12.

Full access
in American Journal of Veterinary Research


Objective—To determine effects of various concentrations of retinoic acid (RA) or a synthetic RA receptor antagonist (LE135) on equine chondrocytes or bone marrow—derived equine mesenchymal stem cells (BMDMSCs) in monolayer cultures.

Sample—Articular cartilage and BMDMSCs from 5 clinically normal horses.

Procedures—Monolayers of chondrocytes cultured in standard media and of BMDMSCs cultured in chondrogenic media were treated with RA at concentrations of 0, 0.1, 1, or 10μM or LE135 at concentrations of 0, 0.1, 1, or 10μM on day 0. On days 7 and 14, samples were analyzed for DNA concentration, chondrocyte morphology or features consistent with chondrogenesis (ie, chondral morphology [scored from 0 to 4]), and gene expression of collagen type Ia (CI), collagen type II (CII), and aggrecan.

Results—Chondrocytes treated with RA had more mature chondral morphology (range of median scores, 3.0 to 4.0) than did untreated controls (range of median scores, 0.5 to 0.5). Chondrocytes treated with LE135 did not sustain chondrocyte morphology. All BMDMSCs had evidence of chondral morphology or high CII:CI ratio. Retinoic acid (1 or 10μM) or LE135 (10μM) treatment decreased DNA content of BMDMSC cultures. At 0.1 and 1μM concentrations, LE135 weakly but significantly increased chondral morphology scores, compared with untreated controls, but lack of aggrecan expression and lack of increased CII:CI ratio, compared with that of controls, did not affect chondrogenesis.

Conclusions and Clinical Relevance—RA promoted maturation and hypertrophy in chondrocytes but not BMDMSCs in monolayer cultures. Deficiency or blockade of RA may prevent hypertrophy and maturation of differentiated chondrocytes.

Full access
in American Journal of Veterinary Research



To advance the understanding of how alterations in exercise speed and grade (flat vs 17° incline or decline) affect the quality of tendon healing, and to determine if a biomarker relationship exists between serum levels of a ColX breakdown product (CXM) and animals exposed to treadmill running protocols.


35 male mice (C57BL/6J), 8 weeks of age.


Mice were preconditioned on a treadmill for 14 days. Tendinopathy was then induced by 2 intra-tendinous TGFβ1 injections followed by randomization into 7 exercise groups. Exercise capacity and objective gait analysis were measured weekly. Mice were euthanized and histopathologic analysis and evaluation of serum CXM levels were performed. Statistics were conducted using a 2-way ANOVA (exercise capacity), Mixed Effects Model (gait analysis, effect of preconditioning), and 1-way ANOVA (gait analysis, the effect of injury, and rehabilitation normalized to baseline; CXM serum analysis), all with Tukey post hoc tests and significance set to P < .05.


Exercise at a fast-flat speed demonstrated inferior tendinopathic healing at the cellular level and impaired stance braking abilities, which were compensated for by increased propulsion. Mice exposed to exercise (at any speed or grade) demonstrated higher systemic levels of CXM than those that were cage rested. However, no ColX immunostaining was observed in the Achilles tendon or calcaneal insertion.


Exercise at a fast speed and in absence of eccentric loading components (incline or decline) demonstrated inferior tendinopathic healing at the cellular level and impaired braking abilities that were compensated for by increased propulsion.

Open access
in American Journal of Veterinary Research