Effect of Combined Leukocyte-Poor Platelet-Rich Plasma and Hyaluronic Acid on Bone Marrow-Derived Mesenchymal Stem Cell and Chondrocyte Metabolism.

OBJECTIVE: Given the potential applications of combined biologics, the authors sought to evaluate the in vitro effect of combined platelet-rich plasma (PRP) and hyaluronic acid (HA) on cellular metabolism. DESIGN: Bone marrow-derived mesenchymal stem cells (BMSCs) and chondrocytes were obtained from the femurs of Sprague-Dawley rats. An inflammatory model was created by adding 10 ng/mL interleukin-1-beta to culture media. Non-crosslinked high-molecular-weight HA, activated-PRP (aPRP), and unactivated-PRP (uPRP) were tested. Cellular proliferation and gene expression were measured at 1 week. Genes of interest included aggrecan, matrix metalloproteinase (MMP)-9, and MMP-13. RESULTS: Combined uPRP-HA was associated with a significant increase in chondrocyte and BMSC proliferation at numerous preparations. There was a trend of increased chondrocyte aggrecan expression with combined PRP-HA. The greatest and only significant decrease in BMSC MMP-9 expression was observed with combined PRP-HA. While a significant reduction of BMSC MMP-13 expression was seen with PRP and HA-alone, a greater reduction was observed with PRP-HA. MMP-9 chondrocyte expression was significantly reduced in cells treated with PRP-HA. PRP-alone and HA-alone at identical concentrations did not result in a significant reduction. The greatest reduction of MMP-13 chondrocyte expression was observed in chondrocytes plus combined PRP-HA. CONCLUSIONS: We demonstrated a statistically significant increase in BMSC and chondrocyte proliferation and decreased expression of catabolic enzymes with combined PRP-HA. These results demonstrate the additive in vitro effect of combined PRP-HA to stimulate cellular growth, restore components of the articular extracellular matrix, and reduce inflammation.

Tenogenically differentiated adipose-derived stem cells are effective in Achilles tendon repair in vivo.

The purpose of this study was to characterize rat adipose-derived stem cells, induce adipose-derived stem cell tenogenesis, and analyze adipose-derived stem cell effects on tendon repair in vivo. Adipose-derived stem cells demonstrated an immunomodulatory, pro-angiogenic, and pro-proliferatory profile in vitro. Tenogenesis was induced for 1, 7, 14, and 21 days with 24 combinations of growth differentiation factor-5, 6, and 7 and platelet-derived growth factor-BB. Adipose-derived stem cells expression of scleraxis and collagen type I increased the most after 14 days of induction with growth differentiation factor-6 and platelet-derived growth factor-BB. Achilles excision defects injected with hydrogel alone (Gp2), with undifferentiated (Gp3) adipose-derived stem cells, or tenogenically differentiated (Gp4) adipose-derived stem cells exhibited improved tissue repair compared with untreated tendons (Gp1). Addition of adipose-derived stem cells improved tissue cytoarchitecture and increased expression of collagen type I and III, scleraxis, and tenomodulin. Adipose-derived stem cells significantly improved biomechanical properties (ultimate load and elastic toughness) over time more than hydrogel alone, while tenogenically differentiated adipose-derived stem cells improved the mean histological score and collagen fiber dispersion range closest to normal tendon. In addition, tendon sections treated with GFP-adipose-derived stem cells exhibited green fluorescence and positive GFP immunostaining on microscopy confirming the in vivo survival of adipose-derived stem cells that were injected into tendon defects to support the effects of adipose-derived stem cells on tissue up to 4.5 weeks post injury.

Therapeutic Effects of Doxycycline on the Quality of Repaired and Unrepaired Achilles Tendons.

BACKGROUND: Achilles tendon tears are devastating injuries, especially to athletes. Elevated matrix metalloproteinase (MMP) activity after a tendon injury has been associated with deterioration of the collagen network and can be inhibited with doxycycline (Doxy). HYPOTHESIS: Daily oral administration of Doxy will enhance the histological, molecular, and biomechanical quality of transected Achilles tendons. Additionally, suture repair will further enhance the quality of repaired tendons. STUDY DESIGN: Controlled laboratory study. METHODS: Randomized unilateral Achilles tendon transection was performed in 288 adult male Sprague-Dawley rats. The injured tendons were either unrepaired (groups 1 and 2) or surgically repaired (groups 3 and 4). Animals from groups 2 and 4 received Doxy daily through oral gavage, and animals from groups 1 and 3 served as controls (no Doxy). Tendons were harvested at 1.5, 3, 6, and 9 weeks after the injury (n = 18 per group and time point). The quality of tendon repair was evaluated based on the histological grading score, collagen fiber orientation, gene expression, and biomechanical properties. RESULTS: In surgically repaired samples, Doxy enhanced the quality of tendon repair compared with no Doxy ( P = .0014). Doxy had a significant effect on collagen fiber dispersion, but not principal fiber angle. There was a significant effect of time on the gene expression of MMP-3, MMP-9 and TIMP1, and Doxy significantly decreased MMP-3 expression at 9 weeks. Doxy treatment with surgical repair increased the dynamic modulus at 6 weeks but not at 9 weeks after the injury ( P < .001). Doxy also increased the equilibrium modulus and decreased creep strain irrespective of the repair group. Doxy did not have a significant effect on the histology or biomechanics of unrepaired tendons. CONCLUSION: The findings indicate that daily oral administration of Doxy accelerated matrix remodeling and the dynamic and equilibrium biomechanics of surgically repaired Achilles tendons, although such enhancements were most evident at the 3- to 6-week time points. CLINICAL RELEVANCE: The inhibition of MMPs at the optimal stage of the repair process may accelerate Achilles tendon repair and improve biomechanical properties, especially when paired with surgical management.