Doxycycline inhibits collagen synthesis by differentiated articular chondrocytes

A Systematic Review of Basic Science and Animal Studies on the Use of Doxycycline to Reduce the Risk of Posttraumatic Osteoarthritis After Anterior Cruciate Ligament Rupture/Transection

BACKGROUND

Posttraumatic osteoarthritis (PTOA) after injury to the anterior cruciate ligament (ACL) is common.

PURPOSE

To perform a systematic review of basic science and animal studies to determine the effect of doxycycline treatment on the prevention of PTOA after ACL rupture/transection.

STUDY DESIGN

Systematic review.

METHODS

A systematic review was performed by searching the PubMed, Cochrane Library, and Embase databases to identify basic science and animal studies evaluating the effect of doxycycline treatment on the prevention of PTOA of the knee joint after ACL/cranial cruciate ligament (CCL) injury. The search phrase used was "doxycycline cruciate ligament." Inclusion criteria were basic science and animal studies evaluating the effect of oral administration of doxycycline in ACL/CCL-deficient animals with or without a control group.

RESULTS

Seven studies met inclusion criteria and were included in this systematic review. Five studies were performed in dogs, 1 in rabbits, and 1 in mice. Overall, the effects of doxycycline treatment on the prevention of PTOA after ACL/CCL rupture/transection were mixed. In dogs, no significant effects of doxycycline treatment were found in terms of matrix metalloproteinase (MMP) activity, while a mouse study found significantly lower MMP-13 expression on the tibia in doxycycline-treated animals, suggesting that doxycycline may protect against proteoglycan loss and decrease osteoarthritis progression. Cartilage nitric oxide concentrations were lower in doxycycline-treated dogs compared with untreated dogs, suggesting decreased cartilage degradation among doxycycline-treated dogs, although there were no significant effects on cartilage stromelysin levels with no significant effects in terms of physiological remodeling or catabolism of cartilage. Bone formation or resorption was not found to be affected by doxycycline treatment. One study demonstrated a substantial beneficial effect of doxycycline on gross morphology of the medial femoral condyle. Doxycycline was found to conserve bone strain energy density and appeared to limit subchondral bone loss in 1 study.

CONCLUSION

Based on the limited available animal studies, doxycycline appears to demonstrate some benefits in the prevention of PTOA after ACL/CCL rupture/transection. Additional studies are needed to further characterize the potential benefits, side effects, dosage, and duration of this treatment after ACL injury in human patients.

Inhibition of extracellular matrix production and remodeling by doxycycline in smooth muscle cells

Alterations in the extracellular matrix (ECM) production and remodeling of smooth muscle cells (SMCs) have been implicated in processes related to the differentiation in atherosclerosis. Due to the anti-atherosclerotic properties of the tetracyclines, we aimed to investigate whether cholesterol supplementation changes the effect of doxycycline over the ECM proteins synthesis and whether isoprenylated proteins and Rho A protein activation are affected. SMC primary culture isolated from chicks exposed to atherogenic factors in vivo (a cholesterol-rich diet, SMC-Ch), comparing it with control cultures isolated after a standard diet (SMC-C). After treatment with 20 nM doxycycline, [H³]-proline and [H³]-mevalonate incorporation were used to measure the synthesis of collagen and isoprenylated proteins, respectively. Real-time PCR was assessed to determine col1a2, col2a1, col3a1, fibronectin, and mmp2 gene expression and the pull-down technique was applied to determine the Rho A activation state. A higher synthesis of collagens and isoprenylated proteins in SMC-Ch than in SMC-C was determined showing that doxycycline inhibits ECM production and remodeling in both SMC types of cultures. Moreover, preliminary results about the effect of doxycycline on protein isoprenylation and Rho A protein activation led us to discuss the possibility that membrane G-protein activation pathways could mediate the molecular mechanism.

Multifunctional nanoparticles for doxycycline delivery towards localized elastic matrix stabilization and regenerative repair

Abdominal aortic aneurysms (AAAs) are abnormal expansions of the aortic wall, typically characterized by chronic up-regulation of matrix metalloproteases (MMPs)-2 and -9. These MMPs degrade elastin and elastic matrix within the aortic wall, leading to a progressive loss of elasticity of the abdominal aorta as the condition progresses. Doxycycline (DOX) is a tetracycline-based antibiotic which has shown significant promise in delaying and slowing the growth of AAAs in both clinical studies and animal models. However, it has been found to inhibit elastic matrix deposition by vascular cells at dosages in the μg ml(-1) range, which is typically observed in the circulation, in addition to systemic side effects, following oral dosage. In this paper, we describe the development of DOX-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles for localized, controlled and sustained DOX delivery towards AAA therapy. Further, we demonstrate that surface functionalization of these nanoparticles with cationic amphiphiles not only imparts them with a positive charge for potentially enhanced aortic uptake, but also enables enhanced elastin binding via hydrophobic interactions, as well as up-regulating activity of the elastin crosslinking enzyme lysyl oxidase. In addition to the DOX released from the nanoparticles being effective in inhibiting MMP-2 production and activity, we also demonstrate that surface functionalization of the nanoparticles cationic amphiphiles may also play a role in MMP-2 inhibition via (i) electrostatic interactions with negatively charged residues in the active-site of MMP-2 or (ii) steric blockade of the active site on account of the presence of two dodecyl chains in the DMAB molecule. Thus, in addition to enhanced aortic uptake and retention illustrated in studies by other groups, we have demonstrated that cationic functionalization of PLGA nanoparticles enhances elastogenic outcomes by targeted binding to elastin, as well as their potential to inhibit elastolysis. These results establish their multifunctionality as a localized delivery system for AAA therapy. Overall, this delivery system has the potential to enhance regenerative outcomes at sites of proteolytic matrix disruption/degradation by enabling targeted, controlled and long-term release of therapeutic agents.

Advances in biomimetic regeneration of elastic matrix structures

Elastin is a vital component of the extracellular matrix, providing soft connective tissues with the property of elastic recoil following deformation and regulating the cellular response via biomechanical transduction to maintain tissue homeostasis. The limited ability of most adult cells to synthesize elastin precursors and assemble them into mature crosslinked structures has hindered the development of functional tissue-engineered constructs that exhibit the structure and biomechanics of normal native elastic tissues in the body. In diseased tissues, the chronic overexpression of proteolytic enzymes can cause significant matrix degradation, to further limit the accumulation and quality (e.g., fiber formation) of newly deposited elastic matrix. This review provides an overview of the role and importance of elastin and elastic matrix in soft tissues, the challenges to elastic matrix generation in vitro and to regenerative elastic matrix repair in vivo, current biomolecular strategies to enhance elastin deposition and matrix assembly, and the need to concurrently inhibit proteolytic matrix disruption for improving the quantity and quality of elastogenesis. The review further presents biomaterial-based options using scaffolds and nanocarriers for spatio-temporal control over the presentation and release of these biomolecules, to enable biomimetic assembly of clinically relevant native elastic matrix-like superstructures. Finally, this review provides an overview of recent advances and prospects for the application of these strategies to regenerating tissue-type specific elastic matrix structures and superstructures.

In vitro inhibition of aggrecanase activity by tetracyclines and proteoglycan loss from osteoarthritic human articular cartilage

Tetracyclines were reported to slow down the progression of cartilage damage both in an animal model of osteoarthritis (OA) and in humans. In search for the underlying mechanisms we examined whether tetracyclines possess an inhibitory potential on the activity of aggrecanases and inflammatory mediators and can thus prevent proteoglycan (PG) loss from human articular cartilage. In vitro activity of aggrecanase-1 and -2 was recorded in the presence of 1-100 microM tetracycline, minocycline, or doxycyline. Human knee articular cartilage explants were sorted according to the degree of OA and treated for 10 days with tetracycline derivatives in the presence of interleukin-1 (IL-1beta). Synthesis and loss of PGs, nitric oxide (NO), and prostaglandin E(2) (PGE(2)), as well as the viability were determined. Tetracyclines derivatives dose-dependently inhibited the activities of both aggrecanases in vitro, whereas no inhibitory effect of tetracyclines on any proteoglycanolytic activities within IL-1beta-treated human cartilage explants were found. Tetracyclines can significantly modulate NO and PGE(2) levels, but have no effect on PG synthesis and loss within the same human cartilage explant cultures. Altogether, our data show that tetracyclines have no inhibitory potential on any proteoglycanolytic activities within mild or moderately affected human OA cartilage at therapeutic achievable plasma levels.

Doxycycline alters vascular smooth muscle cell adhesion, migration, and reorganization of fibrillar collagen matrices

Remodeling of injured blood vessels is dependent on smooth muscle cells and matrix metalloproteinase activity. Doxycycline is a broad spectrum matrix metalloproteinase inhibitor that is under investigation for the treatment of acute coronary syndromes and aneurysms. In the present study, we examine the mechanisms by which doxycycline inhibits smooth muscle cell responses using a series of in vitro assays that mimic critical steps in pathological vascular remodeling. Doxycycline treatment dramatically increased smooth muscle cell adhesion to the substrate, as evidenced by interference reflection microscopy and immunostaining for paxillin and phosphotyrosine. Cell aggregation was also potentiated after treatment with doxycycline. Treatment with 104 mumol/L doxycycline reduced thymidine uptake by 58% compared with untreated cells (P < 0.05) and inhibited closure of a scrape wound made in a smooth muscle cell monolayer by 20% (P < 0.05). Contraction of a three-dimensional collagen gel was used as an in vitro model for constrictive vessel remodeling, demonstrating that treatment with 416 mumol/L doxycycline for 12 hours inhibited collagen gel remodeling by 37% relative to control (P < 0.05). In conclusion, we have shown that doxycycline treatment leads to dramatically increased smooth muscle cell adhesion, which in turn might limit responses in pathological vascular remodeling.

A nonantibiotic chemically modified tetracycline (CMT-3) inhibits intimal thickening

Recent research has shown that the tetracycline antibiotics are pluripotent drugs that inhibit the activity of matrix metalloproteinases (MMPs) and affect many cellular functions including proliferation, migration, and matrix remodeling. We have shown that doxycycline inhibits MMP activity and intimal thickening after injury of the rat carotid artery, however we do not know whether these effects are because of the antibiotic, anti-MMP, or other actions of doxycycline. Recently, chemically modified tetracyclines have been synthesized that lack antibiotic activity but retain anti-MMP activity (CMT-3), or lack both antibiotic and anti-MMP activity (CMT-5). In the current study we have assessed the effects of treatment with CMT-3 or CMT-5 on intimal thickening after balloon catheter injury of the rat carotid artery. Rats were treated by oral gavage with 15 mg/kg/day CMT-3 or CMT-5. CMT-3 significantly reduced smooth muscle cell (SMC) proliferation in both the medial and intimal layers of the injured rat carotid artery compared to CMT-5. Furthermore, CMT-3 inhibited SMC migration from the media to the intima by 86% at 4 days after injury. CMT-3 also decreased MMP-2 activity. Finally, we found that CMT-3 treatment resulted in a significant reduction in intimal cross-sectional area from 0.23 +/- 0.01 mm(2) in the CMT-5 control group to 0.19 +/- 0.01 mm(2). There was also a reduction in elastin and collagen accumulation within the intima. We conclude that CMT-3 attenuated intimal thickening after arterial injury by inhibiting SMC proliferation, migration and MMP activity, and accumulation of extracellular matrix. The inhibitory effects of CMT-3 were independent of the antibiotic properties, but were dependent on the anti-MMP activity of the tetracycline family.

Doxycycline modulates smooth muscle cell growth, migration, and matrix remodeling after arterial injury

The tetracyclines function as antibiotics by inhibiting bacterial protein synthesis, but recent work has shown that they are pluripotent drugs that affect many mammalian cell functions including proliferation, migration, apoptosis, and matrix remodeling. Because all of these processes have been implicated in arterial intimal lesion development, the objective of these studies was to examine the effect of doxycycline treatment using a well-characterized model of neointimal thickening, balloon catheter denudation of the rat carotid artery. Rats were treated with 30-mg/kg/day doxycycline. Doxycycline reduced the activity of matrix metalloproteinase (MMP)-2 and MMP-9 in the arterial wall, and inhibited smooth muscle cell migration from media to intima by 77% at 4 days after balloon injury. Replication of smooth muscle cells in the intima at 7 days was reduced from 28.3 plus minus 2.5% in controls to 17.0 +/- 2.8% in doxycycline-treated rats. The synthesis of elastin and collagen was not affected, but accumulation of elastin was blocked in the doxycycline-treated rats. By contrast, collagen accumulation was not affected, which led to the formation of a more collagen-rich intima. At 28 days after injury, the intimal:medial ratio was significantly reduced from 1.67 +/- 0.09 in control rats to 1.36 +/- 0.06 in the doxycycline-treated rats. This study shows that doxycycline is an effective inhibitor of cell proliferation, migration, and MMP activity in vivo. Further study in more complicated models of atherosclerosis and restenosis is warranted.