Protein Kinase G2 Is Essential for Skeletal Homeostasis and Adaptation to Mechanical Loading in Male but Not Female Mice.

We previously showed that the NO/cGMP/protein kinase G (PKG) signaling pathway positively regulates osteoblast proliferation, differentiation, and survival in vitro, and that cGMP-elevating agents have bone-anabolic effects in mice. Here, we generated mice with an osteoblast-specific (OB) knockout (KO) of type 2 PKG (gene name Prkg2) using a Col1a1(2.3 kb)-Cre driver.

Biomechanics of osteochondral impact with cushioning and graft Insertion: Cartilage damage is correlated with delivered energy.

Articular cartilage is susceptible to impact injury. Impact may occur during events ranging from trauma to surgical insertion of an OsteoChondral Graft (OCG) into an OsteoChondral Recipient site (OCR). To evaluate energy density as a mediator of cartilage damage, a specialized drop tower apparatus was used to impact adult bovine samples while measuring contact force, cartilage surface displacement, and OCG advancement.

Impact insertion of osteochondral grafts: Interference fit and central graft reduction affect biomechanics and cartilage damage.

An osteochondral graft (OCG) is an effective treatment for articular cartilage and osteochondral defects. Impact of an OCG during insertion into the osteochondral recipient site (OCR) can cause chondrocyte death and matrix damage. The aim of the present study was to analyze the effects of graft-host interference fit and a modified OCG geometry on OCG insertion biomechanics and cartilage damage.

Ex vivo loading of trussed implants for spine fusion induces heterogeneous strains consistent with homeostatic bone mechanobiology.

A truss structure was recently introduced as an interbody fusion cage. As a truss system, some of the connected elements may be in a state of compression and others in tension. This study aimed to quantify both the mean and variance of strut strains in such an implant when loaded in a simulated fusion condition with vertebral body or contoured plastic loading platens ex vivo.

Effect of hyaluronidase on tissue-engineered human septal cartilage.

Objectives: Structural properties of tissue-engineered cartilage can be optimized by altering its collagen to sulfated glycosaminoglycan (sGAG) ratio with hyaluronidase. The objective was to determine if treatment of neocartilage constructs with hyaluronidase leads to increased collagen:sGAG ratios, as seen in native tissue, and improved tensile properties.

Study Design: Prospective, basic science.

Evaluation of Autogenous Engineered Septal Cartilage Grafts in Rabbits- A Minimally Invasive Preclinical Model.

Objectives: Evaluate safety of autogenous engineered septal neocartilage grafts.Compare properties of implanted grafts versus controls.

Study Design: Prospective, basic science.

Flexural properties of native and tissue-engineered human septal cartilage.

Objective: To determine and compare the bending moduli of native and engineered human septal cartilage.

Study Design: Prospective, basic science.

Setting: Research laboratory.

Culture of human septal chondrocytes in a rotary bioreactor.

Objectives: (1) To show that extracellular matrix deposition in 3-dimensional culture of human septal chondrocytes cultured in a rotary bioreactor is comparable to the deposition achieved under static culture conditions. (2) To demonstrate that the biomechanical properties of human septal chondrocytes cultured in a bioreactor are enhanced with time and are analogous to beads cultured under static culture.

Study Design: Prospective, basic science.

Shaped, stratified, scaffold-free grafts for articular cartilage defects.

One goal of treatment for large articular cartilage defects is to restore the anatomic contour of the joint with tissue having a structure similar to native cartilage. Shaped and stratified cartilaginous tissue may be fabricated into a suitable graft to achieve such restoration. We asked if scaffold-free cartilaginous constructs, anatomically shaped and targeting spherically-shaped hips, can be created using a molding technique and if biomimetic stratification of the shaped constructs can be achieved with appropriate superficial and middle/deep zone chondrocyte subpopulations.

Short-term retention of labeled chondrocyte subpopulations in stratified tissue-engineered cartilaginous constructs implanted in vivo in mini-pigs.

It is likely that effective application of cell-laden implants for cartilage defects depends on retention of implanted cells and interaction between implanted and host cells. The objectives of this study were to characterize stratified cartilaginous constructs seeded sequentially with superficial (S) and middle (M) chondrocyte subpopulations labeled with fluorescent cell tracking dye PKH26 (*) and determine the degree to which these stratified cartilaginous constructs maintain their architecture in vivo after implantation in mini-pigs for 1 week. Alginate-recovered cells were seeded sequentially to form stratified S*/M (only S cells labeled) and S*/M* (both S and M cells labeled) constructs.

Tensile biomechanical properties of human nasal septal cartilage.

Background: The biomechanical properties of human septal cartilage have yet to be fully defined and thereby limits our ability to compare tissue-engineered constructs to native tissue. In this study, we analyzed the tensile properties of human nasal septal cartilage with respect to axis of tension, age group, and gender.

Methods: Fifty-five tensile tests were run on human septal specimens obtained from 28 patients.

Biomechanical assessment of tissue retrieved after in vivo cartilage defect repair: tensile modulus of repair tissue and integration with host cartilage.

Failure to restore the mechanical properties of tissue at the repair site and its interface with host cartilage is a common problem in tissue engineering procedures to repair cartilage defects. Quantitative in vitro studies have helped elucidate mechanisms underlying processes leading to functional biomechanical changes. However, biomechanical assessment of tissue retrieved from in vivo studies of cartilage defect repair has been limited to compressive tests.

Analysis of stored osteochondral allografts at the time of surgical implantation.

Background: To date, the morphological, biochemical, and biomechanical characteristics of articular cartilage in osteochondral allografts that have been stored have not been fully described.

Hypothesis: Osteochondral allografts procured and stored commercially for a standard period as determined by tissue banking protocol will have compromised chondrocyte viability but preserved extracellular matrix quality.

Study Design: Controlled laboratory study.

Prolonged storage effects on the articular cartilage of fresh human osteochondral allografts.

Background: Fresh osteochondral allograft transplantation is a well-established technique for the treatment of cartilage defects of the knee. It is believed that the basic paradigm of the technique is that the transplantation of viable chondrocytes maintains the articular cartilage matrix over time. Allograft tissue is typically transplanted up to forty-two days after the death of the donor, but it is unknown how the conditions and duration of storage affect the properties of fresh human osteochondral allografts.