CAMKK2 is upregulated in primary human osteoarthritis and its inhibition protects against chondrocyte apoptosis

OBJECTIVE

To investigate the role of calcium/calmodulin-dependent protein kinase kinase 2 (CAMKK2) in human osteoarthritis.

MATERIALS AND METHODS

Paired osteochondral plugs and articular chondrocytes were isolated from the relatively healthier (intact) and damaged portions of human femoral heads collected from patients undergoing total hip arthroplasty for primary osteoarthritis (OA). Cartilage from femoral plugs were either flash frozen for gene expression analysis or histology and immunohistochemistry. Chondrocyte apoptosis in the presence or absence of CAMKK2 inhibition was measured using flow cytometry. CAMKK2 overexpression and knockdown in articular chondrocytes were achieved via Lentivirus- and siRNA-mediated approaches respectively, and their effect on pro-apoptotic and cartilage catabolic mechanisms was assessed by immunoblotting.

RESULTS

CAMKK2 mRNA and protein levels were elevated in articular chondrocytes from human OA cartilage compared to paired healthier intact samples. This increase was associated with elevated catabolic marker matrix metalloproteinase 13 (MMP-13), and diminished anabolic markers aggrecan (ACAN) and type II collagen (COL2A1) levels. OA chondrocytes displayed enhanced apoptosis, which was suppressed following pharmacological inhibition of CAMKK2. Levels of MMP13, pSTAT3, and the pro-apoptotic marker BAX became elevated when CAMKK2, but not its kinase-defective mutant was overexpressed, whereas knockdown of the kinase decreased the levels of these proteins.

CONCLUSIONS

CAMKK2 is upregulated in human OA cartilage and is associated with elevated levels of pro-apoptotic and catabolic proteins. Inhibition or knockdown of CAMKK2 led to decreased chondrocyte apoptosis and catabolic protein levels, whereas its overexpression elevated them. CAMKK2 may be a therapeutic target to prevent or mitigate human OA.

Clinical applications of immunohistochemistry in gynecological malignancies

Over the past two decades, immunohistochemical techniques have improved to such a degree that it is now a common adjuvant test to the traditional hematoxylin and eosin-stained histologic sections. It is used in most realms of surgical pathology and can often aid in final diagnosis and, in some cases, prognosis. However, immunohistochemistry (IHC) is not always helpful and many pitfalls to its use exist. Understanding the basics of IHC, its utility and difficulties will aid clinicians in better understanding how diagnoses are rendered. This study reviews the general principles of IHC and demonstrates its utility with several commonly encountered problematic areas in gynecological pathology.

A delta T-cell receptor deleting element transgenic reporter construct is rearranged in alpha beta but not gamma delta T-cell lineages

T cells can be divided into two groups on the basis of the expression of either alpha beta or gamma delta T-cell receptors (TCRs). Because the TCR delta chain locus lies within the larger TCR alpha chain locus, control of the utilization of these two receptors is important in T-cell development, specifically for determination of T-cell type: rearrangement of the alpha locus results in deletion of the delta coding segments and commitment to the alpha beta lineage. In the developing thymus, a relative site-specific recombination occurs by which the TCR delta chain gene segments are deleted. This deletion removes all D delta, J delta, and C delta genes and occurs on both alleles. This delta deletional mechanism is evolutionarily conserved between mice and humans. Transgenic mice which contain the human delta deleting elements and as much internal TCR delta chain coding sequence as possible without allowing the formation of a complete delta chain gene were developed. Several transgenic lines showing recombinations between deleting elements within the transgene were developed. These lines demonstrate that utilization of the delta deleting elements occurs in alpha beta T cells of the spleen and thymus. These recombinations are rare in the gamma delta population, indicating that the machinery for utilization of delta deleting elements is functional in alpha beta T cells but absent in gamma delta T cells. Furthermore, a discrete population of early thymocytes containing delta deleting element recombinations but not V alpha-to-J alpha rearrangements has been identified. These data are consistent with a model in which delta deletion contributes to the implementation of a signal by which the TCR alpha chain locus is rearranged and expressed and thus becomes an alpha beta T cell.

Megakaryocyte growth and development factor ameliorates carboplatin-induced thrombocytopenia in mice

Megakaryocyte growth and development factor (MGDF) administered intraperitoneally (IP) to mice causes a dose-dependent thrombocytosis accompanied by a decrease in mean platelet volume. MGDF increases the number of megakaryocytes in the bone marrow and spleen. MGDF does not affect the circulating number of leukocytes. Carboplatin, a chemotherapeutic agent that causes thrombocytopenia in humans, administered to mice as a single IP injection at a nonlethal dose causes a significant, but reversible thrombocytopenia. The carboplatin-induced thrombocytopenia is accompanied by an increase in circulating endogenous MGDF that precedes the return of circulating platelets to a normal level. MGDF mRNA is constitutively present in the liver. After carboplatin treatment, hepatic MGDF mRNA does not increase in concordance with circulating MGDF. Circulating soluble MGDF receptor levels (c-mpl) do not change significantly during the course of carboplatin-induced thrombocytopenia. MGDF injected IP once daily beginning 1 day after injection of carboplatin reverses carboplatin-induced thrombocytopenia in a dose-dependent fashion. The normalization of circulating platelet numbers in carboplatin plus MGDF-treated mice is accompanied by a normalization of megakaryocyte numbers in the bone marrow. In conclusion, MGDF, by increasing the number of marrow megakaryocytes and circulating platelets is an effective therapy for carboplatin-induced thrombocytopenia in mice.

Cloning and characterization of the human megakaryocyte growth and development factor (MGDF) gene

The megakaryocyte growth and development factor (MGDF) is a cytokine that regulates megakaryocyte development and is a ligand for the MPL receptor. In this study, we describe the genomic structure of the human MGDF gene. The MGDF gene was found to consist of seven exons and six introns spanning 8 kilobases. The protein is encoded by exons 3 through 7. The human MGDF gene has been mapped to chromosome 3q26.3. In addition to the previously described full-length cDNA, two cDNA variants were isolated from human fetal liver. Comparison of these two cDNA sequences with the genomic sequence indicates that they arise by differential splicing.