Biomechanical, biochemical, and histological characterization of sacroiliac joint cartilage in the Yucatan minipig.

Although the sacroiliac (SI) joint can be a source of lower back and buttock pain, no comprehensive characterization studies on SI cartilage have been conducted. Using the minipig as a large animal model, this study conducted the first biomechanical, biochemical, and histological characterization of SI joint cartilage. Because previous literature has reported that sacral cartilage and iliac cartilage within the SI joint are histologically distinct, concomitantly it was expected that functional properties of the sacral cartilage would differ from those of the iliac cartilage. Creep indentation, uniaxial tension, biochemical, and histological analyses were conducted on the sacral and iliac cartilage of skeletally mature female Yucatan minipigs (n = 6-8 for all quantitative tests). Concurring with prior literature, the iliac cartilage appeared to be more fibrous than the sacral cartilage. Glycosaminoglycan content was 2.2 times higher in the sacral cartilage. The aggregate modulus of the sacral cartilage was 133 ± 62 kPa, significantly higher than iliac cartilage, which only had an aggregate modulus of 51 ± 61 kPa. Tensile testing was conducted in both cranial-caudal and ventral-dorsal axes, and Young's modulus values ranged from 2.5 ± 1.5 MPa to 13.6 ± 1.5 MPa, depending on anatomical structure (i.e., sacral vs. iliac) and orientation of the tensile test. The Young's modulus of sacral cartilage was 5.5 times higher in the cranial-caudal axis and 2.0 times higher in the ventral-dorsal axis than the iliac cartilage. The results indicate that the sacral and iliac cartilages are functionally distinct from each other. Understanding the distinct differences between sacral and iliac cartilage provides insight into the structure and function of the SI joint, which may inform future research aimed at repairing SI joint cartilage.

Biochemical and biomechanical characterization of the cervical, thoracic, and lumbar facet joint cartilage in the Yucatan minipig.

Facet joint arthrosis causes pain in approximately 7 % of the U.S. population, but current treatments are palliative. The objective of this study was to elucidate structure-function relationships and aid in the development of future treatments for the facet joint. This study characterized the articular surfaces of cervical, thoracic, and lumbar facet cartilage from skeletally mature (18-24 mo) Yucatan minipigs. The minipig was selected as the animal model because it is recognized by the U.S. Food and Drug Administration (FDA) and the American Society for Testing and Materials (ASTM) as a translationally relevant model for spine-related indications. It was found that the thoracic facets had a ∼2 times higher aspect ratio than lumbar and cervical facets. Lumbar facets had 6.9-9.6 times higher % depth than the cervical and thoracic facets. Aggregate modulus values ranged from 135 to 262 kPa, much lower than reported aggregate modulus in the human knee (reported to be 530-701 kPa). The tensile Young's modulus values ranged from 6.7 to 20.3 MPa, with the lumbar superior facet being 304 % and 286 % higher than the cervical inferior and thoracic superior facets, respectively. Moreover, 3D reconstructions of entire vertebral segments were generated. The results of this study imply that structure-function relationships in the facet cartilage are different from other joint cartilages because biochemical properties are analogous to other articular cartilage sources whereas mechanical properties are not. By providing functional properties and a 3D database of minipig facet geometries, this work may supply design criteria for future facet tissue engineering efforts.

Engineering of a miniaturized, robotic clinical laboratory.

The ability to perform laboratory testing near the patient and with smaller blood volumes would benefit patients and physicians alike. We describe our design of a miniaturized clinical laboratory system with three components: a hardware platform (ie, the miniLab) that performs preanalytical and analytical processing steps using miniaturized sample manipulation and detection modules, an assay-configurable cartridge that provides consumable materials and assay reagents, and a server that communicates bidirectionally with the miniLab to manage assay-specific protocols and analyze, store, and report results (i.e., the virtual analyzer). The miniLab can detect analytes in blood using multiple methods, including molecular diagnostics, immunoassays, clinical chemistry, and hematology. Analytical performance results show that our qualitative Zika virus assay has a limit of detection of 55 genomic copies/ml. For our anti-herpes simplex virus type 2 immunoglobulin G, lipid panel, and lymphocyte subset panel assays, the miniLab has low imprecision, and method comparison results agree well with those from the United States Food and Drug Administration-cleared devices. With its small footprint and versatility, the miniLab has the potential to provide testing of a range of analytes in decentralized locations.