Light and electron microscopic study of the medial collateral ligament epiligament tissue in human knees

Abstract

AIMTo examine the normal morphology of the epiligament tissue of the knee medial collateral ligament (MCL) in humans.METHODSSeveral samples of the mid-substance of the MCL of the knee joint from 7 fresh human cadavers (3 females and 4 males) were taken. Examination of the epiligament tissue was conducted by light microscopy and photomicrography on semi-thin sections of formalin fixed paraffin-embedded blocks that were routinely stained with haematoxylin and eosin, Mallory stain and Van Gieson’s stain. Electron microscopy of the epiligament tissue was performed on ultra-thin sections incubated in 1% osmium tetroxide and contrasted with 2.5% uranyl acetate, lead nitrate, and sodium citrate.RESULTSThe current light microscopic study demonstrated that the epiligament of the MCL consisted of fibroblasts, fibrocytes, adipocytes, neuro-vascular bundles and numerous multidirectional collagen fibers. In contrast, the ligament body was poorly vascularised, composed of hypo-cellular fascicles which were formed of longitudinal groups of collagen fibers. Moreover, most of the vessels of the epiligament-ligament complex were situated in the epiligament tissue. The electron microscopic study revealed fibroblasts with various shapes in the epiligament substance. All of them had the ultrastructural characteristics of active cells with large nuclei, well developed rough endoplasmic reticulum, multiple ribosomes, poorly developed Golgi apparatus, elliptical mitochondria and oval lysosomes. The electron microscopy also confirmed the presence of adipocytes, mast cells, myelinated and unmyelinated nerve fibers and chaotically oriented collagen fibers.CONCLUSIONSignificant differences exist between the normal structure of the ligament and the epiligament whose morphology and function is to be studied further.

Comparison between Operative and Non-Operative Treatment of the Medial Collateral Ligament: Histological and Ultrastructural Findings during Early Healing in the Epiligament Tissue in a Rat Knee Model

“…Later, we extended the investigations on the morphology of the EL of the MCL in human knee [Georgiev et al, 2017a]. We made a detailed description of the normal morphology of the EL and demonstrated differences between the structure of the EL and that of the ligament tissue.…”

“…This structure has been described as a "surrounding adherent connective tissue removed simultaneously with the ligament but which was grossly distinguishable from ligament tissue proper." Recent reports by Georgiev and Vidinov [2009a-c], Georgiev et al [2010aGeorgiev et al [ , b, 2015aGeorgiev et al [ , b, 2016Georgiev et al [ , 2017bGeorgiev et al [ , 2018, and Iliev et al [2016] in a rat model have turned the attention to the role of the EL. These studies described in detail the histological appearance, ultrastructural characteristics, and immunohistochemical expression of various substances in the EL under normal conditions and in the setting of experimental ligament injury.…”

“…According to these authors, the EL is the main source of fibroblasts, progenitor cells, and blood vessels, which proliferate and migrate towards the body of the ligament through the endoligament during ligament healing. Fibroblasts in the EL tissue are not static cells -they normally produce collagen types I, III, V [Georgiev et al, 2010a[Georgiev et al, , 2015a, fibronectin [Georgiev et al, 2016], and matrix metalloproteinases-2 and 9 [Georgiev et al, 2017b[Georgiev et al, , 2018, which are essential for the normal functioning of the ligament and their synthesis is increased in order to promote adequate repair after injury. They also emphasized its important role in understanding the normal recovery of the ligament, thus providing a basis for new treatment strategies.…”

Characterization of a Novel Diarrheagenic Strain of Proteus mirabilis Associated With Food Poisoning in China

“…After that, fixed cells were cut into sections and then washed with 0.1 mol/L of sodium cacodylate, dehydrated in ethanol, and finally embedded in Agar 100 resin. Sections were mounted on copper grids, stained with uranyl acetate and lead citrate, and examined using transmission electron microscopy (TEM) (Georgiev et al, 2017).…”

Light Microscopic Morphological Characteristics and Data on the Ultrastructure of the Cardiomyocytes

“…The change in the quantity of the collagen fibres of the connective tissue is the most significant marker of physiological processes such as aging of the myocardium, as well as pathological conditions associated with increased load and impaired function of the heart. [20][21][22][23] The intercalated disc is the zone of contact between the adjacent cardiomyocytes in longitudinal direction. It consists of two parts: transversal part and lateral part.…”