Structure of the rat subcutaneous connective tissue in relation to its sliding mechanism

Abstract

Mammalian skin can extensively slide over most parts of the body. To study the mechanism of this mobility of the skin, the structure of the subcutaneous connective tissue was examined by light microscopy. The subcutaneous connective tissue was observed to be composed of multiple layers of thin collagen sheets containing elastic fibers. These piled-up collagen sheets were loosely interconnected with each other, while the outer and inner sheets were respectively anchored to the dermis and epimysium by elastic fibers. Collagen fibers in each sheet were variable in diameter and oriented in different directions to form a thin, loose meshwork under conditions without mechanical stretching. When a weak shear force was loaded between the skin and the underlying abdominal muscles, each collagen sheet slid considerably, resulting in a stretching of the elastic fibers which anchor these sheets. When a further shear force was loaded, collagen fibers in each sheet seemed to align in a more parallel manner to the direction of the tension. With the reduction or removal of the force, the arrangement of collagen fibers in each sheet was reversed and the collagen sheets returned to their original shapes and positions, probably with the stabilizing effect of elastic fibers. Blood vessels and nerves in the subcutaneous connective tissue ran in tortuous routes in planes parallel to the unloaded skin, which seemed very adaptable for the movement of collagen sheets. These findings indicate that the subcutaneous connective tissue is extensively mobile due to the presence of multilayered collagen sheets which are maintained by elastic fibers.

Minipig as a potential translatable model for monoclonal antibody pharmacokinetics after intravenous and subcutaneous administration

“…29 The structure of the hypodermis in pigs differs from that in furred animals like rodents and cynomolgus monkeys, which have less abundant elastic fiber, and thus looser skin. 30 Similar to humans, the dermis of pigs is connected to the deep fascia via a fibrous network in the hypodermis. 29 Finally, pigs/minipigs have an easily accessible SC space with a tissue thickness similar to humans, making this species suitable to mimic the human situation for SC administration of proteins in preclinical studies.…”

“…43 As established models, rodents and monkeys are generally the default animal species of choice to characterize mAb PK. However, there are known differences in the skin architecture and physiology between humans and rodents or non-human primates, 12,30 and the predictability of these species for human SC PK of macromolecules has been poor. 7 The minipig is a potentially better predicative animal model given its similarity in skin physiology to human.…”

Mechanistic Determinants of Biotherapeutics Absorption Following SC Administration

“…In rodents such as rats, the SC connective tissue consists of multiple layers of connective tissue (Fig. 2), which are only loosely connected with each other due to the scarcity of fibers interconnecting adjacent collagen sheets (72). This loosely connected tissue allows SC administration of a relatively large fluid volume (15).…”

Comparison between a weight compression and a magnet compression for experimental pressure ulcers in the rat. Histological studies and effects of anesthesia

“…1a, 2a). While monitoring the level meter on top of the weight, the setting angle of the steel plate was adjusted to keep the weight standing at the correct angle on the abdominal wall to avoid any sliding since the subcutaneous connective tissue is easily movable (Kawamata et al, 2003). To protect the rat during compression, a case was hung over the weight without touching it in case it fell.…”