A novel technique for simultaneous whole-body and multi-organ decellularization: umbilical artery catheterization as a perfusion-based method in a sheep foetus model

What's old is new again: The anatomical studies of Franklin P. Mall and the fascial-interstitial spaces

Franklin Mall was one of the foremost scientists of the turn of the 19th century, an exemplary mentor as well as researcher, and his revolutionary contributions are still relevant today. Mall's early training in Leipzig with Wilhelm His and Carl Ludwig provided him with an unusual perspective on the integration of anatomy and physiology, and his interest in the links between structure and function guided the work he carried out after joining the faculty of the new Johns Hopkins University School of Medicine. Mall carried out innovative studies on the one hand using dye injection to trace blood and lymphatic supplies to different organs and on the other hand using "putrefaction" to digest tissues and study the organization of the reticular space, demonstrating that it was the underlying source of support for all the organs. These two studies of Mall's, carried out independently, provide the basis for modern studies integrating the understanding of fascia and interstitial spaces.

Quantifying cerebrospinal fluid dynamics: A review of human neuroimaging contributions to CSF physiology and neurodegenerative disease

Cerebrospinal fluid (CSF), predominantly produced in the ventricles and circulating throughout the brain and spinal cord, is a key protective mechanism of the central nervous system (CNS). Physical cushioning, nutrient delivery, metabolic waste, including protein clearance, are key functions of the CSF in humans. CSF volume and flow dynamics regulate intracranial pressure and are fundamental to diagnosing disorders including normal pressure hydrocephalus, intracranial hypotension, CSF leaks, and possibly Alzheimer's disease (AD). The ability of CSF to clear normal and pathological proteins, such as amyloid-beta (Aβ), tau, alpha synuclein and others, implicates it production, circulation, and composition, in many neuropathologies. Several neuroimaging modalities have been developed to probe CSF fluid dynamics and better relate CSF volume and flow to anatomy and clinical conditions. Approaches include 2-photon microscopic techniques, MRI (tracer-based, gadolinium contrast, endogenous phase-contrast), and dynamic positron emission tomography (PET) using existing approved radiotracers. Here, we discuss CSF flow neuroimaging, from animal models to recent clinical-research advances, summarizing current endeavors to quantify and map CSF flow with implications towards pathophysiology, new biomarkers, and treatments of neurological diseases.

Characterization of perfusion decellularized whole animal body, isolated organs, and multi-organ systems for tissue engineering applications

To expand the application of perfusion decellularization beyond isolated single organs, we used the native vasculature of adult and neonatal rats to systemically decellularize the organs of a whole animal in situ. Acellular scaffolds were generated from kidney, liver, lower limb, heart‐lung system, and a whole animal body, demonstrating that perfusion decellularization technology is applicable to any perfusable tissue, independent of age. Biochemical and histological analyses demonstrated that organs and organ systems (heart‐lung pair and lower limb) were successfully decellularized, retaining their extracellular matrix (ECM) structure and organ‐specific composition, as evidenced by differences in organ‐specific scaffold stiffness. Altogether, we demonstrated that organs, organ systems and whole animal bodies can be perfusion decellularized while retaining ECM components and biomechanics.

Evidence for continuity of interstitial spaces across tissue and organ boundaries in humans

Bodies have continuous reticular networks, comprising collagens, elastin, glycosaminoglycans, and other extracellular matrix components, through all tissues and organs. Fibrous coverings of nerves and blood vessels create structural continuity beyond organ boundaries. We recently validated fluid flow through human fibrous tissues, though whether these interstitial spaces are continuous through the body or discontinuous, confined within individual organs, remains unclear. Here we show evidence for continuity of interstitial spaces using two approaches. Non-biological particles (tattoo pigment, colloidal silver) were tracked within colon and skin interstitial spaces and into adjacent fascia. Hyaluronic acid, a macromolecular component of interstitial spaces, was also visualized. Both techniques demonstrate interstitial continuity within and between organs including within perineurium and vascular adventitia traversing organs and the spaces between them. We suggest that there is a body-wide network of fluid-filled interstitial spaces that has significant implications for molecular signaling, cell trafficking, and the spread of malignant and infectious disease.

Human-Derived Scaffold Components and Stem Cells Creating Immunocompatible Dermal Tissue Ensuing Regulated Nonfibrotic Cellular Phenotypes

Regeneration of large-sized acute and chronic wounds provoked by severe burns and diabetes is a major concern worldwide. The availability of immunocompatible matrix with a wide range of regenerative medical applications, more specifically, for nonhealing chronic wounds is an unmet clinical need. Extrapolating the in vitro tissue engineering knowledge for in vivo guided wound regeneration could be a meaningful approach. This study aimed to develop a completely human-derived and minimally immune-responsive scaffold comprising of acellular amniotic membrane (AM), fibrin (FIB) and hyaluronic acid (HA), termed AMFIBHA. The potential for in vivo guidance of skin regeneration was validated through in vitro dermal tissue assembly on the combination scaffold by growing human fibroblasts, differentiated from human adipose tissue-derived mesenchymal stem cells (hADMSCs). An effective method was standardized for obtaining decellularized amnion (dAM) for assuring better immuno-compatibility. The biochemical stability of dAM upon plasma sterilization (pdAM) confirms its suitability for both in vitro and in vivo tissue engineering. The problem of poor handling characteristics was solved by combining the dried dAM with fibrin derived from a clinically used fibrin sealant kit. An additional constituent HA, derived from human umbilical cord tissue, imparts the required water absorption and retention property for better cell migration and growth. Post sterilization, the combination scaffold AMFIBHA demonstrated hemo-/cytocompatibility, confirming the absence of detergent residuals. Upon long-term (20 days/40 days) culture of hADMSC-derived fibroblasts, the suppleness of generated tissue was established by demonstrating regulated deposition of collagen, elastin, and glycosaminoglycans using both qualitative and quantitative measurements. Regulated expressions of transforming growth factors-beta 1 (TGF-β1) & TGF-β3, alpha smooth muscle actin (α-SMA), fibrillin-1, collagen subtypes, and elastin suggest non-fibrotic fibroblast phenotype, which could be an effect of microenvironment endowed by the AM, FIB, and HA. In burn wound model experiments, immune response to cellular AM was prominent as compared to untreated/sham control wounds and decellularized AM-treated and AMFIBHA-treated wounds, ensuring biocompatibility. Wound regeneration with complete epithelialization, angiogenesis, development of rete pegs, and other skin appendages were clearly visualized in 28 days after treating large-sized (4 × 4 cm²), debrided, full-thickness third-degree burn wounds, indicating guided wound regeneration potential of AMFIBHA dermal substitute.

Preparation and characterization of human size whole heart for organ engineering: scaffold microangiographic imaging

Definitive treatment for end-stage heart failure is heart transplantation, however, this is associated with several limitations. Aim: We decellularized and assessed ovine hearts through coronary perfusion. To evaluate in situ recellularization, a decellular graft was transplanted hetrotopically into the omental wrap. Results: Cell removal was confirmed by DNA count (11.68 ± 3.42 ng/mg dry weight). Elastic, reticular and collagen fiber were well preserved. There was a slight change in both glycosaminoglycan (7.01 ± 1.36 to 8.37 ± 0.32 μg/mg) and collagen (32.37 ± 2.3 to 36.31 ± 2.1) μg/mg (p > 0.05). Angiography and blood circulation revealed an intact vascular network. Implantation led to proper vascularization. Image J indicated CD31: 23.98 ± 12.3; CD34: 48.67 ± 19.5 and αSMA: 78.33 ± 27.8 inch/cm. Conclusion: Bio-scaffold of human size heart is achievable for future steps employing this technique.