Enhanced phagocytic activity of lymph node macrophages after intranodular injection of autologous red blood cells

Time course analysis of hypoxia, granulation tissue and blood vessel growth, and remodeling in healing rat cutaneous incisional primary intention wounds

Hypoxia and the development and remodeling of blood vessels and connective tissue in granulation tissue that forms in a wound gap following full-thickness skin incision in the rat were examined as a function of time. A 1.5 cm-long incisional wound was created in rat groin skin and the opposed edges sutured together. Wounds were harvested between 3 days and 16 weeks and hypoxia, percent vascular volume, cell proliferation and apoptosis, alpha-smooth muscle actin, vascular endothelial growth factor-A, vascular endothelial growth factor receptor-2, and transforming growth factor-beta1 expression in granulation tissue were then assessed. Hypoxia was evident between 3 and 7 days while maximal cell proliferation at 3 days (123.6+/-22.2 cells/mm2, p<0.001 when compared with normal skin) preceded the peak percent vascular volume that occurred at 7 days (15.83+/-1.10%, p<0.001 when compared with normal skin). The peak in cell apoptosis occurred at 3 weeks (12.1+/-1.3 cells/mm2, p<0.001 when compared with normal skin). Intense alpha-smooth muscle actin labeling in myofibroblasts was evident at 7 and 10 days. Vascular endothelial growth factor receptor-2 and vascular endothelial growth factor-A were detectable until 2 and 3 weeks, respectively, while transforming growth factor-beta1 protein was detectable in endothelial cells and myofibroblasts until 3-4 weeks and in the extracellular matrix for 16 weeks. Incisional wound granulation tissue largely developed within 3-7 days in the presence of hypoxia. Remodeling, marked by a decline in the percent vascular volume and increased cellular apoptosis, occurred largely in the absence of detectable hypoxia. The expression of vascular endothelial growth factor-A, vascular endothelial growth factor receptor-2, and transforming growth factor-beta1 is evident prior, during, and after the peak of vascular volume reflecting multiple roles for these factors during wound healing.

An arteriovenous loop in a protected space generates a permanent, highly vascular, tissue‐engineered construct

A major obstacle to 3-dimensional tissue engineering is incorporation of a functional vascular supply to support the expanding new tissue. This is overcome in an in vivo intrinsic vascularization model where an arteriovenous loop (AVL) is placed in a noncollapsible space protected by a polycarbonate chamber. Vascular development and hypoxia were examined from 3 days to 112 days by vascular casting, morphometric, and morphological techniques to understand the model's vascular growth and remodeling parameters for tissue engineering purposes. At 3 days a fibrin exudate surrounded the AVL, providing a scaffold to migrating inflammatory, endothelial, and mesenchymal cells. Capillaries formed between 3 and 7 days. Hypoxia and cell proliferation were maximal at 7 days, followed by a peak in percent vascular volume at 10 days (23.20+/-3.14% compared with 3.59+/-2.68% at 3 days, P<0.001). Maximal apoptosis was observed at 112 days. The protected space and spontaneous microcirculatory development in this model suggest it would be applicable for in vivo tissue engineering. A temporal window in a period of intense angiogenesis at 7 to 10 days is optimal for exogenous cell seeding and survival in the chamber, potentially enabling specific tissue outcomes to be achieved.

[Erythrocytes in cervical lymph nodes of the human as a sequela of stasis and/or lymph drainage. Questionable diagnostic significance in strangulation and mechanical injuries of the head]

Information on the diagnostic significance of follicular hemorrhage and/or presence of red blood cells in the lymph node sinus was obtained by microscopic investigation of the superficial and deep human cervical lymph nodes. Fifty cases were selected on the basis of the following criteria: (1) cases without strangulation or mechanical head trauma; (2) cases in which death occurred by strangulation without additional mechanical head trauma; (3) cases without strangulation but with mechanical head trauma; (4) cases with strangulation and mechanical head trauma. The usual degree of stasis and hemorrhages and the dilation of the veins and/or capillaries are not sufficient to discriminate between cases with and cases without strangulation. Moreover, erythrocytes, erythrophages, and siderophages were encountered in the lymph node sinus of both cases with and cases without mechanical head trauma. Neither follicular hemorrhage nor the presence of red blood cells in the sinus is therefore diagnostically significant in forensic pathology.

[Blood destruction in pulmonary alveoli: signs of vitality and determination of survival time]

Lungs from 26 cases were examined in which blood was present as a result of a gunshot wound, a stab wound, or aspiration. Signs of vitality and of a time-dependent reaction sequence were evaluated to determine survival time. Only those morphologic criteria were considered that could be obtained on paraffin sections. In addition to H & E staining, siderin was identified with the Prussian blue reaction and the activities were determined of tartrate-resistant acid phosphatase, as macrophage marker, and naphthol AS-D chloracetate esterase, as granulocyte marker. The following criteria were evaluated: granulocyte emigration, erythrocyte adherence to the surface of macrophages, macrophage ingestion of erythrocytes, and determination of siderin as indicator of intracellular erythrocyte digestion. Adherence was also observed in those cases that did not survive. The initial sign of vitality was granulocyte emigration, which was observed for the first time after a survival time of 5 min. Erythrophages were found after a survival time of 30 min at least, siderophages after 17 h at the earliest. Literature dealing with vitality and age determination, as well as the pathogenesis of the reaction sequence, is discussed.

Destruction of intracerebrally applied red blood cells in cervical lymph nodes. Experimental investigations

In rabbits, intracerebrally applied erythrocytes can move with the cerebrospinal fluid along connecting pathways between the subarachnoid space and the cervical lymph nodes. This study compares the time dependency for the degradation of intracerebrally injected erythrocytes in the brain as well as in the cervical lymph nodes. Rabbits were killed at various predetermined intervals after the intracerebral erythrocyte injection. Microscopic and histologic examination of the brain and the cervical lymph nodes revealed the following findings: (1) Erythrophages first appeared in the brain 24 h after the injection; siderophages, 4 days after the injection. Siderophages were still demonstrable at the conclusion of the study, i.e. 240 days after the injection. (2) In the cervical lymph nodes erythrophages were first observed 1 h after the injection; siderophages, 9 h after the injection. Only isolated erythrophages and siderophages were found in the lymph nodes 12 days after intracerebral injection of red blood cells. Later on no erythrocytes or siderophages were observed in the lymph nodes. The findings indicate that non-phagocytized red blood cells arriving at the lymph nodes were ingested by local macrophages. The extremely rapid ingestion and digestion of the red blood cells by lymph node macrophages as well as the possible reasons were discussed.