In our experimental model, bone marrow-derived mesenchymal stem cells injection improved muscle regeneration and increased contractile function of anal sphincters after injury and repair. Therefore, mesenchymal stem cells may represent an attractive tool for treating anal sphincter lesions in humans. Investigations into the biologic basis of this phenomenon should increase our knowledge on underlying mechanisms involved in sphincter repair.

A fibrillar elastic apparatus around the wall of human lymph capillaries is demonstrated by means of histochemical and ultrastructural techniques. This apparatus consists of three interlinked components listed here in order of increasing distance from the capillary wall: 1) oxytalan fibres connected to the abluminal surface of the endothelial cells, known also as "anchoring filaments" and consisting of bundles of microfibrils; 2) elaunin fibres consisting of microfibrils and a small amount of elastin; and 3) typical elastic fibres consisting of microfibrils and abundant elastin. The microfibrillar constituent has similar ultrastructural features in the three components of the elastic apparatus. Microfibrils have a diameter of 12-14 nm, an electron-transparent core and a wall with 3-5 electron-dense subunits and oblique cross striations with a period of 15-17 nm. Microfibrils are the common element of the three components of the elastic apparatus and they link them to one another and to the elastic network of the perivascular connective tissue. An elastic apparatus was not found around blood capillaries and it can thus provide a histological marker to identify lymph capillaries. The possible role of the lymphatic elastic apparatus in the physiological activity of the lymphatic absorbing network is discussed and it is proposed that its disconnection from the elastic network of the tissue may promote pathological conditions such as lymphoedema or diseases related to impaired immune responses.

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Few and controversial data are available in the literature regarding the presence of lymphatic vessels in the human dental pulp. The present study was designed to examine morphologically the existence of a lymph drainage system in human dental pulp. Human dental pulp and skin sections were immunohistochemically stained with specific antibodies for lymphatic endothelium (D2-40, LYVE-1, VEGFR-3 [vascular endothelial growth factor receptor-3], and Prox-1), with the pan-endothelial markers CD31 and von Willebrand factor (vWF), and with the blood-specific marker CD34. Several blood vessels were identified in human pulps and skin. Lymphatic vessels were found in all human skin samples but in none of the pulps examined. Western blotting performed on human dermis and on pulps treated with collagenase (to remove odontoblasts) confirmed these results. Transmission electron microscopy indicated that vessels which, by light microscopy, appeared to be initial lymphatic vessels had no anchoring filaments or discontinuous basement membrane, both of which are typical ultrastructural characteristics of lymphatic vessels. These results suggest that under normal conditions human dental pulp does not contain true lymphatic vessels. The various theories about dental pulp interstitial fluid circulation should be revised accordingly.