reference is now made to fig1 , which is a schematic illustration of apparatus 20 comprising a housing 22 configured for implantation into the body of a patient , e . g ., subcutaneously or at another site , in accordance with an embodiment of the present invention . housing 22 is coupled to functional cells 30 , such as pancreatic islet cells that are in islets , and an oxygen supply 24 , positioned within housing 20 . typically , oxygen supply 24 generates or contains sufficient oxygen to sustain functional cells 30 during the period preceding vascularization of fibrotic tissue that forms around housing 22 . for example , the oxygen supply may generate oxygen in real - time , by photosynthesis ( e . g ., using algae and an electric light source ), photolysis , hydrolysis , or by a chemical reaction . alternatively or additionally , the oxygen supply comprises a vessel comprising gaseous oxygen . in either case , the oxygen released by oxygen supply 24 typically travels through a gas - and / or water - permeable membrane 26 whereby it enters solution ( if necessary ) and is uptaken by functional cells 30 . typically , the real - time generation of oxygen or the total supply of stored oxygen is limited in duration to a quantity that will support the functional cells for a maximum duration that may be as low as several hours , weeks , or months ( e . g ., 12 hours to one week , or one week to two months ) or up to many months ( e . g ., up to 6 , 12 , or 24 months ). in any case , the oxygen supply typically supports the functional cells for only a small portion of their total lifespan with the patient . functional cells 30 are typically disposed within a liquid , gel , and / or fibrillar matrix 28 . housing 22 comprises a selectively - permeable membrane 32 encapsulating either the entire housing , or portions thereof ( typically including at least all of cells 30 ). membrane 32 is characterized by a molecular cut - off weight of about 11 , 000 - 100 , 000 daltons , that is adapted to allow passage of nutrients and substances produced or consumed by the cells , such as oxygen , carbon dioxide , glucose , insulin , or water . membrane 32 of housing 22 also typically immunoisolates functional cells 30 by preventing passage therethrough of cells of the patient &# 39 ; s body , e . g ., white blood cells . reference is now made to fig2 , which is a schematic illustration of apparatus 20 described hereinabove , in accordance with another embodiment of the present invention . in the embodiment shown in fig2 , oxygen supply 24 is positioned outside of housing 22 , and is coupled thereto by a tube 34 . for some applications , supply 24 is disposed within the body of the patient , e . g ., at a suitable subcutaneous or other location . alternatively , the oxygen supply remains outside of the patient &# 39 ; s body , and tube 34 transcutaneously couples the oxygen supply to housing 22 . it is to be appreciated that the positioning of oxygen supply 24 shown in fig2 is by way of illustration and not limitation , and that the scope of the present invention includes alignments in close proximity to or far away from housing 22 ( rather than adjacent , as shown ). additionally , the scope of the present invention also includes the oxygenation of transplanted cells other than pancreatic islet cells , such as transplanted cells described in references cited in the background section of the present patent application . for some applications , vascularization around housing 22 is enhanced using one or more biochemical and / or angiogenic factors ( e . g ., vegf , bfgf , and / or platelets ) coupled to or in a vicinity of housing 22 , in addition to or instead of the enhancement of vascularization described above due to secretions by the functional cells . the scope of the present invention includes embodiments described in one or more of the following : pct patent application pct / il01 / 00031 to vardi et al ., entitled , “ implantable device ,” filed jan . 12 , 2001 ; u . s . patent application ser . no . 10 / 466 , 069 to vardi et al ., entitled , “ implantable device ,” filed mar . 12 , 2004 ; u . s . patent application ser . no . 11 / 001 , 556 to rotem et al ., entitled “ implantable device ,” filed nov . 30 , 2004 ; pct patent application pct / il2005 / 001262 to evron et al ., entitled , “ implantable device ,” filed nov . 27 , 2005 ; u . s . provisional patent application 60 / 860 , 632 to rotem et al ., entitled , “ protecting algae from body fluids ,” filed nov . 22 , 2006 , which is assigned to the assignee of the present patent application and is incorporated herein by reference . for some applications , techniques described in that provisional patent application are performed in combination with techniques described herein ; u . s . provisional patent application 60 / 861 , 592 to rotem et al ., entitled , “ oxygen supply for cell transplant and vascularization ,” filed nov . 28 , 2006 ; and a us provisional patent application , entitled “ air gaps for supporting cells ,” to rozy et al ., filed sep . 7 , 2007 . for some applications , techniques described herein are practiced in combination with techniques described in one or more of the patent references above , or the references cited in the cross - references section or background section of the present patent application , which are incorporated herein by reference . it will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove . rather , the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove , as well as variations and modifications thereof that are not in the prior art , which would occur to persons skilled in the art upon reading the foregoing description .
apparatus is provided , including a housing , configured for insertion into a body of a patient ; a photosynthetic oxygen supply configured to supply oxygen ; and functional cells , coupled to the housing . the functional cells are adapted to receive the oxygen and to secrete at least one factor that induces vascularization in a vicinity of the housing when the housing is in the body of the patient . other embodiments are also described .